1.0 Disclaimer

This report has been written by an undergraduate student. Any information described

herein needs to be verified and approved by a professional engineer prior to be issued

for construction.

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2.0 Nomenclature

A - outside diameter of joining flange (m)

A’b - total cross-sectional area of bolts required for operating conditions = W/Sb

Ab - cross-sectional area of = π d2 (m2)

B - inside diameter of joining flange (m)

C - bolt circle diameter (m)

d - bolt nominal diameter (m)

g0, g1 - thickness of clamping shell (m)

H - total hydrostatic end force (N)

HC - balancing reaction force outside the bolt circle in opposition to moments due

to loads inside the bolt circle (N)

hc - radial distance from bolt circle to outer edge of flange on which HC acts (m)

Le - effective length of the clamping shell (m)

M - moment due to loads inside the bolt circle (Nm)

n - total number of bolts required for operating conditions

p - design pressure (Pa)

R - radial distance from bolt circle to point of intersection of clamping shell and

back of flange (m)

Sb - maximum permissible bolt design stress at design temperature (Pa)

W - minimum bolt load required for operating conditions (N)

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3.0 Results

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4.0 Design Of Bolt Holes In Joining Flange (work in progress)

Since the leaking fluid would be sealed by injected sealant, there would be no gasket

required and, hence, the joining flange would be metal-to-metal contact. For flanges

with metal-to-metal contact outside the bolt circle, Clause 3.21.10-AS 1210 suggested

design method in Appendix Y, ASME BPV VIII-1, “Rules for construction of pressure

vessels”, as an equivalent method. It should be noted that the rules have applied to

circular flanged connections where the assemblage comprised of identical flange pairs,

and where the flanges were flat faced and were in uniform metal-to-metal contact across

their entire face during assembly before the bolts were tightened. This method assumed

the flanges were in tangential contact at their outside diameter. The analytical procedure

was based on the prying effect. Illustration of this effect has been shown in Figure 1:

Figure 1: A bolt subjected to full external load and full prying load

From Figure 1, due to the flange interaction beyond the bolt circle to resist the bending

moment developed by the external load, H , a bolt was not only subjected to the full

external load, H , but also the prying load, H R, or the joint would fail. Hence, the bolt

load would satisfy the following condition:

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FB ≥ H +H R (1)

It was important to note that the operating bolt stress was relatively insensitive to

changes in prestress up to a certain point and that thereafter the two stresses were

essentially the same. In other words, the assembly stress in the bolts would have no

significant effect on the actual operating stress in the bolts.

General arrangement of the assemblage has been shown in Figure 2:

Figure 2: General arrangement of joining flange and bolt holes

Location of forces and bending moments have been illustrated in Figure 3 below:

Figure 3: Location of forces and bending moments at joining flange induced by internal

pressure

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According to Appendix Y-9, ASME BPV VIII-1, the total cross-secional area of bolts

required for operating conditions has been defined by the following equation:

Ab' =

H +2 M P

( A−C )Sb

(2)

The Equation 2 provided for circular flange. For rectangular flange, using Figure (3)

and Equation (1) for minimum bolt load required at operating conditions:

W =FB=H2

+H c (3)

in which H has been defined by Equation (15) (Semester 1-progress report),i.e.,

H=PB Le . Also,

H c=2 M c

A−C (4)

Substituing Equation (4) into Equation (3):

W =H2

+2 M c

A−C=1

2A

b

'

Sb (5)

The expression Ab' Sb multiplieing by

12

indicated the bolt load in each pair of joining

flange. Rearranging Equation (5) would yield the total cross-secional area of bolts

required for operating conditions for rectangular flanges:

Ab' =

H +4 M c

( A−C )Sb

(6)

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Due to symmetry the balancing moment, M c, could be obtained by:

M c=H2

×C2=

M p

2 (7)

From Figure 2,

C=2(g+R) (8)

In which g could be obtained from Equation 2, semester 1- progress report; R should be

sufficient to provide clearance for washer seating,i.e., dimension ‘D’ Appendix A, and

welding at flange connection to clamping shell defined in Section 5:

R ≥D2

+F (9)

Dimension ‘F’ could be seen in Appendix D as a reference.

From Figure 2,

A=C+2 hc (10)

According to Clause 9.6, AS 3990, the minimum and maximum distance from bolt

centre to edge of flange could be designed in accordance with AS 3990 – Clause 9.6:

hcmin=1.5d (11)

hcmax=12 g but not exceed 150 mm (12)

For bolt grade 8.8 described in Appendix A, the minimum tensile strength, Fuf ,would be

800 MPa and the minimum yield strength, FYf ,would be 640 MPa. According to AS

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3990 – Page 58, Table 9.5.2, the maximum permissible stress, F tf , subjected to tension

would be the smaller of:

0.60 FYf=0.60 ×640=384 MPa (13)

0.45 Fuf=0.45 ×800=360 MPa (14)

Hence, the maximum permissible stress of the bolt, F tf=Sb, would be 360 MPa.

The number of bolts required would satisfy the following condition:

n ≥Ab

'

Ab(15)

Refering to Figure 2 and Equation 6, the prying force could be reduced, and hence the

bolt load, by increasing the distance hc, minimising the distance R, or increasing the

flange thickness.

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5.0 Design of Joining Flange Connection to Clamping Shell (work in progress)

The welded joint between the flange and the clamping shell has been designed in

accordance with AS 1210, AS 1554.1, and AS 3990. There have been many types of

flange attachement specified by AS 1210 (Page 189, Figure 3.21.3). It has been

suggested by Dave Landwehr that full penetration butt weld would be employed for the

design. The advantages of this type were that there would be no limit in maximum

calculation pressure and temperatures (AS 1210, Clause 3.21.3.3),i.e., it could be still

applicable when the design pressure and temperature were needed to be improved, and

no calculations were neccessary as the maximum permissible stresses would be the

minimum value pertaining the components jointed (AS 3990, Clause 9.8.2). However,

for butt welds, the members to be connected had to fit perfectly when they were lined

up for welding and edge preparation was also required,i.e., chamfering. Normally, a

backup plate was also temporarily required to ensure full penetration and a sound weld.

Hence, this attachment method would require more skilled supervision and be costlier.

Various type of the butt welds could be seen in Appendix B as a reference. The typical

arrangement of full penetration welded joining flanges has been shown in Figure 4:

Figure 4: Full penetration welded-on joining flange

(AS 1210, pg.189, Figure 3.21.3 (c))

In which t n (or go) was the nominal clamping shell thickness. In such connection, the

joining flange was considered to be the equivalent of an integral structure and the clamp

shell was considered to act as a hub. However, this design provided for circular flanges.

Design for rectangular flanges could be refered to AS/NZS 1554 (Clause 3.2) in which

the joining flanges were attached to the clamping shell to form a T-joint. As specified

by this clause, weld size would be the thickness of the joining flanges, which was also

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known as throat thickness. The effective length of the weld could be taken as the length

of the joining flange in which a continous full-size weld was achieved. The effective

area would be the product of the effective length and the design throat thickness. For

this type of joint, a small fillet weld of 6 mm size was also superimposed on each

welded face. Definitions of size of butt and fillet weld could be refered to Appendix C.

Weld preparations have been designed in accordance with AS 1210 (Page 170, Figure

3.19.3(D).(c)), which could be seen in Appendix D. Details of the full penetration butt

weld have been shown in Figure 5:

Figure 5: Full penetration butt weld – Details

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6.0 References

Committee ME-001, Pressure Equipment. 2010. As 1210. Standard Australia Limited

Committee ME-001, Pressure Equipment. 2008. As 1548-Fine Grained, Weldable Steel

Plates for Pressure Equipment. Standards Australia

Committee ME/5, Cranes. 1993. As 3990-Mechanical Equipment-Steelwork. Standards

Asutralia (Standards Association of Australia)

Consultants, PDC. 2007. High Strength Bolts – Grade 8.8.

Engineers, The American Society of Mechanical. 2004. Rules for Construction of Pressure Vessels. V.N.Vazirani, M.M.Ratwani. 1985. Steel Structures and Timber Structures: Analysis, Design and Details of Structures. Vol. 3. Delhi: Khanna.

V.N.Vazirani, M.M.Ratwani. 1985. Steel Structures and Timber Structures: Analysis, Design and Details of Structures. Vol. 3. Delhi: Khanna.

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Appendix A – HIGH STRENGTH BOLTS – GRADE 8.8 (consultants, 2007)

Size A B C D E FX

(Min.)

Min.

Length

M12 18 20 8 28 4.6 32 24 25

M16 27 31 11 34 4.6 32 28 40

M20 32 37 14 39 4.6 38 32 40

M24 41 47 16 50 4.6 44 36 50

M30 50 58 20 60 4.6 57 42 75

M36 60 69 24 72 4.6 57 48 90

Note: All dimensions in millimetres.

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Appendix B – Different Types Of Butt Weld (V.N.Vazirani,1985,p.g 71)

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Appendix C – Butt And Fillet Weld Size Illustration

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Appendix D - Standard and Recommended Weld Preparation Details

LEGENDS (AS 1210, Page 170, Figure 3.19.3(D).(c)):

α = 50o min.

S2 = 0 to 3 (mm)

g2 = 3 (mm) min.

Dimensions E and F have been designed based on the reccomended α of 50o, S2 of 3

mm, and g2 of 3 mm and defined by the following expressions:

E=t f −3

2

F=E × tan (500 ) (16)

Tabulation of E and F corresponding with various commercial plate thicknesses has

been shown in table below:

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Flange thickness, t f (mm) E (mm) F (mm)

14 6 7

16 7 8

18 8 9

20 9 11

22 10 12

25 11 14

28 13 15

30 14 17

32 15 18

36 17 20

40 19 22

45 21 25

50 24 28

55 26 31

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