Embed Size (px)
Citation preview
1
JOSÉ CARLOS VEIGA
INDUSTRIALGASKETS
3rd Edition
2
©José Carlos Veiga, 2004
Desenvolvido no Brasil / Developed in Brazil
ISBN 85-98256-01-3
CoverAlexandre Sampaio
PublishingRodrigo Xavier
RevisionGary M. Springer
GráficaBrasilform Editora e Ind. Gráfica
Drawing of this Edition: 3000 exemplares
Print History
Portuguese Language1st Edition, 1989 – 3000 books2nd Edition, 1993 – 3000 books3rd Edition, 1999 – 1000 books4th Edition 2003 – 3000 books
English Language1st Edition, 1994 – 10000 books2nd Edition, 1999 – 3000 books3rd Edition, 2003 - 3000 books
Spanish Language1st Edition, 2003 –2000 books
Library of CongressCatalog Card Number: 99-75712
Price per Copy US$ 20,00
3
To my wife,MARIA ODETE
4
AUTHORS’S NOTE
The author wishes tothank The Teadit Groupfor support in publishing
its book.
5
Preface
The idea for this book arose by chance. At the end of a technical discussionthat we were having with a client, one of the participants asked why we couldn’torganize all of the information and examples that we had just presented into onecomplete book. He had never seen such a book in the market and knew it would bebeneficial to him and his co-workers.
Based on this simple request and our acknowledgement that the industry wasvoid of this type of tool, we then decided to create book that could be used by allaspects of industry. We would compile and organize all the knowledge that our technicalteam had with the information of product applications received from our clients. Thisapplication information was critical in establishing a precise correlation between theoryand practice.
The guiding influence in our business philosophy is Research andDevelopment. Active participation in product applications along with the continuoussearch for technical and scientific innovations puts us in an outstanding position asit relates to the knowledge of “Best Practices” and the development of the new,innovative solutions. We are always striving for product life cycle improvement andrecognize that the constant search for excellence is never ending. The search forexcellence is evident in our Development Engineering, our Application Engineeringand in our industry experts’ constant work in the field. Our knowledge and commitmentshows through the ability to interact with both Production and Engineering departmentsand our close monitoring of product performance. The goal is not to just satisfy ourclients but to educate. We hold ourselves to standards set by leading edge technologywhich is evident in our product and service offering.
We have observed the evolution of the fluid sealing industry in the enviableposition of a Global Premier manufacturer for more than 50 years. This experiencealong with being a guiding member of the main global organizations of the sector(FSA – Fluid Sealing Association, ESA – European Sealing Association, ASTM, PVRCand many others) has given us the ability to amalgamate the past experience with thepresent data and future prospective.
Our purpose with this book is create a directory of information that would beuseful to the experts working in this field and fielding the vast majority of the dailyissues met in the industry.
6
7
INDEX
Chapter 1 – Introduction ..........................................................11
Chapter 2 – Design and the New Gasket Constants ..............131. Leaks .............................................................................................. 132. Sealing ............................................................................................ 143. Forces in a Flanged Joint ............................................................... 144. ASME Code ................................................................................... 155. Notation .......................................................................................... 206. Bolt Torque Calculation.................................................................. 217. Surface Finish................................................................................. 238. Parallelism of Sealing Surfaces ..................................................... 269. Waviness of the sealing Surfaces .................................................. 2710. Styles of Flanges ............................................................................ 2711. The New Gasket Constants ........................................................... 3012. Gasket Maximum Seating Stress ................................................... 41
Chapter 3 – Materials for Non-Metallic Gaskets .................451. Material Selection .......................................................................... 452. P x T or Service Factor.................................................................. 463. Sheet Packing................................................................................. 464. Polytetrafluoretylene - PTFE......................................................... 475. Flexible Graphite - Graflex . ........................................................ 476. Elastomers ...................................................................................... 497. Cellulose Fiber Sheet ..................................................................... 518. Cork ................................................................................................ 519. Fabric and Tapes ............................................................................ 5110. Tadpole ........................................................................................... 51
8
11. Ceramic Fiber Blankets. ................................................................ 5212. Ceramic Fiber Millboard ................................................................ 5213. Beater Addition .............................................................................. 52
Chapter 4 – Compressed Non-Asbestos Gaskets Sheets ....... 571. Teadit Compressed Non-Asbestos Gaskets Sheets ...................... 572. Fibers .............................................................................................. 573. Elastomers ...................................................................................... 584. Wire Mesh ...................................................................................... 585. Finishing ......................................................................................... 586. Sheet Dimensions ........................................................................... 587. Physical Characteristics ................................................................. 598. Design ............................................................................................ 609. Manufacturing Tolerances ............................................................. 6210. Large Diameter Gaskets ................................................................ 6211. Gasket Thickness ........................................................................... 6412. Bolt Load ........................................................................................ 6413. Gasket Finish .................................................................................. 6414. Finish of the Flange Sealing Surface ............................................. 6515. Storage ........................................................................................... 6516. Teadit Compressed Non-Asbestos Gasket Sheets ........................ 65
Chapter 5 – PTFE Gaskets ................................................................. 891. Polytetrafluorethylene (PTFE) ...................................................... 892. Styles of PTFE Sheets ................................................................... 893. TELON* - Restructured Filled PTFE Sheet ................................. 914. Expanded PTFE ............................................................................. 975. Sintered PTFE Sheets .................................................................... 1016. PTFE Envelope Gaskets ................................................................ 102
Chapter 6 – Materials for Metallic Gaskets .................................... 1211. Corrosion ........................................................................................ 1212. Carbon Steel ................................................................................... 1213. Stainless Steel Aisi 304 .................................................................. 1224. Stainless Steel Aisi 304L ................................................................ 1225. Stainless Steel Aisi 316 .................................................................. 122
9
6. Stainless Steel Aisi 316L ................................................................ 1227. Stainless Steel Aisi 321 .................................................................. 1228. Stainless Steel Aisi 347 .................................................................. 1229. Monel .............................................................................................. 12310. Nickel 200 ...................................................................................... 12311. Copper ............................................................................................ 12312. Aluminum ....................................................................................... 12313. INCONEL ...................................................................................... 12314. TITANIUM .................................................................................... 123
Chapter 7 – Spiral Wound Gaskets ......................................... 1331. Spiral Wound Gaskets .................................................................... 1332. Materials ........................................................................................ 1343. Gasket Density ............................................................................... 1354. Gasket Dimensions ......................................................................... 1355. Thickness ....................................................................................... 1366. Dimensional and Thickness Limitations ......................................... 1377. Manufacturing Tolerances........................................................... 1388. Finish of the Flange Sealing Surface ............................................. 1389. Gasket Maximum Seating Stress ................................................... 13910. Gasket Styles .................................................................................. 13911. Style 911 Gaskets .......................................................................... 13912. Style 913 Gaskets Per Asme B16.20 (Api 601) ............................ 14113. Other Standards ............................................................................. 14514. Style 913 Gasket Design ................................................................ 14515. Style 914 ........................................................................................ 146
Chapter 8 – Jacketed Gaskets ..................................................1631. Description ..................................................................................... 1632. Metallic Jacket ............................................................................... 1643. Filler ................................................................................................ 1644. Design ............................................................................................ 1645. Styles and Applications .................................................................. 1646. Gaskets for Heat Exchangers ........................................................ 1677. Style 927 Gaskets for Heat Exchangers ........................................ 173
10
Chapter 9 – Metallic Gaskets ............................................. 1771. Metallic Gaskets ............................................................................. 1772. Flat Metallic Gaskets ..................................................................... 1773. Materials ........................................................................................ 1784. Finish of the Flange Sealing Surface ............................................. 1785. Styles of Flat Metallic Gaskets ...................................................... 1786. Ring-Joints ...................................................................................... 183
Chapter 10 – Camprofile Gaskets ...........................................1991. Introduction .................................................................................... 1992. Materials ........................................................................................ 2003. Pressure and Temperature Limits .................................................. 2014. Bolting Calculation ......................................................................... 2015. Surface Finish................................................................................. 2026. Design and Manufacturing Tolerances .......................................... 2027. Shapes ............................................................................................ 2038. Camprofile Gaskets for Asme B16.5 Flanges ............................... 2039. Dimensions nad Tolerances ........................................................... 204
Chapter 11 – Gaskets for Electrical Insulation ...................2071. Eletrochemical Corrosion ............................................................... 2072. Cathodic Protection........................................................................ 2093. Insulation System for Flanges ........................................................ 2094. Specifications for the Gasket Material .......................................... 213
Chapter 12 – Installation and Fugitive Emissions ...............2151. Installation Procedure .................................................................... 2152. Torque Values................................................................................. 2163. Allowable Bolt Stress ..................................................................... 2164. Leakage .......................................................................................... 2175. Misaligned Flanges ......................................................................... 2176. Live Loading ................................................................................... 2187. Fugitive Emissions .......................................................................... 221
Chapter 13 – Conversion Factors............................................227
Bibliography ...............................................................................229
11
CHAPTER
1
INTRODUCTION
This book was written with the purpose of providing better design andapplication of Industrial Gaskets. It has been very successful in several countries andhas become a reference for gasket applications. This Third English Language Edition,revised and expanded, incorporates the latest advances in gasket technology sincethe last printing.
On analyzing certain leaks - which at first glance seemed to be caused bygasket deficiencies – we verified, after a more careful observation, that little attentionhad been paid to details such as:
• Flange and Gasket design.• Correct choice of gasket materials.• Installation procedures.The great problems confronted by industries such as explosions, fires and
environmental pollution caused by leaks, can be avoided with the correct gasketdesign and installation.
The objective of this book is to help prevent accidents by promulgating awider understanding of industrial gaskets, specialty sheet packing and spiral woundgaskets; undoubtedly the types most widely used in industrial applications.
Existing North America market conditions were carefully taken intoconsideration. Materials and gasket styles, which are not commercially available ordifficult to find, were omitted; emphasis being given to the most accessible and widelyused products and materials.
This book is divided in chapters that cover the following:• Design and the New Gasket Constants.• Non-Metallic Gasket Materials.• Sheet Packing Gaskets.• PTFE Gaskets.• Metallic Gasket Materials.
12
• Spiral Wound Gaskets.• Jacketed and Heat Exchanger Gaskets.• Metallic Gaskets.• Camprofile Gaskets.• Insulation Gaskets for Flanges.• Installation Procedures and Fugitive Emissions.• Conversion Factors.
The most important changes to this Third Edition are:• The Chapter about PTFE Gaskets has been expanded to include the Tealon*
restructured PTFE gasket sheet.• New Non-Asbestos Sheet Packing materials.• Serrated Metallic Camprofile Gaskets for ASME B16.5 flanges• All tables were revised, updated and expanded.The author would welcome commentaries and suggestions that can be sent
to Av. Matin Luther King Jr., 8939, 21530-011, Rio de Janeiro, RJ, Brazil.
* Tealon is a trademark of E.I. DuPont De Nemours and Company and is used underlicense by Teadit.
13
CHAPTER
2
DESIGN AND THENEW GASKET CONSTANTS
1. LEAKS
Based on the fact of the non-existence of “zero leakage”, to determine if agasket is leaking or not depends on the method of measurement or on the criterionutilized. In certain applications the maximum leak index can be, for example, only onedrop of water per second. In other applications it can be the absence of soap bubbleswhen the equipment or piping is under pressure. More rigorous conditions can evencall for tests with mass spectrometers or other leak detection equipment.
In order to establish criteria for measuring maximum admissible leakage thefollowing should be considered:
• Fluid to be sealed.• Impact on the immediate environment, if fluid escapes into the atmosphere.• Danger of fire or explosion.• Other relevant factors in each particular situation.For industrial applications, “zero leakage” is commonly defined as Helium
leakage between 10-4 and 10-8cm3/sec or less. The Johnson Space Center (NASA) inHouston, Texas, establishes the value of 1.4 x 10-3cm3/sec of N
2 at 300 psi at room
temperature. For reference, we can establish that a drop of liquid has an averagevolume of 0.05cm3. Thus 20 drops will be necessary to make 1cm3. This is goodreference value to define the maximum leakage tolerated in industrial applications.
With the need to control fugitive emissions the Environmental ProtectionAgency (EPA) has initially set the limit of 500 parts per million (ppm) as maximum leakfor flanges. However this value has been considered too high and there has been atrend to revise it to 100 ppm.
The leakage rate is a relative concept and in critical situations must bejudiciously established.
14
2. SEALING
If it were technically and economically feasible to manufacture perfectlysmooth and polished flanges and if we could maintain these surfaces in permanentcontact, there would be no need for gaskets. This technical and economic impossibilityresults from:
• Size of the vessel and/or the flanges.• Difficulty in maintaining these surfaces perfectly smooth during the handling
and/or assembling of the vessel or piping.• Corrosion or erosion of the surface by time.• To overcome these difficulties, gaskets are used as a sealing element. When
a gasket is seated against the flange surface, it flows, filling the imperfectionsbetween them and providing the necessary sealing. Therefore, in order toobtain adequate sealing we must consider four factors:
• Seating stress: we must provide an adequate way of seating the gasket soit will be able to flow and fill the flange imperfections. The minimum initialseating stress is recommended by the American Society of MechanicalEngineers (ASME) Pressure Vessel and Boiler Code, which will be explainedlater. This seating stress must be limited in order to prevent the destructionof the gasket by an excess of compression.
• Sealing force: a residual stress on the gasket must be maintained, in orderto keep it in contact with the flange surfaces, thus avoiding leakage.
• Material selection: The gasket material must resist the pressure as well asthe fluid to which it is subjected. The correct selection of materials will becovered in several chapters of this book.
• Surface finish: There is a recommended flange surface finish for each styleof gasket and class of service. The use of surface finish not compatiblewith the gasket is one of the primary causes of leakage.
3. FORCES IN A FLANGED JOINT
The Figure 2.1 shows the forces in a flanged joint.• Radial force: originated by the internal pressure; it tends to blow out thegasket.• Separation force: also originated by internal pressure; it tends to separate
the flanges.• Bolt load: it is the total load exercised by the bolts.• Flange load: it is the force, which compresses the flanges against the gasket.
The seating stress initially applied to the gasket, besides causing flow ofthe gasket material, must:
• Compensate for the separation force caused by internal pressure.• Be sufficient to maintain a residual stress on the gasket, avoiding fluid
leakage.
15
From a practical point of view, the residual stress, in order to maintain thesealing, must be “x” times the internal pressure. This “x” value is known as the factor“m” in the ASME Code and varies according to the style of the gasket used. The “m”value is the ratio between the residual stress on the gasket (bolt load minus separationforce) and the internal pressure. The larger the “m” value is, the greater it will be thesystem’s security against leakage.
Figure 2.1
4. ASME CODE
The Division 2 Section VIII of the ASME Pressure Vessel and Boiler Codesuggests the equations for gasket design and the “m” (gasket factor) and “y” (minimumgasket seating stress) values. These values are not mandatory; however they arebased on the results of successful practical applications. The designer has the freedomto use different values as long as the available data justifies the need for doing so.
The Appendix 2 of the Section VIII requires that a calculation of a boltedflanged joint be made for two independent conditions: operating pressure and minimumseating stress.
16
4.1. OPERATIONAL CONDITIONS
This condition determines a minimum bolt load as per the equation:
Wm1
= (π G2 P / 4) + (2 b π G m P) (eq. 2.1)
This equation establishes that the minimum bolt load necessary to fulfill theoperational conditions is equal to the sum of the pressure force plus a residual loadover the gasket times a factor and times the internal pressure. Or, interpreting it in adifferent way, this equation establishes that the minimal bolt load must be such thatthere always will be a residual pressure applied to the gasket greater than the internalpressure of the fluid. The ASME Code establishes the minimum values of factor “m”for diverse styles of gaskets as shown in Table 2.1.
4.2. MINIMUM GASKET SEATING STRESS
The second condition determines a minimum seating gasket stress withouttaking into consideration the fluid pressure. This seating force is calculated by theformula:
Wm2
= π b G y (eq. 2.2)
where “b” is defined as the effective gasket width and “y” is the value of the minimumseating stress, obtained in Table 2.1. The “b” value is calculated by:
b = b0 when b
0 is equal to or less than 1/4" (6.4 mm)
orb = 0.5 ( b
0 ) 0.5 when b
0 is greater than 1/4" (6.4 mm)
The ASME Code also explains how to calculate b0 according to the face of the
flange as shown in Tables 2.1 and 2.2.
4.3. BOLT AREA
The minimum bolt area Am must be calculated as follows:
Am1
= (Wm1
) / Sb (eq. 2.3)
or
Am2
= (Wm2
) / Sa (eq. 2.4)
17
where Sb is the maximum admissible bolt stress at the working temperature and S
a is
the maximum admissible bolt stress at room temperature.The value of A
m should be the greater of the values obtained in equations 2.3
and 2.4.
4.4. BOLT CALCULATION
The bolts should be selected so that the sum of their maximum stress areas isequal to or greater than A
m:
Ab = ( number of bolts ) x ( minimum bolt area, sqin )
Ab should be equal or greater than A
m.
4.5. MAXIMUM GASKET STRESS
The maximum stress on the gasket is calculated by the formula:
Sg(max)
= (Wm) / ((π/4) (OD2 - ID2) )) (eq. 2.5)
or
Sg(max)
= (Wm) / ((π/4) ( (OD - 0,125)2 - ID2)) ) (eq. 2.6)
Where Wm is the greater of the values obtained in equations 2.1 and 2.2. The
equation 2.5 should be used for spiral wound gaskets and equation 2.6 for otherstyles of gaskets.
The Sg value, calculated by equations 2.5 or 2.6, should be less than themaximum stress, which the gasket can resist. If Sg value is larger, another style ofgasket must be used or, when not possible, the gasket area must be enlarged.
18
Gasket Material m y(psi)
GasketStyle
Colunnb0
FacingSketchTable 2.
Elastomer - less than 75 Shore A - 75 Shore A or higher - with cotton fabricSheet Packing 1/8" thick
1/16" thick1/32" thick
Vegetable Fiber
Spiral Wound Stainless Steel or MonelAsbestos filledCorrugated metal Asbestos filled
AluminumCopper or BrassCarbon SteelMonelStainless Steel
Corrugated MetalCopper or BrassCarbon SteelMonelStainless Steel
Jacketed Metal Asbestos filledAluminumCopper or BrassCarbon SteelMonelStainless Steel
Grooved Metal AluminumCopper or BrassCarbon SteelMonelStainless Steel
Solid Flat Metal AluminumCopper or BrassCarbon SteelMonelStainless Steel
Ring Joint Carbon SteelMonelStainless Steel
0.501.001.252.002.753.501.75
3.00
2.502.753.003.253.502.753.003.253.503.75
3.253.503.753.503.753.253.503.753.754.254.004.755.506.006.505.506.006.50
0200400
1600370065001100
10000
2900370045005500650037004500550065007600
550065007600800090005500650076009000
101008800
13000180002180026000180002180026000
flat
flat
flat
911, 913914
926
900
923
941, 942
940
950, 951
II
II
II
II
II
II
II
II
I
I
(la) (lb) (1c)(1d) (4) (5)
(la) (lb) (1c)(1d) (4) (5)
(la) (lb) (1c)(1d) (4) (5)
(la) (1b)
(la) (1b)
(la) (1b) (1c)(1d)
(la) (1b) (1c)(1d) (2)
(6)
(la) (1b) (1c)(1d) (2) (3)
(la) (1b) (1c)(1d) (2) (3)
(4) (5)
Table 2.1Gasket Factor m and Minimum Design Seating Stress y
19
20
Table 2.2 (Continued)Location of Gasket Load Reaction
5. NOTATION
Ab
= bolt cross-sectional area at the root of the thread or the smallest area under stress (sqin).
Am
= total bolt cross-sectional area. Is considered as the greatest value for Am1
and A
m2 (sqin).
Am1
= total bolt cross-sectional area calculated for operational conditions (sqin).
Am2
= total bolt cross-sectional area necessary to seat the gasket (sqin).
B = effective gasket width or gasket contact width with the flange surface (in).
b0
= basic gasket seating width (in).
OD = gasket external diameter (in).
ID = gasket internal diameter (in).
G = diameter of the location of gasket load reaction, Table 2.2 (in).
m = gasket factor, Table 2.1.
N = radial width used to determine the basic width of the gasket, Table 2.2 (in).
21
P = design pressure (psi).
Sa
= maximum allowable bolt stress at room temperature (psi)
Sb
= maximum allowable bolt stress at design temperature (psi).
Sg
= stress over the gasket surface (psi).
Wm
= bolt load as the greater of the values Wm1
and Wm2
.
Wm1
= minimum bolt load for operational conditions (psi).
Wm2
= minimum bolt load to seat the gasket (psi).
y = minimum gasket seating stress (psi).
6. BOLT TORQUE CALCULATION
6.1. TIGHTENING FACTOR
The frictional force is the principal responsible factor for keeping a bolttightened. Suppose we have a spiral thread “unwound” which we represent by aninclined plane. When a torque is applied to it, the result will be similar to the oneproduced by a heavy block pushed up an inclined plane subject to the forces shownin Figure 2.2.
Figure 2.2
22
Where:a = inclination angle of the thread.d = bolt diameter.F = bolt load.F
a= frictional force.
Fn
= bolt force perpendicular to the thread.k = tightening factor.N
p= number of bolts.
r = bolt radius.T = torque applied to bolt.u = coefficient of friction
In keeping the balance between the forces acting in parallel direction to theinclined plane we have:
(T/r) cos a = uFn + F
p sin a (eq. 2.7)
In the perpendicular direction to the inclined plane, we have:
Fn = F
p cos a + (T/r) sin a (eq. 2.8)
Since the angle of the thread is very small for ease of calculation we canignore the factor (T/r) sin (a) in the equation 2.8. By replacing value F
n in equation 2.7,
we have:
(T/r) cos a = uFp cos a + F
p sin a (eq. 2.9)
By calculating T value we have:
T = Fp r (u + tg a) (eq. 2.10)
Since the coefficient of friction is constant for a determined lubricationcondition and since tg(a) is constant for each thread, exchanging r for d, we have:
T = k Fp d (eq. 2.11)
Where k is a factor experimentally determined. In Table 2.3 we show k valuesfor bolts very well lubricated with oil and graphite. Those values are based in practicaltests. Non-lubricated bolts show approximately a 50% difference. Different lubricantscan produce values different from the ones shown in Table 2.3. These values must bedetermined in actual tests.
23
6.2. TIGHTENING TORQUE
To calculate the tightening torque we should verify the value of the bolt loadneeded W
m1 or W
m2as it has been calculated in equations 2.1 and 2.2. By modifying
equation 2.11, we have:
T1 = (k W
m1 d) / N
p (eq. 2.12)
T2 = (k W
m2 d) / N
p (eq. 2.13)
The value of T must be the greater of the values obtained in equations 2.12 and
Table 2.3STEEL OR ALLOY STEEL BOLTS OR STUDS
7. SURFACE FINISH
For each style of gasket there is a recommended finish for the flange sealingsurface. This finish is not mandatory, however is based in successful practicalapplications.
As a general rule, it is necessary that the surface be serrated for non-metallicgasket materials like sheet-packing, rubber and PTFE. Metallic gaskets require asmoother finish. The reason for this difference is that non-metallic materials must be
l/45/163/87/16l/2
9/165/83/47/81
1 1/81 1/41 3/81 1/21 5/81 3/41 7/8
2
2018161413121110987766
5 1/255
4 1/2
0.230.220.180.190.200.210.190.170.170.180.200.190.200.180.190.200.210.19
0.0270.0450.0680.0930.1260.1620.2020.3020.4190.5510.6930.8901.0541.2941.5151.7442.0492.300
Nominal Diameterinches
Number of Threadsper inch
Tightening Factor- k
Cross SectionalThread Area - sqin
24
“bitten” by the sealing surface, therefore avoiding an excessive extrusion or expulsionof the gasket by the radial force.
Solid metallic gaskets require very high force “to flow” the material into theflange surface. Consequently, the smoother the surface the lesser will be the possibilityof leakage.
Spiral wound gaskets require some degree of superficial roughness in orderto avoid “sliding” under stress. They show a tendency of buckling inwards which iscritical especially with Flexible Graphite filled gaskets.
The style of the gasket, therefore, shall determine the finish of the sealingsurface, and there is no “optimum finish” to fit the diverse styles of gaskets.
The gasket material should always be softer than the flange, so the gasketwill always be seated by the flange, maintaining the finish of the flange surfaceunaltered.
7.1. RECOMMENDED FINISH FOR SEALING SURFACES
The flange surfaces can vary from a rough casting finish to polished. However,the most common commercially available is concentric or phonographic spiral groovesas shown in Figure 2.3. Both are machined with a tool with a tip radius of 1/16" (1.6 mm)and 45 to 55 grooves per inch. This is known as a 125 µpol R
a (3.2 µm R
a) to 250 µpol
Ra (6.3 µm R
a) finish.
Figure 2.3
Table 2.4 indicates the type of finish used for industrial gaskets. Per the MSSSP-6 Standards Finishes for Contact of Pipe Flanges and Connecting-End Flanges ofValves and Fittings, the Roughness Average (Ra) is expressed in micro-inches ormicrometers. It must be measured by visual comparison.
25
Gasket Description
Flat Non-Metallic
Corrugated Metallic
Covered Corrugated Metallic
Spiral Wound
Metal Jacketed
Flat Metallic
Metallic Grooved
Covered Metallic Grooved(Camprofile)
Ring-Joint
TeaditStyle
810820
900
905
911913914
920
923
926
927
929
940
941
942
950
951
RX
BX
1.6
3.2 a 6.3
1.6
3.2
2.0 a 6.3
1.6 a 2.0
1.6
1.6
1.6 a 2.0
125 a 250
63
125
63
80 a 250
63 a 80
63
63
63 a 80
Surface FinishRaGasket Cross
Section µµµµµm µµµµµ pol
Table 2.4Finish of the Flange Sealing Surface
26
7.2. SURFACE FINISH AND SEALABILITY
Following are some rules, which must be observed in order to harmonize thesurface finish and the style of gasket:
• The surface finish has a great influence on the ability to seal.• A minimum stress force must be obtained in order to flow the gasket through the
flange imperfections. A soft gasket (like cork) requires a seating stress lesser thana denser gasket (like sheet packing).
• The seating force is proportional to the flange contact area. It can be reduced bydiminishing the width of the gasket or of the flange contact area.
• Whatever the style of gasket or finish used it is important that there are no scratchesor radial tool marks on the sealing surface of the flanges.
• Phonographic grooves are more difficult to seal than the concentric ones becausethe gasket, when seated, must flow up to the bottom of the grooves. This preventsany leak path to be formed from one end of the spiral to the other.
• Since the materials have different hardness and flow characteristics, the choice ofa type of flange surface finish is going to depend basically on the gasket styleand/or material.
8. PARALLELISM OF SEALING SURFACES
Tolerance for parallelism is shown on Figure 2.4. The right figure is less criticalsince the bolt force tends to correct the problem.
Figure 2.4
Total Deviation: 1 + 2 < = 1/64”
27
9. WAVINESS OF THE SEALING SURFACES
The maximum deviation of the sealing surfaces depends on the type of gasket(figure 2.5):
• Sheet packing or rubber gaskets: 0.030 in (0.8 mm)• Spiral wound gaskets : 0.015 in (0.4 mm)• Solid metallic gaskets: 0.00 5in (0.1 mm)
Figure 2.5
10. STYLES OF FLANGES
Even though flange design is beyond the scope of this book, in the followingfigures we show the most common combinations of flange faces.
10.1. FLAT FACE
Non-confined gasket (Figure 2.6). Contact surfaces in both flanges are flat.The gasket can be style RF with the external diameter of the gasket touching the bolts.
Or FF with the gasket covering the entire flange surface. Flat flanges arenormally used in flanges made out of fragile materials.
Figure 2.6
28
10.2. RAISED FACE
Non-confined gasket (Figure 2.7). Contact surfaces are raised about 1/16 in(1.6 mm) or ¼ in (6.4 mm). Normally the gasket covers up the bolts. It allows theassembly and removal of the gasket without having to separate the flanges, facilitatingmaintenance work. This type is used more often in piping.
Figure 2.7
10.3. TONGUE AND GROOVE
Totally confined gasket (Figure 2.8). The groove depth is equal or greaterthan the tongue high. The gasket has, usually, the same width as the tongue. It isnecessary to separate the flanges in order to change the gasket. Since this style offlange exerts high seating stress on the gasket, it is not recommended for non-metallicgaskets.
Figure 2.8
29
10.4. MALE AND FEMALE
Semi-confined gasket (Figure 2.9). The most common style is the one on theleft. The depth of the female is equal or less than the height of the male in order toavoid the possibility of direct contact of the flanges when the gasket is compressed.
The female external diameter is up to 1/16 in (1.6 mm) larger than the male. Theflanges must be separated to change the gasket. In the figures at the right and left, thegaskets are confined by the external diameter. In the center figure it is confined by theinternal diameter.
10.5. FLAT FACE AND GROOVE
Totally confined gasket (Figure 2.10). The external face of one of the flangesis plain and the other has a groove where the gasket is assembled. They are used inapplications where the distance between flanges must be precise. When the gasket isseated the flanges touch each other. Only very resilient gaskets can be used in thesetype of flanges. Spiral-wound, O-Rings, non-solid metallic, pressure activated andjacketed with metallic fillers are recommended.
Figure 2.10
30
10.6. RING-JOINT
Also called API Ring (Figure 2.11). Both flanges have channels with walls ina 23º angle. The gasket is made out of solid metal with an oval or octagonal profile. Theoctagonal profile is more efficient.
Figure 2.11
11. THE NEW GASKET CONSTANTS
Traditionally calculations for piping flanges and gaskets use values andformulas recommended by the American Society of Mechanical Engineers (ASME)Section VIII of Pressure Vessel and Boiler Code.
The ASME Code recommends values for minimum seating stress “y” and themaintenance factor “m” for various styles of gaskets. These values were determinedfrom experimental work in 1943.
With the development of materials like Flexible Graphite, PTFE and thereplacement of asbestos-based gaskets for other materials, it became necessary todetermine the values of “m” and “y” for those new materials. In 1974, the PressureVessel Research Committee (PVRC) initiated an experimental program to betterunderstand the behavior of a gasket in a flanged joint since there was no analyticaltheory that allowed determination of this behavior. This work was sponsored by thirtyinstitutions among them ASME, American Petroleum Institute (API), Fluid SealingAssociation (FSA), and American Society for Testing Materials (ASTM) among others.
The University of Montreal, Canada, was contracted to conduct the tests,and present their results and suggestions.
In the course of the research the impossibility of determining the values of“m” and “y” for the new materials was verified and it was also ascertained that thevalues for the traditional materials were not consistent with the experimentally obtainedresults.
The researchers then opted to develop, starting from an experimental basis, amethodology for gasket calculation that was coherent with the practical results. Inthis section this new form of calculation is demonstrated.It is appropriate to point out that the standardization organizations (like ASME, API,ANSI, etc.) have not yet officially published a method to calculate gaskets using the
31
New Gasket Constants. There is a proposal put forth by the researchers now beingdiscussed by the ASME.
11.1. GASKET TESTING
The gaskets chosen for testing were the most represented in industry.• Metallic gaskets flat and corrugated in low carbon steel, soft copper
and stainless steel.• Metal o-rings.• Sheet Packing: NBR and SBR binders with asbestos, aramid and glass
fibers.• Flexible Graphite and PTFE sheets.• Spiral Wound gaskets in stainless steel asbestos, non-asbestos,
flexible graphite and PTFE fillers.• Double Jacketed carbon and stainless steel with asbestos and non-
asbestos fillers.The gaskets were tested in the device shown in Figure 2.12.
Figure 2.12
The tests were conducted under three pressures: 100, 200, and 400 psi withnitrogen, helium, kerosene and water. Sequence of steps followed during the test:
• The initial stress - part A of the chart figure 2.13 -the gasket istightened until deflection Dg keeping Sg constant, pressure isincreased to 100 psi and the leak rate Lr is measured.
32
• The same procedure is repeated for 200 and 400 psi.• The operating stress - part B of the Figure 2.13 - with pressure
constant (100, 200 and 400 psi) Sg is decreased at regular intervals,deflection, Dg, and leak rate, Lr, are measured.
• This procedure is repeated until Lr exceeds the leak detectormeasuring capacity.
• Keeping the pressure constant, Sg is increased measuring Dg and Lrat regular intervals.
The Figure 2.14 shows an example of the fluid pressure as a function of massleak rate for each value of gasket stress.
Figure 2.13
33
Figure 2.14
From experiments conducted at the University of Montreal variousconclusions were reached:
• The gaskets demonstrate similar behavior no matter what style, ormaterial they are made of.
• The tightness of a gasket is a direct function of the seating stress.• The non-dimensional Tightness Parameter, Tp, was suggested as the
best way to represent the behavior of the diverse styles of gaskets and materials.
Tp = (P/P*) x (L
rm*/ (L
rm x D
t))a
where:0.5 < a < 1.2 being 0.5 for gases and 1.2 for liquids
P = Fluid Pressure (MPa)
P* = Atmospheric Pressure (0.1013 MPa)
Lrm
= mass leak rate per unit of diameter (mg/sec-mm)
Lrm
* = mass leak rate with 1 mg/sec-mm reference. Normally taken for a reference gasket with a 150 mm outside diameter.
Dt = gasket outside diameter (mm)
The Tightness Parameter can be defined as the pressure necessary to createa certain level of leakage. For example a Tp equal to 100 signifies that a pressure of 100atmospheres (1470 psi or 10.1 MPa) is necessary to create a leak of 1mg/sec in a gasketwith an external diameter of 150 mm (6 in).
By plotting on a scale log-log the experimental values of the TightnessParameter in function of the Gasket Stress we have the chart in Figure 2.15.
34
Figure 2.15
From the chart we can establish the Gasket Constants, obtained experimentally,that determine the gasket behavior. The constants are:
Gb = intersection point of the seating stress line (part A of the test)
a = inclination of the seating stress lineG
s = focal point of the gasket stress relief lines (part B of the test)
In Table 2.5 are the constants obtained in the PVRC study. The ASTM isdeveloping a method to determine the gasket constants.
35
Compressed Asbestos Sheet1/16" thick1/8" thick
Compressed Non-Asbestos Sheet 1/16" (1.6 mm) thickTeadit NA 1001Teadit NA 1080Teadit NA 1081Teadit NA 1100
Expanded PTFE Sheet Teadit 24SH 1/16" thick
Expanded PTFE Cord Teadit 24B
Tealon® Restructured PTFE SheetTF 1570TF 1580TF 1590
Flexible Graphite - Graflex
Monolithic - style TJBTanged Core - style TJEStainless Steel insert - style TJRPolyester insert – style TJP
Spiral Wound Gasket Graflex filledWithout inner ring ( style 913 )With inner ring (style 913 M )
Spiral Wound Gasket PTFE filledWithout inner ring (style 913 )With inner ring (style 913 M )
Jacketed Gasket Graflex filledFlat (style 923 )Corrugated (style 926 )
Flat Metal Gasket (style 940 )AluminumCopper or Brass
17.2402.759
0.938
0.9032.945
8.786
244114260
6.6909.6555.6286.690
15.86217.448
31.03415.724
20.000
58.621
10.51734.483
0.1500.380
0.45
0.440.313
0.193
0.310.4470.351
0.3840.3240.377
0.384
0.2370.241
0.1400.190
0.230
0.134
0.2400.133
0.8070.690
5 E-4
5.4 E-33 E-4
1.8 E-14
1.28 x 10-2
1.6 x 10-3
6.3
3.448 E-46.897 E-54.552 E-4
3.448 E-4
0.0900.028
0.4830.462
0.103
1.586
1.3791.779
Gasket MaterialG b
(MPa) aGs
(MPa)
Table 2.5Gasket Constants
36
In Figure 2.16 the chart of a spiral wound gasket with Flexible Graphite filler.
Figure 2.16
11.2. TIGHTNESS CLASS
One of the most important concepts introduced by the PVRC studies is of theTightness Class. As it is not possible to have a perfect seal as suggested by thefactors “m” and “y”, the PVRC has proposed the introduction of the Tightness Classcorresponding to three levels of maximum leak rates.
Table 2.6Tightness Class
It is possible to have a classification of the different fluids by tightness class,taking in consideration the danger to the environment, fire hazards, explosions, etc.
Environmental authorities have not published such classification at the timeof the publication of this book.
We can visualize the proposed values with a practical example. A spiral woundgasket with dimensions per ASME B16.20 for an ASME B16.5 4 in class 150-psi flange,with a standard tightness class, leaks 0.002 mg/sec-mm. The overall leak of this gasketis:
Tightness Class Leak Rate ( mg / sec-mm ) Tightness Constant - C Air, Water 0.2 ( 1/5 ) 0.1
Standard 0.002 ( 1/500 ) 1.0Tight 0.000 02 ( 1/ 50 000 ) 10.0
37
Leak Rate (Lrm
) = 0.002 x outside diameter
Lrm
= 0.002 x 149.4 = 0.2988 mg/sec = 1.076 g/hour
As mass leak rate is difficult to visualize, below are some practical tables fora better understanding.
Table 2.7Volumetric Equivalent
Table 2.8Bubble Equivalent
Mass Leak Rate Volumetric Equivalent Bubble Equivalent 10-1 mg / sec 1 ml each 10 seconds Constant flow 10-2 mg / sec 1 ml a each 100 seconds 10 bubbles per second 10-3 mg / sec 3 ml per hour 1 bubble per second 10-4 mg / sec 1 ml each 3 hours 1 bubble each 10 seconds
11.3. JOINT ASSEMBLY EFFICIENCY
Studies show a great variation in the bolt load of each bolt even in situationswhere the torque is applied in a controlled form. The PVRC has suggested theintroduction of an Assembly Efficiency Factor as shown in Table 2.9.
Table 2.9Assembly Efficiency
Fluid Mass - mg / seg Volume - l / hWater 1 0.036Nitrogen 1 3.200Helium 1 22.140
Volumetric Equivalent
Tightening Method Assembly Efficiency “Ae”
Power impact, lever or striker (manual or power) wrench 0.75 Accurately applied torque ( ± 3 % ) 0.85 Simultaneous multiple application of direct stud tension 0.95 Direct measurement of stud stress or strain 1.00
38
11.4. BOLT LOAD USING THE PVRC PROPOSED PROCEDURE
The proposed PVRC Method of bolt loading design calculations, to make thecalculation easier, has several simplifications, which can generate values with variationswhen compared with exact values. These variations are shown in the Paper “ TheExact Method”, presented by Mr. Antonio Guizzo, Teadit´s Technical Director, at the6th Annual Fluid Sealing Association Technical Symposium, Houston, TX, October1996. The same author has presented at the Sealing Technical Symposium, Nashville,TN, April 1998, a paper showing the actual experimental results compared with theexpected values from the PVRC proposed procedure. Copies of both papers can beobtained from Teadit at the address shown at the end of this book.
Important note: The ASME has not approved this method, proposed by thePVRC. Its use must be carefully applied in order to avoid personal and material injuriesderiving from uncertainties that still exist in its application.
• Determine from Table 2.5, the constants Gb, a, e G
s for the gasket to be
used.• Determine from Table 2.6, the Tightness Class and the Tightness Constant, C.• Determine from Table 2.9, the Assembly Efficiency, Ae, in accordance with
the Tightening Method to be used.• Calculate the Gasket Stress Area, A
g
• Determine from the ASME material tables the bolts allowable stress at theroom temperature: Sa
• Determine from the ASME material tables the bolts allowable stress at theoperating temperature: Sb
• Calculate the area affected by the action of the fluid pressure (HydrostaticArea), A
i, according the ASME Code:
Ai = ( π /4 ) G2
G = OD - 2bb = .5 ( b ) 0.5 or b = b
o if b
o less than ¼” ( 6.4 mm)
bo = N / 2
where G is the Effective Diameter per the ASME Code. See Tables 2.1 and 2.2.
• Calculate the Minimum Tightness Parameter, Tpmin
;
Tpmin
= 18.0231 C Pd
where C is the Tightness Constant and Pd is the Design Pressure.
• Calculate the Assembly Tightness Parameter, Tpa
. This value of Tpa
mustbe reached during the seating of the gasket, to assure that the value of T
p,
in operation be equal or higher than Tpmin
.
39
Tpa
= X Tpmin
were X > = 1.5 ( Sa / S
b)
where Sa is the Bolt Allowable Stress at the room temperature and S
b is the
Bolt Allowable Stress at the operating temperature.
• Calculate the Tightness Parameter ratio:
Tr = Log (T
pa) / Log (T
pmin)
• Calculate the minimum Operating Gasket Stress, Sml
. This pressure isrequired to resist the Hydrostatic End Force and to maintain on the gasketsufficient compression to assure the required minimum tightness, T
pmin.
Sml
= Gs [(G
b / G
s) ( Tpa )a ] (1/Tr)
• Calculate the minimum Gasket Assembly Stress, Sya
:
Sya
= (Gb / Ae) ( T
pa )a
where Ae is the Assembly Efficiency, from Table 2.9
• Calculate the Seating Design Gasket Stress, Sm2
:
Sm2
= [( Sb / S
a )( S
ya / 1.5 )] - P
d (A
i / A
g)
where Ag is the gasket contact area with the flange sealing surface.
• Calculate the minimum Bolt Load, Wmo
:
Wmo
= ( Pd A
i )
+ ( S
mo A
g )
where Smo
is the larger of Sm1
, Sm2
or 2 Pd.
• Calculate the minimum Bolt Stress Area, Am:
Am = W
mo / S
b
• Number of bolts:
The actual Bolt Stress Area, Ab, must be equal or larger than A
m
40
11.5. EXAMPLE OF CALCULATION BY THE PVRC METHOD
A Spiral Wound Gasket with a Nominal Diameter 6 inches, Pressure Class of300 psi, dimensions per Norma ASME B16.20, with stainless steel and Flexible Graphiteand Carbon Steel guide ring. Flange with 12 bolts of 1 inch diameter in ASTM AS193-B7.
• Design Pressure: Pd = 2 MPa (290 psi)
• Test Pressure: Pt = 3 MPa (435 psi)
• Design Temperature: 450o C, (842 F)• Bolts ASTM AS 193-B7, Allowable Stresses:• Room temperature: Sa = 172 MPa• Operating temperature: Sb = 122 MPa• Quantity: 12 bolts• From Table 2.5:
Gb = 15.862 MPa
a = 0.237G
s = 0.090 MPa
• Tightness Class: standard, Lrm
= .002 mg/sec-mm• Tightness Constant: C = 1• Bolting with a Torque Wrench: Ae = 0.75• Gasket Contact Area, A
g:
Ag = ( π /4 ) [(od - 3.2)2 - id2] = 7271.390 sqmm
OD = 209.6 mmID = 182.6 mm
• Hydrostatic Area. Ai :
Ai = ( π /4 ) G2 = 29711.878 sqmm
G = (OD - 3.2) - 2b = 194.50 mmb = b
0 = 5.95 mm
bo = N/2 = ((OD - 3.2) - ID)/4 = 5.95 mm
• Minimum Tightness Parameter:
Tpmin
= 18.0231 C Pd = 36.0462
• Assembly Tightness Parameter:
Tpa
= X Tpmin
= 1.5 ( 172 / 122 ) 36.0462 = 76.229
• Tightness Parameter ratio:
Tr = Log (T
pa) / Log (T
pmin) = 1.209
41
• Minimum Gasket Assembly Stress:
Sml
= Gs [( G
b / G
s ) ( T
pa )a ] 1/Tr = 15.171 MPa
• Gasket Assembly Stress:
Sya
= [ Gb/Ae ] ( Tpa
)a = 59.069 MPa
• Seating Design Gasket Stress:
Sm2
= [( Sb / S
a )( S
ya / 1.5 )] - P
d (A
i / A
g) = 19.759 MPa
• Minimum Bolt Load:
Wmo
= ( Pd A
i ) + ( S
mo A
g )
where Smo
is the larger value of
Sm1
= 15.171S
m2 = 19.759
2 Pd = 4
Wmo
= ( Pd A
i ) + ( S
mo A
g ) = 203 089 N
12. GASKET MAXIMUM SEATING STRESS
Sections 4 and 11 of this Chapter show how to calculate the minimum boltload to assure a good sealing. However, as the PVRC studies have shown the moretightened is the gasket the better is the sealing. If the gasket is installed with themaximum possible stress, the sealability will also be the best possible for the operatingconditions.
Gaskets damaged by excess torque are also a very frequent problem. For allgasket styles it is possible to calculate the maximum seating stress, which is themaximum allowable by the gasket without damaging it.
12.1. GASKET MAXIMUM STRESS CALCULATION PROCEDURE
This procedure can be used to calculate the gasket maximum seating stress.
• Calculate the Gasket Contact Area, Ag.
42
• Calculate the Hydrostatic Area, Ai:
Ai = ( π /4 ) G2
G = OD - 2bb = .5 ( b ) 0.5 or b = b
0 if b
0 is less than 1/4” (6.4 mm)
b0 = N/2
where G is the Gasket Effective Diameter.
• Calculate the Hydrostatic End Force, H:
H = Ai P
d
• Calculate the Allowable Bolt Load, Wdisp
:
Wdisp
= Aml
Np S
a
where Aml
is the Bolt Stress Area, Np is the number of bolts and S
a is the
room temperature Bolt Allowable Stress.
• Calculate the Maximum Seating Stress, Sya
:
Sya
= Wdisp
/ Ag
• Determine the Maximum Gasket Seating Stress recommended by the gasketmanufacturer, S
ym.
• The Maximum Seating Stress, Sys, is the lower of the values for Sya
and Sym
.
• Calculate the Maximum Bolt Load, Wmax
:
Wmax
= Sys Ag
• Calculate the Minimum Bolt Load, Wmo
, as shown in Sections 2 and 11 ofthis Chapter.
• If the value for Wmax
is less than Wmo
the gasket and/or the bolts are notadequate for the application.
• If Wmax
is larger than Wmo
the gaskets and bolts are adequate for theapplication.
• With the value for the Maximum Bolt Load, it is then possible to calculateand determine if the value for other flange stresses are within the limitsestablished by the ASME Code. This calculation is beyond the scope ofthis book.
43
12.2. GASKET MAXIMUM STRESS CALCULATION EXAMPLE
From the example in Section 11.5 we can calculate the Maximum Gasket Stress.
• Gasket Contact Area, Ag:
Ag = ( π /4 ) [(OD - 3.2)2 - ID2] = 7271.37 sqmm
OD = 209.6 mmID = 182.6 mm
• Calculate the Hydrostatic Area, Ai:
Ai = ( π /4 ) G2 = 29711.8 sqmm
G = (OD - 3.2) - 2b = 194.50 mmb = b
0 = 5.95mm
bo = N/2 = ((OD - 3.2) - ID)/4 = 5.95 mm
• Calculate the Hydrostatic End Force, H:
H = Ai P
d = 29711 x 2 = 59 423 N
• Calculate the Allowable Bolt Load, Wdisp
:
Wdisp
=Aml
Np S
a = 391 x 12 x 172 = 807 024 N
• Calculate the Maximum Seating Stress, Sya
:
Sya
= Wdisp
/ Ag
= 807 024 / 7271 = 110.992 MPa
• Determine the Maximum Gasket Seating Stress recommended by the gasketmanufacturer, S
ym:
Sym
= 210 MPa
• The Maximum Seating Stress, Sys, is the lower of the values for Sya
and Sym
:
Sys = 110 MPa
• Calculate the Maximum Bolt Load, Wmax
:
Wmax
= Sys Ag = 110 x 7271 = 799 810 N
• Calculate the Minimum Bolt Load, Wmo
, as shown in Sections 2 and 11 ofthis Chapter:
Wmo
= 203 089 N
44
• Since Wmax
is larger than Wmo
the gaskets and bolts are adequate for theapplication.
• With the values for the Minimum and the Maximum Bolt Load we cancalculate the Minimum and the Maximum Bolt Torque:
Tmin
= k Wmo
dp / Np = 0.2 x 203 089 x 0.0254 / 12 = 85.97 N-m
Tmax
= k Wmax
dp / Np = 0.2 x 799 810 x 0.0254 / 12 = 338.58 N-m
45
CHAPTER
3
MATERIALS FORNON-METALLIC GASKETS
1. MATERIAL SELECTION
The selection of a non-metallic gasket material is difficult due to the existencein the market of several choices. Materials with similar performance and price areoffered by the manufacturers, which, with the Asbestos replacement have beendeveloping several alternatives to meet the demand for each application.
It is not practical to list and have the characteristics of all materials. For thisbook the most commonly used were listed with their properties. If a deeper knowledgeis required it is recommended to consult with the manufacturer.
The four basic conditions, which must be observed on selecting a gasketmaterial, are:
• Operating pressure.• Bolt load.• Resistance to chemical attack (corrosion)• Operating temperature.
Operating pressure and bolt load are analyzed in Chapter 2 of this book.
The corrosion resistance can be influenced by several factors, mainly:• Concentration of the corrosive agent: a greater concentration does not
necessarily make the fluid more corrosive.• Temperature of the corrosive agent: usually high temperatures accelerate
the corrosion.
46
• Dew point: the fluid excursion through the dew point, in the presence ofsulfur and water frequently found in gases resulting from combustion, canlead to extremely corrosive condensates.
In critical applications, laboratory tests are necessary in order to determinethe compatibility of the gasket material with the fluid at the operational conditions.
To design a gasket, an evaluation must be done, starting by the type offlange, bolt load, seating stress, etc. The definition of the style and material of thegasket must follow all steps. Usually gasket selection can be simplified by using thePressure x Temperature Factor, as shown in this Chapter.
2. P x T OR SERVICE FACTOR
The Pressure x Temperature Factor or Service Factor is a good starting pointin the selection of a gasket material. It is obtained by multiplying the pressure in psiby the temperature in degrees Fahrenheit and comparing the result with the values onthe Table 3.1. If the value is more than 625,000, a metallic gasket must be selected.
Table 3.1Service Factor
The temperature limit and the P x T values cannot be taken as absolute valuesas with the increase of the operating temperature, the maximum operating pressuredecreases. In each case, conditions such as gasket material, flange design and otherpeculiarities of each application have to be evaluated.
Important note: All recommendations of this chapter are generic and theparticular conditions of each case must be carefully evaluated.
3. SHEET PACKING
Since its introduction in the market by the end of last century, sheet packinghas been the most used material in flange sealing. It has the characteristic of sealabilitythat can be applied to a wide spectrum of operating conditions. Due to its importancein the field of industrial sealing, the Chapter 4 of this book is entirely dedicated tosheet packing gaskets.
P x T Temperature oF Gasket materialmaximum maximum 15000 300 Rubber 40000 250 Vegetable fiber 75000 500 PTFE 400000 1000 Sheet packing 625000 1100 Sheet packing with wire mesh
47
4. POLYTETRAFLUORETYLENE - PTFE
PTFE, because of its exceptional chemical resistance, is the most used plasticfor industrial sealing. The Chapter 5 of this book deals with the several choices ofgaskets with PTFE.
5. FLEXIBLE GRAPHITE - GRAFLEX®
The Flexible Graphite produced from natural graphite has a Carbon contentbetween 90% to 99.9%.
Graphite flakes are treated with acid, neutralized with water and dried. Theflakes are then subjected to high temperature, and the water, after vaporizing, “explodes”the flakes, which increase 200 times or more than its original volume. Those expandedflakes are calendered without any additive or binder, producing sheets of flexiblematerial.
Flexible Graphite shows low creep defined as a continuous plastic deformationin a material subject to pressure. Therefore, there is a small loss of bolt load, whichreduces the need for retightening of bolts.
Due to its characteristics, Flexible Graphite is one of the most reliable sealingmaterials. If offers excellent resistance to acids, alkaline solutions and organiccomposites. However it is not recommended for use in oxidant service in temperaturesabove 840o F (450o C), the heated Carbon reacts with the Oxygen forming CarbonDioxide (CO
2). The result of such a reaction is the reduction of the gasket mass and,
consequently of bolt load. Temperature limits: -400o F (-240o C) to 5400o F (3000o C), inreducing or neutral service without contact with Oxygen. For oxidant service theupper limit is 840o F (450o C).
The chemical compatibility and temperature limits for several chemical andorganic compounds are shown on Annex 3.1 at the end of this Chapter.
5.1. GRAFLEX® SHEETS
Being a material with low mechanical strength Graflex Flexible Graphite sheetsare supplied with an AISI 316 Stainless Steel or Polyester insert. Sheet dimensions are1000 mm x 1000 m (39" x 39") and the standard thickness are 0.8 mm (1/32"), 1.6 mm (1/16") and 3.2 mm (1/8"). The different styles are shown on Table 3.2. It is necessary toverify the chemical and temperature compatibility of the insert when designing gasketswith Graflex sheets.
The values for “m” and “y” and the PVRC Gasket Constants are shown onTable 3.4.
48
Style
Insert
Use for
2661Bonded AISI316L stainlesssteel foilGeneralservice, steam,hydrocarbonservice
2663Tanged AISI316L stainlesssteel foilGeneral service,steam, hydrocarbonservice, heattransfer fluids
2664
Polyester foil
Generalservice, fragileflanges
Table 3.2Styles of Graflex® sheets
Service
Neutral / reducingOxidant
Steam
Mínimum
Mínimum
Temperature ºF
Table 3.3Service Temperature
Stylem
y (psi)G
b (MPa)
aG
s (MPa)
Maximumgasket stress (MPa)
26612
1 000
5.628
0.377
4.555 E-4
165
26632
2 800
9.655
0.324
6.897 E-5
165
26641.5
900
6.690
0.384
3.448 E-4
165
Table 3.4Gasket Constants
5.2. GRAFLEX® TAPE
Graflex® can also be used in tapes with or without adhesive backing, flat orcorrugated, 0.4 mm (1/64") thick. The Table 3.5 shows the styles and recommendations
2660 2662
Homogeneous
General service
AISI 316Lstainless steelscreenGeneralservice, steam,hydrocarbonservice
-400-400
-400
2661870450
650
2663870450
650
26643 000450
26605430840
1200
2662870450
650 Not recom-mend
26601.5
900
6.690
0.384
3.448 E-4
165
26622
2 800
N/A
N/A
N/A
165
49
6. ELASTOMERS
Rubber is very often used in gasket manufacturing due to its sealabilitycharacteristics. In the market there are several types of polymers and formulations,which allow a great variety of choices.
6.1. PROPERTIES
The principal properties that make rubber a good material for gaskets are:• Resilience: rubber is a material with high resilience. Being extremely elastic, it
fills out the flange imperfections even when low stress is applied.• Polymers: there are various polymers with different physical and chemical
characteristics.• Combination of Polymers: the combination of various polymers in a
formulation allows one to obtain different physical and chemicalcharacteristics such as strength, resistance to chemical attack, hardness, etc.
• Variety: sheets or rolls with different thickness, colors, width, length andsurface finishes can be manufactured to fulfill the needs of each application.
6.2. SELECTION PROCESS
Elastomeric gaskets are usually used at low pressure and temperatureapplications. In order to improve the mechanical resistance, reinforcement with one ortwo layers of cotton lining may be used. Normal hardness for industrial applications is55 to 80 Shore A and thickness is 0.8 mm (1/32") to 6.4 mm (1/4"). Following there is alist of elastomers used frequently in industrial gaskets. The ASTM designation isshown in parentheses. The Annex 3.2 shows the chemical guidelines for elastomerselection.
Style
Description
Service
2550
Flat tape adhesive backing
Piping and connections threadsealant
2551
Corrugated tape no adhesivebacking
Valve stem packing molded in placerings
Table 3.5Graflex® Tape
50
6.3. NATURAL RUBBER (NR)
The NR rubber offers good resistance to inorganic acids, ammonia, weakacids and alkali; low resistance to oil, solvents and chemical compounds. It ages dueto ozone attack losing its strength and characteristics; not recommended for use inapplications exposed to sun and oxygen. It has good mechanical and friction resistancebut very limited temperature range: from –60o F (-50o C) to 195o F (90o C).
6.4. STYRENE-BUTADIENE (SBR)
SBR rubber commonly called “synthetic rubber” was developed as analternative to the natural rubber. Recommended for service in cold and hot water, air,steam and some weak acids. It should not be used with strong acids, oils, grease andchlorates. It offers little resistance to ozone and to the majority of hydrocarbons.Temperature limits: -60o F (-50o C) to 250o F (120o C).
6.5. CHLOROPRENE (CR)
CR rubber is also known by its commercial name Neoprene (trademark of DuPont). It has excellent resistance to oils, ozone, sunlight and aging. Low permeabilityto gases. Recommended for use with gasoline and non-aromatic solvents. It offerslittle resistance to strong oxidants and to aromatic and chlorate hydrocarbons. Temperaturelimits: -60o F (-50o C) to 250o F (120o C).
6.6. NITRILE (NBR)
NBR rubber is also know as Buna-N. It offers good resistance to oils, solvents,aromatic and aliphatic hydrocarbons and gasoline. Little resistance to strong oxidantagents, chlorate hydrocarbons, ketones and esters. Temperature limits: -60o F (-50o C)to 250o F (120o C).
6.7. FLUORELASTOMER (CFM, FVSI, FPM)It is also known by its commercial name Viton (trademark of Du Pont). It offers
excellent resistance to strong acids, oils, gasoline, chlorate solvents and aliphatic andaromatic hydrocarbons. Not recommended for use with aminos, esters, ketones andsteam. Temperature limits: -40o F (-40o C) to 400o F (204o C).
6.8. SILICONE (SI)
Silicone rubber offers excellent resistance to the aging process, beingunaffected by sunlight or ozone. For that reason it is often used in hot air. It has littlemechanical resistance. It does not resist aliphatic and aromatic hydrocarbons or steam.Temperature limits: -150o F (-100o C) to 500o F (260o C).
51
6.9. ETHYLENE-PROPILENE (EPDM)
EPDM rubber has good resistance to ozone, steam, strong acids and alkali.Not recommended for use with solvents and aromatic hydrocarbons. Temperaturelimits: -60o F (-50o C) to 250o F (120o C).
6.10. HYPALON
Hypalon, similar to Neoprene rubber, offers excellent resistance to ozone,sunlight, chemical products and good resistance to oils. Temperature limits: -150o F(-100o C) to 300o F (150o C).
7. CELLULOSE FIBER SHEET
Cellulose fiber sheet is manufactured from cellulose with glue and glycerinbinders. It is often used in sealing oil products, gases and diverse solvents. It isavailable in rolls with 0.5 mm (0.20") to 1.6 mm (1/16") thick. Maximum temperature:250o F (120o C).
8. CORK
Cork grains and rubber is bound to obtain cork compressibility, with thebenefits of synthetic rubber. Largely used when the seating force is limited, as inflanges made out of thin stamped metallic sheets or fragile materials such as ceramicor glass. Recommended for service with water, lubricant oils and other oil derivativeproducts at pressures up to 50 psi (3.5 bar). It offers little resistance to aging and isnot recommended for service with inorganic acids, alkali or oxidant solutions.Temperature limits: -20o F (-30o C) to 250o F (120o C).
9. FABRIC AND TAPES
Gaskets can be made of Asbestos, Silica, Fiberglass, Ceramic or Aramid fabricsimpregnated with Elastomers like SBR, Chloroprene, Fluorelastomer or Silicone.
To improve the mechanical resistance the fabric may be reinforced with metallicwire.
Fabrics are folded and molded to form the gaskets. These gaskets are usedmainly for boiler manholes and handholes, oven doors and large ducting access panels.
They can be circular, oval, square or any other form.Its thickness can be from 10.8 mm (1/32") to 3.2 mm (1/8"). Greater thickness can beobtained by folding layers.
10. TADPOLE
Fabrics can be rolled around a core as shown in Figure 3.2. The fabrics can beimpregnated with Elastomers. The fabric overlaps the core, forming a flat lip in which
52
Figure 3.2
11. CERAMIC FIBER BLANKETS
In the form of blankets it is used to manufacture gaskets for use in hot gasesand low pressure service. This material is also used as filler for metallic gaskets.Temperature limit: 2190o F (1200o C).
12. CERAMIC FIBER MILLBOARD
Millboards, originally designed as a thermal insulation material, can be cutinto gaskets for low pressure, high temperature ducting systems. Temperature limit:1450o F (800o C).
13. BEATER ADDITION
The Beater Addition process (BA) used in the manufacture of gasket materialsis similar to the one used in paper manufacture. Synthetic, organic or mineral fibers arebeaten with binders which “open” them, providing a large contact area with the binders.
This enlarged area of contact increases the mechanical resistance of theproduct. Several binders can be used such as Nitrile Latex and SBR rubber. Due to itslimited pressure and temperature resistance BA materials are used mainly as fillers formetallic gaskets. The most common application is the Mica-Graphite filler for lowtemperature Spiral Wound gaskets.
Materials produced by the BA process are available in reels up to 48"(1200 mm) wide with 0.012" (0.30 mm) to 1/16" (1.6 mm) thick.
holes for bolts can be cut. The circular section offers a reliable sealing for irregularsurfaces subject to frequent opening and closing, such as oven doors and largeducting access panels.
53
Annex 3.1GRAFLEX® CHEMICAL COMPATIBILITY*
* Please see note at the end of this table
ProductAcetic acidAcetic anhydride 100%AcetoneAirAlumAluminum chlorideAmmonium bifluorideAmmonium bisulfateAmmonium hydroxideAmmonium sulfateAmmonium thiocyanate 0 - 63%Amyl alcohol 100%Aniline 100%Aniline hydrochloride 0 - 60%Arsenic acidArsenic trichloride 100%Benzene 100%Benzene hexachloride 100%Benzyl sulfonic acidBoric acidBromineBromine waterButyl alcoholButyl cellosolveCalcium chlorateCalcium hypochloriteCarbon tetrachloride 100%Carbonic acidChloral hydrateChloroethylbenzene 100%Chloroform 100%Citric acidCopper sulfateCupric chlorideDioxaneEthyl alcohol
Maximum Temperature °F (oC)AllAllAll
840 (450)AllAllAllAllAllAllAllAllAllAllAllAllAllAllAllAll
Not recommendedAllAllAll
Not recommendedNot recommended
AllAllAllAllAllAllAllAllAllAll
54
Ethyl chlorideEthyl mercaptan – waterEthylene chlorohydrin 0-8%Ethylene dibromide 100%Ethylene dichloride 100%Fatty acidsFerric chlorideFerrous chlorideFerrous sulfateFormic acidFluorineFolic acidGasoline 100%GlycerinHeat transfer fluidsHydrogen chlorideHydrobromic acidHydrochloric acidHydrofluoric acidHydrofluosilicic acid 0-20%Hydrogen sulfide + waterIodineIsopropyl acetate 100%Isopropyl alcoholIsopropyl ether 100%Kerosene 100%Lactic acidManganous sulfateMannitolMethyl alcoholMethyl isobutyl ketone 100%Monochloroacetic acid 100%Monochlorobenzene 100%MonoethanoamineMonovinyl acetateNickel chlorideNitric acid
AllAllAllAllAllAll
RoomAllAllAll
Not recommendedAllAllAllAllAllAllAllAllAllAll
Not recommendedAllAllAllAllAllAllAllAllAllAllAllAllAllAll
Not recommended
Annex 3.1 (continued)GRAFLEX® CHEMICAL COMPATIBILITY*
* Please see note at the end of this table
Product Maximum Temperature °F (oC)
55
Octyl alcohol 100%Oxalic acidParaldehyde 100%Phosphoric acid 0-65%Phosphorous trichloride 100%Refrigerant fluidsSodium chlorideSodium chloriteSodium hydroxideSodium hypochloriteStannic chloriteSteamStearic acid 100%Sulfur dioxideSulfur monochloride 100%Sulfurous acidSulfuric acid >70%Tetrachlorothane 100%Trichloroetylene 100%WaterXyleneZinc ammonium chlorideZinc chlorideZinc sulfate
AllAllAllAllAllAllAll
Not recommendedAll
Not recommendedAll
1200 (650)AllAllAllAll
Not recommendedAllAllAllAllAllAllAll
Annex 3.1 (Continued)GRAFLEX® CHEMICAL COMPATIBILITY*
*NOTE: Properties and application parameters shown throughout this Graflex ChemicalCompatibility Chart are typical. Your specific application should not beundertaken without independent study and evaluation for suitability. Forspecific application recommendations consult with TEADIT. Failure to selectproper sealing products could result in property damage and/or seriouspersonal injury. Specifications subject to change without notice; this editioncancels all previous issues.
Product Maximum Temperature °F (oC)
56
ANNEX 3.2ELASTOMER RESISTANCE GUIDELINES
1: excellent 3: fair2: good 4: poor
NBR: Nitrile SBR: Styrene-ButadieneFPM : Fluorelastomer NR : NaturalCR : Chloroprene SI : Silicone
Service
Acid
Alkali
Hydrocarbons
Diluted ( <10%)ConcentratedDiluted ( <10%)ConcentratedAliphaticAromatic
Flame propagationGas permeability
GasolineAromaticNon Aromatic
Halogenated solventsKetonesMineral oilsOzoneSunlightWater
NR2323444344444442
SBR2423444344444441
CR3322341142443314
NBR2423124343441241
FPM1224112222241213
SI3434444342444113
*NOTE: Properties and application parameters shown throughout this ElastomerResistance Guidelines are typical. Your specific application should not beundertaken without independent study and evaluation for suitability. Forspecific application recommendations consult with TEADIT. Failure to selectproper sealing products could result in property damage and/or seriouspersonal injury. Specifications subject to change without notice; this editioncancels all previous issues.
57
CHAPTER
4
COMPRESSED NON-ASBESTOSGASKETS SHEETS
1. TEADIT COMPRESSED NON-ASBESTOS GASKETS SHEETS
Manufactured by vulcanization under pressure of mineral or synthetic fiberswith a combination of elastomers. Because of its low cost compared with performanceit is the product most used to fabricate industrial gaskets. Because of its manufacturingprocess it is also known as Compressed Sheet. Sheet Packing covers an ample spectrumof applications.
Its major characteristics are:• High resistance to seating stress.• Low creep relaxation.• Wide range of operating temperatures and pressures.• Resistance to an extensive range of chemical products.
2. FIBERS
Fibers provide the structural function and give the high mechanical resistancecharacteristic of Compressed Sheet. The most used fibers are Asbestos, Glass, Aramid,Carbon and Cellulose.
In Asbestos based sheets the problem of personal hazard for the user isreduced because the fibers are mixed and bonded with rubber. However it is necessaryto use any Asbestos product properly; any scraping, filling or other dust generatingprocesses should be avoided.
58
3. ELASTOMERS
The Elastomer, vulcanized under pressure with fibers, determines the chemicalresistance of Compressed Sheet. They also give the flexibility and elastic properties.The most used elastomers are:
• Natural Rubber (NR): a natural product extracted from tropical plants, ithas excellent elasticity, flexibility. It has low resistance to chemical products and hightemperature.
• Styrene-Butadiene Rubber (SBR): also known as synthetic rubber, wasdeveloped as an alternative for natural rubber and has similar properties.
• Chloroprene (CR): better known by its commercial name Neoprene. It offersexcellent resistance to oil, gasoline, and ozone.
• Nitrile Rubber (NBR): better chemical and temperature resistance whencompared to SBR and CR rubbers. It has excellent resistance to oils, gasoline, aliphaticand aromatic hydrocarbonates as well as animal and vegetable oils.
• Hypalon: it has excellent chemical resistance as well as resistance to acidsand alkali.
4. WIRE MESH
A wire mesh is used to increase the compression resistance. Sheets with wiremesh are recommended where it is necessary to have high mechanical strength. Thewire mesh is usually made of carbon steel. However for corrosive service it can be ofstainless steel.
Sheet Packing with wire mesh insertion has less sealability because the sheet/mesh interface increases the leak rate of the gasket. It also makes it more difficult tocut the gasket. Its use should be avoided.
5. FINISHING
The several styles of Teadit Compressed Sheets are manufactured with threesurface finishes, all of them Teadit branded:
• Natural: produces greater adherence to the flange.• Graphite: avoids adherence to the flange; it is used when the gasket is
frequently replaced.• Anti-sticking: if graphite cannot be used, another anti-sticking product
such as silicone is used.
6. SHEET DIMENSIONS
Teadit Compressed Sheets are available in the following sizes:• 59 in (1500 mm) by 63 in (1600 mm).• 59 in (1500 mm) by 126 in (3200 mm).• 118 in (3000 mm) by 126 in (3200 mm).
59
The thickness range is from 1/64 in (0.4 mm) up to 1/8 in (3.2 mm). Some styles also areavailable in thickness up to 1/4 in (6.4 mm).
7. PHYSICAL CHARACTERISTICS
Standardization organizations have issued several standards to assureproduct consistency and uniformity, as well as to compare products from differentmanufacturers. The most common physical tests are shown below:
7.1.1. COMPRESSIBILITY AND RECOVERY
Measured according the ASTM F36A. The compressibility is the thicknessreduction when the material is compressed by a load of 5000 psi (34.5 MPa). It isexpressed as percentage of the original thickness.
The recovery is the increase in thickness after the load removal. It is expressedas percentage of the compressed thickness. Compressibility indicates the capacity ofthe material to flow and fill up flange imperfections. A higher compressibility materialis easier to seat.
The recovery indicates the material capacity to resist pressure and temperaturechanges.
7.1.2. SEALABILITY
Sealability is measured according the ASTM F37. It indicates the material’ssealing performance under controlled conditions with Isooctane at 14.7 psi (0.101MPa) and a seating stress from 125 psi (0.86 MPa) to 4000 psi (27.58 MPa).
7.1.3. TORQUE RETENTION
The torque retention is measured according the ASTM F38. It indicates howthe material retains the bolt load as a function of time. It is expressed as a percentageof the initial load. A stable sheet will retain a high residual load. On the opposite, anunstable sheet will show a continuous loss of load and consequently a loss ofsealability. The test parameters are initial load 3045 psi (21 MPa), temperature 212ºF(100ºC) for 22 hours.
An increase in the sheet thickness or in the service temperature decreasesthe torque retention.
7.1.4. FLUID IMMERSION
It is used to determine changes in the material when in contact with fluids incontrolled conditions of temperature and pressure. The standard used is ASTM F146.The most used fluids are ASTM No. 3 Petroleum based oil and ASTM Fuel B which is70% Isooctane and 30% Toluene. After the immersion, the compressibility, recovery,
60
increase in thickness, tensile strength and increase in volume results are comparedwith values before the immersion.
7.1.5. TENSILE STRENGTH
The tensile strength is measured according the ASTM F152. It is used as aquality control parameter in sheet manufacturing. Its values are not directly related tothe gasket sealability.
7.1.6. IGNITION LOSS
Measured according ASTM F495 it indicates the material loss of mass withthe temperature.
7.1.7. PRESSURE X TEMPERATURE DIAGRAMS
There is no internationally recognized standard to measure Compressed Sheetoperational limits of pressure and temperature. The Teadit Research and DevelopmentLaboratory has developed a procedure to determine the maximum recommendedoperating pressure as a function of the service temperature. The test fluid is Nitrogen.
8. DESIGN
8.1. OPERATIONAL CONDITIONS
To initiate a gasket design it is necessary to verify the operating conditions.The service pressure and temperature must be compared with maximum valuesrecommended for the material to be used.
Then the Service Factor is calculated by multiplying design pressure in psiby temperature in ºF. The value is then compared with the maximum valves indicatedby the manufacturer.
Because the Service Factor is not constant along the temperature range ofmaterial, Teadit has developed the Pressure x Temperature for its Compressed Sheet.To verify if the material is adequate for the service conditions the design pressure andtemperature must be within the recommended range. If the operating conditions fallbetween the curves other factors such as the product to be sealed and thermal cyclehave to be examined. Consult with Teadit since the material may not be recommendedfor the application.
8.2. CHEMICAL RESISTANCE
Before deciding on the use of a specific style Compressed Sheet it is necessaryto verify its chemical resistance to the fluid to be sealed. The Annex 4.2 at the end ofthis Chapter shows the compatibility for several products and Teadit sheets.
61
Important: the recommendations of the Annex 4.2 are generic and the operatingconditions of the application must be verified before using a specific material.
8.3. ASME FLANGE GASKET DIMENSIONS
The ASME B16.21 Non-Metallic Gaskets for Pipe Flanges shows gasketdimensions for use in several ASME standard flanges, including the B16.5 flanges,the most used in industrial applications. Annexes 4.3 to 4.10 have the gasket dimensionsfor ASME flanges. The gaskets can be of two styles: Raised Face or Full Face. It isrecommended to use the style RF whenever possible since it is more economical andallows greater seating stress with the same bolt load.
8.3.1. RAISED FACE (RF)
Raised face (RF): the outside diameter reaches as far as the bolts (Figure 4.1).
Figure 4.1
8.3.2. FULL FACE (FF)
Full face or flat face (FF): the gasket outside diameter is equal to the flangeoutside diameter (Figure 4.2).
Figure 4.2
62
8.4. GASKETS FOR HEAT EXCHANGERS
It is very common to use Compressed Sheet gaskets in Shell and Tube HeatExchangers. Due the small flange width of their tongue and groove flange facings, it isrecommended to control the maximum seating pressure, to avoid crushing the gasket.
8.5. DIN FLANGE GASKET DIMENSIONS
Dimensions for DIN Flanges are shown in Annex 4.11.
8.6. NON STANDARD FLANGES
The use of Compressed Sheet gaskets in non-standard flanges is very frequentas in heat exchangers, reactors and other equipment. In this case, designrecommendations of the Chapter 2 must be carefully observed.
9. MANUFACTURING TOLERANCES
The manufacturing tolerances based on the ASME B16.21 are shown on Table 4.1.
Table 4.1Manufacturing Tolerances
10. LARGE DIAMETER GASKETS
When the gasket dimensions are larger than the sheet or when manufacturingin sections is recommended for economical reasons, two kinds of splicing are used:dovetail and bevelled.
10.1. DOVE-TAIL GASKETS
This splice is more frequently used in industrial applications. It can be usedto make gaskets of almost any size or thickness (Figure 4.3). Each section of male andfemale is adjusted in such a way as to have a minimum gap between the mating parts.
It is recommended that the gasket is produced as follows:
External Diameter
Internal Diameter
Bolt CircleBolt holes center to center
Up to 300 mm (12")
More than 300 mm (12")
Up to 300 mm (12")
More than 300 mm (12")
+0 -1.5 (0.06)
+0 -3.0 (0.12)
± 1.5 (0.06)
± 3.0 (0.12)
± 1.5 (0.06)
± 0.8 (0.03)
Dimension Tolerance - mm (in)
63
Gaskets with a flange width ( L ) equal or less than 8" (200 mm):
A = B = C = (.3 a .4 ) LGaskets with a flange width ( L ) more than 8" (200 mm):
A = (.15 to .2 ) L
B = (.15 to .25 ) L
C = (.25 to .3 ) L
Figure 4.3
10.2. BEVELLED SPLICE
When the seating stress is not adequate for dove tailed gaskets, bevelledand glued splices can be used (Figure 4.4). Due to manufacturing difficulty, this styleof splicing can only be used for gaskets with a minimum thickness of 1/8 in (3.2 mm).
Figure 4.4
64
11. GASKET THICKNESS
The ASME Code recommends three thicknesses for industrial applications: 1/32 in (0.8 mm), 1/16 in (1.6 mm) and 1/8 in (3.2 mm).
To specify the gasket thickness it is necessary to know the roughness of theflange sealing surface. As a general rule it is recommended that the gasket should be asthin as possible but capable of filling out flange irregularities. Experience recommends thethickness to be equal to four times the groove depth. Thickness above 1/8 in (3.2 mm)must be used only when strictly necessary. In very worn out, twisted or in large dimensionflanges, thickness of up to 1/4 in (6.4 mm) can be used.
In smooth or polished flanges the minimum possible thickness should be used.But because there are no grooves or irregularities to “bite” the gasket, it can be expelledby the radial force.
12. BOLT LOAD
The bolt load must be calculated according to recommendations in Chapter 2 ofthis book. The bolt load should not produce an excessive seating stress crushing thegasket. At the room temperature the Maximum Seating Stress is 30,000 psi (210 MPa) for1/16 “ (1.6 mm) thick gaskets. The maximum bolt load reduces as the thickness increases.Table 4.2 shows the Gasket Constants for ASME calculations.
Table 4.2Gasket Constants
13. GASKET FINISH
Natural finish is used the most. The use of anti-sticking compounds such asgraphite, silicone, oils or greases decrease the friction with the flanges making sealingmore difficult and decreasing resistance to high pressure.
A graphite finish should be used only when removal of the gasket is frequent.Graphite finish on both sides is used for high temperature service. The graphiteincreases the superficial heat resistance.
Gb (MPa)
aG
s (MPa)
NA 10012
2
3500
3500
0.697
0.45
1 x 10-4
NA 10803.2
3.8
3500
5000
7.4
0.264
0.0179
NA 10812.2
2.2
4000
4000
20
0.203
0.0124
NA 11002.9
4.1
3500
3500
0.903
0.44
5.4 x 10-3
Style1/16”1/8”
1/16”1/8”
m
y (psi)
65
14. FINISH OF THE FLANGE SEALING SURFACE
The flange surface finish in contact with the gasket should be rough to “bite”the gasket. Either concentric or phonographic serrated grooves recommended by theASME B16.5 or MSS SP-6 Standards, usually found in commercial flanges, areacceptable. They are made with a rounded tip tool with a radius of 1/16 in (1.6 mm) orgreater, with 45 to 55 grooves per inch. The resulting roughness is 125 min (3.2 mm) Rato 250 min (6.3 mm) Ra.
Concentric 90 degree “V” grooves with a pitch of .025" (0.6 mm) to 0.040 in(1.0 mm) are also acceptable.
Flanges with phonographic grooves are more difficult to seal. A leak pathmay result if the seating stress does not flow the gasket material up to the root of thegrooves.
Radial tool marks or scratches are difficult to seal and must be avoided.
15. STORAGE
Sheet Packing as well as finished gaskets should not be stored for long periodsof time. The elastomer used as a binder ages changing its physical characteristics.
A dry cool place without direct solar light should be used for storage. Directcontact with water, oil and chemicals should to be avoided. Sheets and gaskets mustbe kept preferably flat, without folds or wrinkles. Also it is recommended not to hangor roll them in order to prevent permanent deformations.
16. TEADIT COMPRESSED NON-ASBESTOS GASKET SHEETS
Teadit Compressed Non Asbestos Gasket Sheets for industrial applicationsavailable at the time of the publication of this book are shown in this Section. Being aproduct in continuous development new formulations are often offered, please consultwith Teadit for special application requirements.
16.1. NA 1001 NBR, Aramid Fiber Sheet
Style NA-1001 is a compressed non-asbestos sheet gasket produced from acombination of aramid and other fibers and bonded with Nitrile Rubber (NBR).It has numerous applications in the process industries and in water andwastewater industries. Style NA1001 is suitable for service handling thefollowing general media categories: mild acids; alkalies; water; brine; air;industrial gases; animal and vegetable oils; petroleum and derivates; neutralsolutions and refrigerantsColor: green or white.ASTM line call out - F104: F712120E22M5.
66
NA 1001 Pressure x Temperature diagram
16.1. NA 1080 SBR, Aramid Fiber Sheet
Style NA-1080 is a compressed non-asbestos gasket sheet produced from aramidfibers, reinforced fillers and bonded with styrene butadiene rubber (SBR). StyleNA1080 is a high quality general service sheet product with excellent sealabilityand creep relaxation characteristics. It is especially recommended for hot waterand steam service. In addition, Style NA1080 is suitable for service handling thefollowing general media categories: mild acids; diluted alkalies; water; brine;saturated steam; air; industrial gases; neutral solutions and refrigerantsColor: white.ASTM line call out - F104: F712940E44M5.
NA 1080 Pressure x Temperature diagram
67
16.1. NA 1081 NBR, Aramid Fiber Sheet
Style NA1081 is a compressed non-asbestos gasket sheet produced from acombination of aramid fiber, inorganic fillers and bonded with Nitrile Rubber(NBR). Style NA1081 has numerous applications in the process industrieshandling media like: mild acids and alkalis, water, hydrocarbons, oils, gasoline,steam, air, industrial gases, general chemicals, neutral solutions.Color: blue.ASTM line call out - F104: F712120E23M5
NA 1081 Pressure x Temperature diagram
16.1. NA 1082 NBR, Aramid Fiber Sheet
Style NA1082 is a compressed non-asbestos sheet gasket sheet produced froma combination of aramid, inert and reinforced fillers and bonded with NitrileRubber (NBR). Style NA1082 is a high performance sheet that has numerousapplications in the process industries handling media like: mild acids and alkalis,water, hydrocarbons, oils, gasoline, steam, air, industrial gases, generalchemicals, neutral solutions.Color: gray.ASTM line call out - F104: F712120E12M5
NA 1082 Pressure x Temperature diagram
68
16.1. NA 1085 Hypalon, Aramid Fiber Sheet
Style NA1085 is a compressed non-asbestos sheet gasket sheet produced froma combination of aramid fibers, reinforced fillers, PTFE and bonded withHypalon® rubber. Style NA1085 is a severe service non-asbestos sheet that isspecifically formulated to provide an effective seal against most acids in theprocess industries. Style NA 1085 is suitable for service handling the followinggeneral media categories: mild acids, strong acids, alkalies, water, brine, air.Color: cobalt blue.ASTM line call out - F104: F712000E00M5
NA 1085 Pressure x Temperature diagram
69
NA 1100 Pressure x Temperature diagram
16.1. NA 1100 NBR, Carbon Fiber Sheet
Style NA-1100 is a compressed non-asbestos gasket sheet produced fromCarbon fibers and Graphite bonded with Nitrile Rubber (NBR). Style NA 1100 isa premium grade, multi-service gasket sheet, designed to handle the extremes ofpressure and temperature, and it cuts very easily and cleanly. The versatility ofthis sheet enables a plant to standardize on one sheet for a multitude ofapplications and avoid the confusion of having to choose from several differentsheets. NA1100 is suitable for service handling the following general mediacategories: mild acids, alkalies,water, brine, saturated steam, solvents, neutralsolutions, refrigerants, air, industrial gases, oils, petroleum and derivativesColor: black.ASTM line call out - F104: F712120E23M6.
70
Physical Properties
NA
100
1
NA
108
0
NA
108
1
NA
108
2
NA
110
0
Temperature Limit
Pressure Limit
Minimum
Maximum
ContinuousService
Maximum
ContinuousService
o Fo Co Fo Co Fo Cpsibarpsibarlb/ft3
g/cm3Density
Compressibility – ASTM F36A - %Recovery – minimum - ASTM F36A - %
Tensile Strain Across Grain -ASTM F152
Sealability – ASTM F37 – ml/hThickness Increase –max – ASTM F 146 - %
Weight Increase – maxASTM F 146 - %
Creep Relaxation ASTM F 38 - %
ASTM IRM 903Fuel BASTM IRM 903Fuel B
psi
MPa
-40
-40
750
400
460
240
1595
110
725
5 0
109
1.75
7-17
4 5
1670
11.5
0.25
1 2
1 0
1 5
1 5
2 5
-40
-40
720
380
520
270
1015
7 0
725
5 0
122
1.96
7-17
4 5
2030
1 4
0.25
4 0
2 0
3 0
3 0
2 2
-40
-40
750
400
500
260
1595
110
725
5 0
120
1.92
7-17
5 0
1820
12.5
0.2
1 5
1 5
1 5
1 5
2 2
-40
-40
750
400
500
260
1595
110
725
5 0
122
1.95
5-15
5 0
1740
1 2
0.2
1 5
1 0
1 5
1 0
2 0
-40
-40
840
450
520
270
1900
130
1015
7 0
103
1.65
5-15
5 0
2175
1 5
0.2
1 5
1 5
1 5
1 5
2 2
Annex 4.1Physical Properties – Teadit Compressed Non-Asbestos Sheet Materials*
*NOTE: Values shown throughout this Compressed Non Asbestos Sheets PhysicalProperties Table are typical. Your specific application should not be undertakenwithout independent study and evaluation for suitability. For specific applicationrecommendations consult with TEADIT. Failure to select proper sealingproducts could result in property damage and/or serious personal injury.Specifications subject to change without notice; this edition cancels all previousissues.
71
Physical Properties
NA
108
5
Temperature Limit
Pressure Limit
Minimum
Maximum
ContinuousService
Maximum
ContinuousService
o Fo Co Fo Co Fo Cpsibarpsibarlb/ft3
g/cm3Density
Compressibility – ASTM F36A - %Recovery – minimum - ASTM F36A - %
Tensile Strain Across Grain -ASTM F152
Sealability – ASTM F37 – ml/hThicknessIncrease withacids – max - %
Weight Increasewith acids –max - %
Creep Relaxation ASTM F 38 - %
H2SO4 @ 25% concentr.HCl @ 25% concentr.HNO3 @ 25% concentr.H2SO4 @ 25% concentr.HCl @ 25% concentr.HNO3 @ 25% concentr.
psi
MPa
-40
-40
460
240
390
200
1015
7 0
725
5 0
106
1.70
5-15
4 0
2030
1 4
0.2
6
5
6
6
5
6
2 6
Annex 4.1 (Continued)Physical properties – Teadit Compressed Non-Asbestos Sheet Materials*
*NOTE: Values shown throughout this Compressed Non Asbestos Sheets PhysicalProperties Table are typical. Your specific application should not be undertakenwithout independent study and evaluation for suitability. For specific applicationrecommendations consult with TEADIT. Failure to select proper sealingproducts could result in property damage and/or serious personal injury.Specifications subject to change without notice; this edition cancels all previousissues.
72
Annex 4.2Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable B: Consult with TEADIT C: Not recommended
* Please see note at the end of this table.
B
A
A
C
C
A
A
A
A
A
A
A
C
C
A
A
B
C
A
C
B
C
A
C
B
A
B
A
A
A
B
A
C
A
A
C
B
B
A
C
C
B
A
A
B
B
A
A
A
A
A
A
B
C
A
A
C
C
A
C
B
A
A
C
C
A
A
A
A
A
A
A
C
C
A
A
B
C
A
C
Acetaldehyde
Acetamide
Acetic Acid (T< 90ºC)
Acetic Acid (Te” 90ºC)
Acetone
Acetylene
Adipic Acid
Air
Aluminum Acetate
Aluminum Chloride
Aluminum Sulfate
Ammonia – Cold (Gas)
Ammonia – Hot (Gas)
Ammonium Carbonate
Ammonium Chloride
Ammonium Hydroxide 30% (T<50ºC)
Amyl Acetate
Aniline
Barium Chloride
Benzene
NA1081NA1082NA1100
NA1001 NA1080 NA1085Fluid
73
B
A
A
A
C
A
C
B
A
A
A
B
A
C
B
A
B
C
C
C
C
B
A
A
A
C
C
C
C
A
A
A
C
A
C
C
A
B
C
C
C
C
B
A
A
A
B
A
C
C
A
A
A
A
A
C
C
A
B
C
C
C
C
B
A
A
A
C
A
C
B
A
A
A
B
A
C
B
A
B
C
C
C
C
Benzoic Acid
Boiler Feeder Water
Boric Acid
Brines
Butadiene
Butane
Butanone (MEK)
Butyl Acetate
Butyl Alcohol (Butanol)
Calcium Chloride
Calcium Hydroxide (T<50ºC)
Calcium Hypochlorite
Carbon Dioxide
Carbon Disulfide
Carbon Tetrachloride
Castor Oil
Chlorine (Dry)
Chlorine (Wet)
Chlorine Dioxide
Chloroform
Chromic Acid
NA1081NA1082NA1100
NA1001 NA1080 NA1085
Annex 4.2Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable B: Consult with TEADIT C: Not recommended
* Please see note at the end of this table.
Fluid
74
A
A
A
A
B
A
C
A
A
A
C
C
B
C
A
B
B
A
A
A
B
A
A
A
C
C
C
C
C
C
C
C
C
B
C
A
C
C
B
A
B
A
A
A
A
C
C
C
C
B
C
B
C
C
B
C
A
C
B
C
A
B
A
A
A
A
A
B
A
C
A
A
A
C
C
B
C
A
B
B
A
A
A
B
Citric Acid
Condensate
Copper Sulfate (T<50ºC)
Creosote
Cresol
Cyclohexane
Cyclohexanone
Cyclohexyl Alcohol
Decane
Diesel Oil
Dimethylformamide
Dowtherm
Ethane
Ethyl Acetate
Ethyl Alcohol (Ethanol)
Ethyl Chloride
Ethyl Ether
Ethylene
Ethylene Glycol
Formaldehyde
Formic Acid
NA1081NA1082NA1100
NA1001 NA1080 NA1085
Annex 4.2Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable B: Consult with TEADIT C: Not recommended
* Please see note at the end of this table.
Fluid
75
A
C
A
A
A
A
A
A
A
A
A
C
C
A
A
A
A
A
A
A
A
C
A
A
C
C
C
C
C
C
C
A
B
C
A
C
A
A
A
C
A
A
C
B
A
B
A
A
C
A
B
A
A
C
A
C
A
A
A
A
A
A
A
A
A
C
C
A
A
A
A
A
Freon 12
Freon 22
Freon 32
Gasoline
Glycerin
Glycol
Grease
Heptane
Hexane
Hydraulic Oil – Petroleum Base
Hydrochloric Acid 10%
Hydrochloric Acid 37%
Hydrofluoric Acid
Hydrogen
Hydrogen Peroxide <30%
Isooctane
Isopropyl Alcohol
Kerosene
NA1081NA1082NA1100
NA1001 NA1080 NA1085
Annex 4.2Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable B: Consult with TEADIT C: Not recommended
* Please see note at the end of this table.
Fluid
76
A
A
B
A
A
A
A
C
A
A
A
C
C
C
A
A
A
B
C
C
A
A
B
A
C
C
A
C
C
C
B
C
C
C
A
C
C
B
C
C
A
A
A
A
C
B
A
C
B
C
A
A
C
C
A
C
B
B
B
A
A
A
B
A
A
A
A
C
A
A
A
C
C
C
A
A
A
B
C
C
Lactic Acid 50%
Magnesium Chloride
Magnesium Hydroxide (T<50ºC)
Magnesium Sulfate
Maleic Acid
Methane
Methyl Alcohol (Methanol)
Methyl Chloride
Mineral Oil
Naphtha
Natural Gas - GLP
Nitric Acid ≤50% (T<50ºC)
Nitric Acid >50%
Nitrobenzene
Nitrogen
Octane
Oleic Acid
Oxalic Acid
Oxygen
Ozone
NA1081NA1082NA1100
NA1001 NA1080 NA1085
Annex 4.2Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable B: Consult with TEADIT C: Not recommended
* Please see note at the end of this table.
Fluid
77
A
A
B
A
A
C
B
A
A
A
B
A
A
A
C
C
A
A
A
A
A
A
C
B
B
C
C
B
C
C
C
B
A
B
B
B
B
C
C
C
A
A
B
A
A
A
C
B
B
B
C
B
A
C
C
C
A
A
A
A
B
B
C
C
A
A
A
A
A
A
C
A
A
A
B
A
A
C
B
A
A
A
B
A
A
A
C
C
A
A
A
A
A
A
C
B
Palmitic Acid
Pentane
Perchloroethylene
Petroleum
Petroleum Ether
Phenol
Phosphoric Acid
Potassium Acetate
Potassium Chloride
Potassium Dichromate
Potassium Hydroxide (T<50ºC)
Potassium Nitrate
Potassium Permanganate
Propane
Propylene
Pyridine
Sea Water
Silicone Oil
Sodium Bicarbonate
Sodium Bisulfite
Sodium Carbonate
Sodium Chloride (T<50ºC)
Sodium Hydroxide (T≥50ºC)
Sodium Hydroxide (T<50ºC)
NA1081NA1082NA1100
NA1001 NA1080 NA1085
Annex 4.2Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable B: Consult with TEADIT C: Not recommended
* Please see note at the end of this table.
Fluid
78
A
A
A
A
A
C
C
C
C
C
B
A
A
B
C
A
A
B
A
A
C
A
A
A
A
A
C
B
C
C
C
B
A
A
C
C
C
C
B
C
A
C
A
A
A
B
B
C
A
C
A
B
A
A
A
C
C
B
C
A
C
A
C
A
A
A
A
A
C
C
C
C
C
B
A
A
B
C
A
A
B
A
A
C
Sodium Silicate
Sodium Sulfate
Sodium Sulfide
Steam
Stearic Acid
Styrene
Sulfur Dioxide
Sulfuric Acid, oleum
Sulfuric Acid d” 90%
Sulfuric Acid 95%
Sulfurous Acid
Tannic Acid
Tartaric Acid
Tetrachloroethene
Toluene
Transformer Oil
Trichlorotrifluoroethane
Triethanolamine – TEA
Turpentine
Water
Xylene
NA1081NA1082NA1100
NA1001 NA1080 NA1085
Annex 4.2Chemical Compatibility Chart*
Teadit Compressed Non-Asbestos Sheet Materials
A: Suitable B: Consult with TEADIT C: Not recommended
*NOTE: Properties and application parameters shown throughout this Compressed Non AsbestosSheets Chemical Compatibility Chart are typical. Your specific application should notbe undertaken without independent study and evaluation for suitability. For specificapplication recommendations consult with TEADIT. Failure to select proper sealingproducts could result in property damage and/or serious personal injury. Specificationssubject to change without notice; this edition cancels all previous issues.
Fluid
79
1/2
3/4
1
1 1/4
1 1/2
2
2 1/2
3
3 1/2
4
5
6
8
10
12
14
16
18
20
24
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
FF
RF
0.84
1.06
1.31
1.66
1.91
2.38
2.88
3.50
4.00
4.50
5.56
6.62
8.62
10.75
12.75
14.00
16.00
18.00
20.00
24.00
3.50
1.88
3.88
2.25
4.25
2.62
4.63
3.00
5.00
3 .38
6.00
4.12
7.00
4.88
7.50
5.38
8.50
6.38
9.00
6.88
10.00
7.75
11.00
8.75
13.50
11.00
16.00
13.38
19.00
16.13
21.00
17.75
23.50
20.25
25.00
21.62
27.50
23.88
32.00
28.25
3.75
2.12
4.62
2.62
4.88
2.88
5.25
3.25
6.12
3.75
6.50
4.38
7.50
5.12
8.25
5.88
9.00
6.50
10.00
7.12
11.00
8.50
12.50
9.88
15.00
12.12
17.50
14.25
20.50
16.62
23.00
19.12
25.50
21.25
28.00
23.50
30.50
25.75
36.00
30.50
2.38
2.75
3.12
3.50
3.88
4.75
5.50
6.00
7.00
7.50
8.50
9.50
11.75
14.25
17.00
18.75
21.25
22.75
25.00
29.50
2.62
3.25
3.50
3.88
4.50
5.00
5.88
6.62
7.25
7.88
9.25
10.62
13.00
15.25
17.75
20.25
22.50
24.75
27.00
32.00
4
4
4
4
4
4
4
4
8
8
8
8
8
1 2
1 2
1 2
1 6
1 6
2 0
2 0
4
4
4
4
4
8
8
8
8
8
8
1 2
1 2
1 6
1 6
2 0
2 0
2 4
2 4
2 4
0.62
0.62
0.62
0.62
0.62
0.75
0.75
0.75
0.75
0.75
0.88
0.88
0.88
1.00
1.00
1.12
1.12
1.25
1.25
1.38
0.62
0.75
0.75
0.75
0.88
0.75
0.88
0.88
0.88
0.88
0.88
0.88
0.88
1.12
1.25
1.25
1.38
1.38
1.38
1.62
NominalDiameter
Style InsideDiameter 150 psi 300 psi 150 psi 300 psi 150 psi 300 psi 150 psi 300 psi
Outside Diameter Bolt Circle No. of Bolts Hole Diameter
Annex 4.3FF and RF gasket dimensions per ASME B16.21 for ASME 16.5 flanges
Pressure Class 150 and 300 psi - dimensions in inches
80
1/2
3/4
1
1 1/4
1 1/2
2
2 1/2
3
3 1/2
4
5
6
8
10
12
14
16
18
20
24
0.84
1.06
1.31
1.66
1.91
2.38
2.88
3.50
4.00
4.50
5.56
6.62
8.62
10.75
12.75
14.00
16.00
18.00
20.00
24.00
400
2.12
2.62
2.88
3.25
3.75
4.38
5.12
5.88
6.38
7.00
8.38
9.75
12.00
14.12
16.50
19.00
21.12
23.38
25.50
30.25
600
2.12
2.62
2.88
3.25
3.75
4.38
5.12
5.88
6.38
7.62
9.50
10.50
12.62
15.75
18.00
19.38
22.25
24.12
26.88
31.12
900
2.50
2.75
3.12
3.50
3.88
5.62
6.50
6.62
-
8.12
9.75
11.38
14.12
17.12
19.62
20.50
22.62
25.12
27.50
33.00
Outside DiameterInsideDiameter
NominalDiameter
RF Gasket dimensions per ASME B16.21 for flanges ASME B16.5Pressure Class 400, 600 and 900 psi - dimensions in inches
81
1/2
3/4
1
1 1/4
1 1/2
2
2 1/2
3
3 1/2
4
5
6
8
10
12
0.84
1.06
1.31
1.66
1.91
2.38
2.88
3.50
4.00
4.50
5.56
6.62
8.62
10.75
12.75
3.50
3.88
4.25
4.62
5.00
6.00
7.00
7.50
8.50
9.00
10.00
11.00
13.50
16.00
19.00
4
4
4
4
4
4
4
4
8
8
8
8
8
12
12
0.62
0.62
0.62
0.62
0.62
0.75
0.75
0.75
0.75
0.75
0.88
0.88
0.88
1.00
1.00
2.38
2.75
3.12
3.50
3.88
4.75
5.50
6.00
7.00
7.50
8.50
9.50
11.75
14.25
17.00
3.75
4.62
4.88
5.25
6.12
6.50
7.50
8.25
9.00
10.00
11.00
12.50
15.00
-
-
4
4
4
4
4
8
8
8
8
8
8
12
12
-
-
0.62
0.75
0.75
0.75
0.88
0.75
0.88
0.88
0.88
0.88
0.88
0.88
1.00
-
-
2.62
3.25
3.50
3.88
4.50
5.00
5.88
6.62
7.25
7.88
9.25
10.63
13.00
-
-
NominalDiameter
InsideDiam. Outside
DiameterNo. ofBolts
HoleDiam
BoltCircle
OutsideDiameter
No. ofBolts
HoleDiam
BoltCircle
Pressure Class 150 Pressure Class 300
Annex 4.5FF Gasket dimensions per ASME B16.21 for flanges ASME B16.24
Cast Copper Alloy Flanges, Classes 150 and 300 psi - dimensions in inches
82
22 (1)
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
22.00
26.00
28.00
30.00
32.00
34.00
36.00
38.00
40.00
42.00
44.00
46.00
48.00
50.00
52.00
54.00
56.00
58.00
60.00
26.00
30.50
32.75
34.75
37.00
39.00
41.25
43.75
45.75
48.00
50.25
52.25
54.50
56.50
58.75
61.00
63.25
65.50
67.50
300
27.75
32.88
35.38
37.50
39.62
41.62
44.00
41.50
43.88
45.88
48.00
50.12
52.12
54.25
56.25
58.75
60.75
62.75
64.75
400
27.63
32.75
35.12
37.25
39.50
41.50
44.00
42.26
44.58
46.38
48.50
50.75
53.00
55.25
57.26
59.75
61.75
63.75
66.25
600
28.88
34.12
36.00
38.25
40.25
42.25
44.50
43.50
45.50
48.00
50.00
52.26
54.75
57.00
59.00
61.25
63.50
65.50
67.75
150NominalDiameter
InsideDiameter
Outside Diameter
Annex 4.6RF Gaskets per ASME B16.21 for flanges ASME B16.47 Series A
Classes 150, 300, 400 and 600 psi - Dimensions in inches
NOTE: The 22” flange is for reference only. It does not belong to ASME B 16.47
83
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
26.00
28.00
30.00
32.00
34.00
36.00
38.00
40.00
42.00
44.00
46.00
48.00
50.00
52.00
54.00
56.00
58.00
60.00
27.88
29.88
31.88
33.88
35.88
38.31
40.31
42.31
44.31
46.50
48.50
50.50
52.50
54.62
56.62
58.88
60.88
62.88
150
28.56
30.56
32.56
34.69
36.81
38.88
41.12
43.12
45.12
47.12
49.44
51.44
53.44
55.44
57.62
59.62
62.19
64.19
300
30.38
32.50
34.88
37.00
39.12
41.25
43.25
45.25
47.25
49.25
51.88
53.88
55.88
57.88
61.25
62.75
65.19
67.12
400
29.38
31.50
33.75
35.88
37.88
40.25
-
-
-
-
-
-
-
-
-
-
-
-
75NominalDiameter
InsideDiameter
Outside Diameter
600
30.12
32.25
34.62
36.75
39.25
41.25
-
-
-
-
-
-
-
-
-
-
-
-
Annex 4.7RF Gaskets per ASME B16.21 for flanges ASME B16.47 Series B
Pressure Class 75, 150, 300, 400 and 600 psi - dimensions in inches
84
NominalDiameter
InsideDiameter
1/4
3/8
1/2
3/4
1
1 1/4
1 1/2
2
2 1/2
3
4
5
6
8
10
12
14
16
18
20
24
0.56
0.69
0.84
1.06
1.31
1.66
1.91
2.38
2.88
3.50
4.50
5.56
6.62
8.62
10.75
12.75
14.00
16.00
18.00
20.00
24.00
2.50
2.50
3.50
3.88
4.25
4.62
5.00
6.00
7.00
7.50
9.00
10.00
11.00
13.60
16.00
19.00
21.00
23.50
25.00
27.50
32.00
4
4
4
4
4
4
4
4
4
4
8
8
8
8
12
12
12
16
16
20
20
0.44
0.44
0.62
0.62
0.62
0.62
0.62
0.75
0.75
0.75
0.75
0.88
0.88
0.88
1.00
1.00
1.12
1.12
1.25
1.25
1.38
1.69
1.69
2.38
2.75
3.12
3.50
3.88
4.75
5.50
6.00
7.50
8.50
9.50
11.75
14.25
17.00
18.75
21.25
22.75
25.00
29.50
OutsideDiameter
Number ofBolts
HoleDiameter
Bolt CircleDiameter
Annex 4.8FF Gasket dimensions per ASME B16.21 for flanges MSS SP-51
Class 150LW - dimensions in inches
85
NominalDiameter
InsideDiameter
4
5
6
8
10
12
14
16
18
20
24
30
36
42
48
54
60
72
84
96
4.50
5.56
6.62
8.62
10.75
12.75
14.00
16.00
18.00
20.00
24.00
30.00
36.00
42.00
48.00
54.00
60.00
72.00
84.00
96.00
6.88
7.88
8.88
11.12
13.63
16.38
18.00
20.50
22.00
24.25
28.75
35.12
41.88
48.50
55.00
61.75
68.12
81.38
94.25
107.25
9.00
10.00
11.00
13.50
16.00
19.00
21.00
23.50
25.00
27.50
32.00
38.75
46.00
53.00
59.50
66.25
73.00
86.50
99.75
113.25
8
8
8
8
12
12
12
16
16
20
20
28
32
36
44
44
52
60
64
68
0.75
0.75
0.75
0.75
0.75
0.75
0.88
0.88
0.88
0.88
0.88
1.00
1.00
1.12
1.12
1.12
1.25
1.25
1.38
1.38
7.50
8.50
9.50
11.75
14.25
17.00
18.75
21.25
22.75
25.00
29.50
36.00
42.75
49.50
56.00
62.75
69.25
82.50
95.50
108.50
OutsideDiameter
OutsideDiameter
Number ofBolts
HoleDiameter
BoltCircle
RF gaskets Juntas FF
Annex 4.9Gasket dimensions per ASME B16.21 for ASME B16.1
Class 25 Cast Iron Flanges - dimensions in inches
86
1
1 ¼
1 ½
2
2 ½
3
3 ½
4
5
6
8
10
12
14
16
18
20
24
30
36
42
48
1.31
1.66
1.91
2.38
2.88
3.50
4.00
4.50
5.56
6.62
8.62
10.75
12.75
14.00
16.00
18.00
20.00
24.00
30.00
36.00
42.00
48.00
2.62
3.00
3.38
4.12
4.88
5.38
6.38
6.88
7.75
8.75
11.00
13.38
16.12
17.75
20.25
21.62
23.88
28.25
34.75
41.25
48.00
54.50
4.25
4.62
5.00
6.00
7.00
7.50
8.50
9.00
10.00
11.00
13.50
16.00
19.00
21.00
23.50
25.00
27.50
32.00
38.75
46.00
53.00
59.50
4
4
4
4
4
4
8
8
8
8
8
12
12
12
16
16
20
20
28
32
36
44
0.62
0.62
0.62
0.75
0.75
0.75
0.75
0.75
0.88
0.88
0.88
1.00
1.00
1.12
1.12
1.25
1.25
1.38
1.38
1.62
1.62
1.62
3.12
3.50
3.88
4.75
5.50
6.00
7.00
7.50
8.50
9.50
11.75
14.25
17.00
18.75
21.25
22.75
25.00
29.50
36.00
42.75
49.50
56.00
NominalDiameter
InsideDiameter Outside
DiameterOutside
DiameterNumber of
BoltsHole
DiameterBolt
Circle
RF gaskets Juntas FF
Annex 4.10Gasket dimensions per ASME B16.21 for ASME B16.1
Class 125 Cast Iron Flanges - dimensions in inches
87
Annex 4.11RF Gasket dimensions per DIN 2690 – dimensions in mm
468
101520253240506580100125150175200250300350400450500600700800900
1000120014001600180020002200240026002800300032003400360038004000
61014182228354349617790115141169195220274325368420470520620720820920
1020122014201620182020202220242026202820302032203420362038204020
129014901700190021002305250527052920312033203520373039304130
6-
283338435363758595
11513215218220723726231837342347352857868078589099010901305152017201930213523452555276029703170338035903800
--
328378438490540595695810915
101511201340154517701970218023802590279030103225
-----
1621922182482733303854454975576187358059101010112513401540176019602165237525852785
-------
2552853424024585155656257308309401040115013601575179520002230
----------
40-
3843455060708292
10712714216819522526729235341847554757262874585097010801190139516151830
------------
UseClassPN 6
Use Class PN 40
UseClassPN 16
Outside Diameter – PN Class1 and 2.5 10
-16-
2530
InsideDiameter
DN
88
89
CHAPTER
5
PTFE GASKETS
1. POLYTETRAFLUORETHYLENE (PTFE)
Polymer with exceptional chemical resistance, Polytetrafluorethylene – PTFE,is the most widely used plastic for industrial sealing. The only products that chemicallyattack PTFE are liquid alkaline metals and free fluorine.
Sintering or extruding PTFE, pure or mixed with other materials, obtains gasketproducts, which are used in services where it is necessary to have a high chemicalresistance. There are materials with distinct physical properties to meet the needs ofeach application. As with any fluid sealing material there is some overlapping betweeneach other. Several materials can be used successfully in the same application. Themost popular materials, with specific applications, characteristics and advantages arediscussed in the following paragraphs.
The PTFE also has excellent properties for electrical insulation, anti-stick,impact resistance and low friction coefficient.
2. STYLES OF PTFE SHEETS
PTFE gaskets are used in services where it is necessary to have a high chemicalresistance. There are materials with distinct physical properties to meet the needs ofeach application. As with any fluid sealing material there is some overlapping betweeneach other. Several materials can be used successfully in the same application. Themost popular materials, with specific applications, characteristics and advantages arediscussed in the following paragraphs.
90
2.1. MOLDED SINTERED PTFE SHEET
The Molded Sintered PTFE sheets were the first products introduced in themarket. They are manufactured from virgin or reprocessed PTFE resin, without fillers,in a process of molding, compressing and sintering. As any plastic product the PTFEexhibits a characteristic of creep when subjected a compression force. Thischaracteristic is very detrimental to the gasket performance since it requires frequentretightening of the gasket to avoid or reduce leaks. This creep behavior is increasedwith the temperature. The main advantages are the low cost, ample market availabilityand high chemical resistance.
2.2. SKIVED PTFE SHEET
They are manufactured from virgin or reprocessed PTFE resin, without fillers,in a process of skiving a sintered PTFE billet. This process was developed to overcomemanufacturing deficiencies of the Molded Process, however its products have thesame creep behavior problems.
2.3. MOLDED OR SKIVED FILLED PTFE SHEET
To reduce the creep behavior of Molded or Skived PTFE sheets mineral fillersor fibers are added to reduce it. However, due to the manufacturing process (moldingor skiving) this reduction is not enough to produce a long-term effective seal.
2.4. RESTRUCTURED FILLED PTFE SHEET
To reduce the creep a new manufacturing process was developed to produceFilled PTFE sheets. The material is subjected to a lamination before sintering, creatinga highly fibrillated structure. Creep at both room and high temperature is substantiallyreduced. The first material in the market using this technology was the Gylon. To meetthe chemical service needs several mineral or artificial fillers are used, like Barite,Mineral and Synthetic Silica, Barium Sulphate or Hollow Glass Micro-Spheres. Eachfiller has an specific service application but there is a major overlapping of all of themfor normal applications. The most used fillers are:
• Barite: mineral used to produce sheets for strong caustic service. It is alsoconsidered FDA compliant. It seems to be the most commonly used sheet,it has a wide range of service applications including strong acids andgeneral chemical products.
• Mineral Silica: used to produce sheets for strong acidic service. Is alsoused as a general service sheet since it has a broad range of applicationsincluding mild caustic solutions.
• Hollow Glass Micro-Spheres: this filler produces a sheet with a highcompressibility for use with fragile or glass lined flanges replacing PTFEenvelope gaskets. It is not recommended for either strong hot caustic service.
91
• Synthetic Silica: it is used by some manufactures as a substitute for GlassMicro-spheres since it yields sheets with compressibility closer to it.
2.5. EXPANDED PTFE
As an alternative to overcome the creep of PTFE is the hot expansion of itbefore sintering. Gasket products expanded in one direction (cords or tapes) or bi-axially (sheets) can be produced. Expanded PTFE has a high chemical resistance; italso exhibit a very high compressibility and is ideal for use with fragile or glass linedflanges. Most Expanded PTFE products in the market do not have fillers. Its maindrawback is the handling and installation of large gaskets or when it is not possible toseparate the flanges. It is often used as a replacement for the Hollow Glass Micro-Spheres sheet.
3. TEALON® RESTRUCTURED FILLED PTFE SHEET
Tealon® gasket sheets were developed to meet the highest demands for PTFEgaskets. Its lamination process before sintering creates a highly fibrillated structure,which combined with a selected choice of fillers, results in a product with reducedcreep at both room and high temperature. To meet the chemical service needs thefillers are: Barite, Mineral Silica and Hollow Glass Micro-Spheres.
TEALON® is a trademark of E.I. DuPont De Nemours and Company and isused under license by Teadit.
3.1. TEADIT TEALON® STYLE 1570 SHEETS
Tealon® 1570 is produced with virgin Teflon resin filled with Hollow GlassMicro-Spheres. The Table 5.1 shows the characteristics of Style 1570 Sheets.
Due to its filler carachteristics this product exhibits high compressibility andis recommended for use in fragile or lined flanges, for service handling strong acids,moderate caustic, chlorine dioxide, gases, solvents, water, steam, hydrocarbons andchemical products. It is not recommended for strong and hot caustic media since itcan attack the Hollow Glass Micro-Spheres.
It is available in sheets 59" x 59" (1500 mm x 1500 mm), thickness range 1/16"(1.6 mm) to 1/4" (6.4 mm), blue dyed.
3.2. TEADIT TEALON® STYLE 1580 SHEETS
Tealon® 1580 is produced with virgin PTFE resin filled with Barite. The Table5.1 shows the characteristics of Style 1580 Sheets.
Due to its exceptional resistance it is recommended for strong and hot causticservice, solvents, gases, water, steam, hydrocarbons and chemical products. It alsomeets the requirements of the Food and Drug Administration (FDA) for use in food
92
and pharmaceutical applications. It has no dyes and can be used when contaminationis an issue.
It is available in sheets 59" x 59" (1500 mm x 1500 mm), thickness range 1/16"(1.6 mm) to 1/4" (6.4 mm).
3.3. TEADIT TEALON® STYLE 1590 SHEETS
Tealon® 1590 is produced with virgin PTFE resin filled with Mineral Silica.The Table 5.1 shows the characteristics of Style TF1590 Sheets.
Tealon® 1590 is General Service Sheet recommended for service handling strongacids (except hydrofluoric), moderate caustic, gases, solvents, water, steam,hydrocarbons and chemical products.
It is available in sheets 60" x 60" (1500 mm x 1600 mm), thickness range 1/16"(1.5 mm) to 1/4" (6.4 mm), fawn dyed.
Physical Chracteristics Test Method 1570 1580 1590
Minimum Temperature
Maximum Temperature
Maximum Pressure
o Co Fo Co F
bar
psi
------
-
-
-
ASTM F 36 A
ASTM F 36 A
ASTM 152
ASTM D 792
ASTM F 38
ASTM F 37 A
DIN 3535
ASTM
-210
-350
260
500
55
800
0 - 14
12 000
8 600
350 000
250 000
30-50
30
14
20001.70106
40
0.12
< 0.015F456999A9B7
E99M6
-210
-350
260
500
83
1200
0 - 14
12 000
8 600
350 000
250 000
4 - 10
40
140
2000
2.90
181
11
0.04
< 0.015F451999A9B2E99M6
-210
-350
260
500
83
1200
0 - 14
12 000
8 600
350 000
250 000
7 - 12
40
140
20002.10
131
18
0.20
< 0.015F451999A9B4
E99M6
pH Range
P x T Factorbar x oC
psi x oF
1.5 mm thick3 mm thick1/16" thick
1/8" mm thick
Compressibility, %
Recovery, %
Tensile Strenght
Specific Gravity
Creep Relaxation, %
Sealability, ml/hr ( .7 bar ) 1000 psi
Gas Permeability, cm3/min
ASTM Callout
MPapsi
g/cm3
lb/cu.ft
TEALON Style
93
3.4. TEALON® PERFORMANCE TESTS
3.4.1. HOT COMPRESSION TEST
Gaskets produced from Tealon® and from skived PTFE sheets were subjectedto a compression stress of 10 MPa (1500 psi) at 260o C (500o F) for 1 hour. The Figure5.1 shows the test result. It can clearly be seen that the Tealon gasket has retained itsshape. Due to its high creep behavior the skived PTFE has lost its initial shape.
Figure 5.1
3.4.2. HOT CAUSTIC SODA IMMERSION
To verify the performance samples of Tealon were immersed in Caustic Soda,33% concentration at 110ºC (230ºF), for 24 days. Figure 5.2 shows the weight change.
94
The 1580 Barite filled product showed the lowest change of the tested sheets.The 1590 Silica filled sheet on the other hand showed severe weight loss. A visualinspection of the samples after 24 days of immersion showed the Silica filled sheetshad some discoloration and pitting. The 1580 filled sheets showed no evidence ofchemical attack and for this reason is the recommended product for caustic media.
3.4.3. SULPHURIC ACID IMMERSION
To verify the performance in acidic services samples of Tealon® RestructuredSheets were immersed in Sulfuric Acid, 20% concentration at 85o C (185o F), for 8 days.Figure 5.3 shows the weight change.
Figure 5.3
Both 1580 Barite and 1590 Silica filled sheets had only a small weight increaseunder these test conditions. A visual inspection of the samples showed no evidenceof chemical attack.
3.4..4. PRESSURE LOSS WITH THERMAL CYCLING
Gaskets made of Tealon® TF1570 and PTFE Skived Sheet were tested underthermal cycling conditions.The objective of the test was to compare the pressure loss(leak rate) of both gaskets. The Test Protocol used is as follows:
• Install the gasket with a seating stress of 35 MPa (5000 psi).
95
• Wait 30 minutes for the initial relaxation and increase the seating stressagain to 35 MPa (5000 psi).
• Increase the temperature to 200º C (392º F).• Pressurize the Test Bench with 42 bar (600 psi). The gas inlet is then closed
for the remaining of the test.• The temperature is kept constant at 200º C (392º F) for 4 hours.• Turn the heating system off and let the Test Bench cool down.• When the temperature reaches 30º C (86º F) it is increased to 200º C (392º F).• The temperature is kept constant at 200º C (392º F) for 30 minutes.• This cycle is repeated 2 times.• The pressure, temperature and seating stress are recorded throughout the test.
The test results are shown in Figures 5.4 and 5.5.
Figure 5.4
Figure 5.5
96
This test is a good example of the difference between a skived sheet andrestructured PTFE sheets like Tealon®. As shown in Figure 5.5, the PTFE Skived Sheetloses 44% of its initial seating stress as the gaskets thermocycle. This loss of seatingstress is the cause of the higher pressure loss for the PTFE Skived Sheet gasket asshown in Figure 5.4 and is typical for this kind of product. Restructured PTFE productslike Tealon®, due to its fibrillated structure, have a better retention of the initial seatingstress and maintain a higher sealability.
3.4.5. HOT BLOW OUT TEST (HOBT-2)
To verfy the pressure resistance at elevated temperatures samples of Tealon®
were tested at the TTRL (Tigthness Testing and Research Laboratory of the Universityof Montreal, Canada and by the CETIM (Centre de Industries Mechaniques), Nantes,France. A summary of the test protocol known as HOBT-2 is as follows:
• Flanges ASME B16.5 DN 3"- Class 150 psi.• Test Media: Helium.• Test Pressure: 435 psi.• Seating Stress: 5000 psi (34.5 MPa).• Test procedure: install gasket and pressurize the test bench. Increse the
temperature until the gasket blows out or it reaches 360º C (680º F).
Test results are as follows:• TF1570:• TF1580: reached 313º C (595º F)• TF1590: the test reached its maximum temperature of 360º C (680º F) without
a gasket failure.
3.4.6. HOT GAS SERVICE
Tealon® gaskets have been approved by the DVGW – Deutscher Verein desGasund Wasserfaches e.V. (Germany) per DIN 3535 for hot gas service.
3.4.7. OXYGEN SERVICE
Tealon® 1580 has been approved by the Bundesansalt für Materialforschungund –prüfung (BAM), Berlin, Germany, for Oxygen service in pressures up to 1200 psi(83 bar) and 250o C (482o F).
3.4.8. TA-LUFT APPROVAL FOR REFINERY AND CHEMICAL SERVICE
Tealon® gaskets have been approved by the Staatliche Materialprüfungsanstalt –Universität Stuttgart (MPA), Germany, according to the VDI 2440, for service inRefineries, Petrochemical and Chemical plants. The maximum allowed leak rate is10 -4 mbar-l/(s-m). The test results are shown in Table 5.2:
97
Table 5.2Tealon® TA-Luft Test Results
Style
1570
1580
1590
Leak Rate - mbar·l/(s·m)
3.7·10-6
5.9·10-7
1.1·10-6
3.5. TEALON® CHEMICAL COMPATIBILITY
Annex 5.1 shows the Chemical Compatibility of the Tealon® sheets with severalchemical products.
3.6. BOLTING CALCULATIONS
The Contants for ASME calculations for (1/16") 1.5 mm gasket thickness areshown in Table 5.3.
Table 5.3ASME Gasket Constants
Stylem
y - psi
Gb - MPa
a
Gs - MPa
Maximum Gasket
Stress – MPa (psi)
15702
1500
244
0.31
1.28 x 10-2
276 (40 000)
15802
1800
114
0.447
1.6 x 10-3
276 (40 000)
15904.4
2500
260
0.351
6.3
276 (40 000)
4. EXPANDED PTFE
The exceptional properties which distinguish the expanded PTFE productsare the result of a special stretching process which produces a highly fibrilatedmicrostructure with millions of fibrils connected with each other. This gives the materialits unique strength and pressure resistance, without the cold flow and creepcharacteristics of the sintered PTFE.
98
Expanded PTFE Products have outstanding plastic malleability and flexibility;they conform easily to irregular and rough surfaces. At the same time they withstandhigh flange loads and high internal pressures.
4.1. SERVICE CHARACTERISTICS
The most important service characteristics are as follows:
• Pure PTFE without fillers or additives for better chemical resistance, pHranges from 0 to 14. Not recommended for molten alkali and elemental fluorine)
• Temperature range 400o F (–240o C) to 500o F (+270o C), for continuousservice and up to 590o F (310o C) for short periods.
• Pressure range from full vacuum to 2900 psi (200 bar).• Low creep not requiring frequent retightening of bolts like sintered PTFE.• High compressibility recommended for fragile flange materials like ceramic,
glass or plastic.• Conforms easily to irregular and rough surfaces. .• Physiologically harmless up to 500o F (+270o C). It has no smell and is
tasteless.• It is non-toxic and does not contaminate.• Microorganisms or fungi do not influence it.• Approved by the FDA (Food and Drug Administration – USA) for use with
foods and drugs.• It contains no extractable substances.• Unlimited shelf life, it is non-aging.• Atmospheric agents like sunlight, ozone and ultraviolet light (UV) do not
attack it.
4.2. APPROVALS
Teadit Expanded PTFE products have been approved by several internationalorganizations for use with gas, potable water, foods and oxygen:
• BAM Tgb. No. 6228/89 4-2346: for use in steel, copper and copper alloysflat faced or tongue and groove flanges, in oxygen service in pressures upto 1500 psi (100 bar) and 195o F (90o C).
• DVGW Reg. No. G88e089: for gas line service with pressures up to 240 psi(16 bar) and temperatures from 14o F (–10o C) up to 120o F (+50o C).
• FMPA Reg. No. V/91 2242 Gör/Gö: for food products service.• British Oxygen Corporation (BOC) Reg. No. 1592 4188/92: for use in gaseous
and liquid oxygen service.• British Water Research Council (WRC) Reg. No. MVK/9012502: for cold
and hot potable water service.• TA-Luft: Teadit 24SH sheets have been approved by the Staatliche
Materialprüfungsanstalt – Universität Stuttgart (MPA), Germany, accordingto the VDI 2440, for service in Refineries, Petrochemical and Chemical plants.The leak rate was: 2.6·10-7 mbar·l/(s·m).
99
4.3. TEADIT STYLE 24B JOINT SEALANT
The most common form of Expanded PTFE is a tape with an adhesive strip onone side. This tape is placed over the sealing surface of one of the flanges. Theadhesive strip backing makes the installation very easy as shown in Figure 5.6, evenfor irregular shaped flanges.
After seating, Expanded PTFE gaskets are reduced to a very thin cross sectionwith high tensile strength. This very thin cross section reduces the gasket tendencyto blowout increasing its pressure resistance.
Figure 5.6
For standard size flanges the size recommendations are in Table 5.4. For non-standard flanges the recommended width is 1/3 to 1/2 of the flange sealing surface.For flanges with scratches, tool marks and other irregularities choose the thickestpossible size.
Flange Nominal Diameter - inUp to 1/2¾ to 1 1/2
2 to 45 to 8
10 to 1618 to 2424 to 36
36 and up
Style 24B size - in1/8
3/16
1/4
3/8
1/2
5/8
3/4
1
Table 5.4Size Recommendations
100
4.4. EXPANDED PTFE TAPES 24BB AND SHEETS 24 SH
Sheets and tapes are manufactured by expanding virgin PTFE using aproprietary process that produces a uniform and highly fibrilated microstructure withequal tensile strength in all directions. The resulting product exhibits characteristicssignificantly different than conventional PTFE. It is softer and more flexible, conformingeasily to irregular and rough surfaces. It is also easier to compress and has a reducedcold flow and creep. It is ideally suited to cut or punch gaskets, for flanges with anarrow sealing area or where a defined gasket width after seating is needed.
Tapes are supplied with or without a self-adhesive backing strip to facilitateeasy installation.
Thicknessin
1/641/321/161/8
1/2
100
50
25
25
3/4
100
50
25
25
1
100
50
25
25
2
100
50
25
25
4
NA
50
25
25
6
NA
50
25
25
8
NA
50
25
25
Width - in
Table 5.524 BB Tape Standard Sizes – feet per roll
Available 24 SH sheet size is 60" x 60" (1500 mm x 1500 mm), thickness 1/32"(0.8 mm), 1/16" (1.6 mm), 3/32" (2.4 mm), 1/8" (3.2 mm), 3/16" (4.8 mm) and 1/4" (6.4 mm).
4.5. GASKET PARAMETERS
The parameters for gasket design are shown in Table 5.6.
Characteristicm
y (psi)
Gb (MPa)
a
Gs (psi)
Maximum Seating Stress (MPa)
24 B Joint Sealant2
2 800
8.786
0.193
1.862 E-14
150
24 SH Sheet2
2 800
2.945
0.313
2.621 E-5
150
Table 5.6Gasket Constants
24BB Tape2
2 800
2.945
0.313
2.621 E-5
150
101
The Figure 5.7 shows the minimum seating stress to achieve a level ofsealability of 0.01 mg/sec-m with Nitrogen. Higher seating pressures than indicatedreduce the leakage to less than 0.01 mg per second per meter of gasket length.
Figure 5.7
4.6. CHEMICAL COMPATIBILITY
The Annex 5.1 shows the chemical compatibility of Teadit Expanded PTFEwith several chemical products.
5. SINTERED PTFE SHEETS
Teadit has available three basic styles of Sintered PTFE sheets: virgin,mechanical grade and glass reinforced.
5.1. VIRGIN PTFE STYLE 1500 SHEET
The Teadit Style 1500 Virgin PTFE Sheets are manufactured from Virgin PTFEpolymer. They are particularly recommended for applications in the food and beverageindustry where high purity materials are required. It is also used where contaminationor discoloration of flow media cannot be tolerated.
Thicknesses are 1/64", 1/32", 1/16", 3/32", 1/8", 3/16", 1/4". Sheet sizes are48" x 48", 60" x 60" and 48" or 60" wide continuous rolls.
102
5.2. GLASS FILLED PTFE STYLE 1525 SHEET
The Teadit Style 1525 PTFE Sheets are filled with 25% Glass Fibers by weight.The filled material significantly reduces cold flow and creep and increases wearresistance compared to unfilled PTFE sheet. Style 1525 can handle a very broad rangeof chemicals with the exception of molten alkali metals and elemental fluorine.
5.3. MECHANICAL GRADE PTFE STYLE 1550 SHEET
The Teadit Style 1550 Mechanical Grade PTFE Sheets are particularlyrecommended for applications in the industrial process industries where high puritymaterials are not required. It is more economical than virgin PTFE sheet.
Thicknesses are 1/64", 1/32", 1/16", 3/32", 1/8", 3/16", 1/4". Sheet sizes are48" x 48", 60" x 60" and 48" or 60" wide continuous rolls.
Thicknesses are 1/64", 1/32", 1/16", 3/32", 1/8", 3/16", 1/4". Sheet sizes are48" x 48" or 48" wide continuous rolls.
6. PTFE ENVELOPE GASKETS
PTFE Envelope gaskets are manufactured from a Compressed Sheet gasketcore with a PTFE protection cover. They combine the mechanical strength, resilienceand bolt load retention of Compressed Gasket Sheet with the chemical resistance ofPTFE. They are used in equipment with glass; ceramic or glass coated steel flanges.Maximum service temperature is 500ºF (260ºC), the limit for PTFE. A Beater Addition orRubber core can also be used.
6.1. STYLE 933-V
It is the most common and economical style (Figure 5.8). Its total thickness islimited to approximately 1/8 in (3.2 mm). Due to the high cost of PTFE the envelope isnormally manufactured in raised face dimensions. In some applications to help theassembly of the gasket the sheet core can be made with the same drilling as the flange.
103
Figure 5.8
6.2. TYLE 933-U
When a gasket capable of absorbing more irregularities or with higher resiliencycorrugated stainless steel core is added to the core as shown in Figure 5.9.
Figure 5.9
104
Abietic Acid A A A AAcetaldehyde A A A AAcetamide A A A AAcetic Acid (Crude,Glacial,Pure) A A A AAcetic Anhydride A A A AAcetone A A A AAcetonitrile A A A AAcetophenone A A A A2-Acetylaminofluorene A A A AAcetylene A A A AAcrolein B B B AAcrylamide B B B AAcrylic Acid B B B AAcrylic Anhydride A A A AAcrylonitrile B B B AAir A A A AAllyl Acetate A A A AAllyl Chloride A A A AAllyl Methacrylate A A A AAluminum Chloride A A A AAluminum Fluoride B A C AAluminum Hydroxide (Solid) A A A AAluminum Nitrate A A A AAluminum Sulfate A A A AAlums A A A A4-Aminodiphenyl A A A AAmmonia, Liquid or Gas A A A AAmmonium Chloride A A A AAmmonium Hydroxide A A A AAmmonium Nitrate A A A AAmmonium Phosphate, Monobasic A A A AAmmonium Phosphate, Dibasic A A A AAmmonium Phosphate, Tribasic A A A AAmmonium Sulfate A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
105
Amyl Acetate A A A AAmyl Alcohol A A A AAniline, Aniline Oil A A A AAniline Dyes A A A Ao-Anisidine A A A AAqua Regia A A A AAroclors A A A AAsphalt A A A AAviation Gasoline A A A ABarium Chloride A A A ABarium Hydroxide A A A ABarium Sulfide A A A ABaygon A A A ABeer A A A ABenzaldehyde A A A ABenzene, Benzol A A A ABenzidine A A A ABenzoic Acid A A A ABenzonitrile A A A ABenzotrichloride A A A ABenzoyl Chloride A A A ABenzyl Alcohol A A A ABenzyl Chloride A A A ABiphenyl A A A ABis(2-chloroethyl)ether A A A ABis(chloromethyl)ether A A A ABis(2-ethylhexyl)phthalate A A A ABlack Sulfate Liquor B A C ABlast Furnace Gas A A A ABleach (Sodium Hyprochlorite) A A A ABoiler Feed Water A A A ABórax A A A ABoric Acid A A A ABrine (Sodium Chloride) A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
106
Bromine A A A ABromine Trifluoride C C C CBromoform A A A ABromomethane A A A AButadiene B B B AButane A A A A2-Butanone A A A AButyl Acetate A A A AButyl Alcohol,Butanol A A A An-Butyl Amine A A A Atert-Butyl Amine A A A AButyl Methacrylate B B B AButyric Acid A A A ACalcium Bisulfite A A A ACalcium Chloride A A A ACalcium Cyanamide A A A ACalcium Hydroxide A A B ACalcium Hypochlorite A A A ACalcium Nitrate A A A ACalflo AF A A A ACalflo FG A A A ACalflo HTF A A A ACalflo LT A A A ACane Sugar Liquors A A A ACaprolactam A A A ACaptan A A A ACarbaryl A A A ACarbolic Acid,Phenol A A A ACarbon Dioxide,Dry or Wet A A A ACarbon Disulfide A A A ACarbon Monoxide A A A ACarbon Tetrachloride A A A ACarbonic Acid A A A ACarbonyl Sulfide A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
107
Castor Oil A A A ACatechol A A A ACetane (Hexadecane) A A A AChina Wood Oil A A A AChloramben A A A AChlorazotic Acid (Aqua Regia) A A A AChlordane A A A AChlorinated Solvents,Dry or Wet A A A AChlorine, Dry or Wet A A A AChlorine Dioxide A A A AChlorine Trifluoride C C C CChloroacetic Acid A A A A2-Chloroacetophenone A A A AChloroazotic Acid (Aqua Regia) A A A AChlorobenzene A A A AChlorobenzilate A A A AChloroethane A A A AChloroethylene A A A AChloroform A A A AChloromethyl Methyl Ether A A A AChloronitrous Acid (Aqua Regia) A A A AChloroprene A A A AChlorosulfonic Acid A A A AChrome Plating Solutions B A B AChromic Acid A A A AChromic Anhydride A A A AChromium Trioxide A A A ACitric Acid A A A ACoke Oven Gas A A A ACopper Chloride A A A ACopper Sulfate A A A ACorn Oil A A A ACotton Seed Oil A A A ACreosote A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
108
Cresols, Cresylic Acid A A A ACrotonic Acid A A A ACrude Oil A A A ACumene A A A ACyclohexane A A A ACyclohexanone A A A A2,4-D, Salts and Esters A A A ADetergent Solutions B A B ADiazomethane A A A ADibenzofuran A A A ADibenzylether A A A A1,2-Dibromo-3-chloropropane A A A ADibromoethane A A A ADibutyl Phthalate A A A ADibutyl Sebacate A A A Ao-Dichlorobenzene A A A A1,4-Dichlorobenzene A A A A3,3-Dichlorobenzidene A A A ADichloroethane (1,1 or 1,2) A A A A1,1-Dichloroethylene B B B ADichloroethyl Ether A A A ADichloromethane A A A A1,2-Dichloropropane A A A A1,3-Dichloropropene A A A ADichlorvos A A A ADiesel Oil A A A ADiethanolamine A A A AN,N-Diethylaniline A A A ADiethyl Carbonate A A A ADiethyl Sulfate A A A A3,3-Dimethoxybenzidene A A A ADimethylaminoazobenzene A A A AN,N-Dimethyl Aniline A A A A3,3-Dimethylbenzidine A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
109
Dimethyl Carbamoyl Chloride A A A ADimethyl Ether A A A ADimethylformamide A A A ADimethyl Hydrazine, Unsymmetrical A A A ADimethyl Phthalate A A A ADimethyl Sulfate A A A A4,6-Dinitro-o-Cresol and Salts A A A A2,4-Dinitrophenol A A A A2,4-Dinitrotoluene A A A ADioxane A A A A1,2-Diphenylhydrazine A A A ADiphyl DT A A A ADowfrost A A A ADowfrost HD A A A ADowtherm 4000 A A A ADowtherm A A A A ADowtherm E A A A ADowtherm G A A A ADowtherm HT A A A ADowtherm J A A A ADowtherm Q A A A ADowtherm SR-1 A A A AEpichlorohydrin A A A A1,2-Epoxybutane A A A AEthane A A A AEthers A A A AEthyl Acetate A A A AEthyl Acrylate B B B AEthyl Alcohol A A A AEthylbenzene A A A AEthyl Carbamate A A A AEthyl Cellulose A A A AEthyl Chloride A A A AEthyl Ether A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
110
Ethyl Hexoate A A A AEthylene A A A AEthylene Bromide A A A AEthylene Dibromide A A A AEthylene Dichloride A A A AEthylene Glycol A A A AEthyleneimine B A B AEthylene Oxide B B B AEthylene Thiourea A A A AEthylidine Chloride A A A AFerric Chloride A A A AFerric Phosphate A A A AFerric Sulfate A A A AFluorine, Gas C C C CFluorine, Liquid C C C CFluorine Dioxide C C C CFormaldehyde A A A AFormic Acid A A A AFuel Oil A A A AFuel Oil, Acid A A A AFurfural A A A AGasoline, Refined A A A A Sour A A A AGelatin A A A AGlucose A A A AGlue, Protein Base A A A AGlycerine, Glycerol A A A AGlycol A A A AGrain Alcohol A A A AGrease, Petroleum Base A A A AGreen Sulfate Liquor B A C AHeptachlor A A A AHeptane A A A AHexachlorobenzene A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
111
Hexachlorobutadiene A A A AHexachlorocyclopentadiene A A A AHexachloroethane A A A AHexadecane A A A AHexamethylene Diisocyanate A A A AHexamethylphosphoramide A A A AHexane A A A AHexone A A A AHydraulic Oil, Mineral A A A A Synthetic A A A AHydrazine A A A AHydrobromic Acid A A A AHydrochloric Acid A A A AHydrocyanic Acid A A A AHydrofluoric Acid, Anhydrous C C C AHydrofluorosilicic Acid C A C AHydrofluosilicic Acid C A C AHydrogen A A A AHydrogen Bromide A A A AHydrogen Fluoride C C C AHydrogen Peroxide,10-90% A A A AHydrogen Sulfide,Dry or Wet A A A AHydroquinone A A A AIodine Pentafluoride B B B BIodomethane A A A AIsobutane A A A AIsooctane A A A AIsophorone A A A AIsopropyl Alcohol A A A AJet Fuels (JP Types) A A A AKerosene A A A ALacquer Solvents A A A ALacquers A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
112
Lactic Acid, 150°F and below A A A A Above 150°F A A A ALime Saltpeter (Calcium Nitrates) A A A ALindane A A A ALinseed Oil A A A ALithium Bromide A A A ALithium, Elemental C C C CLubricating Oils,Mineral or Petroleum Types A A A ALubricating Oils, Refined A A A ALubricating Oils, Sour A A A ALye B B C AMagnesium Chloride A A A AMagnesium Hydroxide A A A AMagnesium Sulfate A A A AMaleic Acid A A A AMaleic Anhydride A A A AMercuric Chloride A A A AMercury A A A AMethane A A A AMethanol, Methyl Alcohol A A A AMethoxychlor A A A AMethylacrylic Acid A A A AMethyl Alcohol A A A A2-Methylaziridine B A B AMethyl Bromide A A A AMethyl Chloride A A A AMethyl Chloroform A A A A4,4 Methylene Bis (2-chloroaniline) A A A AMethylene Chloride A A A A4,4-Methylene Dianiline A A A AMethylene Diphenyldiisocyanate A A A AMethyl Ethyl Ketone A A A AMethyl Hydrazine A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
113
Methyl Iodide A A A AMethyl Isobutyl Ketone (MIBK) A A A AMethyl Isocyanate A A A AMethyl Methacrylate B B B AN-Methyl-2-Pyrrolidone A A A AMethyl Tert.Butyl Ether (MTBE) A A A AMilk A A A AMineral Oils A A A AMobiltherm 600 A A A AMobiltherm 603 A A A AMobiltherm 605 A A A AMobiltherm Light A A A AMolten Alkali Metals C C C CMonomethylamine A A A AMultiTherm 100 A A A AMultiTherm 503 A A A AMultiTherm IG-2 A A A AMultiTherm PG-1 A A A AMuriatic Acid A A A ANaphtha A A A ANaphthalene A A A ANaphthols A A A ANatural Gas A A A ANickel Chloride A A A ANickel Sulfate A A A ANitric Acid, Less than 30% A A A A Above 0,3 A A A A Crude A A A ARed Fuming A A A ANitrobenzene A A A A4-Nitrobiphenyl A A A A2-Nitro-Butanol A A A ANitrocalcite (Calcium Nitrate) A A A ANitrogen A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
114
Nitrogen Tetroxide A A A ANitrohydrochloric Acid (Aqua Regia) A A A ANitromethane A A A A2-Nitro-2-Methyl Propanol A A A ANitromuriatic Acid (Aqua Regia) A A A A4-Nitrophenol A A A A2-Nitropropane A A A AN-Nitrosodimethylamine A A A AN-Nitroso-N-Methylurea A A A AN-Nitrosomorpholine A A A ANorge Niter (Calcium Nitrate) A A A ANorwegian Saltpeter (Calcium Nitrate) A A A AN-Octadecyl Alcohol A A A AOctane A A A AOil, Petroleum A A A AOils, Animal and Vegetable A A A AOleic Acid A A A AOleum B C A AOrthodichlorobenzene B A A AOxalic Acid B A A AOxygen, Gas A A A AOzone A A A APalmitic Acid A A A AParaffin A A A AParatherm HE A A A AParatherm NF A A A AParathion A A A AParaxylene A A A APentachloronitrobenzene A A A APentachlorophenol A A A APentane A A A APerchloric Acid A A A APerchloroethylene A A A APetroleum Oils,Crude A A A A Refined A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
115
Phenol A A A Ap-Phenylenediamine A A A APhosgene A A A APhosphate Esters A A A APhosphine A A A APhosphoric Acid,Crude C A C A Pure, < 45% A A A A Pure, > 45%, >150°F B A B A Pure, > 45%, > 150°F B A C APhosphorus, Elemental A A A APhosphorus Pentachloride A A A APhthalic Acid A A A APhthalic Anhydride A A A APicric Acid, Molten B B B BPicric Acid, Water Solution A A A APinene A A A APiperidine A A A APolyacrylonitrile A A A APolychlorinated Biphenyls A A A APotash, Potassium Carbonate A A A APotassium Acetate A A A APotassium Bichromate A A A APotassium Chromate, Red A A A APotassium Cyanide A A A APotassium Dichromate A A A APotassium, Elemental C C C CPotassium Hydroxide B B C APotassium Nitrate A A A APotassium Permanganate A A A APotassium Sulfate A A A AProducer Gas A A A APropane A A A A1,3-Propane Sultone A A A ABeta-Propiolactone A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
116
Propionaldehyde A A A APropoxur (Baygon) A A A APropyl Nitrate A A A APropylene A A A APropylene Dichloride A A A APropylene Oxide A A A A1,2-Propylenimine B A B APrussic Acid, Hydrocyanic Acid A A A APyridine A A A AQuinoline A A A AQuinone A A A ARefrigerant type 10 A A A A 11 A A A A 12 A A A A 13 A A A A 13B1 A A A A 21 A A A A 22 A A A A 23 A A A A 31 A A A A 32 A A A A 112 A A A A 113 A A A ARefrigerant type 114 A A A A 114B2 A A A A 115 A A A A 123 A A A A 124 A A A A 125 A A A A 134a A A A A 141b A A A A 142b A A A A 143a A A A A 152a A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
117
Refrigerant type 218 A A A A 290 A A A A 500 A A A A 502 A A A A 503 A A A A C316 A A A A C318 A A A A HP62 A A A A HP80 A A A A HP81 A A A ASalt Water A A A ASaltpeter, Potassium Nitrate A A A A2,4-D Salts and Esters A A A ASewage A A A ASilver Nitrate A A A ASkydrols A A A ASoap Solutions A A A ASoda Ash, Sodium Carbonate A A A ASodium Bicarbonate, Baking Soda A A A ASodium Bisulfate, Dry A A A ASodium Bisulfite A A A ASodium Chlorate A A A ASodium Chloride A A A ASodium Cyanide C A C ASodium, Elemental C C C CSodium Hydroxide B A C ASodium Hypochlorite A A A ASodium Metaborate Peroxyhydrate A A A ASodium Metaphosphate A A B ASodium Nitrate A A A ASodium Perborate A A A ASodium Peroxide A A A ASodium Phosphate, Monobasic A A A ASodium Phosphate, Dibasic B A B A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
118
Sodium Phosphate, Tribasic B A C ASodium Silicate B A B ASodium Sulfate A A A ASodium Sulfide A A A ASodium Superoxide A A A ASodium Thiosulfate, Hypo A A A ASoybean Oil10 A A A AStannic Chloride A A A ASteam A A A AStearic Acid A A A AStoddard Solvent A A A AStyrene B B B AStyrene Oxide A A A ASulfur Chloride A A A ASulfur Dioxide A A A ASulfur, Molten A A A ASulfur Trioxide, Dry or Wet A A A ASulfuric Acid, 10%, 150°F and below A A A A 10%, Above 150°F A A A A 10-75%, 500°F and below A A A A 75-98%, 150°F and below A B A A 75-98%, 150°F to 500°F B B A ASulfuric Acid, Fuming B C A ASulfurous Acid A A A ASyltherm 800 A A A ASyltherm XLT A A A ATannic Acid A A A ATar A A A ATartaric Acid A A A A2,3,7,8-TCDB-p-Dioxin A A A ATertiary ButylAmine A A A ATetrabromoethane A A A ATetrachlorethane A A A ATetrachloroethylene A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
119
Tetrahydrofuran, THF A A A ATherminol 44 A A A ATherminol 55 A A A ATherminol 59 A A A ATherminol 60 A A A ATherminol 66 A A A ATherminol 75 A A A ATherminol D12 A A A ATherminol LT A A A ATherminol VP-1 A A A ATherminol XP A A A AThionyl Chloride A A A ATitanium Sulfate A A A ATitanium Tetrachloride A A A AToluene A A A A2,4-Toluenediamine A A A A2,4-Toluenediisocyanate A A A AToluene Sulfonic Acid A A A Ao-Toluidine A A A AToxaphine A A A ATransformer Oil (Mineral Type) A A A ATransmission Fluid A A A A ATrichloroacetic Acid A A A A1,2,4- Trichlorobenzene A A A A1,1,2-Trichloroethane A A A ATrichloroethylene A A A A2,4,5-Trichlorophenol A A A A2,4,6-Trichlorophenol A A A ATricresylphosphate A A A ATriethanolamine A A A ATriethyl Aluminum A A A ATriethylamine A A A ATrifluralin A A A A2,2,4-Trimethylpentane A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
* See note at the end of the table
120
Tung Oil A A A ATurpentine A A A AUCON Heat Transfer Fluid 500 A A A AUCON Process Fluid WS A A A AVarnish A A A AVinegar10 A A A AVinyl Acetate B B B AVinyl Bromide B B B AVinyl Chloride B B B AVinylidene Chloride B B B AVinyl Methacrylate A A A AWater, Acid Mine, with Oxidizing Salt A A A A No Oxidizing Salts A A A AWater, Distilled A A A AWater, Distilled Return Condensate A A A AWater, Distilled Seawater A A A AWater, Distilled Tap A A A AWhiskey and Wines A A A AWood Alcohol A A A AXceltherm 550 A A A AXceltherm 600 A A A AXceltherm MK1 A A A AXceltyherm XT A A A AXylene A A A AZinc Chloride A A A AZinc Sulfate A A A A
Product TF1570 TF1580 TF1590 SH/24BB
Annex 5.1Tealon Chemical Compatibility Chart*
A: recommended B: consult with Teadit C: not recommended
NOTE: Properties and application parameters shown throughout this Tealon ChemicalCompatibility Chart are typical. Your specific application should not be undertakenwithout independent study and evaluation for suitability. For specific applicationrecommendations consult with TEADIT. Failure to select proper sealing productscould result in property damage and/or serious personal injury. Specificationssubject to change without notice; this edition cancels all previous issues.
121
CHAPTER
6
MATERIALS FORMETALLIC GASKETS
1. CORROSION
On specifying the material for a metallic gasket, we must analyze the metal oralloy properties and its reactions under stress and temperature. Special attentionmust be given to:
• Stress Corrosion: stainless steel 18-8 can show stress corrosion in thepresence of certain fluids. The Annex 6.1 shows products that can causestress corrosion in the most frequently used alloys for industrial gaskets.
• Intergranular Corrosion: some chemical products can precipitate carbidesin austenitic stainless steel in temperatures between 790o F (420o C) and1490o F (810o C). This precipitation is known as Intergranular Corrosion.The Annex 6.2 shows products, which induce Intergranular Corrosion.
• Fluid Compatibility: the gasket should resist deterioration or corrosiveaction by the sealed product and at the same time avoid itscontamination. Annex 6.3 presents recommendations for most frequentlyused metallic gasket materials.
Following are the most widely used alloys in manufacturing industrial gaskets,their major characteristics, temperature limits and approximate Brinell hardness (HB).
2. CARBON STEEL
Material frequently used in manufacturing jacketed gaskets and Ring Joints.Due to its low resistance to corrosion it should not be used in water, diluted acids or
122
saline solutions. It may be used in alkalis and concentrated acids. Temperature limit:900o F (500o C). Hardness: 90 to 120 HB.
3. STAINLESS STEEL AISI 304
Alloy with 18% Cr and 8% Ni is the material most used in the manufacturingof industrial gaskets due to its excellent resistance to corrosion, low cost andavailability in the market. Its maximum operating temperature is 1400o F (760o C). Due toStress and Intergranular Corrosion, its continuous service temperature is limited to790o F (420o C). Hardness: 160 HB.
4. STAINLESS STEEL AISI 304L
It has the same resistance to corrosion as the AISI 304. Since its Carboncontent is limited to 0.03%, it has less Intergranular Carbon precipitation and thereforeless Intergranular Corrosion. Its operational limit for continuous service is 1400o F(760o C). It is susceptible to Stress Corrosion. Hardness: 160 HB.
5. STAINLESS STEEL AISI 316
This alloy with 18% Ni, 13% Cr and 2% Mo, offers excellent resistance tocorrosion. It can have carbonate precipitation at temperatures between 860o F (460o C)and 1650o F (900o C), under severe corrosion conditions. Maximum recommendedtemperature for continuous service is 1400o F (760o C). Hardness: 160 HB.
6. STAINLESS STEEL AISI 316L
It has the same chemical composition as the AISI 316 but its Carbon contentis limited to 0.03%, which inhibits the Intergranular Carbon precipitation andconsequently, the Intergranular Corrosion. The maximum service temperature is 1400o
F (760o C). Hardness: 160 HB.
7. STAINLESS STEEL AISI 321
Austenitic stainless steel alloy with 18% Cr and 10% Ni stabilized with Ti,which reduces the Intergranular Carbon precipitation and also the IntergranularCorrosion. It can be used in temperatures up to 1500o F (815o C). Hardness: 160 HB.
8. STAINLESS STEEL AISI 347
Alloy similar to the AISI 304 stabilized with Cb and Ta to reduce carbonateprecipitation and Intergranular Corrosion. It is subject to Stress Corrosion. Has goodperformance in high temperature corrosive service. Maximum temperature: 1550o F(815o C). Hardness: 160 HB.
123
9. MONEL
Alloy with 67% Ni and 30% Cu, it offers excellent resistance to the majority ofacids and alkalis, except to extremely oxidant acids. Subject to stress corrosion andtherefore should not be used in the presence of fluorine-silicon acid and Mercury. Incombination with PTFE, it is used frequently in Spiral Wound gaskets for severecorrosion services. Operating maximum temperature: 1500o F (815o C). Hardness: 95 HB.
10. NICKEL 200
Alloy with 99% Ni, offers great resistance to caustic solutions, even thoughtit does not have the same global resistance of the Monel. It is also used in SpiralWound and jacketed gaskets for special applications. Maximum operating temperature:1400o F (760o C). Hardness: 110 HB.
11. COPPER
Material often used in small dimension gaskets, where the maximum seatingstress is limited. Maximum operating temperature: 500o F (260o C). Hardness: 80 HB.
12. ALUMINUM
Due to its excellent resistance to corrosion and easy handling it is very oftenused in manufacturing gaskets. Maximum service temperature: 860o F (460o C). Hardness:35 HB.
13. INCONEL
Alloy with 70% Ni, 15% Cr and 7% Fe, it has excellent corrosion resistancefrom cryogenic to high temperatures. Temperature limit: 2000o F (1100o C). Hardness:150 HB.
14. TITANIUM
Metal with excellent corrosion properties in elevated temperatures, oxidantservice, Nitric acid and caustic solutions. Temperature limit: 2000o F (1100o C).Hardness: 215 HB.
Besides these materials the most commonly used in industrial applicationsare the ones sometimes recommended as Hastelloy, Carpenter and others, dependingon the operational circumstances. They are not analyzed in this book due the fact thattheir application is restricted to very special situations when the use of an alternativematerial is not possible.
124
ANNEX 6.1STRESS CORROSION CHART*
A: Aluminum C: Carbon Steel S: Stainless Steel 18-8B: Brass M: Monel N: Nickel
SERVICEAmmonium ChlorideAmmonia - dilutedAmmonia – pureAmmonium NitrateButane + Sulfur DioxideCalcium BromideChloridic AcidChromic AcidCresylic Acid vaporCyanogenFluorsilisic AcidHydrochloric AcidHydrogen Chloride + waterHydrogen Cyanide + waterHydrogen Sulfide + waterHydrofluoric AcidInorganic Chlorides + waterInorganic NitratesMercurous NitrateMercuryNitric Acid dilutedNitric Acid vaporNitric Acid + Magnesium ChlorideOleumOrganic Chlorides + waterPickling AcidsPotassium HydroxidePotassium PermanganateSalt water + OxygenSilicofluoride SaltsSodium HydroxideSteamSulfate Liquor (white)Sulfide LiquorSulfuric Acid + Nitric AcidSulfur Compounds
CX
XX
XXX
XXX
X
XX
XX
X
X
X
S
X
XX
XX
X
X
XXX
X
X
XX
B
X
XX
XX
X
M
X
X
XX
X
XXX
N
X
XX
X
A
X
XX
125
ANNEX 6.2PRODUCTS THAT CAN INDUCE INTERGRANULAR CORROSION IN
AUSTENIC STAINLESS STEELS
PRODUCTAcetic AcidAcetic Acid + Salicylic AcidAmmonium NitrateAmmonium SulfateAmmonium Sulfate + Sulfuric AcidBeet JuiceCyanidric AcidCyanidric Acid + Sulfur DioxideCalcium NitrateChromic AcidChromium ChlorideCopper SulfateCrude OilFatty AcidsFerric ChlorideFerric SulfateFormic AcidHydrocyanic AcidHydrocyanic Acid + Sulfur DioxideHydrocyanic Acid + Hydrofluoric AcidLactic AcidLactic Acid + Nitric AcidMaleic AcidNitric Acid + Hydrochloric AcidNitric Acid + Hydrofluoric AcidOxalic AcidPhenol + Naphthenic AcidPhosphoric AcidPhthalic AcidSalt spraySea WaterSilver Nitrate + Acetic AcidSodium BisulfateSodium Hydroxide + Sodium SulfideSodium HypochloriteSulfide
Cooking Liquor
Sulfide Digester Acid
126
ANNEX 6.2 (Continued)PRODUCTS THAT CAN INDUCE INTERGRANULAR CORROSION IN
AUSTENIC STAINLESS STEELS
PRODUCTSulfamic AcidSulfur Dioxide + waterSulfuric AcidSulfuric Acid + Acetic AcidSulfuric Acid + Copper SulfateSulfuric Acid + Ferrous SulfateSulfuric Acid + MethanolSulfuric Acid + Nitric AcidSulfurous AcidWater + Starch + Sulfur DioxideWater + Aluminum Sulfate
127
ANNEX 6.3CORROSION RESISTANCE OF GASKET METALS*
S : Satisfactory U: Unsatisfactory F: Fair
- : No Information C: Copper A: Aluminum
M: Monel N: Nickel S: Iron and Carbon Steel
4 : 304 Stainless Steel 6: 316 Stainless Steel 7: 347 Stainless Steel
SERVICEAcetic Acid, PureAcetic AnhydrideAcetoneAcetyleneAirAluminum ChlorideAluminum SulphateAlumsAmmonia, ColdAmmonium ChlorideAmmonium HydroxideAmmonium NitrateAmmonium PhosphateAmmonium SulphateAmyl AcetateAmyl AlcoholAnilineAsphaltBarium ChlorideBarium HydroxideBarium SulphideBeerBeet Sugar, LiquorsBenzeneBenzineBlack Sulphate LiquorBlast Furnace GasBoraxBoric AcidBromineButaneButanol
* Please see note at the end of this table.
CFUS-SFFF-UUUFFFSUS-UUSSSSFUFFU-S
ASSSSSU--SUFFF-F-U-UU-SSSS--FS-S-
MSSSSSSFFSF--SSSSSS--SSSSSS-SS-SS
NF-S------F--S-----SS-------SS---
SU-SSSFUUS-SSUS--SS---SSSSSSSUUSS
4FFSSSUFFSFSSSSS-SSFSSSSSSS-SSU--
6FFSS-UFFSFSSSSS-S-S-SSSSS--SSUS-
7-FS-SFFF--SS-SS-S---S-----SSSU--
128
Butyl AcetateCalcium BisulphideCalcium ChlorideCalcium HydroxideCaliche LiquorsCane Sugar LiquorsCarbolic Acid
CSUS--SUSFUU--SUSUU-USS----SSUSSS-SSUU
AS----SSSFS--SSUSUU-US-UUSSSSSUSF--SUU
M-UFSSSSSSS-SSSUSS-FFSSFSSSSF--SSSSSUU
N---S-------------F--------------SS-UU
S-USSSS-SFSS-SSUSUU--USFUSSSFSSSS-SSUU
4S--FSSSSSSS-SSUS-UF-S-USSSS----S-SSUF
6SS-F-SSSSSS--S---U-SSSUSSSSS---S-SSUS
7SS--------S------U----------------SU-
DryWet
Carbon Dioxide
Carbon BisulphideCarbon Monoxide, HotCarbon TetrachlorideCastor Oil
DryWetDryWet
Chlorine
Chlorinated Solvents
Chloroacetic AcidChlorosulphonic AcidChromic AcidCitric AcidCoke Oven GasCopper ChlorideCopper SulphateCorn OilCotton Seed OilCreosoteCresylic Acid
AE
Dowtherm
EthersEthyl AcetateEthyl CelluloseEthyl ChlorideEthylene GlycolFerric ChlorideFerric Sulphate
SERVICE
ANNEX 6.3 (Continued)CORROSION RESISTANCE OF GASKET METALS*
* Please see note at the end of this table.
129
SERVICEFormaldehydeFormic AcidFreonFuel OilFurfuralGasolineGelatinGlucoseGlueGlycerol, GlycerinGreen Sulphate LiquorHydrobromic AcidHydrochloric AcidHydrocyanic Acid
CFFSSSS-S-F--U--FUF-SUUUUUS--SSFUSUUSS-
AFUS-SSSSSS-UU-UUUU-SSSSSS-S-SSUU-UUS-S
MS-SSSSSSSSS--SFS-S-SFSUSUSSSSSFSSUSSSS
N--------------U-U---FSUSU--S--FS-U---S
SFU-SSS-SSSSUU-UFU-USUSU-US-USSFSS-SSSS
4SF-SSSSSSS--USUUUUUSSS-S-SS-SSFSSUSS--
6SF--SSSSSS--USUUUUUSSS-S-SSFS-FSSUSS-S
7--------------UUUUU--SSSS--F-S---U----
Less than 65%More than 65%Less than 65%More than 65%
Cold
HotHydrofluoric Acid
Hydrofluosilicic AcidHydrogen, ColdHydrogen Peroxide
ColdHotColdHot
Dry
WetHydrogen Sulphide
KeroseneLacquers, Lacquer SolventsLactic Acid, ColdLinseed OilLubricating Oils, RefinedMagnesium ChlorideMagnesium HydroxideMagnesium SulphateMercuric ChlorideMercuryMethanolMethyl ChlorideMilk
ANNEX 6.3 (Continued)CORROSION RESISTANCE OF GASKET METALS*
* Please see note at the end of this table.
130
SERVICEMineral OilsNatural GasNickel ChlorideNickel Sulphate
CS-UUUUFUS-SUSUFFUSUUS-----F-FUU--F--
ASSUUSU-S-SS-SS-UF-UUS-UF-U-UUUUUSSSS
MSS--UU-SSSSSSUFFUSSSSSSSSSSSSFS-SSSS
N----UU-S-----U--US-SS----SS-S-S-SSSS
SSS--UUS-S-SSSSUUSSS-SS-FS-USSSSU-S--
4SSFSFS-S--SSSSSSSSSFFSFFSS-SF-FUSFSS
6SSFSFSSS--SSSSSSSSSFFSFF-S-SSSFU-SSS
7-----------S------------------------
ANNEX 6.3 (Continued)CORROSION RESISTANCE OF GASKET METALS*
ConcentratedDiluted
Nitric Acid
NitrobenzeneOleic AcidOleum SpiritsOxalic Acid
ColdHot 260 a 540ºC
Oxygen
Palmitic AcidPetroleum Oils > 500F
Less than 45%More than 45%, ColdPhosphoric Acid
Picric Acid, MoltenPotassium ChloridePotassium CyanidePotassium HydroxidePotassium SulphatePropaneSeawaterSewageSoap SolutionsSodium BicarbonateSodium BisulphateSodium CarbonateSodium ChlorideSodium CyanideSodium HydroxideSodium HypochloriteSodium MetaphosphateSodium NitrateSodium PerborateSodium Peroxide
* Please see note at the end of this table.
131
SERVICE C-SU-SUU-US-UUSS-UUUUUU-S------SSUU
ASSUU-UU-US-S-SS---U-U--USSS-S-S-U-
MSSSSSF--USSU-SS------UUS--SSSSSSSS
NSSSSSF--USSU-S--U-U-UUUS------S---
S--SSSS---S-S-SSUUUU-F-S-SSS---SU--
4----SSSS-SSF-SSFUUUSU-UFSS--SFSFUS
6SSSSSSSS-SSF-S-FFFUSUF-FF---SSSSUS
7----SS---S------------------------
ANNEX 6.3 (Continued)CORROSION RESISTANCE OF GASKET METALS*
MonobasicDibasicTribasic
Sodium Phosphate
Sodium SilicateSodium SulphateSodium SulphideSodium ThiosulphateSoybean OilStannic ChlorideSteam <200ºCStearic AcidSulphurSulphur ChlorideSulphur Dioxide, drySulphur Trioxide, dry
ColdHotColdHotColdHot
Less than 10%
10% to 75%
75% to 95%
Sulphuric Acid
FumingSulphurous AcidTannic AcidTarTartaric AcidTolueneTrichloroethyleneTurpentineVinegarWaterWhiskey and WinesZinc ChlorideZinc Sulphate
*NOTE: Properties and application parameters shown throughout this Corrosion Resistance of GasketMetals Chart are typical. Your specific application should not be undertaken without independentstudy and evaluation for suitability. For specific application recommendations consult with TEADIT.Failure to select proper sealing products could result in property damage and/or serious personal injury.Specifications subject to change without notice; this edition cancels all previous issues
132
133
CHAPTER
7
SPIRAL WOUNDGASKETS
1. SPIRAL WOUND GASKETS
Spiral Wound gaskets are made of a preformed metallic strip and a soft fillerwound together under pressure (Figure 7.1). When the gasket is seated, the fillerflows, filling up the imperfections of the flanges. The metal strip holds the filler, givingmechanical resistance and resiliency to the gasket. Its “V” shape acts as a ChevronRing reacting to changes in pressure and temperature.
Spiral wound gaskets can be manufactured in several combinations ofmaterials, wide range of dimensions and shapes. They are widely utilized covering anample range of applications. ASME B16.5 flanges spiral wound gaskets are standardizedand produced in high volumes at a competitive price, when compared with othergasket styles of same performance.
Figure 7.1
134
This Chapter presents the styles, design values, materials and otherinformation related to Spiral Wound gaskets.
2. MATERIALS
2.1. METALLIC STRIP
The metallic strip has a standardized thickness of 0.008 in (0.20 mm) and thewidth according to the thickness of the gasket. Metals normally available on themarket in strip form are adequate for the manufacture of spiral wound gaskets. Howeverthe most common materials are:
• Stainless steel AISI 304 and 304L: are the most widely used materials as aresult of their price and good resistance to corrosion.
• Stainless steel AISI 316 and 316L for chemical service.• Stainless steel AISI 321 for high temperature service.• Monel.• Nickel 200.• Inconel.• Titanium
The characteristics and recommended uses of these materials are in Chapter6 of this book.
2.2. FILLER
The filler material provides the sealability of the gasket. It is recommendedthat the edge of the filler be flush with or above the metal strip. It should never bebelow it.
2.2.1. FLEXIBLE GRAPHITE - GRAFLEX®
The characteristics of low permeability, thermal stability, low creep andchemical resistance of Flexible Graphite makes it an excelent filler for spiral-wond gaskets.
In neutral or reducing services, it can be used from 330ºF (-200ºC) up to5430ºF (3000ºC). Flexible graphite has very good chemical resistance. It can be used inservices with organic and inorganic acids and bases, solvents, hot wax and oils. It isnot recommended for extremely oxidizing compounds, such as concentrated nitric andsulfuric acids, chromium and permanganate solutions, chlorine acid and liquid alkalinemetals. Temperatures above 660º F (450º C) in oxidizing services, including air, degradesthe material. In this case, it is necessary to encapsulate the gasket, protecting theflexible graphite from direct contact with the oxidizing medium.
135
Flexible Graphite can be used in oxygen, in any concentration, up to 930º F(500º C) as long as the sealing element is completely enclosed between the flanges.
The operational temperature limit for steam and hydrocarbons rich in hydrogenis 1200º F (650º C). Flue gas service should be avoided at this temperature.
According to tests by The Pressure Vessel Research Committee (PVRC)Flexible Graphite filled spiral wound gaskets are fire-safe. Its use is recommended inrefineries, chemical plants and services with flammable media.
2.2.2. PTFE
PTFE is used as a filler when higher chemical resistance is needed. The servicetemperature range is from cryogenic up to 500º F (260º C). PTFE filled gaskets shouldbe confined in a grooved flange or with an inner reinforcing ring to increase itsmechanical resistance and avoid inward buckling of the winding.
2.2.3. MICA-GRAPHITE
A chlorite, graphite and cellulose based Beater Addition sealing paper with aNBR latex binder. Due to its similar sealability and overall performance it has beenused as an Asbestos paper replacement in services up to 450º F (232º C). Above thistemperature it degrades. This material is not considered fire-safe. It is not recommendedfor use in refineries, chemical plants or any service with flammable media where a fire-safe gasket is required.
2.3. GUIDE RING
The guide ring, since it does not come into direct contact with containedfluid, is normally made of carbon steel AISI 1010/1020. In extremely aggressive servicesthey can be made of the same material as the metal strip. Carbon steel guide rings areelectro-plated or painted to avoid corrosion.
3. GASKET DENSITY
In the process of manufacturing the gasket, the metallic strip and the filler arewound together under pressure. Gaskets of different densities can be made bycombining this winding pressure and the thickness of the filler. As a general rulegaskets of higher density are used with higher pressures as they have higher seatingstress.
4. GASKET DIMENSIONS
The gasket designed for non-standard flanges should be made in such a waythat the winding is always in contact with the sealing surface of the flanges. If thewinding is smaller than the inside diameter or larger than the outside diameter of the
136
flange it can break, losing its sealability. If the winding protrudes into the insidediameter, pieces of the gasket can be carried out by the fluid, damaging the equipment.
The following recommendation should be used in dimensioning non-standardgaskets.
• Gaskets confined by the inside and outside diameters• Gasket inside diameter = inside diameter of the groove plus 1/16 in (1.6 mm).• Outside diameter of the gasket = outside diameter of the groove less 1/16 in (1.6 mm).
• Gaskets confined only by the outside diameter:• Inside diameter of the gasket = inside diameter of the female plus a minimum
of ¼ in (6.4 mm).• Outside diameter of the gasket = outside diameter of the male less 1/16 in (1.6 mm).
• Gaskets for raised or flat faced flanges:• Inside diameter of the gasket = inside diameter of the face plus a minimum of
¼ in (6.4 mm).• Outside diameter of the gasket = outside diameter of the face less a minimum
of ¼ in (6.4mm).
The gasket outside and inside diameters should be adjusted in order to meetthe seating and operating stress recommendations in Chapter 2 of this book.
5. THICKNESS
The standard manufacturing thickness for spiral wound gaskets are 1/8 in(3.2 mm), 0.175 in (4.45 mm), 3/16 in (4.76 mm) and ¼ in (6.4 mm).The recommended thickness after seating should be in accordance with Table 7.1. Thefinal thickness indicated is what experience demonstrates to be the best for maximumgasket resiliency.
137
Table 7.1Gasket Thickness
Manufacturing Thickness - in (mm)1/8 (3.2)
0.175 (4.45)3/16 (4.76)
¼ (6.4)
Thickness after Seating - in (mm)0.90 to 0.100 (2.3 to 2.5)0.125 to 0.135 (3.2 a 3.4 )0.125 to 0.145 (3.2 a 3.4)0.180 to 0.200 (4.6 a 5.1)
6. DIMENSIONAL AND THICKNESS LIMITATIONS
Spiral wound gaskets can be manufactured in diameters ranging from ½ in (12mm) up to 150 in (3800 mm). Table 7.2 shows maximum diameter and flange width as afunction of the gasket thickness. These limitations are generic and can vary accordingto the metallic strip and the filler. Gaskets with dimensions other than shown areunstable and difficult to manufacture and handle.
Table 7.2Dimensional Limits
Thicknessin (mm)1/8 (3.2)
0.175 (4.45)3/16 (4.76)
¼ (6.4)
Maximum Inside Diameterin (mm)40 (1000)70 (1800)75 (1900)150 (3800)
Maximum Widthin (mm)¾ (19)1 (25)1 (25)
1 ¼ (32)
PTFE filled gaskets are less stable and can unwind during shipping andhandling. They have dimensional limits as shown in Table 7.3.
Table 7.3Dimensional Limits for PTFE Filled Gaskets
Thicknessin (mm)1/8 (3.2)
0.175 (4.45)3/16 (4.76)
¼ (6.4)
Maximum Inside Diameterin (mm)20 (500)
45 (1100)45 (1100)150 (3800)
Maximum Widthin (mm)¾ (19)1 (25)1 (25)
1 ¼ (32)
138
Table 7.4Manufacturing Tolerances
Inside Diameterin (mm)
Up to 8 (200)8 to 24 (200 to 600)
24 to 35 (600 to 900)35 to 60 (900 to 1500)
Over 60 (1500)
Inside± 1/64 (± 0.4)± 1/32 (± 0.8)± 3/64 (± 1.2)± 1/16 (± 1.6)± 3/32 (± 2.4)
Outside± 1/32 (± 0.8)
+1/16, -1/32 (+ 1.6, - 0.8)± 1/16 (± 1.6)± 3/32 (± 2.4)± 1/8 (± 3.2)
Diameter Tolerance – in (mm)
The tolerance of the winding thickness is plus or minus 0.005 in (0.13 mm),measured across the metallic strip. In gaskets with PTFE filler or with an internaldiameter less than 1 in (25 mm) or with a flange thickness greater than 1 in (25 mm) thetolerance is plus 0.010 in (0.25 mm) minus 0.005 in (0.13 mm).
8. FINISH OF THE FLANGE SEALING SURFACE
As explained early in this Chapter, spiral wound gaskets depend on thecombined action of both metallic strip and filler for efficient sealing. When the gasketis compressed, the filler flows, filling up the flange irregularities. The metallic stripprovides mechanical resistance and resiliency. Proper finishing of the sealing surfaceis very important for good sealing. A scratched surface will be difficult to seal. Asmooth and polished surface can permit the gasket to inward buckle.
Although most of commercial flange finishes can be used, the experienceindicates that the following are the most appropriate.
Table 7.5Finish of the Flange Sealing Surface
Important: The sealing surfaces of flanges cannot have scratches or radial tool marksgoing from the inside to the outside diameter. These irregularities makethe sealing very difficult for any style of gasket and especially for spiralwound gaskets.
µµµµµ m6.33.22.0
µµµµµ in25012580
Flange Sealing Surface Finish - Ra
General useDangerous Service and gases
Vacuum service
7. MANUFACTURING TOLERANCES
The manufacturing tolerances for the inside and outside diameters of spiralwound gaskets are indicated in Table 7.4.
Media
139
9. GASKET MAXIMUM SEATING STRESS
The maximum Spiral Wound Gasket Seating Stress (Sg), as explained inChapter 2 is 30,000 psi (210 MPa) for all Spiral Wound Gasket Styles, except for Style913M, which is 43,000 psi (300 MPa). These values are for all filler materials.
10. GASKET STYLES
Spiral wound gaskets are manufactured in several geometrical forms such ascircular, oval, diamond, square, rectangular and others.
Guide rings or inner rings can be incorporated to the gaskets to better meetspecific service requirements.
11. STYLE 911 GASKETS
This is the simplest style of spiral wound gasket, consisting of a circularwinding without guide or inner rings. Spiral wound gaskets Style 911 are mainly usedin tongue and groove (Figure 7.2) or male and female (Figure 7.3) ASME B16.5 flanges.
They are also used in equipment with space and weight limitations.
Figure 7.2 Figure 7.3
11.1. DIMENSIONS
The dimensions of the gaskets for flanges ASME B16.5 are in Annex 7.1 at theend of this Chapter.
For other applications, when it is necessary to have non-standard dimensions,the winding should be designed to be totally under compression between the flanges.
The recommendations of Section 4 of this Chapter should be carefully followed.
140
11.2. THICKNESS
The standard thicknesses for style 911 gaskets is 1/8 in (3.2 mm). For largediameters they can be manufactured in thickness of 3/16 in (4.76 mm) and ¼ in (6.4mm).
11.3. STYLE 911-M
A style 911-M gasket is a sealing winding with an inner ring (Figure 7.4). Thepurpose of this ring is to fill out the space between the flanges, avoiding turbulencein the flow of the fluid or as a protection against corrosion or erosion. It is also usedas a compression limit when the seating stress is greater than 30,000 psi (210 MPa)and for vacuum rervice.
Gaskets with PTFE filler have a tendency to inward buckle thus the use of aninner ring is recommended if the gasket is to be installed with a non-confined insidediameter.
Figure 7.4
11.4. STYLE 911-T
Double jacketed bars are welded into the winding (Figure 7.5). They are usedin shell and tube heat exchangers with several passes. The bars are manufactured inthe same material and are plasma or spot welded to the winding. The thickness of thebar is normally a little less than the winding to reduce the seating force of the gasket.
Style 911-T has a better sealability than conventional heat exchanger double-jacketed gaskets.
141
Figure 7.5
12. STYLE 913 GASKETS PER ASME B16.20 (API 601)
Gaskets per ASME B16.20 have the winding with an external guide on thecentering ring as shown in Figure 7.6. This solid metallic ring centralizes the gasket onthe flange surface, limits the compression and reinforces the gasket.
Several countries developed dimensional standards for this style of gasket. OnMarch 30th, 1993 the American Society of Mechanical Engineers (ASME) and theAmerican National Standards Institute (ANSI) issued a new edition of the ASME B16.20.This edition includes spiral wound gaskets specifications and dimensions previouslycovered by the API 601 which is no longer be published by the American PetroleumInstitute (API).
The ASME B16.20 (API 601) standard is one of the most used, worldwide. Gasketsmanufactured following the recommendations of the ASME B16.20 are produced inlarge quantities. They are low priced compared with other gaskets of equivalentperformance. When specifying a metallic gasket they should be the first design option.The use of another type of metal gasket should only be recommended if required bythe specific application conditions.
12.1. APPLICATION
The ASME B16.20 gaskets were designed for use in ASME B16.5 flanges orASME 16.47 (API 605 and MSS SP-44). Therefore, when ordering a spiral woundgasket for these flanges dimensions are not necessary. It is enough to inform materials
142
for the metallic strip and filler, which should be compatible with the fluid to be sealed,the nominal diameter and the pressure class of the flange. In Annexes 7.1 to 7.3, at theend of this Chapter, are the dimensions, manufacturing tolerances for ASME B16.20gaskets.
Figure 7.6
12.2. MATERIALS
The most common materials are:• Metallic strip: all metals and alloys in strip can be used for spiral wound
gaskets. Gaskets are commercially available in stainless steels AISI 304,316, 321 and 347, Monel, Inconel and Nickel.
• Filler: fillers commercially available are Flexible Graphite, Mica-Graphite,PTFE and Asbestos.
• Guide ring: carbon steel AISI 1010/1020 or for very corrosive service, thesame material of the metallic strip.
• Inner ring: it is normally made with the same material of the metallic strip.
12.3. WINDING
The winding has the following construction:• At least three initial plies of metallic strip without filler.• The initial two plies of metallic strip shall be spot-welded circumferentially
with a minimum of three welds spaced at a maximum distance of three inches(76.2 mm).
143
• The outer windings shall have a minimum of three plies of metallic withoutfiller, spotwelded circumferentially with a minimum of three welds, the lastbeing the terminal weld. The distance of the first weld from the terminalweld shall be no greater than 1.5 in (38.1 mm).
• Up to four additional loose preformed metal windings beyond the terminalweld may be used to retain the gasket into the guide ring. These free turnsare not included in determining the winding outside diameter.
• The winding thickness is 0.175 in (4.45 mm) plus or minus 0.005 in (0.127 mm)measured across the metallic strip not including the filler, which may protrudeslightly beyond the metal.
12.4. INNER RING
To avoid an over compression due to high seating stress in high pressureservice it is necessary to use an inner ring as shown in Figure 7.7. It is also used toreduce turbulence in the flange area. It is normally made of the same material as thegasket metallic strip and increases substantially the gasket cost.
Its use is also mandatory in services with abrasive fluids. In high corrosiveservices like Fluoridic Acid (HF) a PTFE inner ring is used to reduce the contact of thegasket and inner surface of the flange with the fluid.
PTFE filled gaskets can inward buckle due to the low compressibility of thePTFE. This buckling reduces the sealability of the gasket. It is mandatory to use innerrings in PTFE filled gaskets regardless of size and pressure class.
Flexible Graphite gaskets can also have a tendency to inward buckle and it isrecommended to use inner rings. It is alo recommended to use inner rings for vacuam service.
Inner rings are mandatory for gaskets NPS 24 and larger class 900, NPS 12 andlarger class 1500 and NPS 4 and larger class 2500.
Inner ring thickness shall be 0.112 in (2.85 mm) to 0.131 in (3.33 mm). TheAnnexes 7.1 to 7.3 have the inner ring dimensions as per the ASME B16.20.
Figure 7.7
144
12.5. IDENTIFICATION
The guide ring is permanently marked with lettering at least 1/8 in (3.2 mm)height with the following information:
• Manufacturer’s name or trademark.• Flange size (NPS).• Pressure class.• Winding metal abbreviation.• Filler material abbreviation.• Guide and inner ring metal abbreviation, except that the abbreviation may
be omitted when carbon steel is used for the guide ring and 304 stainlesssteel is used for the inner ring.
• Standard identification: ASME B16.20.• Flange identification for ASME B16.47 gaskets. For ASME B16.5. gaskets
the flange identification is not required.
12.6. COLOR CODING
The outer edge of the guide ring is painted in such a way as to help theidentification of the gasket in stock. The identification of the metallic strip materialshould be painted continuously on the outer edge of the guide ring. The filler materialis identified with a minimum of four intermittent stripes equally spaced on the outeredge of the guide ring. The color-coding is on Tables 7.7 and 7.8
Table 7.7Metallic Strip Color Coding
Metallic StripAISI 304AISI 316AISI 347AISI 321
MonelNickel
Carbon SteelInconel
ColorYellowGreenBlue
TurquoiseOrange
RedSilverGold
Table 7.8Filler Color Coding
FillerAsbestos
PTFEFlexible Graphite
Mica-Graphite
ColorNot painted
WhiteGrayPink
145
13. OTHER STANDARDS
There are several other standards like BS (United Kingdom), DIN (Germany),JIS (Japan), etc.
Spiral Wound Gasket dimensions for DIN flanges are shown in the Annex 7.7.
14. STYLE 913 GASKET DESIGN
Following, are the recommendations that should be followed to design a style913 gasket
Figure 7.8
14.1. WINDING
• Inside diameter (IG): equal to the inside diameter of flange raised face plusa minimum of 1/4 in (6.4 mm).
• Outside diameter (OG): designed to meet the recommendations of seatingand operating stresses recommendations in Chapter 2. The maximum widthshould follow the recommendations of Section 6 of this Chapter.
• Thickness (TK): standard manufacturing thickness are .175 in (4.45 mm), 3/16 in (4.8 mm) and 1/4 in (6.4 mm). Whenever possible .175 in should be used.
• Manufacturing tolerances: are indicated in Section 7 of this Chapter.
146
14.2. GUIDE RING
• Thickness (TR): 1/8" (3,2mm).• Inside diameter (IR): equal to the outside diameter of the winding minus
1/8 in (3.2 mm).• Outside diameter (OR): equal to the bolt circle diameter minus the diameter
of the bolt.• Manufacturing tolerance: of the outside diameter of the guide ring is plus
or minus 1/32 in (0.8 mm).• Dimensional limitations: as a result of the manufacturing process limitations
and the stability of the winding, there are limitations. Minimum widths forguide rings are according to indications on Table 7.9.
Table 7.9Guide Ring Dimensional Limitations
Guide Ring Inside Diameter in ( mm )Up to 10 (250)
10 to 24 (250 to 600)24 to 60 (600 to 1500)60 (1500) or greater
Minimum Width in ( mm )3/8 (10)1/2 (12)5/8 (16)3/4 (20)
14.3. INNER RING
As already mentioned, it is used to minimize turbulence in the gasket area,avoid corrosion or erosion of the winding. In gaskets with PTFE filler, it avoids inwardbuckling of the winding.
14.4. GASKETS WITH DOUBLE JACKETED BARS
Similar to the style 911-T with double-jacketed bars used in shell and tubeheat exchangers.
14.5. GUIDE RING WITH BOLT HOLES
To help the fitting on the equipment the guide ring can be manufactured withthe same overall diameter and drilling of the flanges.
15. STYLE 914
Style 914 spiral wound gaskets are windings in non-circular forms like oval,rectangular and square with rounded corners, diamond, oblong or pear shaped asshown in Figure 7.9.
147
Figure 7.9
15.1. APPLICATION
Style 914 gaskets are used in boiler handholes and manholes, equipment,engine head-gaskets and exhaust systems.
15.2. DESIGNING
There is no specific standard for this type of gasket, depending on the designcalculations it can be made using the recommendations of the ASME Code.
When ordering 914 gaskets due to its odd shapes it is always necessary toprovide complete specifications, a drawing or a sample.
15.3. THICKNESS
The thickness available for style 914 gaskets are 1/8 in (3.2 mm), 0.175 in(4.45 mm), 3/16 in (4.76 mm) and 1/4 in (6.4 mm).
148
15.4. GASKETS FOR BOILERS HANDHOLES AND MANHOLES
The majority of boiler manufacturers use the same size of manholes andhandholes in their equipment. Therefore even not being standardized some oval gasketsare considered standard in the industry. The dimensions of these gaskets are shownin Annex 7.4.
Figure 7.10
149
1/23/41
1 1/41 1/2
22 1/2
34568
10121416182024
150, 300, 400, 6001.251.561.882.382.753.383.884.755.887.008.2510.3812.5014.7516.0018.2520.7522.7527.00
900, 1500, 25001.251.561.882.382.753.383.884.755.887.008.2510.1312.2514.5015.7518.0020.5022.5026.75
Gasket Outside Diameter per Pressure Class - inchesNominalDiameter
Annex 7.1Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.5 Flanges
150
1/23/41
1 1/41 1/2
22 1/2
34568
10121416182024
1500.751.001.251.882.132.753.254.005.006.137.199.1911.3113.3814.6316.6318.6920.6924.75
3000.751.001.251.882.132.753.254.005.006.137.199.1911.3113.3814.6316.6318.6929.6924.75
400(1)(1)(1)(1)(1)(1)(1)(1)
4.755.816.888.8810.8112.8814.2516.2518.5020.5024.75
6000.751.001.251.882.132.753.254.004.755.816.888.8810.8112.8814.2516.2518.5020.5024.75
900(1)(1)(1)(1)(1)(1)(1)
3.754.755.816.888.7510.8812.7514.0016.2518.2520.5024.75
15000.751.001.251.561.882.312.753.634.635.636.758.5010.5012.7514.2516.0018.2520.2524.25
25000.751.001.251.561.882.312.753.634.635.636.758.5010.6312.50(1)(1)(1)(1)(1)
Gasket Inside Diameter per Pressure Class - inchesNominalDiameter
Annex 7.1 (Continued)Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.5 Flanges
Notes: 1. There are no Class 400 gaskets NPS ½ through NPS 3 (use Class 600), Class900 gaskets NPS ½ through NPS 2 ½ (use Class 1500) and Class 2500 flangesNPS 14 or larger.
2. Inner Rings are required for all PTFE filled gaskets and for Class 900 gaskets,NPS 24; Class 1500 gaskets NPS 12 through NPS 24; and Class 2500, NPS 4through NPS 12.
3. Tolerance in inches:• Winding thickness: ± 0.005" – measured across the metallic
portion of the gasket not including the filler,which may protrude slightly beyond the metal.
• Gasket outside diameter: from ½” to 8" : ± 0.03"from 10" to 24" : + 0.06" – 0.003"
• Gasket inside diameter: from ½” to 8" : ± 0.016"from 10" to 24" : ± 0.03"
151
Annex 7.1 (Continued)Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.5 Flanges
1/23/41
1 1/41 1/2
22 1/2
34568
10121416182024
1501.882.252.633.003.384.134.885.386.887.758.7511.0013.3816.1317.7520.2521.6323.8828.25
3002.132.632.883.253.754.385.135.887.138.509.8812.1314.2516.6319.1321.2523.5025.7530.50
400(1)(1)(1)(1)(1)(1)(1)(1)
7.008.389.7512.0014.1316.5019.0021.1323.3825.5030.25
6002.132.632.883.253.754.385.135.887.639.5010.5012.6315.7518.0019.3822.2524.1326.8831.13
900(1)(1)(1)(1)(1)(1)(1)
6.638.139.7511.3814.1317.1319.6320.5022.6325.1327.5033.00
15002.502.753.133.503.885.636.506.888.2510.0011.1313.8817.1320.5022.7525.2527.7529.7535.50
25002.753.003.384.134.635.756.637.759.2511.0012.5015.2518.7521.63(1)(1)(1)(1)(1)
Guide Ring Outside Diameter per Pressure Class - inchesNominalDiameter
NOTES: 1. There are no Class 400 gaskets NPS ½ through NPS 3 (use Class 600), Class900 gaskets NPS ½ through NPS 2 ½ (use Class 1500) and Class 2500 flangesNPS 14 or larger.
2. Guide Ring outside diameter tolerance: ± 0.03"
152
NominalDiameter
1/23/41
1 1/41 1/2
22 1/2
34568
10121416182024
1500.560.811.061.501.752.192.623.194.195.196.198.5010.5612.5013.7515.7517.6919.6923.75
3000.560.811.061.501.752.192.623.194.195.196.198.5010.5612.5013.7515.7517.6919.6923.75
400(1)(1)(1)(1)(1)(1)(1)(1)
4.195.196.198.2510.2512.5013.7515.7517.6919.6923.75
6000.560.811.061.501.752.192.623.194.195.196.198.2510.2512.5013.7515.7517.6919.6923.75
900(1)(1)(1)(1)(1)(1)(1)
3.194.195.196.197.759.6911.5012.6314.7516.7519.0023.25
15000.560.811.061.311.632.062.503.194.195.196.197.759.6911.5012.6314.5016.7518.7522.75
25000.560.811.061.311.632.062.503.194.195.196.197.759.6911.50(1)(1)(1)(1)(1)
Inner Ring Inside Diameter per Pressure Class - inches
NOTES: 1. There are no Class 400 gaskets NPS ½ through NPS 3 (use Class 600), Class900 gaskets NPS ½ through NPS 2 ½ (use Class 1500) and Class 2500flanges NPS 14 or larger.
2. Inner Ring thickness: 0.117" to 0.131".3. Inner Ring Inside diameter tolerance: from 1¼” to 3": ± 0.03
4" and larger: ± 0.06
Annex 7.1 (Continued)Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.5 Flanges
153
262830323436384042444648505254565860
DI26.5028.5030.5032.5034.5036.5038.5040.5042.5044.5046.5048.5050.5052.5054.5056.5058.5060.50
DE27.7529.7531.7533.8835.8838.1340.1342.1344.2546.3848.3850.3852.5054.5056.5058.5060.5062.50
DA30.5032.7534.7537.0039.0041.2543.7545.7548.0050.2552.2554.5056.5058.7561.0063.2565.5067.50
DI27.0029.0031.2533.5035.5037.6338.5040.2542.2544.5046.3848.6351.0053.0055.2557.2559.5061.50
DE29.0031.0033.2535.5037.5039.6340.0042.1344.1346.5048.3850.6353.0055.0057.2559.2561.5063.50
DA32.8835.3837.5039.6341.6344.0041.5043.8845.8848.0050.1352.1354.2556.2558.7560.7562.7564.75
DI27.0029.0031.2533.5035.5037.6338.2540.3842.3844.5047.0049.0051.0053.0055.2557.2559.2561.75
DE29.0031.0033.2535.5037.5039.6340.2542.3844.3846.5049.0051.0053.0055.0057.2559.2561.2563.75
DA32.7535.1337.2539.5041.5044.0042.2544.3846.3848.5050.7553.0055.2557.2559.7561.7563.7566.25
NominalDiameter
Gasket Dimensions per Pressure Class - inches
150 300 400
Annex 7.2Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series A
154
262830323436384042444648505254565860
DI27.0029.0031.2533.5035.5037.6339.0041.2543.5045.7547.7550.0052.0054.0056.2558.2560.5062.75
DE29.0031.0033.2535.5037.5039.6341.0043.2545.5047.7549.7552.0054.0056.0058.2560.2562.5064.75
DA34.1336.0038.2540.2542.2544.5043.5045.5048.0050.0052.2554.7557.0059.0061.2563.5065.5068.25
DI27.0029.0031.2533.5035.5037.7540.7543.2545.2547.5050.0052.00
DE29.0031.0033.2535.5037.5039.7542.7545.2547.2549.5052.0054.00
DA34.7537.2539.7542.2544.7547.2547.2549.2551.2553.8856.5058.50
600 900
There are no Class 900 flangesNPS 50 and larger
Gasket Dimensions per Pressure Class - inchesNominalDiameter
Annex 7.2 (Continued)Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series A
1. Inner Rings are required for all PTFE filled gaskets and for Class 900, NPS 26 throughNPS 48.
2. Tolerance in inches:
• Winding thickness: ± 0.005" – measured across the metallic portion of thegasket not including the filler, which may protrudeslightly beyond the metal.
• Gasket outside diameter: ± 0.06"
• Gasket inside diameter:from 26" to 34" : ± 0.03"36" and larger : ± 0.05"
• Guide Ring outside diameter : ± 0.03"
155
262830323436384042444648505254565860
15025.7527.7529.7531.7533.7535.7537.7539.7541.7543.7545.7547.7549.7551.7553.5055.5057.5059.50
30025.7527.7529.7531.7533.7535.7537.5039.5041.5043.5045.3847.6349.0052.0053.2555.2557.0060.00
40026.0028.0029.7532.0034.0036.1337.5039.3841.3843.5046.0047.5049.5051.5053.2555.2557.2559.75
60025.5027.5029.7532.0034.0036.1337.5039.7542.0043.7545.7548.0050.0052.0054.2556.2558.0060.25
90026.0028.0030.0032.0034.0036.2539.7541.7543.7545.5048.0050.00
There areno Class
900 flangesNPS 50 and
larger.
NominalDiameter
Inner Ring Inside Diameter per Pressure Class - inches
Tolerances:Inner Ring thickness: 0.117" to 0.131".Inner Ring Inside diameter tolerance: ± 0.12".
Annex 7.2 (Continued)Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series A
156
262830323436384042444648505254565860
DI26.5028.5030.5032.5034.5036.5038.3740.2542.5044.2546.5048.5050.5052.5054.5056.8859.0761.31
DE27.7029.5031.5033.5035.7537.7539.7541.8843.8845.8848.1950.0052.1954.1956.0058.1860.1962.44
DA28.5630.5632.5634.6936.8138.8841.1343.1345.1347.1349.4451.4453.4455.4457.6359.6362.1964.19
DI26.5028.5030.5032.5034.5036.5039.7541.7543.7545.7547.8849.7551.8853.8855.2558.2560.4462.56
DE28.0030.0032.0034.0036.0038.0041.2543.2545.2547.2549.3851.6353.3855.3857.2560.0061.9464.19
DA30.3832.5034.8837.0039.1341.2543.2545.2547.2549.2551.8853.8855.8857.8860.2562.7565.1967.19
DI26.2528.1330.1332.0034.1336.1338.2540.3842.3844.5047.0049.0051.0053.0055.2557.2559.2561.75
DE27.5029.5031.7533.8835.8838.0040.2542.3844.3846.5049.0051.0053.0055.0057.2559.2561.2563.75
DA29.3831.5033.7535.8837.8840.2542.2544.3846.3848.5050.7553.0055.2557.2559.7561.7563.7566.25
NominalDiameter
Gasket Dimensions per Pressure Class - inches
150 300 400
Annex 7.3Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series B
157
262830323436384042444648505254565860
DI26.1327.7530.6332.7535.0037.0039.0041.2543.5045.7547.7550.0052.0054.0056.2558.2560.5062.75
DE28.1329.7532.6334.7537.0039.0041.0043.2545.5047.7549.7552.0054.0056.0058.2560.2562.5064.75
DA30.1332.2534.6336.7539.2541.2543.5045.5048.0050.0052.2554.7557.0059.0061.2563.5065.5068.25
DI27.2529.2531.7534.0036.2537.2540.7543.2545.2547.5050.0052.00
DE29.5031.5033.7536.0038.2539.2542.7545.2547.2549.5052.0054.00
DA33.0035.5037.7540.0042.2544.2547.2549.2551.2553.8856.5058.50
600 900
There are no Class 900 flangesNPS 50 and larger.
Gasket Dimensions per Pressure Class - inchesNominalDiameter
Annex 7.3 (Continued)Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series B
1. Inner Rings are required for all PTFE filled gaskets and for Class 900, NPS 26 throughNPS 48.
2. Tolerance in inches:
Winding thickness: ± 0.005" – measured across the metallic portion of thegasket not including the filler, which may protrudeslightly beyond the metal.
Gasket outside diameter: ± 0.06"
Gasket inside diameter:from 26" to 34" : ± 0.03"36" and larger : ± 0.05"
Guide Ring outside diameter: ± 0.03"
158
262830323436384042444648505254565860
15025.7527.7529.7531.7533.7535.7537.7539.7541.7543.7545.7547.7549.7551.7553.5055.5057.5059.50
30025.7527.7529.7531.7533.7535.7537.5039.5041.5043.5045.3847.6349.0052.0053.2555.2557.0060.00
40026.0028.0029.7532.0034.0036.1337.5039.3841.3843.5046.0047.5049.5051.5053.2555.2557.2559.75
60025.5027.5029.7532.0034.0036.1337.5039.7542.0043.7545.7548.0050.0052.0054.2556.2558.0060.25
90026.0028.0030.2532.0034.0036.2539.7541.7543.7545.5048.0050.00
There areno Class
900 flangesNPS 50 and
larger.
NominalDiameter
Inner Ring Inside Diameter per Pressure Class - inches
Annex 7.3 (Continued)Spiral Wound Gasket Dimensions per ASME B16.20 for ASME B16.47 Series B
Tolerances:Inner Ring thickness: 0.117" to 0.131".Inner Ring Inside diameter tolerance: ± 0.12".
159
A111111111111111111
11 ¼1212121212121212
B141414151515151515
15 ½1616161616161616
3/41
1 ¼½¾¾1
1 ¼1 ¼¾
5/16½¾7/811
1 ¼1 1/4
3/163/163/163/163/16¼
3/163/16¼
3/163/163/163/163/163/16¼
3/161/4
Width - W - in Thickness - E - inInside Dimensions - in
Annex 7.4Style 914 Spiral Wound Gaskets
160
½¾1
1 ¼1 ½2
2 ½3
3 ½456810121416182024
Ie1
1 5/16
1 ½1 7/
8
2 1/82 7/
8
3 3/8
4 ¼4 ¾5 3/
16
6 5/16
7 ½9 3/
8
11 ¼13 ½14 ¾
1719 ¼
2125 ¼
Ee1 3/
8
1 11/16
22 ½2 7/
8
3 5/8
4 1/8
55 ½
6 3/16
7 5/16
8 ½10 5/
8
12 ¾15
16 ¼18 ½
2123
27 ¼
Ie1
1 5/16
1 ½1 7/
8
2 1/8
2 7/8
3 3/8
4 ¼4 ¾
5 3/16
6 5/16
7 ½9 3/
8
11 ¼13 ½14 ¾16 ¾19 ¼
2125 ¼
Ee1 3/
8
1 11/16
1 7/8
2 ¼2 ½3 ¼3 ¾4 5/
8
5 1/85 11/
16
6 13/16
81012
14 ¼15 ½17 5/
8
20 1/8
2226 ¼
Large SmallNominalDiameter
Gasket Dimensions - in
Standard thickness: 3.2 mm (1/8").
Annex 7.5 Style 911 for Tongue and Groove Flanges
161
¼½¾1
1 ¼1 ½2
2 ½3
3 ½4568
10121416182024
Ie½1
1 5/16
1 ½1 7/
8
2 1/8
2 7/8
3 3/8
4 ¼4 ¾5 3/
16
6 5/16
7 ½9 3/
8
11 ¼13 ½14 ¾
1719 ¼
2125 ¼
Ee1
1 3/8
1 11/16
22 ½2 7/
8
3 5/8
4 1/8
55 ½6 3/
16
7 5/16
8 ½10 5/
8
12 ¾15
16 ¼18 ½
2123
27 ¼
Ie-
13/16
1 1/16
1 ¼1 5/
8
1 7/8
2 3/8
33 ¾
-4 ¾5 ¾6 ¾8 ¾10 ¾
13-----
Ee-
1 3/8
1 11/16
22 ½2 7/
8
3 5/8
4 1/8
5-
6 3/16
7 5/16
8 ½10 5/
8
12 ¾15-----
Class 150 to 1500 psi Class 2500 psiGasket Dimensions - inches
NominalDiameter
Standard thickness: 3.2 mm (1/8").
Annex 7.6Style 911 for Male and Female ASME B16.5 Flanges
162
101520253240506580
100125150175200250300350400450500600700800900
1000
1620283543506177901151401671912152673183604104605106107108109101010
24283643515873891021271521792032272793303804304805306307308309301030
1091221471742012292533073584104625165666667708749741078
36405057677491
111126151178205235259315366418470
628
254284340400457514
62473182294210421154
40465161718292107127142168194224265290352417474546
628
63
113138148174210247277309364424486543
100
287
391
458
1605661
82
103119144154180217257284324388458
2506772
83
109124154170202242284316358442
2 to 64 100 to 250
D3 – PressureClass -bar D4 – Pressure Class - barDN D1 D2
25
Annex 7.7Gasket Dimensions for Styles 913 and 913M per DIN 2699
163
CHAPTER
8
JACKETED GASKETS
1. DESCRIPTION
A Jacketed Gasket is comprised of a soft pliable core inside a metallic jacketas shown in Figure 8.1. This Chapter covers several styles and applications.
Figure 8.1
164
2. METALLIC JACKET
Almost any metal or alloy found in sheet form can be used as a jacket; itschoice must take into consideration the fluid to be sealed as explained in Chapter 6 ofthis book. The metallic jacket is 0.016 in (0.4 mm) to 0.024 in (0.6 mm) thick.
3. FILLER
The standard filler material is Flexible Graphite. Other fillers like ceramic,asbestos, mica-graphite, PTFE or another metal can be used.
4. DESIGN
The following recommendations are based on successful practical applications:
• Gaskets confined by the inside and outside diameters:• Gasket inside diameter = groove inside diameter plus 1/16 in (1.6 mm).• Gasket outside diameter = groove outside diameter less 1/16 in (1.6 mm).
• Gaskets confined by outside diameter:• Gasket inside diameter = flange inside diameter plus a minimum of 1/8 in (3.2 mm).• Gasket outside diameter = groove outside diameter less 1/16 in (1.6 mm).
• Non confined gaskets:• Gasket inside diameter = flange inside diameter plus 1/8 in (3.2 mm).• Gasket outside diameter = bolt circle diameter less bolt diameter.
• Gasket width: to have adequate seating stress, the design recommendationsof Chapter 2 should be followed.
5. STYLES AND APPLICATIONS
5.1. STYLE 920
The style 920 is a round single jacket gasket as shown in Figure 8.2. Used inapplications where the seating stress and width are limited. It can be manufactured incircular or oval shape. The maximum gasket width is 1/4 (6.4 mm) and the standardthickness is 3/32 in (2.4 mm).
165
Figure 8.2
5.2. STYLE 923
The style 923 is a flat double jacket gasket as shown in Figure 8.3. Its mosttypical applications are as pipe flange gaskets and in Heat Exchangers. ASME B16.20shows the gasket dimensions for ANSI B16.5 flanges. The standard thickness is 1/8 in(3.2 mm). Section 7 of this Chapter deals with the gaskets for Heat Exchangers.
Style 923 gaskets are also used in large size reactors in chemical plants. Anotherimportant use is for flanges in the large, low pressure ducting in Steel Mill BlastFurnaces. To compensate for distortions and irregularities of these flanges gasketshave the thickness from 5/32 in (4 mm) to 1/4 in (6 mm).
Figure 8.3
166
5.3. STYLE 926
Similar to style 923 but the metallic jacket is corrugated as shown in Figure8.4. The corrugations act as a labyrinth increasing the sealability. For ASME B16.5flanges, the gasket dimensions are also covered by the ASME B16.20 standard.
Figure 8.4
5.4. STYLE 929
Similar to style 926 with a grooved metallic filler (Figure 8.5). Used inapplications where it is necessary to have a gasket without non-metallic materials,temperature limits and chemical resistance depend upon of the metal only
Figure 8.5
167
6. GASKETS FOR HEAT EXCHANGERS
6.1. HEAT EXCHANGERS
There are several kinds of Heat Exchangers, some of them so incorporated inour life style that we hardly notice them, like car radiators or home heating units. All ofthem transfer heat from one fluid to the other, cooling (radiator) or heating (homeheating), according to the process needs.
In industry there are several kinds of Heat Exchangers, some have specificnames like radiators, boilers, chillers, etc. However when we refer to a Heat Exchangergenerically we may be referring to any of them. However the term Heat Exchanger, inmost process industries is referred to as the “Shell and Tube Heat Exchanger”. As thename implies, it is equipment that has a “shell” and a bundle of “ tubes”. One of thefluids flows inside the shell and outside the tubes and the other fluid inside the tubes.
6.2. TEMA STANDARD
The great majority of the Shell and Tube Heat Exchangers are manufacturedfollowing the recommendations of the “Standards of the Tubular ExchangerManufactures Association – TEMA”, which sets the guidelines for design,construction, testing, installation and maintenance of this equipment. The TEMAStandard defines three classes of Heat Exchangers:• Class R: are designed for the generally severe requirements of Petroleum and relatedprocessing applications. For this service double jacketed metal (Teadit Style 923, 926or 927) or solid metal (Teadit Style 940, 941 or 942) gaskets shall be used for internalfloating head joints, all joints for pressure of 300 psi and over, and for all joints incontact with hydrocarbons.• Class B: are designed for the chemical process service. For this service doublejacketed metal (Teadit Style 923, 926 or 927) or solid metal (Teadit Style 940, 941 or 942)gaskets shall be used for internal floating head joints, all joints for pressure of 300 psiand over. For 300 psi and lower, composition gaskets may be used for external joints,unless temperature and the corrosive nature of the contained fluid indicates otherwise.• Class C: are designed for the generally moderate requirements of commercial andgeneral process applications. Gasket selection follows the same requirements of ClassB service.
6.3. GASKETS STYLE 923
Style 923 is the gasket used most in shell and tube heat exchangers. It can bemanufactured in a wide range of sizes, shapes and with bars for heat exchangers withseveral passages. The primary seal is at the inside diameter where there is a highergasket density after seating. The outside of the gasket is also denser after seating andacts as a secondary seal. A nubbin of 1/64 in (0.4mm) height and 1/8 in (3.2 mm) widthcan be machined on the face of the flange to increase gasket sealability. Figure 8.6shows the gasket and how it should be installed in Tongue and Groove flanges.
168
Figure 8.6
To increase the gasket sealability a 1/64" (0.4 m) high by 1/8" (3.2 mm) widenubbin is machined on the flange surface. This nubbin pressing where the gasket isthinner increases the seating stress in this area. The Figure 8.7 shows how a gasket isinstalled in a flange with a nubbin.
Figure 8.7
169
6.4. MATERIALS
Gaskets for heat exchangers can be manufactured in almost any metal or alloyavailable in sheets of 0.016 in (0.4 mm) to 0.020 in (0.5 mm) thick. The choice of jacketmaterial should take into account the operating conditions and the recommendationsin Chapter 6 of this book. The standard filler is Flexible Graphite.
6.5. GASKETS WITH INTEGRAL BARS
Traditionally double-jacketed gaskets for heat exchangers are manufacturedwith integral bars as shown in the Figure 8.8. There is a radius of concordance betweenthe bars and the inside diameter of the gasket.
Figure 8.8
170
6.6. GASKETS WITH WELDED BARS
Gaskets with welded bars (Figure 8.9) avoid one of the greatest problems ofconventional gaskets, which are the cracks in the radius of concordance area as shownin Figure 8.8.
The gasket material can crack due to the stresses during the forming of theradius. The primary seal as explained in Section 1 is broken. The secondary sealprovides all the sealing.
The greater area of the “radius of concordance” region decreases the gasketseating stress and thus reduces the sealability in the radius region.
Gaskets with welded bars as shown in Figure 8.9 have been developed toovercome the above deficiencies. The primary and secondary seal are 360º around thegasket. The gasket has a greater sealability, reducing leaks to the environment aroundthe equipment.
The bar seal between the heat exchanger passes. There is a small leak path atthe end of each bar. However due to the low pressure differential, these leaks do notchange the overall performance of the equipment.
The bars are Plasma or TIG welded with spot welds at each end. This way thebars are attached without reducing the gasket sealability. These welds should be softand small to avoid areas of increased resistance to seating.
Figure 8.9
171
Gasket MaterialAluminum
CopperCarbon Steel
Stainless SteelNickel
Radius of Concordance minimum - mm68101210
6.7. DESIGN
The Annex 8.1 shows the most common shapes of gaskets for heat exchangers.The normal dimensions for heat exchanger gaskets are:
• Gasket and bar width: 3/8 in (10 mm), 1/2 in (12.7 mm) and 5/8 in (15.9 mm).• Gasket thickness: 3.2 mm (1/8 pol).• Assembly gap: to allow the seating and assembly of the gasket it is
recommended there be a gap of 1/8 in (3.2 mm) between the gasket and itsgroove.
Table 8.1Radius of Concordance
6.8. MANUFACTURING TOLERANCES
Gaskets have to follow the recommendation of Tables 8.2 and Figure 8.10.
Table 8.2Manufacturing Tolerances
Characteristic
Outside Diameter (A)
Outside Diameter Eccentricity
Width (B)Thickness (E)
Overlap (S)Partition Bar Width (C)
Partition Bar Location (F)
Gaskets without barsGaskets with bars
Gaskets without barsGaskets with bars
± 1/16 (average)± 1/165/321/16
+0.0, -1/32+1/32, 0.0
Equal to or larger than 1/8+0.0, -1/32
± 1/32
Tolerance - in
172
Figure 8.10
6.9. PARTITION BAR WELDING
Partitions are welded in such a way it does not protrude beyond the gasketsealing surface, as shown in figures 8.11.
Figure 8.11
173
Style 923 GasketCorrugated FlexibleGraphite Tape
Figure 8.12
7. STYLE 927 GASKETS FOR HEAT EXCHANGERS
Style 927 gaskets are manufactured covering both sides of a Style 923 gasketwith Flexible Graphite Corrugated Tape, as shown in Figure 8.12. The gasketconstruction follows the recommendations of Section 6 of this Chapter.
The Flexible Graphite cover increases the gasket sealability, especially if theflange sealing surfaces have pitting, tool marks or other small irregularities oftenfound in these kinds of equipment.
The Style 927 gaskets combine the welded bar construction advantages withthe excellent sealability of the Flexible Graphite, which fill up the small irregularities,providing a high sealability seal. It is recommended to use them if the operationalconditions are suitable.
174
Annex 8.1Schedule of Standard Heat Exchanger Gaskets
175
Annex 8.1 (Continued)Schedule of Standard Heat Exchanger Gaskets
176
Annex 8.1 (Continued)Schedule of Standard Heat Exchanger Gaskets
177
CHAPTER
9
METALLIC GASKETS
1. METALLIC GASKETS
Metallic gaskets can be divided into two principal categories: Flat gasketsand Ring-Joint gaskets as shown in Figure 9.1. Both are manufactured from a metal oralloy without a soft filler.
Figure 9.1
2. FLAT METALLIC GASKETS
Defined as gaskets of relatively small thickness compared with its width.They are normally produced from a sheet with or without a machined sealing surface.
To have an effective seal, the flange must force the gasket material; thereforethe gasket must always be softer than the flange.
178
3. MATERIALS
Any material available in sheet that can be cut, machined, or stamped can beused. The recommendations in Chapter 6 of this book should be followed to specifythe material of the gasket.
To manufacture gaskets larger than the maximum sheet size, it is necessary toweld the gasket. This welding must not be harder than the flange material or it willdamage the sealing surface.
4. FINISH OF THE FLANGE SEALING SURFACE
For better performance, the use of flanges with a fine finish is recommended.The roughness should be 63 µin Ra (1.6 µm Ra). Under no circumstances should thefinish exceed 125 µin Ra (3.2 µm Ra). Scratches or radial tool marks are practicallyimpossible to seal with metallic gaskets.
5. STYLES OF FLAT METALLIC GASKETS
5.1. STYLE 940
The style 940 (Figure 9.2) is a metallic gasket that has a smooth sealing surfaceand can be manufactured practically in any shape. Their typical applications are invalves, heat exchangers, hydraulic presses and tongue and groove flanges. The strongpoints are mechanical and chemical attack resistance and they can be used in elevatedtemperature and pressure service.
The width of the gasket sealing surface should be at least equal to 1.5 timesits thickness.
Figure 9.2
179
These gaskets depending upon their material have high maximum seatingstress. The values for the maximum and minimum seating stress are shown in Table 9.1.
Table 9.1Seating Stress for Style 940 Gaskets
Soft IronAISI 1006/1008AISI 1010/1020AISI 304/316/321AISI 309NickelCopperAluminum
340003400038500486005800027500196000000
760007600087000109000130000740004350020300
Mínimum Máximum
Seating StresspsiMaterial
5.2. STYLE 941
Style 941 is a flat gasket with concentric grooves as shown in Figure 9.3.They combine the advantage of the style 940 with a reduced area of contact
with the flange to increase the seating stress.Used when a metallic gasket is required but the available seating force is not
enough to seal a style 940. Minimum manufacturing thickness: 3/64 in (1.2 mm).
Figure 9.3
180
5.3. STYLE 943
If the service requires the use of style 941 but the flanges need to be protected toavoid being damaged, the 941 gasket can be jacketed as shown in (Figure 9.4).
Figure 9.4
5.4. STYLE 900
Style 900 is a corrugated metal gasket as shown in Figure 9.5. They are usedin low pressure applications where there are limitations of weight and space. Thethickness of the sheet should be 0.010 in (0.25 mm) to 0.04 in (1 mm) depending on themetal and number of corrugations. Due to the thickness of the sheet, the force requiredto seat the gasket is greatly reduced when compared with gasket styles 940 and 941.
A minimum of 3 corrugations is necessary to obtain satisfactory sealing. Asmall flat area on the inside and outside diameters of the gasket is recommended toincrease its mechanical strength. The corrugation pitch can vary between 0.045 in (1.1mm) to 1/4 in (6.4 mm). The total thickness of the gasket is 40% to 50% of the corrugationpitch. The metal used determines the service temperature limit. Maximum servicepressure: 500 psi.
Figure 9.5
181
Figure 9.6
Figure 9.7
5.5. METALBEST STYLE 905
Metalbest Style 905 is a corrugated gasket style 900 metal core with FlexibleGraphite facings as shown in Figure 9.6. It combines the sealing properties of theFlexible Graphite with the extrusion resistance of the corrugated metal core. It isdesigned to maintain a positive seal through thermo-cycling and shock load conditions.These gaskets have passed industry fire tests, which are relative indicators of gasket’sability to resist fire conditions.
Style 905 gaskets can also be manufactured with a cover of Ceramic Fiber felt(Figure 9.7), for use with large size ducts at high temperature and low pressure like inBlast Furnaces and gas turbine exhaust. The metal thickness is 0.020 in (0.5 mm) andthe corrugation pitch is 5/32 in (4 mm), 3/16 in (4.8 mm) or 1/4 in (6.4 mm) depending onthe width of the gasket.
182
5.5.1. STYLE 905 GASKETS FOR ASME B16.5 FLANGES
Style 905 gaskets with Flexible Graphite facings have gained popularity in themarketplace in Class 150 and 300 ASME B16.5 flanges due to its ability to seal at lowbolt loads. Style 905 gaskets meet the Fugitive Emissions requirements, have been firetested and approved according the requirements of the PVRC Fire Tightness Test(FITT) procedure and have been sealbility tested per ROTT procedure. The PVRCdesign gasket constants 905 Gaskets with Flexible Graphite covering layers are asfollows:
• Gb: 90 psi• a: 0.547• Gs: 0.388 psi
The gasket dimensions for ASME are shown in Appendix 9.4. The standardmaterial for the metal core is 316 Stainless Steel. Other alloys are available uponrequest.
5.5.2. STYLE 905 GASKETS FOR HEAT EXCHANGERS
One of the most frequent uses of Style 905 Gaskets are in Shell and Tube HeatExchangers, due to their ability of to avoid mechanical shearing problems associatedother gasket types in heavy thermal cycling applications. The standard core materialis 316 Stainless Steel and the covering layer is Flexible Graphite. Other alloys areavailable upon request. The gasket thickness before seating is 0.080 in (2 mm) and theother dimensions, tolerances and shapes follow the indications of the Chapter 6 Section6 of this book.
183
6. RING-JOINTS
Metallic Ring-Joints are produced according to the standards established bythe American Petroleum Institute (API) and the American Society of MechanicalEngineers (ASME) for application at elevated temperatures and pressures. A typicalapplication of Ring-Joints is the “Christmas Trees” used in oil fields (Figure 9.8).
The seal is obtained in a line of contact by a wedge action with high seatingpressures thus, forcing the material to flow. The small sealing area with high contactpressure results in great reliability. However the contact surfaces of the gasket andthe flange should be carefully finished. Some styles of Ring-Joints are pressureactivated, that is, the greater the pressure the better the sealability. Ring-Joints aremanufactured according the ASME B16.20 and API 6A standards.
Figure 9.8
184
6.1. MATERIALS
The materials should be forged or laminated. Cast materials should not beused. The Table 9.2 shows the standard materials recommended by the ASME B16.20for Ring-Joint gaskets.
Table 9.2Ring-Joints Materials per ASME B16.20
Soft IronCarbon Steel
AISI 502AISI 410AISI 304AISI 316AISI 347
MonelNickelCopper
90120130170160160160125120
-
566872868383837068-
538538649704
Note 1Note 1Note 1Note 1Note 1Note 1
DSF5
S410S304S306S347MN
CU
MaterialMaximumHardnessBrinell
MaximumHardness
Rockwell B
MaximumTemperature
o F (°°°°°C )
MaterialCode
Note1:Maximum service temperature for styles 950 and 951. For styles BX and RX themaximum is 250O F (121o C).
6.2. SURFACE FINISH
The gasket sealing surface finish has a maximum roughness of 63 µin Ra (1.6 µm Ra)for styles 950, 951 and RX and a maximum of 32 µin Ra (0.8 µm Ra) for style BX.
6.3. HARDNESS
The maximum hardness for each gasket material is shown in Table 9.2.It is recommended that the hardness of the gasket be always less than that of theflange so as not to damage it. When the materials of the flange and the gasket aresimilar, it is recommended to heat treat the gasket to produce a hardness at least 30 HBless than the flange.
185
6.4. DIMENSIONS AND TOLERANCES
The following standards have the dimensions, tolerances and applicationrecommendations for Ring-Joints.• ASME B16.5 – Steel Pipe-Line Flanges• ASME B16.20 – Metallic Gaskets for Pipe Flanges• ASME B16.47 – Steel Pipe-Line Flanges• API 6A – Specification for Wellhead Equipment.• API 6B – Specification for Wellhead Equipment.• API 6D – Steel Gate, Plug, Ball and Check Valves for PipeLine Service.
Annexes 9.1, 9.2 and 9.3, at the end of this Chapter have the dimensions forRing-Joints per ASME B16.20.
6.5. STYLES
6.5.1. STYLE 950
Style 950, which is frequently referred to as the oval ring, was the gasket that wasinitially standardized (Figure 9.9). Later developments resulted in other styles. If theflange was designed using the older version of the gasket standard, for use with anoval ring, then it should be used only with style 950 gaskets.
Figure 9.9
186
6.5.2. STYLE 951
Style 951 has an octagonal section as shown on Figure 9.10. Style 951 hasbetter sealing performance than Style 950 and its use is recommended for newapplications. For this style flanges are manufactured according to new issues of ASMEand API standards and have grooves with a profile designed to work with styles 950and 951.
Figure 9.10
6.5.3. STYLE RX
Style RX (Figure 9.11) is a pressure-activated gasket. Its shape is designed touse the fluid pressure to increase the sealability. The outside sealing surface of thegasket makes the initial contact with the flange seating the gasket. As the internalpressure of the piping or equipment is increased the contact pressure between gasketand flange also increases due to the shape of the gasket. High seating pressures arecreated increasing the sealability. This design characteristic makes this gasket stylemore resistant to vibrations, pressure surges and shocks that occur during oil welldrilling. Style RX is interchangeable with style 950 and 951, using the same flangegrooving.
Figure 9.11
187
6.5.4. STYLE BX
Style BX gasket has a square cross section with bevelled corners as shown inFigure 9.12. Designed for use only in flanges API 6BX. Style BX is recommended forpressures from 5000 psi up to 20 000 psi. The average diameter of the gasket is slightlygreater than that of the flange groove. This way when the gasket is seated it stays pre-compressed by the outside diameter creating a high seating stress.
Figure 9.12
6.5.5. OTHER STYLES
There are several other styles of metallic gaskets such as the lens, delta andBridgeman styles, which are outside of the scope of this book due to their restricteduse in specific applications.
188
R-11R-12R-13R-14R-15R-16R-17R-18R-19R-20R-21R-22R-23R-24R-25R-26R-27R-28R-29R-30R-31R-32R-33R-34
1.3441.5631.6881.7501.8752.0002.2502.3752.5632.6882.8443.2503.2503.7504.0004.0004.2504.3754.5004.6254.8755.0005.1885.188
0.2500.3130.3130.3130.3130.3130.3130.3130.3130.3130.4380.3130.4380.4380.3130.4380.4380.5000.3130.4380.4380.5000.3130.438
0.440.560.560.560.560.560.560.560.560.560.690.560.690.690.560.690.690.750.560.690.690.750.560.69
0.380.500.500.500.500.500.500.500.500.500.630.500.630.630.500.630.630.690.500.630.630.690.500.63
0.1700.2060.2060.2060.2060.2060.2060.2060.2060.2060.3050.2060.3050.3050.2060.3050.3050.3410.2060.3050.3050.3410.2060.305
0.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.06
RingNumber
PitchDiameter
Width ofRing
Height of RingOval
BOctogonal
H
WidthStyle 951
RadiusStyle 950
R
Annex 9.1Dimensions for Styles 950 and 951 in inches
189
R-35R-36R-37R-38R-39R-40R-41R-42R-43R-44R-45R-46R-47R-48R-49R-50R-51R-52R-53R-54R-55R-56R-57R-58R-59R-60R-61R-62R-63R-64R-65R-66R-67R-68R-69R-70R-71R-72R-73R-74
5.3755.8755.8756.1886.3756.7507.1257.5007.6257.6258.3138.3139.0009.75010.62510.62511.00012.00012.75012.75013.50015.00015.00015.00015.62516.00016.50016.50016.50017.87518.50018.50018.50020.37521.00021.00021.00022.00023.00023.000
0.4380.3130.4380.6250.4380.3130.4380.7500.3130.4380.4380.5000.7500.3130.4380.6250.8750.3130.4380.6251.1250.3130.4380.8750.3131.2500.4380.6251.0000.3130.4380.6251.1250.3130.4380.7501.1250.3130.5000.750
0.690.560.690.880.690.560.691.000.560.690.690.751.000.560.690.881.130.560.690.881.440.560.691.130.561.560.690.881.310.560.690.881.440.560.691.001.440.560.751.00
0.630.500.630.810.630.500.630.940.500.630.630.690.940.500.630.811.060.500.630.811.380.500.631.060.501.500.630.811.250.500.630.811.380.500.630.941.380.500.690.94
0.3050.2060.3050.4130.3050.2060.3050.4850.2060.3050.3050.3410.4850.2060.3050.4130.5830.2060.3050.4130.7800.2060.3050.5830.2060.8790.3050.4130.6810.2060.3050.4130.7800.2060.3050.4850.7800.2060.3410.485
0.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.060.090.060.060.060.060.090.060.060.090.060.060.060.090.060.060.060.090.060.060.06
RingNumber
PitchDiameter
P
Width ofRing
A
Height of RingOval
BOctogonal
H
WidthStyle 951
C
RadiusStyle 950
R
Annex 9.1 (Continued)Dimensions for Styles 950 and 951 in inches
190
R-74R-75R-76R-77R-78R-79R-80R-81R-82R-84R-85R-86R-87R-88R-89R-90R-91R-92R-93R-94R-95R-96R-97R-98R-99
R-100R-101R-102R-103R-104R-105
23.00023.00026.50027.25027.25027.25024.25025.0002.2502.5003.1253.5633.9384.8754.5006.12510.2509.00029.50031.50033.75036.00038.00040.2509.25029.50031.50033.75036.00038.00040.250
0.7501.2500.3130.6251.0001.3750.3130.5630.4380.4380.5000.6250.6250.7500.7500.8751.2500.4380.7500.7500.7500.8750.8750.8750.4381.1251.2501.2501.2501.3751.375
1.001.560.560.881.311.75
-----------
0.69-------------
0.941.500.500.811.251.630.500.750.630.630.690.810.810.940.941.061.500.630.940.940.941.061.061.060.631.381.501.501.501.631.63
0.4850.8790.2060.4130.6810.9770.2060.3770.3050.3050.3410.4130.4130.4850.4850.5830.8790.3050.4850.4850.4850.5830.5830.5830.3050.7800.8790.8790.8790.9770.977
0.060.090.060.060.090.090.060.060.060.060.060.060.060.060.060.060.090.060.060.060.060.060.060.060.060.090.090.090.090.090.09
RingNumber
PitchDiameter
P
Width ofRing
A
Height of RingOval
BOctogonal
H
WidthStyle 951
C
RadiusStyle 950
R
Annex 9.1 (Continued)Dimensions for Styles 950 and 951 in inches
Tolerances:• Pitch Diameter P: ±0.007.• Width of Ring A: ±0.007.• Height B and H: +0.05,0-0.02. The variation in height along the Ring cannot
exceed 0.02.• Width of Flat C: ±0.008.• Radius R: ±0.02.• Angle 23o : ± 0.5o.
191
R-11R-12R-13R-14R-15R-16R-17R-18R-19R-20R-21R-22R-23R-24R-25R-26R-27R-28R-29R-30R-31R-32R-33R-34R-35R-36R-37R-38R-39R-40R-41R-42R-43R-44R-45R-46R-47R-48R-49R-50R-51R-52R-53R-54R-55R-56R-57R-58
RingNumber
R
1
1 ¼
1 ½
2
2 ½
3
3 ½
4
5
6
8
1 0
1 2
½
¾
1
1 ¼
1 ½
2
2 ½
33
3 ½
4
5
6
8
1 0
1 2
½
¾
1
1 ¼
1 ½
2
2 ½
3
4
5
6
8
1 0
1 2
½
¾
1
1 ¼
1 ½
2
2 ½
3
4
5
6
8
1 0
1 2
½
¾
1
1 ¼
1 ½
2
2 ½
3
4
5
6
8
1 0
1
1 ¼
1 ½
2
2 ½
3
4
5
6
8
1 0
1 2
1
1 ¼
1 ½
2
2 ½
3
4
5
6
8
1 0
1 2
1
1 ¼
1 ½
2
2 ½
3
4
5
6
8
1 0
1 2
1
1 ¼
1 ½
2
2 ½
3
3 ½
4
5
6
8
1 0
1 2 1 2
150 300600
900 1500 2500 720960
2000 3000 5000 150 300600
900
ASME B16.5 API 6B ASME B16.47 Séries A
Pressure Class and Nominal Diameter
Annex 9.1 (Continued)Application Data for Styles 950 and 951
192
R-59R-60R-61R-62R-63R-64R-65R-66R-67R-68R-69R-70R-71R-72R-73R-74R-75R-76R-77R-78R-79R-80R-81R-82R-84R-85R-86R-87R-88R-89R-90R-91R-92R-93R-94R-95R-96R-97R-98R-99
R-100R-101R-102R-103R-104R-105
RingNumber
R
1 4
1 6
1 8
2 0
2 4
1 4
1 6
1 8
2 0
2 4
1 4
1 6
1 8
2 0
2 4
1 4
1 6
1 8
2 0
2 4
1 21 4
1 6
1 8
2 0
1 4
1 6
1 8
2 0
8
1 4
1 6
1 8
2 0
8
11 ½
22 ½
34
3 ½5
1 0
2 2
150 300600
900 1500 2500 720960
2000 3000 5000 150 300600
900
ASME B16.5 API 6B ASME B16.47 Séries A
Pressure Class and Nominal Diameter
1 4
1 6
1 8
2 0
2 4
2 2
2 62 83 03 23 43 6
1 4
1 6
1 8
2 0
2 4
2 62 83 03 23 43 6
Annex 9.1 (Continued)Application Data for Styles 950 and 951
193
RX-20RX-23RX-24RX-25RX-26RX-27RX-31RX-35RX-37RX-39RX-41RX-44RX-45RX-46RX-47RX-49RX-50RX-53RX-54RX-57RX-63RX-65RX-66
3.0003.6724.1724.3134.4064.6565.2975.7976.2976.7977.5478.0478.7348.7509.65611.04711.15613.17213.28115.42217.39118.92218.031
0.3440.4690.4690.3440.4690.4690.4690.4690.4690.4690.4690.4690.4690.5310.7810.4690.6560.4690.6560.4691.0630.4690.656
0.1820.2540.2540.1820.2540.2540.2540.2540.2540.2540.2540.2540.2540.2630.4070.2540.3350.2540.3350.2540.5820.2540.335
0.1250.1670.1670.1250.1670.1670.1670.1670.1670.1670.1670.1670.1670.1880.2710.1670.2080.1670.2080.1670.3330.1670.208
0.7501.0001.0000.7501.0001.0001.0001.0001.0001.0001.0001.0001.0001.1251.6251.0001.2501.0001.2501.0002.0001.0001.250
0.060.060.060.060.060.060.060.060.060.060.060.060.060.060.090.060.060.060.060.060.090.060.06
-----------------------
RingNumber
OutsideDiameter
OD
WidthA
WidthC
HeightCH
HeightH
RadiusR
HoleD
Annex 9.2Dimensions for Style RX in inches
194
RX-69RX-70RX-73RX-74RX-82RX-84RX-85RX-86RX-87RX-88RX-89RX-90RX-91RX-99
RX-201RX-205RX-210RX-215
21.42221.65623.46923.6562.6722.9223.5474.0784.4535.4845.1096.87511.2979.6722.0262.4533.8445.547
0.4690.7810.5310.7810.4690.4690.5310.5940.5940.6880.7190.7811.1880.4690.2260.2190.3750.469
0.2540.4070.2630.4070.2540.2540.2630.3350.3350.4070.4070.4790.7800.2540.1260.1200.2130.210
0.1670.2710.2080.2710.1670.1670.1670.1880.1880.2080.2080.2920.2970.1670.057
0.072 (2)0.125 (2)0.167 (2)
1.0001.6251.2501.6251.0001.0001.0001.1251.1251.2501.2501.7501.7811.0000.4450.4370.7501.000
0.060.090.060.090.060.060.060.060.060.060.060.090.090.06
0.02 (3)0.02 (3)0.03 (3)0.06 (3)
----
0.060.060.060.090.090.120.120.120.12
-----
RingNumber
OutsideDiameter
OD
WidthA
WidthC
HeightCH
HeightH
RadiusR
HoleD
Note 1
Annex 9.2 (Continued)Dimensions for Style RX in inches
Notes:1. For Rings RX-82 to RX-91 only one hole is required2. The Tolerance for these dimensions is +0, -0.015.3. The Tolerance for these dimensions is +0.02, - 0.
Tolerances:• Outside Diameter OD: +0.020, -0.• Width A: +0.008, -0. The variation of the width cannot exceed 0.004 around
the ring.• Width C: +0.006, -0.• Height CH: +0, -0.03.• Height H: +0.008, -0. The variation of the height cannot exceed 0.004 around
the ring..• Radius R: ± 0.02.• Angle de 23o : ± 0.5o.
Hole D: ±0.02.
195
RX-20RX-23RX-24RX-25RX-26RX-27RX-31RX-35RX-37RX-39RX-41RX-44RX-45RX-46RX-47RX-49RX-50RX-53RX-54RX-57RX-63RX-65RX-66RX-69RX-70RX-73RX-74RX-82RX-84RX-85RX-86RX-87RX-88RX-89RX-90RX-91RX-99
RX-201RX-205RX-210RX-215
720 - 960 - 20001 ½2
2 ½
3
4
5
6
8
10
12
16
18
20
8
2900
11 ½2
2 ½34
3 ½510
30001 ½
2
2 ½3
4
5
6
8
10
12
16
18
20
8
50001 ½
23 1/
8
2 ½
3
4
5
68
8
10
14
1 3/8
1 13/16
2 9/16
4 1/16
Pressure Class and Nominal Diameter - API 6BRX RingNumber
Annex 9.2 (Continued)Application Data for Style RX
196
BX-150BX-151BX-152BX-153BX-154BX-155BX-156BX-157BX-158BX-159BX-160BX-161BX-162BX-163BX-164BX-165BX-166BX-167BX-168BX-169BX-170BX-171BX-172BX-303
1 11/16
1 13/16
2 1/16
2 9/16
3 1/16
4 1/16
7 1/16
9
11
13 5/8
13 5/8
16 5/8
16 5/8
18 3/4
18 3/4
21 1/4
21 1/4
26 3/4
26 3/4
5 1/8
6 5/8
8 9/16
11 5/32
30
2.842
3.008
3.334
3.974
4.600
5.825
9.367
11.593
13.860
16.800
15.850
19.347
18.720
21.896
22.463
24.595
25.198
29.896
30.128
6.831
8.584
10.529
13.113
33.573
0.366
0.379
0.403
0.448
0.488
0.560
0.733
0.826
0.911
1.012
0.938
1.105
0.560
1.185
1.185
1.261
1.261
1.412
1.412
0.624
0.560
0.560
0.560
1.494
0.366
0.379
0.403
0.448
0.488
0.560
0.733
0.826
0.911
1.012
0.541
0.638
0.560
0.684
0.968
0.728
1.029
0.516
0.632
0.509
0.560
0.560
0.560
0.668
2.790
2.954
3.277
3.910
4.531
5.746
9.263
11.476
13.731
16.657
15.717
19.191
18.641
21.728
22.295
24.417
25.020
29.696
29.928
6.743
8.505
10.450
13.034
33.361
0.314
0.325
0.346
0.385
0.419
0.481
0.629
0.709
0.782
0.869
0.408
0.482
0.481
0.516
0.800
0.550
0.851
0.316
0.432
0.421
0.481
0.481
0.481
0.457
0.06
0.06
0.06
0.06
0.06
0.06
0.12
0.12
0.12
0.12
0.12
0.12
0.06
0.12
0.12
0.12
0.12
0.06
0.06
0.06
0.06
0.06
0.06
0.06
RingNumber
BX
NominalDiameter
DiameterOD
HeightH
WidthA
DiameterODT
WidthC
HoleD(1)
Annex 9.3 Dimensions for Style BX in inches
197
BX-150BX-151BX-152BX-153BX-154BX-155BX-156BX-157BX-158BX-159BX-160BX-161BX-162BX-163BX-164BX-165BX-166BX-167BX-168BX-169BX-170BX-171BX-172BX-303
2 000
26 ¾
30
3 000
26 ¾
30
5 000
13 5/8
16 ¾16 ¾18 ¾
21 1/4
10 0001 11/
16
1 13/16
2 1/16
2 9/16
3 1/16
4 1/16
7 1/16
911
13 5/8
16 ¾
18 ¾
21 1/4
5 1/8
6 5/8
8 9/16
11 5/32
15 0001 11/
16
1 13/16
2 1/16
2 9/16
3 1/16
4 1/16
7 1/16
911
13 5/8
16 ¾
18 ¾
6 5/8
8 9/16
11 5/32
20 000
1 13/16
2 1/16
2 9/16
3 1/16
4 1/16
7 1/16
911
13 5/8
BX RingNumber
Pressure Class and Nominal Diameter - API 6BX
Application Data for BX Rings
Annex 9.3 (Continued)Dimensions for Style BX in inches
1. For all Rings only one hole is required.
Tolerances:• Outside Diameter OD: +0, -0.005.• Height H: +0.008, -0. . The variation of the height cannot exceed 0.004 around the ring.• Width A: +0.008, -0. . The variation of the width cannot exceed 0.004 around the ring.• Diameter ODT: ± 0.002.• Width C: +0.006, -0.• Hole D: ±0.02.• Height CH: +0, -0.03.• Radius R: de 8% a 12% of Ring height H.
Angle 23o : ± 0.25o.
198
Annex 9.4Style 920 Gasket Dimensions for for ASME B16.5 Flanges in inches
1/2 0.84 1.88 2.13 2.13 2.13 2.50 2.50 2.75
3/4 1.06 2.25 2.63 2.63 2.63 2.75 2.75 3.00
1 1.31 2.63 2.88 2.88 2.88 3.13 3.13 3.38
1 1/4 1.66 3.00 3.25 3.25 3.25 3.50 3.50 4.13
1 1/2 1.91 3.38 3.75 3.75 3.75 3.88 3.88 4.63
2 2.38 4.13 4.38 4.38 4.38 5.63 5.63 5.75
2 1/2 2.88 4.88 5.13 5.13 5.13 6.50 6.50 6.63
3 3.50 5.38 5.88 5.88 5.88 6.63 6.88 7.75
3 1/2 4.00 8.50 9.00
4 4.50 6.88 7.13 7.00 7.63 8.13 8.25 9.25
5 5.56 7.75 8.50 8.38 9.50 9.75 10.00 11.00
6 6.62 8.75 9.88 9.75 10.50 11.38 11.13 12.50
8 8.62 11.00 12.13 12.00 12.63 14.13 13.88 15.25
10 10.75 13.38 14.25 14.13 15.75 17.13 17.13 18.75
12 12.75 16.13 16.63 16.50 18.00 19.63 20.50 21.63
14 14.00 17.75 19.13 19.00 19.38 20.50 22.75
16 16.00 20.25 21.25 21.13 22.25 22.63 25.25
18 18.00 21.63 23.50 23.38 24.13 25.13 27.75
20 20.00 23.88 25.75 25.50 26.88 27.50 29.75
24 24.00 28.25 30.50 30.25 31.13 33.00 35.50
NPS(in)
GasketInside
Diameter(in)
Gasket Outside Diameter (in)
150 300 400 600 900 1500 2500
199
CHAPTER
10
CAMPROFILE GASKETS
1. INTRODUCTION
With the continuous advance of the chemical and petrochemical processes, itis necessary to have gaskets for higher pressures and temperatures, especially forShell and Tube Heat Exchangers. The most used gasket type for this equipment is theDouble Jacketed, Teadit Style 923, which is a soft filler with a metallic jacket, as shownin Figure 8.6.
One of the characteristics of gaskets for Heat Exchangers is that they aremanufactured according to the dimensions of each equipment. There are nodimensional standards or shapes.
To be used in a high pressure application a gasket must be able to resist highseating stress, assuring the sealability. The Double Jacketed Gaskets, due to theirdesign, with a soft core, are capable of filling up the flange irregularities. However,because of the soft core, they are not recommended for applications where the seatingstress is higher than 250 MPa (36,000 psi).
For applications that require high seating stresses, flat metal gaskets like theTeadit Style 940 (Figure 9.2) can be used. These gaskets have several manufacturingand installation difficulties. They are very sensitive to any flange irregularity especiallyscratches, pitting or tool marks. Being made from a solid metal or alloy, it is verydifficult to seat and fill up the normal flange irregularities. Due to the large dimensions,some gaskets are larger than the available sheet stock, it becomes necessary to weld,and areas of higher hardness are created during the welding process, making it moredifficult to seat the gasket, or damage the flanges.
200
To avoid the flat metal gasket problems, the alternative is to use serratedmetal gaskets, Teadit Style 941, as shown in Figure 9.3, which have the same highpressure capabilities. The serrated sealing surface creates a high seating stress andadditionally a labyrinth effect. However, the serrated surface, desirable to create agood seal, can damage the flange surface with circumferential marks.
The Camprofile Gaskets, Teadit Style 942, combine the pressure resistance offlat metal gaskets with the excellent sealability of the Flexible Graphite (Graflex) orExpanded PTFE tape (24BB). They have a serrated metal core covered on both sideswith a thin tape of Flexible Graphite or Expanded PTFE, as shown in Figure 10.1.
Figure 10.1
The Teadit Camprofile gaskets have the following characteristics:• Operating pressure up to 3,700 psi (250 bar).• Maximum temperature up to 1100o F (600o C).• Wide range of service.• Less susceptible to flange imperfections than conventional flat metal
gaskets.The serrated metal core produces a high seating stress with a low torque. The
thin Flexible Graphite or Expanded PTFE core fills up the flange irregularities andprevents the serrated finish from damaging the flanges.
2. MATERIALS
2.1. METALLIC CORE
The core material should be chemically and thermally compatible with thefluid to be sealed. If possible the core metal should be the same as used to manufacturethe flanges to avoid corrosion or differential Thermal Expansion. It is recommendedthat the design should follow the recommendations of Chapters 2 and 6 of this book.
GRAFLEX OR PTFE TAPE
201
2.2. SEALING COVER
The most widely used cover material is the Graflex® - Flexible Graphite. Foroperational conditions where the Flexible Graphite is not recommended the 24BBExpanded PTFE tape is used. The Table 10.1 shows the Temperature and Pressurelimits for the cover materials.
Table 10.1Cover Materials Temperature and Pressure Limits
Material
Graflex®
24BB
Temperature - oF (oC)
min max
-400 (-240)-400 (-240)
1200 (650)520 (270)
3700 (250)1500 (100)
Pressure – psi (bar)
3. PRESSURE AND TEMPERATURE LIMITS
The Pressure and Temperature range is related to the range of eachcomponent, as indicated in Chapter 6 and Table 10.1. The Service Range is thecombination of the limit for the metal and cover limits. For example a Teadit CamprofileStyle 942 with a Carbon Steel core and Graflex® cover has the following limits:
• Maximum pressure: 3700 psi (250 bar).• Temperature range F o (oC): -40 to 1200 (-40 to 650)
4. BOLTING CALCULATION
The “m” and “y” values for ASME Code calculation are shown in Table 10.2and the values for DIN Standard calculation are in Table 10.3.
Table 10.2.ASME Gasket Factors
MaterialAluminumCopperBrassCarbon SteelMonelStainless Steel
m3.253.503.503.753.754.25
y5500650065007600900010100
202
AlumínioCobreNíquelAISI 1006/1008AISI 304/316AISI 321AISI 309
1.1 1.1 1.1 1.1 1.1 1.1 1.1
Mín.σσσσσVU
20 20 20 20 20 20 20
Máx.σσσσσVO
140 300 510 500 500 500 600
100
120270500500500500570
200
93195490495450450530
300
150480315420420500
400
240
390460
500
350400
600
240
Material
Gasket Factor
m
InstallationSeating Stress
- MPa -Maximum Operating Stress - MPa
Table 10.3DIN Gasket Calculation
It is recommended that after the calculations per ASME Code, to verify if theMaximum Seating and Operational Stress are lower are indicated in Table 10.3 to avoidcrushing the gasket.
5. SURFACE FINISH
The recommended Surface Finish for the flange sealing surfaces is 63 to 80 µin(1.6 µm a 2.0 µm) Ra. This finish range is known as “smooth finish”.
6. DESIGN AND MANUFACTURING TOLERANCES
The Table 10.4 shows the design recommendations and the Table 10.5 showsthe manufacturing tolerance for Teadit Style 942 gaskets.
Table 10.4Gasket Design
Type of Flange
Tongue and Groove
Gaskets confined bythe outside diameter
Gaskets confined bythe inside diameter
Gasket Diameter
Inside Outside
Groove inside diameterplus 1/16" (1.6mm)
Flange inside diameterplus 1/8" (3.2 mm)
Flange inside diameterplus 1/16" (1.6 mm)
Groove outside diameterless 1/16" (1.6mm)
Flange outside diameterless 1/16" (1.6 mm)
Flange outside diameterless 1/8" (3.2 mm)
203
Table 10.5Manufacturing Tolerances
Gasket InsideDiameter - in (mm)
Up to 20 (500)
From 20 (500) to 60 (1500)
Larger than 60 (1500)
+1/32, 0.0 (+0.8 -0.0)
+1/16, -0.0 (+1.6 -0.0)
+3/32, -0.0 (+2.5 -0.0)
+0.0, -1/32 (+0.0 -0.8)
+0.0, -1/16 (+0.0 -1.6)
+0.0, -3/32 (+0.0 -2.5)
Inside Outside
Tolerance - in (mm)
7. SHAPES
The Annex 8.1 shows the most used shapes for Heat Exchanger gaskets. Thepartitions are welded to the gasket inside perimeter.The standard gasket widths (“B” dimension) are 3/8", 1/2", 5/8" and 3/4" (10, 13, 16and 20 mm).
The standard thickness (dimension “E”) is 5/32" ± 1/128" (4 ±0.2 mm), themetallic core is 1/8" (3.2 mm) and 1/64" (0.4mm) each non-metallic cover.
8. CAMPROFILE GASKETS FOR ASME B16.5 FLANGES
At the time of this edition there is no current standard for Camprofile gaskestfor ASME B16.5 flanges. Several gasket organizations are working towards this goal.
The most commercialy available configuration is shown in Figure 10.2. Themetallic Sealing Ring is covered with Flexible Graphite or PTFE with a thinner metallicCentering Ring.
Figura 10.2
204
9. DIMENSIONS NAD TOLERANCES
Gasket Dimensions for ASME B16.5 flanges are shown in Table 10.6 andAnnex 10.1.
Table 10.6Camprofile Gasket Dimensions
Sealing Ring ThicknessCentering Ring ThicknessCover ThicknessSerrations Depth
CharacteristicMinimuum
0.115
0.024
0.015
0.030
Maximum0.131
0.035
0.030
0.060
Dimensions (inches)
9.1. IDENTIFICATION
The centering ring is permanently marked with lettering at least 1/8 in (3.2 mm)height with the following information:• Manufacturer’s name or trademark.• Flange size (NPS).• Pressure class.• Sealing Ring metal abbreviation.• Cover material abbreviation.• Centering Ring metal abbreviation.
The material code abbreviations are shown in Annex 10.2.
205
1/2
3/4
1
1 1/4
1 1/2
2
2 1/2
3
4
5
6
8
10
12
14
16
18
20
24
0.91
1.13
1.44
1.75
2.06
2.75
3.25
3.87
4.87
5.94
7.00
9.00
11.13
13.37
14.63
16.63
18.87
20.87
24.88
1.31
1.56
1.87
2.37
2.75
3.50
4.00
4.88
6.06
7.19
8.37
10.50
12.63
14.87
16.13
18.38
20.87
22.87
26.87
150
1.88
2.25
2.63
3.00
3.38
4.13
4.88
5.38
6.88
7.75
8.75
11.00
13.38
16.13
17.75
20.25
21.63
23.88
28.25
300
2.13
2.63
2.88
3.25
3.75
4.38
5.13
5.88
7.13
8.50
9.88
12.13
14.25
16.63
19.13
21.25
23.50
25.75
30.50
400
2.13
2.63
2.88
3.25
3.75
4.38
5.13
5.88
7.00
8.38
9.75
12.00
14.13
16.50
19.00
21.13
23.38
25.50
30.25
600
2.13
2.63
2.88
3.25
3.75
4.38
5.13
5.88
7.63
9.50
10.50
12.63
15.75
18.00
19.38
22.25
24.13
26.88
31.13
900
2.50
2.75
3.13
3.50
3.88
5.63
6.50
6.63
8.13
9.75
11.38
14.13
17.13
19.63
20.50
22.63
25.13
27.50
33.00
1500
2.50
2.75
3.13
3.50
3.88
5.63
6.50
6.88
8.25
10.00
11.13
13.88
17.13
20.50
22.75
25.25
27.75
29.75
35.50
2500
2.75
3.00
3.38
4.13
4.63
5.75
6.63
7.75
9.25
11.00
12.50
15.25
18.75
21.63
-
-
-
-
-
Centering Ring Outside Diameter by Pressure Class (in)Sealing RingND(in)
Ins ideDiameter
( in )
Outs ideDiameter
(in)
Annex 10.1Camprofile Gasket Dimensions for ASME B16.5 flanges
Tolerances:• Sealing Ring Inside Diameter:
o DN ½” to DN 8": ± 0.03 ino DN 10" to DN 24": ± 0.06 in
• Sealing Ring Outside Diameter:o DN ½” a DN 8": ± 0.03 ino DN 10" a DN 24": ± 0.06 in
• Centering Ring Outside Diameter: ± 0.06 in
206
Anexo 10.2Códigos dos materiais para Juntas Camprofile para flanges ASME B16.5
Carbon Steel304 SS
304 L SS309 SS310 SS
316 L SS317 L SS347 SS321 SS430 SS
Monel 400Nickel 200Titanium
20Cb-3 alloyHastelloy BHastelloy CInconel 600Inconel 625
Inconel X-750Incoloy 800Incoloy 825
CRS304
304 L309310
316 L317 L347321430
MONNITI
A-20HAST BHAST CINC 600INC 625
INXIN 800IN 825
Graflex - Flexible GraphitePTFE
FGPTFE
Cover
Sealing and Centering RingsMaterial Abbreviation
207
CHAPTER
11
GASKETS FORELECTRICAL INSULATION
1. ELETROCHEMICAL CORROSION
This is the most frequently found type of corrosion. It occurs at roomtemperature. It is the result of a reaction of two metals in contact in an aqueoussolution of salts, acids or alkalis. The Figure 11.1 illustrates electrochemical corrosion.
As can be observed, two reactions take place, one at the anode, the other atthe cathode. Anodic reactions are always oxidation and tend to dissolve the metal ofthe anode or combine it to form an oxide.
The electrons produced in the anodic reaction participate in the cathodicreaction. These electrons flow across the metal as an electrical current.
The cathodic reactions are always reductions and normally do not affect themetal of the cathode, as the majority of the metals cannot be further reduced.
The basis of electrochemical corrosion is the existence of an anodic reactionwhere the metal of the anode gives up electrons. The measurement of the tendency ofthe metal to give up electrons serves as a basic criterion of corrodibility. Thismeasurement, expressed in volts in relation to a gaseous hydrogen cell is found incorrosion manuals.
For Iron the value is 0.44 volts and for Zinc it is 0.76 volts. There is anelectrical current from Zinc to Iron, from the higher potential to the lower. Zinc is theanode and is corroded.
If for example in place of Zinc in Figure 11.1 we had Copper, of 0.34 voltpotential, we would have corrosion of the iron that has a greater potential.This way the relation between the electrochemical potentials of metals in contact witheach other is what is going to determine which of them will be corroded. The principle
208
is extensively used and the Zinc plating of carbon steel is one of the most commonexamples of the controlled use of electrochemical corrosion.
The Table 11.1 shows the relationship between some metals and alloys.
Table 11.1Electrolytic Series in Salt Water
Anode (base)
Cathode (noble)
MagnesiumZinc
Cast IronCarbon Steel
304 Stainless SteelCopper
316 Stainless SteelInconel
TitaniumMonelGold
Platinum
209
2. CATHODIC PROTECTION
Cathodic protection consists of the controlled use of the electrochemicalcorrosion to protect pipelines, tanks and other submerged equipment. Piping orequipment to be protected should be electrically insulated from the rest of the systemto prevent the flow of galvanic current to a non-protected area.
Zinc anodes are installed in sufficient quantities to absorb the galvanic current.These anodes are consumed in the process and should be replaced periodically.
The Figure 11.2 illustrates a submerged pipeline protected by a Zinc electrodeinsulated from the rest of the system.
Figure 11.2
3. INSULATION SYSTEM FOR FLANGES
Insulation gasket sets are used to insulate the protected area from electricalcontact. Figure 11.3 shows an insulating gasket style E. The components of aninsulation gasket set are:
• Gasket made of an insulating material.• Insulating sleeves.• Insulating washers.The gaskets are dimensioned to be used with ASME B16.5 flanges.As shown, to prevent electrical currents, which can cause corrosion, the
protected section, must be electrical insulated from the rest of the system.
210
Gasket materials:• Phenolic Resin reinforced with cotton fabric 1/8" (3.2 mm) thick or Phenolic Resin 0.8" (2 mm) with a 0.02" (0.5 mm) Neoprene coating on each side.• Compressed Sheet Packing.
3.1. INSULATION GASKETS STYLE E
It has the same outside diameter as the flange to prevent any foreign materialfrom penetrating between the flanges and making electrical contact. The Figure 11.3shows a typical system for style E gasket.
Figure 11.3
211
3.2. INSULATION GASKETS STYLE F
It is designed in such a way that its external diameter touches the protectionsleeves of the bolts. They are more economic than style E. It is necessary to protectthe flanges adequately whenever there is a risk of foreign material penetrating betweenthem. Figure 11.4 shows a typical system with gasket style F.
Figure 11.4
3.3. GASKETS STYLES RJD 950 AND 951
The style 950 and 951 insulation gaskets are manufactured for use in flangesfor Ring-Joints. The style RJD 950 has an oval shape and the style RJD 951 an octagonalshape. The gasket dimensions are according the ASME B16.20. It is necessary to
212
adequately protect the flanges whenever there is a risk of foreign materials penetratingbetween them. Figure 11.5 shows a typical system with gasket type RJD style 950.
Gasket material: reinforced phenolic resin
3.4. INSULATION SLEEVES
The insulation sleeves can be manufactured with phenolic resin, polyethyleneor polypropylene plastic. The physical properties of the material for phenolic resininsulation sleeves are the same as for the gasket. Plastic sleeves are highly flexibleand adequate for use in locations of high humidity as they have low water absorption.The insulation sleeve thickness is 1/32 in (0.8 mm).
213
3.5. INSULATION WASHERS
The insulation washers are manufactured with phenolic resin reinforced withcotton cloth. They have the same physical characteristics as the phenolic resin gaskets.Standard thickness is 1/8 in (3.2 mm).
3.6. STEEL WASHERS
To protect the insulation washers against damage steel washers are installedbetween them and the nut or the bolt head. The steel washers are manufactured withelectro-plated carbon steel 1/8 in (3.2 mm) thick.
4. SPECIFICATIONS FOR THE GASKET MATERIAL
Material: phenolic resin reinforced with cotton fabric.
Characteristics:
• Dielectric strength ........................... parallel: 5KV/mm perpendicular: 3KV/mm• Resistance to compression ............. 1800 kgf/cm2
• Bending strength ............................. 1000 kgf/cm2
• Tensile strength ............................... 900 kgf/cm2
• Water absorption ............................. 2,40%• Density ............................................. 1,30 g/cm3
• Hardness Rockwell M ..................... 103• Maximum temperature ..................... 266o F (130o C)
214
215
CHAPTER
12
INSTALLATION ANDFUGITIVE EMISSIONS
1. INSTALLATION PROCEDURE
To obtain a satisfactory seal, it is necessary that basic procedures be followedduring the gasket installation. These procedures are of fundamental importance for asuccessful operation no matter what style of gasket or material used.
a) Inspect the flange-sealing surface. Check for tool marks, dents, scratchesor corrosion. Radial tool marks on the sealing surface are difficult to seal regardless ofthe style of gasket. Be sure that the flange finish is adequate for the style of gasketbeing used.
b) Inspect the gasket. Verify to be sure that the gasket material is compatiblewith the intended service. Check for defects and shipping or storage damage.
c) Inspect and clean bolts, nuts and washers.d) Lubricate bolt threads and the nut contact surfaces. Do not install bolts
and nuts without lubrication. The lubricant should be compatible with the servicetemperature. A good lubricant will provide a better application of the torque and,consequently, higher precision of the Bolt Load.
e) For Raised Face or Flat Faced flanges installed vertically, start installationby bolts on the lower part. Install the gasket then the other bolts.
f) For Male and Female or Tongue and Groove flanges, the gasket should beinstalled in the center of the groove.
g) Install the bolts and hand tighten them in a cross pattern sequence asshown in Annex 12.1. Number the bolts to facilitate the tightening order.
216
h) Tighten the bolts approximately 30% of the final torque following the crosspattern sequence. If the correct tightening sequence is not followed, the flanges canbe misaligned, making it impossible to have uniform seating of the gasket.
i) Repeat step g, elevating the torque to 60% of the final value.j) Continue tightening in clockwise sequence until the final value is reached.
The same bolt normally has to be tightened several times since as the nearest bolts aretightened it loses its force. It is recommended that each bolt be tightened with thefinal torque value at least 5 times.
k) All gaskets relax after seating. Retightening is recommended at least fourhous after the installation to compensate for relaxation, following the rotationalclockwise pattern.
l) Compressed Non-Asbestos Gaskets should not be retightened after theyhave been exposed to high temperatures.
m) All retightening should be performed at ambient temperature andatmospheric pressure.
2. TORQUE VALUES
The most precise method for obtaining the desired Seating Stress is to applythe Bolt Load by measuring its tension. However, in practice, this procedure iscumbersome and of difficult execution. If direct tension measuring is not possible it isrecommended to use hydraulic tools or a torque wrench. The use of manual toolswithout torque control is acceptable only in non-critical applications.
Methods to calculate the Bolt Load and the torque values have been shownin Chapter 2 of this book.
3. ALLOWABLE BOLT STRESS
The ASME Pressure Vessel and Boiler Code, Section VIII, Appendix S dealswith the bolt stress. For example, the designer of the flange should determine thenecessary tightening for the temperature and pressure in the specific operationalconditions, according to the allowable bolt stress at the operating temperature.
Hydrostatic testing, which in the majority of cases is necessary to verify thesystem, is done at one and one half times the design pressure. Consequently, a flangedjoint designed in accordance with the ASME Code, which should be hydrostatic testedwith a pressure higher than the design pressure, has to be tightened for the testconditions.
The ASME Pressure Vessel and Boiler Code, Section VIII, Appendix Sestablishes that in order to pass the hydrostatic test, the bolts must be tightened upto the torque necessary for that purpose. If, in this case, the tension is greater thanwhat is admissible, bolts made with a higher allowable tension material should beused observing the following procedure:
217
• Use bolts with allowable tension compatible with the one necessary topass the hydrostatic test, following the normal installation procedure forthe gasket.
• After the hydrostatic test is completed, loosen the bolts approximately50% of the initial tension.
• Replace the bolts used for the test with the originally designed bolts, oneat a time, tightening until reaching the torque of the other bolts.
• After replacing all bolts, tighten them up to the design torque following thecross pattern sequence.
4. LEAKAGE
One of the most efficient ways to analyze the causes of a leakage is to carefullyanalyze the gasket used when such a leakage has taken place as shown below:
• A very corroded gasket: select a material with a better corrosion resistance.• A very extruded gasket: select a material with a better cold flow resistance
or with a higher seating stress, use a compression limit ring or redesign theflanges.
• Gasket with a damaged sealing surface: verify the gasket and flangedimensions. It could be that the gasket has the inside diameter smaller thanthe inside diameter of the flange or the outside diameter of the gasket islarger than the outside diameter of the flange.
• Gasket not seated: select a softer gasket material or reduce the contact areabetween gasket and flange.
• Gasket thinner at the outside diameter: indication of a “rotation” or flangedeflection. Change the gasket dimensions in a way that it fits closer to thebolts to reduce rotational torque. Select a softer gasket that requires alower seating stress. Reduce the area of the gasket. Reinforce the flange toincrease its rigidity.
• Gasket irregularly seated: incorrect procedure in tightening the bolts. Makesure the tightening sequence of the bolts is followed properly.
• Gasket with regularly varying thickness: indication of flanges with excessivedistance between bolts or without sufficient rigidity. Reinforce the flanges,reduce the distance between bolts or select a softer gasket.
5. MISALIGNED FLANGES
When the flanges are not aligned it is not recommended to align them bytightening the bolts. Misalignments must be corrected prior to the gasket installation.Spacers can be used to correct the misalignment as shown in Figure 12.1
218
Figure 12.1
6. LIVE LOADING
Just after the gasket seating, the process of Stress Relaxation starts, which isthe loss of the Bolt Load. The Relaxation process is a characteristic of flanged jointsand occurs with any kind of gasket.The Relaxation is due to several factors as follows:• Gasket Relaxation: gaskets are designed to, when seated, fill up the flange
irregularities. As this plastic deformation occurs the flanges get closer,reducing the Bolt Load. The amount of this deformation depends upon thegasket style and the operating temperature.
• Bolt Thread Relaxation: when tightened there is a contact between its parts.There are microscopic points where the stress is higher than the Yield Stress for
their materials. With time, the material flows at these points, reducing the stress.Studies have shown a reduction of 5% to 10% of the initial stress.
• Relaxation with temperature: bolts used in high temperature have thetendency to relax with temperature and time. The amount of the relaxationdepends upon the temperature and the time.
• Vibration: under vibration bolts tend to relax. The total loss of the tighteningcan occur at severe vibration condition.
219
• Cross Tightening: normally the tightening follows the cross patternprocedure. When one bolt is tightened the nearest ones lose stress. Ifsimultaneous hydraulic tools are used to install the gasket this problem isreduced.
• Thermal Expansion: when the temperature changes from room to operating,there are several thermal expansions. As the flanges and the gaskets arecloser to the heat source than the bolts there are thermal and consequentlyexpansion gradients. The same problem occurs when the system is turnedoff. These thermal changes relax the flanged joint.
• Thermal Cycle: when the system operates with thermal cycle or is frequentlyturned off, the relaxation due to the thermal changes is greater.
To compensate for the loss of stress due to the Relaxation, the systemelasticity has to be increased. This can be achieved with longer bolts and sleeves orwith spring washers, as shown in Figure 12.2.
The use of longer bolts and sleeves is not recommended since to be effectiveis necessary to have very long bolts, which is not always possible.
The most common system is the use of spring washers, known as Live Loadingor Constant Load.
Figure 12.2
6.1. LIVE LOADING
To compensate for the Relaxation, Teadit has developed the Live LoadingSystem of spring washers specially designed for use in flange applications, as shownin Figure 12.3.
220
Figure 12.3
Before deciding to use a Live Loading System it is necessary to study theneed for it. It increases the installation costs and should be used only when needed.
The Live Loading System does not solve sealing problems, however, as itmaintains the Bolt Load, it reduces problems in critical applications.
Live Loading is recommended for the following conditions:
• Products that can cause extensive environmental damage or loss of lives.• Systems with thermal cycling or operating temperature fluctuations.• When the ratio of the bolt length to its diameter is less than three.• Systems with vibrations.• When the gasket or flange materials have a high tendency to relaxation.• When there is a history of system leakage.
The Teadit Live Loading System is available for three levels of bolt stress asshown in Annex 12.1. When tightened with the torque shown the bolt achieves thestress level of 414 MPa (60,000 psi), 310 MPa (45,000 psi) or 207 MPa (30,000 psi). TheBolt Load at this stress level is also shown.
The Spring Washers are manufactured with alloy steel ASTM A681 type H13,oil finish for use with carbon steel bolts. The recommended temperature is from roomto 1100o F (590o C).
For corrosive applications the Spring Washers can also be manufacturedwith Stainless Steel ASTM A693 type 17-P7 for temperatures of – 400o F (–240o C) to
221
550o F (290o C). Can also be manufactured with Inconel 718 (ASTM B637) fortemperatures – 400o F (-240o C) to 1100o F (590o C).
The gaskets are installed as shown in Figure 12.3, with one spring on eachside of the flange. The spring must have its higher side towards the bolt as indicated;if it is not installed in this way the Bolt Load can be lower than indicated. When thetorque is achieved the spring will be flat.
For equipment such as Heat Exchangers, that operate under thermal cyclemore than one spring on each side may be needed. Please consult with Teadit forthese applications.
7. FUGITIVE EMISSIONS
To assure the life of future generations it has become necessary to reduce thepollutants released into the environment. Additionally the loss of chemical productsinto the environment is a cost to the industry.
The great majority of pollutants like the Oxides of Carbon, Nitrogen and Sulfurare the result of burning of fossil fuels or the evaporation of Hydrocarbons. Theiremissions are part of the industrial process and are subject to specific controls.
However, there are undesirable losses in pump shafts, valve stems and flanges,which in normal condition should not happen. These losses are known as FugitiveEmissions. It has been estimated that in the USA, the Fugitive Emissions are in theorder of 300,000 tons per year. Most of the time it is necessary to have special equipmentto detect them.
The control of the Fugitive Emissions is also a benefit to the plant safety.Non detected leaks are a major cause of fire and explosions in plants and oil refineries.
The USA was one of the first countries to control Fugitive Emissions with the1990 Clean Air Act (CAA), which was a cooperation between the industry and theEnvironmental Protection Agency (EPA). The CAA defined the list of Volatile HazardousAir Pollutants (VHAP). If any product has more than 5% of a VHAP in its compositionit has to be controlled.
To monitor the Fugitive Emissions the EPA has published the ReferenceMethod 21, which uses an Organic Vapor Analyzer (OVA). This equipment, calibratedfor Methane, measures the concentration in parts per million (ppm) of the product.The OVA, pumps the gas through a sensor to determine its concentration.
Flanges, valve stems, pump and agitator’s shafts and any other equipmentthat can cause a leak are subject to monitoring. For flanges, the maximum concentration,measured according to the EPA Method 21 is 500 ppm. There has been a trend towardsreducing this value to 100 ppm.
For flanges, a first measurement must be done at about 1 meter (1 yard) fromthe source, in a direction against the prevailing wind. Then at about 1 centimeter(1/2 in) going around it. The value to be taken is the difference between the initialvalue and the highest value closer to the flange. If the difference is higher than 500ppm the flange is considered as leaking and must be repaired.
222
The EPA Method 21 is a “go-no go” kind of measurement, it determines if theflange is leaking or not. However, it does not give a quantitative value of the leaking.
To obtain a quantitative value the equipment must be encapsulated, which iscostly and not always possible.
The EPA has developed several studies to correlate the value in ppm and theflow per unit of time. The Chemical Manufactures Association (CMA) and the Societyof Tribologists and Lubrication Engineers have also done studies and arrived at similarresults. The leakage in grams per hour can be established as:
Leakage = 0.02784 (SV 0.733) g / hour
Where SV is the value measured in parts per million.
The value obtained by this equation gives an approximate quantity of theproduct being released to the environment. For example if there is a leakage of 5,000ppm we have:
Leakage = 0.02784 (SV 0.733) = 0.02784 (50000.733) = 14.322 g / hour
223
Annex 12.1Tightening Sequence
224
225
ACX00008060ACX00008045ACX00008030ACX00010060ACX00010045ACX00010030ACX00012060ACX00012045ACX00012030ACX00014060ACX00014045ACX00014030ACX00016060ACX00016045ACX00016030ACX00018060ACX00018045ACX00018030ACX00020060ACX00020045ACX00020030ACX00022060ACX00022045ACX00022030ACX00024060ACX00024045ACX00024030ACX00026060ACX00026045ACX00026030ACX00028060ACX00028045ACX00028060ACX00030060ACX00030045ACX00030030ACX00032060ACX00032045ACX00032030ACX00036060ACX00036045ACX00036060ACX00040060ACX00040045ACX00040030ACX00044060ACX00044045ACX00044030ACX00048060ACX00048045ACX00048030
6.73.93.45.44.74.06.55.74.87.66.75.78.77.76.59.98.77.4
11.310.28.4
12.410.99.2
13.511.910.114.913.111.016.114.111.915.615.212.816.716.313.718.818.415.521.020.517.318.722.719.125.524.820.9
4.13.63.05.14.43.66.25.44.47.26.35.28.37.25.99.48.26.8
10.79.67.6
11.810.38.4
13.011.39.2
14.212.410.215.413.411.014.814.411.815.815.412.617.917.414.320.019.516.017.521.517.724.223.519.3
806040
160120
80270200140430330220660500330960720480
13601020680
18401380920
217016301080298022401490407030502030542040702710597044702980862064704310
1193089505970
1606011930
8030209401570010470
378302839018960603604530030230891606690044630
1233009250061700
161700121300
80900210760158100105430266760200100133430328900246700164500397960298500199030474760356100237430554760416100277430508870482100321430584870554100371210751650712100474760937430
88100592100
11464301086100
72410013744301302100
868100
TeaditPart Number
A - mm Torque
N-m
Force
NFree Seated
Annex 12.2Teadit Live Loading System
1/2
5/8
3/4
7/8
1
1 1/8
1 1/4
1 3/8
1 1/2
1 5/8
1 3/4
1 7/8
2
2 1/4
2 1/2
2 3/4
3
Bolt NominalDiameter
inches
226
227
CHAPTER
13
CONVERSION FACTORS
Multiplygallondegree Chpyardkgf / cm2
kgf-mkgf-mkg/m3
poundmegapascal (MPa)megapascal (MPa)milenewtonnewtonfootsquare feetcubic feetinchescubic inchsquare inch
By3.7851.8° C + 32745,70.914414.6959.8077.2386.243 x 10-2
0.454145101,6090.2250.1020.3050,092900.02825.41,639 x 10-5
645.16
to getliterdegree Fwattsmeterlbf/pol.2
newton-meter (N-m)lbf-ftlb/ft3
kglbf/pol.2
barkmlbfkgfmeterm2
m3
millimitercubic metersquare millimiters
228
229
230
