propiedades sf6

Introduction ........................................................................................2Applications

Electrical ....................................................................... 3-6

Nonelectrical .................................................................... 7

PropertiesElectrical Properties............................................................... 8-9

Physical and Thermodynamic Properties .......................... 10-15

Chemical Properties .......................................................... 16-17

Safety Precautions ............................................................................. 18

Specification...................................................................................... 19

Packaging and Auxiliary Equipment ........................................... 20-21Storage and Handling ....................................................................... 22

References .................................................................................. 23-24

Contents

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Contents

Since its discovery in 1900 by Henri

Moissan,(1) sulfur hexafluoride (SF6) has

fascinated man with its interesting and

unusual properties. In 1937 it was dis-

covered that sulfur hexafluoride possess-

es a much higher dielectric strength

than air,(2) a fact that led to its use in the

electrical industry as a dielectric gas and

insulating material. Odorless, colorless,

nonflammable and nontoxic, this versa-

tile gas finds broad use in a variety of

high voltage power applications, as well

as in other areas where its unique phys-

ical characteristics can be utilized.

Honeywell began production of

sulfur hexafluoride in 1948, and since

then has maintained the leadership

position in SF6 production technology.

Our SF6 plant in Metropolis, Illinois,

earned ISO 9002 certification in 1993.

AccuDri SF6 in manufactured to exact-

ing standards and distributed world-

wide in volumes substantial enough to

establish Honeywell as the worlds

largest producer of this remarkable gas.

Honeywell remains committed to

ongoing SF6 research and development

programs, while our dedicated staff of

technical specialists provides a level of

technical service and support second

to none.

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Introduction

Sulfur Hexafluoride is manufactured toexacting standards at Honeywellsfacility in Metropolis, IL.

Sulfur Hexafluoride Applications

Sulfur hexafluoride (SF6) has a uniquecombination of physical and electricalproperties. Some of the outstandingproperties of SF6 that make its use inpower applications desirable are:

Chemical inertness

Thermal stability

Nontoxicity

Excellent heat transfercharacteristics

Non-flammability

High dielectric/breakdown strength

Non-corrosiveness

Ability to regenerate

Sulfur hexafluoride also has low viscos-ity, low velocity of sound transmission,high molecular weight and large molec-ular size. These are characteristics thatenhance its performance in a variety ofnonelectrical applications.

Applications in theElectrical Power Industry

Sulfur hexafluoride is an excellentgaseous dielectric for high voltagepower applications. SF6 does not sufferpermanent breakdown as do soliddielectrics; when breakdown occurs,the dissociation products recombineonce the cause of the breakdown isremoved.(3) (See Electrical Propertiessection). The combined electrical,physical, chemical and thermal proper-ties of SF6 offer many advantages whenused in power switchgear. These advan-tages include:

Size reduction

Simplified design3

Electrical A

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Sulfur hexafluoride is an excellent gaseous dielectric for highvoltage power applications.Photo courtesy: ABB Power T&D, Inc.

Electrical Applications

Weight reduction Ease of installation Reliable operation Ease of handling Quiet operation Ease of maintenance

SF6 has applications as the dielectric orinsulation in high voltage transformers,circuit breakers and switchgear, wave-guides, linear particle accelerators, andVan de Graaff generators. It also hasextensive use in growth applicationssuch as high voltage transmission linesand power distribution substations.

Circuit BreakersOne of the most important applica-tions of SF6 is its use in gas-filled cir-cuit breakers. Dead-tank design circuitbreakers rated at 345 kV/25,000MVA,(4) and live-tank 500 kV/35,000MVA circuit breakers filled with SF6have been used for many years.(5) Morerecently, 765 kV live-tank circuitbreakers with continuous current rat-ings of 3,000 amperes have beeninstalled.(6,7,8)

The need to transport large blocks ofpower brought about the use of extrahigh voltages (EHV, above 345 kV)and has recently led to the use of ultrahigh voltage (UHV, above 1000 kV).(9)As higher voltages are used, suitableSF6-filled circuit breakers can bedesigned. Because of its arc extinguish-ing ability, the advantages of SF6 as adielectric are enhanced at very highvoltages.

The widespread acceptance of pufferbreakers in recent years has resulted ingreatly increased use of SF6 in place ofoil or air in breakers. The puffer break-er design is relatively compact, and isused for both transmission and distri-bution voltage ranges.4

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Gas-filled circuit breakers represent an important application for SF6.Photo courtesy: Mitsubishi Electric Power Products, Inc.

Switches

The use of SF6 in switches ranging from7.5 to 35 kV has increased rapidly. Theability of SF6 to extinguish arcs and pro-vide high dielectric strength are majorfactors for its acceptance in place of oilor vacuum in switches.

Gas InsulatedTransmission (GIT) Lines

The advantages of Gas InsulatedTransmission lines over conventional

overhead air-insulated power lines werewell-known in Europe and Japan formany years before this technology wasapplied in the United States. Some ofthe benefits of transmission lines filledwith SF6 are:

Safety

Aesthetics

Space savings

Extendible to UHV

GIT lines provide a higher safety factorthan conventional air-insulated linesbecause the conductors are completelyenclosed in grounded metal sheaths. For this reason, they can also be laid closetogether, thus saving space. Whileapproximately 150 feet (45m) of right-of-way is necessary for high voltage overheadlines, only one-tenth to one-twentieth ofthe space is required for GIT lines.(10) Inaddition, GIT lines may be buried under-ground or run near the ground on lowpylons, preserving the beauty of the land-scape. GIT lines make detection of insu-lation failure easy with sensitive SF6detectors. Although GIT lines have ahigher initial cost than overhead lines,they become economically feasible inareas where population densities and landcosts are high. The GIT line concept isreadily extendible into the highest voltageranges of the future; moreover, GIT cableis compatible with the minisubstation.


SF6 provides high dielectric strength when used in switches.Photo courtesy: Joslyn Power Products Corporation

SF6 is frequently in place of oilor vacuum in switches.Photo courtesy: G&W Electric Co.

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Minisubstations

Electrical power distribution substationsinclude circuit breakers, transformers,buses, and disconnect switches.Conventional open air substationsrequire extensive land areas to provideadequate insulation distance betweenpieces of apparatus. Due to their size,conventional substations are open, mak-ing them dangerous and unsightly.Metalclad, SF6 insulated substations,which are inherently safe, compact andattractive, are widely used in Europe andJapan, and are becoming increasinglypopular in the United States.(11)

Often referred to as minisubsta-tions, their space requirements are aslittle as 10-20% of air-insulated substa-tions,(12) making installation insidebuildings feasible. A further advantageof minisubstations is that the equipmentis protected from the weather, pollutioncontamination, and vandalism.

Other Electrical Applications

The high dielectric strength and arc-extinguishing capability of SF6 make it anexcellent dielectric for waveguides, Van deGraaff generators, and linear accelerators.SF6 increases the amount of power thatcan be transmitted; SF6 insulated equip-ment carries 7 to 10 times as much poweras air-filled equipment.(13) SF6 has a dielec-tric strength approximately 2.5 times thatof nitrogen, thus allowing more power tobe developed per unit pressure.(14) The useof SF6 in these applications results in upto tenfold increases in microwave powerin waveguides and increased voltage rat-ings for Van de Graaff generators and lin-ear accelerators.

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SF6 is used in Van de Graaff generators, linear accelerators andcommunications equipment.

SF6 insulated substations are compact, safe and attractive,offering numerous benefits to utilities.Photo courtesy: Ontario Hydro

Fluxes have several drawbacks: theycause corrosion, contribute to pollution,and increase metal loss. An alternative isto use a protection atmosphere contain-ing less than 1% SF6-

(15) Such a processis used in the United States, Canada,and Europe.(16) Because only smallamounts of SF6 are used, by-productsare negligible, making SF6 molten mag-nesium protection a sound choice bothin terms of safety and environmentalresponsibility.

Aluminum Degassing

Hydrogen and other gases trapped inmolten aluminum cause porosity in castaluminum components. A gas mixturecontaining less than 2% SF6 , bubbledthrough the aluminum melt, willremove these undesirable gases and

Nonelectrical Applications

SF6 is used in many nondielectric appli-cations because it is chemically inert,nontoxic, nonflammable and noncorro-sive. SF6 finds applications in suchdiverse areas as: molten magnesium andaluminum protection and purification,leak detection, tracer gas studies, propel-lants, insulating windows, shockabsorbers, lasers, and in the electronicsindustry as a plasma etchant gas.

Magnesium Casting

Unprotected magnesium alloys used fordie casting bloom and burn in ambientair at temperatures above 1100F(593C). Formerly, protective moltensalt fluxes were the only technologyavailable to prevent this oxidation.

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Nonelectrical Applications

bring solid impurities to the surface,where they can be removed. This tech-nology is not only safer, but is moreenvironmentally friendly than the for-mer practice of introducing chlorine orchlorofluorocarbons (CFCs) into themelt.(17)

Leak Detection and Gas-Air Tracers

SF6 has a very low viscosity and can beeasily detected, making it superb forequipment leak testing. It is also used asa gas-air tracer for meteorological stud-ies of moving air masses, such as indus-trial stack effluents(18) There are sensitivedevices on the market that can detectSF6 in amounts as low as 0.01 ppb andleak rates as small as 1 x 10-10cc/sec.(19)

SF6 can be blended with nitrogen or air,thereby producing a low cost leak-detecting gas. SF6 is detected by elec-tron-capture and separated from theother components of moist air by gaschromatography, a technique that isselective for SF6 regardless of back-ground gases. Stainless steel collectionvessels should be used rather than glass,as SF6 will be retained on glass surfaces.This interferes with accurate resultswhere trace quantities of SF6 areinvolved.

Other Applications

Sulfur hexafluorides high molecularweight and density slow the velocity ofsound to about one-third that in air.(20)

This sonic property, plus the fact thatSF6 is nontoxic, resists hydrolysis, andhas a low coefficient of permeation,makes SF6 an ideal medium for fillingsound-insulating windowpanes. SF6 isalso used in other diverse applicationsfrom shock absorbers to chemical lasersand semiconductor etching.

Degassing aluminum with SF6 produces cast components with low porosity.Photo courtesy: AGA Gas, Inc.

Electronegativity

The superb insulating and dielectricperformance of SF6 may be directlyattributed to its electron affinity (or elec-tronegativity). SF6 is an efficient elec-tron scavenger, capturing and attachingelectrons as shown by the reversibleequation in Diagram 1.(21)

Sulfur hexafluorides high dielectricstrength helps minimize arcing, and theSF6 dissociation products rapidlyrecombine after the source of arcing isremoved.(3) (See equation in Diagram 1).This characteristic makes SF6 uniquelyeffective in quenching arcs when spu-rious arcing occurs, SF6 is approximate-ly 100 times as effective as air in quench-ing the arc. Figure 1 compares the arc-quenching properties of SF6 and air.

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This property of SF6 may be due toseveral factors, including its large colli-sion diameter, estimated to be 4.77.(23)

If stray electrons in an electrical field areabsorbed through collision before theyattain sufficient energy to create addi-tional current-carrying particles, thebreakdown mechanism can be slowed,or even stopped. The large collisiondiameter of the SF6 molecule increasesthe efficiency of electron capture.

The possibility of storing energy afterelectron attachment may be more sig-nificant. Energy can be stored in thevibrational levels of the SF6 molecule,forming stable negative ions of lowmobility. These negative ions can reducethe positive space charge around an elec-trode, requiring a higher voltage to pro-duce an arc across the gap betweenpotential surfaces.

High Frequency Dielectric Strength

Sulfur hexafluorides is a nonpolar com-pound, and therefore maintains aboutthe same dielectric strength from powerto communication frequencies. Thedielectric strength of SF6 in the electricfield of a multiplate capacitor, relative tonitrogen = 1, has been found to varybetween 2.3 and 2.5 at 1.2 megahertz(MHz). In a uniform field, a similarresults has been observed at frequencies

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Electrical Properties

from 60 Hz to 15 MHz. At 3 gigahertz(GHz), SF6 insulated equipment carriesten times the power of air-filled equip-ment. This property makes SF6 anexcellent dielectric for coaxial cables,waveguides, etc. An SF6 insulated wave-guide operating at 9.375 GHz carries7.5 times more power than the samewaveguide filled with air.(12)

Diagram 1: Arc-Quenching

Figure 1: Arc-Quenching Ability of SF6 vs. Air

Dielectric Constant

The dielectric constant for SF6 is 1.002,and since SF6 has no dippole moment,its dielectric constant does not vary withfrequency. In microwave studies at23.340 GHz, this property was foundto increase slightly with pressure. Over apressure range of 22 atmospheres (22.3x 105 Pa), the changes in dielectric con-stant was about 7%.(12) This variationwith pressure makes SF6 useful for tun-ing resonant cavities.

Loss Tangent

In a perfect dielectric, the currentleads the voltage by exactly 90 degrees.The loss tangent or angle (tan ), is theangle by which the current vector of adielectric is less than 90 degrees. Thisproperty describes the deviation from

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Comparison of SF6 with othertypes of dielectrics

Solids

SF6 does not suffer permanent break-down as do solid dielectrics. Whenbreakdowns occur, the SF6 dissociationproducts recombine once the cause ofthe breakdown is removed.

Liquids

Oil is the primary dielectric used intransformers and lower voltage circuitbreakers. Sulfur hexafluoride offersmany advantages over liquid dielectrics.SF6 is nonflammable, so there is no firehazard as with transformer oil. SF6 isnontoxic, unlike askarels. Significantweight and space savings can beachieved by using SF6 in place of liquiddielectrics, and equipment filled withSF6 is easier to maintain and repair than liquid-filled devices, strong surges ofpressure may result form the sudden for-mation of gaseous products, resulting inpossible unit rupture. In a device filledwith SF6 , the only pressure rise willresult form the thermal expansion of thegas.

Gases

Sulfur hexafluoride has more than twicethe dielectric strength of air or carbondioxide and about three times that ofnitrogen. SF6 contains no carbon as dohalogenated hydrocarbons; if break-down does occur with SF6 , there will beno deposits of conducting carbon as isthe case with halogenated hydrocarbondielectrics. Figure 2 compares the break-down voltage and field strength versuspressure for SF6 and nitrogen.

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perfection for a dielectric. Alsoknown as the dissipation factor, theloss tangent for SF6 is extremely low,varying from 2 x 10-7 at 1 atmosphereto 0.4 x 10-6 at 21 atmospheres.(13)

Effect of Decomposition onDielectric Strength

In addition to possessing high dielec-tric strength that prevents arcs fromoccurring, SF6 can undergo consider-able decomposition without loss ofdielectric strength. Researchers investi-gating the permanent decompositionof electronegative gases in electric dis-charges subjected a sample of SF6 to30 minutes of continuous arcing.Even after this severe treatment, whichcaused 30% decomposition of thesample, the SF6 retained its originaldielectric strength.(24)

Figure 2: Breakdown Voltage and Field Strength vs.Pressure for SF6 and N2

General Physical Properties

Sulfur hexafluoride is a colorless, odor-less gas. With a vapor density five timesthat of air, it is one of the heaviestknown gases. SF6 is nonflammable, non-corrosive, and nontoxic.

SF6 is a gas at normal operating tem-peratures up to about 250 psi. The lowsublimation temperature of SF6 (-59Fat 20 psig) ensures that it remains in thevapor phase under normal operatingconditions. Under severe winter operat-ing conditions (-25 to -40C), unitheaters may be required to prevent condensation.

Heat Transfer

Sulfur hexafluoride has excellent heattransfer characteristics. This ability totransfer heat is an extremely importantproperty of a gaseous dielectric, criticalin transmission lines or transformers.Comparison of thermal conductivitiesalone may lead to erroneous conclusionsabout heat transfer properties. Whilethe thermal conductivity of helium isten times greater than that of SF6, thehigher molar heat capacity of SF6,together with its low gaseous viscosity,enables it to transfer heat more effective-ly than air, helium or nitrogen, as shownin Figure 3.(22)

These data were developed as part ofa research program sponsored byHoneywell, using a simulated transmis-sion line. In this test, an AC voltage, upto 800 kV, was obtained from a modu-lated Van de Graaff generator. The testequipment consisted of concentric alu-minum electrodes with a 1.5 inch gap.

Solubility

In Transformer Oil, T, C cc SF6/mL, Oilone atmosphere:(25) 27 0.408

50 0.34470 0.302

In Water, T, C cc SF6/1000 H2Oone atmosphere:(26) 5 11.39

10 9.1120 6.3150 3.52

Solubility of Water in SF6:(27) 0.0097% by weight

Figure 3: Comparative Heat Transfer of SF610

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Physical &ThermodynamicProperties

Thermodynamic Equations

Honeywell has prepared extensivetables(28) of vapor pressure, density, spe-cific volume, enthalpy and entropy forSF6. These tables cover the saturatedregion between -58F (-50C) and thecritical temperature 114F (45.6C),

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and the superheated region within thefollowing limits.:

Pressure 0.8 to 1000 psia

Temperature -100F to 600F(-73C to 315C)

Density 0.01 to 61 lbs/ft3

The tables were derived from the set ofequations in Diagram 2.(28,29) Allunits in these equations are expressed inEnglish equivalents (equations with SIunits also available). Pressure and tem-perature are given as absolutes.

Liquid Density Equation

(lb./cu. ft.) = c+ Di (1-Tr)i/3i = 1

where c = 0.4526082645 x 102

D1 = 0.9190127075 x 102 D3 = 0.8131779698 x 10

2

D2 = -0.1765965598 x 102 D4 = -0.3923550307 x 10

2

Vapor Pressure Equation

In(Pvap/psai) = A + B + CT + DT2 + E(F-T) In (F-T); T Rankine

T T

where A = 0.1035925977 x 102 D = -0.1704580367 x 10-4

B = -0.5839935378 x 104 E = 0.9426178300 x 100

C = 0.2034555556 x 10-1 F = 0.5876287200 x 103

Equation of State

P = RT + Ai + BiT + Ci exp (-KTr)(v - b) (v - b)ii = 2

P (psia), v(cu. ft./lb.), T(R), Tr = T/Tc

where R = 0.073479 B2 = 0.1134-12993 x 10-2

b = 0.5244071186 x 10-2 B3 = -0.1106173657 x 10-4

K = 0.6883021832 x 101 B4 = 0.00Tc = 573.84 B5 = 0.9298260796 X 10

-9

A2 = -0.1857216332 x 101 C2 = -0.8841985563 x 10

2

A3 = 0.2458758890 x 10-1 C3 = 0.1680833656 x 101

A4 = -0.1540211976 x 10-3 C4 = 0.00

A5 = -0.7494727319 x 10-8 C5 = -0.4715362420 x 10-4

Diagram 2

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Figure 4: Pressure Variation of SF6 at Constant Specific Volumes

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Figure 5: Vapor Pressure vs. Temperature for SF6

Figure 6: Mollier Diagram for SF614

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SF6 Properties CAS Registry No. 2551-62-4

PROPERTY VALUE REFERENCEChemical Symbol SF6Molecular Weight 146.05Odor None 30Toxicity None (TLV = 1000 ppm 31Combustible No 30Supports Combustion No 30Combustion Limits N/A 30

PHYSICAL PROPERTY VALUE REFERENCEPhysical State Liquid and GasSublimation Temperature -83F / -63.9C (1 atm) 32Melting Point -59.4F / -50.8C (32.5 psia) 33Boiling Point -83F / -63.9C (1 atm; sublimes) 34Specific Gravity (Air = 1.0) 5.11 (68F, 1 atm) 33Density (Vapor) 0.382 lbs/ft3/6.139 g/L (70F, 1 atm) 28Density (Liquid) 86.1 lbs/ft3 (70F) 28Vapor Pressure 313 psia/298 psig (70F) 28Surface Tension 8.02 dyne/cm (-20C) 22Viscosity (Vapor) 0.015 cP (25C, 1 atm) 35Viscosity (Liquid) 0.277 cP (25C, 1atm) 36Index of Refraction 1.000783 (0C, 1 atm) 37Solubility in Transformer Oil 0.408 cc SF6/mL oil (27C, 1 atm) 25Solubility in Water 0.0063 cc SF6/mL water (20C, 1 atm) 26Solubility of Water in SF6 0.0097% w/w 27

THERMODYNAMIC PROPERTY VALUE REFERENCESpecific Volume 2.5 ft3/lb (70F, 1 atm) 33Specific Heat 0.1552 Btu/lb x F (60F, 1 atm) 28Specific Heat Ratio 1.0960 (60F, 1 atm) 28Specific Heat Ratio 1.0932 (80F, 1 atm) 28Heat of Formation -1221.66 kJ/mol 29Latent Heat of Vaporization 28.4 Btu (70) 28Latent Heat of Sublimation 69.6 Btu/lb 33Molar Heat Capacity 97.23 J/mol K 29Free Energy of Formation -1117.73 kJ/mol 39Critical Temperature 114.2F 33Critical Pressure 544.3 psia/530.50 psig 28Critical Volume 1.356 mL/g 29Critical Density 0.737 8/ml (45.3 lb.ft.3) 29Triple Point Temperature 2.23150 x 102 K (-50C; -58F) 34Triple Point Pressure 2.32670 x 105 Pa (33.7 psi) 34Lbs Liquid per Gallon Liquid 11.5 lb/gal @ 68F; 312.7 psia 33Vol. Expansion Liq. > Gas 220/230 (70F, 1 atm) Calc.Std. ft3 Gas per Pound Liquid 2.64 ft.3/lb (70F, 1 atm) Calc.Thermal Conductivity 3.36 x 10-5 Cal/(sec)(cm)(C) @ 30C 38Base Enthalpy and Entropy 0.00 (-40F) 28Enthalpy 61.95 Btu/lb (70F, 1 atm) 28Entropy 0.15887 Btu/lb (70F, 1 atm, R) 28

ELECTRICAL PROPERTY VALUE REFERENCEDielectric Strength 2.3 - 2.5 (N2 = 1.0) 12Dielectric Constant 1.002 (25C/77F) 12Loss Tangent < 2 x 10-7 @ 1 atm 13

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Stability

Sulfur hexafluoride is an extremely sta-ble gas, and is chemically inert undernormal conditions. SF6 will not reactwith water, alkali hydroxides, ammoniaor hydrochloric acid,(12) and SF6 is unaf-fected in quartz at temperatures as highas 500C (932F).(40)

Material compatible studies conductedby Honeywell(41) indicated negligibledecomposition of SF6 after long-termexposure to metals at constant elevatedtemperatures. Stabilities at 200C(392F) and 250C (482F) are shownin Diagram 3.

At ambient temperatures, sulfur hexa-fluoride is inert and noncorrosive to allmetals and materials of construction.The exclusion of moisture from any system improves the stability of SF6with respect to these metals. It is alsoimportant to exclude moisture to main-tain the electrical stability of the gas.(42) Itis recommended that the dew point ofSF6 be kept below -25

(43) (originalequipment manufacturers should beconsulted for specific requirements per-taining to their products). HoneywellsAccuDri dewpoint of -65C meets allcurrent specifications.

SF6 Arc By-products

Sulfur hexafluoride may be partially dis-sociated in electric arcs or at very hightemperatures, absorbing large amountsof electrical energy and heat in theprocess. After an arcing event, the dis-sociation reverses and most of the SF6fragments recombine; however, thisrecombination may not be complete.Some of the fragments produced duringarcing can react with air, moisture,and materials of construction in the

vicinity of the arc. The extent of decom-position depends on the duration andintensity of the discharge; other factorsare air and moisture levels inside theequipment. The decomposition prod-ucts may be gaseous or solid, and essen-tially consist of lower sulfur fluorides,metal fluorides, and their secondaryreaction products.(44) Generally, S2F2and SF4 are present but rapidly reactwith moisture to yeld hydrogen fluo-ride (HF) and stable oxyfluorides suchas SOF2 and SO2F2,

(45) (See Diagram4).

All of the by-products must be con-sidered to be hazardous. The HF pro-

duced may react rapidly with the unitwalls to form metal fluorides and can beextremely irritating and dangerouswhen inhaled or in contact with skin oreyes. (See Safety Precautions section).While only slight decomposition of SF6occurs in a corona inception voltage, noSF6 chemical changes can be observedin a period of one year, although tracesof fluoride and sulfide might be foundon the copper electrodes of a test cell.

Chemical Properties

Stability of Sulfur Hexafluoridein Various Materials of Construction

Decomposition, % Per Year

Material 200C 250C

Aluminum 0.006Copper 0.18 1.4

Silicon Steel 0.005 0.01a

Mild Steel 0.2 ca 2

aestimated

NOTE: Chemical equations left unbalanced for simplicity.

Diagram 3

Diagram 4

S F6 S F4 S O F2 + HFH 2Oe-

S O F4 S O2F2 + HFO 2 H 2O

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Treatment of Arced SF6The lower fluorides of sulfur and manyother by-products of arced SF6 can beneutralized by the use of soda lime (50-50 mixture of NaOH+CaO). They maybe also removed by absorption on acti-vated alumina (specially dried Al2O3)or molecular sieves. Adsorbents such asmolecular sieves also help to maintainlow moisture levels inside the equip-ment, where a dry operating environ-ment helps prevent SF6 decompositionand contributes to extended equipmentlife. The preferred granule size for sodalime or alumina is 8 to 12 mesh; how-ever, other sizes may be used.

It is not possible to predetermine the

amount of decomposition productsthat could form, or the amount of adsor-bent required to control these products.As a suggested rule of thumb, use aweight of adsorbent corresponding to10% of the weight of the gas. Locate theadsorbent to provide maximum contactwith the gas. If both liquid and gaseousSF6 are present, place the adsorbent sothat it contacts both liquid and gaseousphases. If this is not possible, place it inthe liquid phase.

Removal of acidic and gaseous con-taminants from arced SF6 is bestaccomplished through the use of filterscontaining the adsorbing componentslisted above. The SF6 may be circulatedthrough a filter attached to the equip-

ment itself, or may be transferred to agas cart for processing. Any freshly acti-vated adsorbent filters or scrubbersshould be cooled to ambient tempera-tures before introducing SF6, to avoiduncontrollable exothermic reactions.Gas carts with filters are available from anumber of manufacturers in sizes to suitmost applications, and their use for on-site recycling of SF6 is highly recom-mended.

The SF6 gas from a faulted breaker,once treated to remove acidic by-products and moisture, should becarefully analyzed prior to reuse toensure that the material meets unitspecifications. Repeated recycle of thegas through treatment towers may berequired to reduce contamination toacceptable levels.

Honeywell Gas Analysis Service

Honeywell maintains a fully equippedanalytical laboratory at its SF6 manufac-turing facility in Metropolis, Illinois.Technologically advanced methodologysuch as computerized GasChromatography is used to analyzesamples for the most commonly foundimpurities, including Air, CarbonDioxide, CF4, SO2, SO2F2, SOF2, andCOS. Honeywells sensitive gaschromatographs can detect and quan-tify these contaminants in the partsper million (ppm) range. In additionto the standard analysis, the GasAnalysis Lab can determine and quan-tify Oxygen/Nitrogen percentages, oilcontent, and moisture content in asample. Maintaining low levels ofthese contaminants is critical to thecontinued high performance of gas-insulated equipment.

Gas carts with filters are available in a range ofsizes for on-site recycling of SF6.Photo courtest: DILO Company 17

Chem

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Safety Precautions

In addition to reviewing the informa-tion presented here, anyone handlingor using AccuDri SF6 should reviewthe Material Safety Data Sheet(MSDS) for this product.

Sulfur hexafluoride has beendescribed as a physiologically inertgas.(46) Albino rats have been exposedto a mixture of 80% SF6 and 20% oxy-gen (this mixture approximates theaverage concentration of oxygen in air)for periods of 16-24 hours. The ratsshowed no sign of intoxication, irrita-tion or any other toxic effect, either dur-ing exposure or afterward. AllHoneywell AccuDri sulfur hexafluo-ride is certified non-toxic before packag-ing and shipping.

Because AccuDri SF6 is non-poison-ous, colorless and odorless, it is not eas-ily detected by humans. Since SF6 isheavier than air, it tends to collect inlow areas. Thus, it can displace air andcause suffocation. Caution must beobserved in areas where SF6 is used.Good ventilation must be available at alltimes in buildings, breaker tanks, andother enclosed areas where pockets ofSF6 could accumulate. Proper tankentry procedures(47) should be followedprior to entry into any confined spacethat has recently contained SF6.The procedures should include amethod of determining whether suffi-cient oxygen is available for breathing;continuous monitoring of oxygen levelsin enclosed spaces may be desirable.

Decomposition Products of SF6At very high temperatures, or in thepresence of an electric arc, SF6 can beslowly decomposed. Decompositionproducts include lower fluorides of sul-fur, which are hydrolyzable, yieldingSO2 and HE. (See Chemical Propertiessection).

Solid SF6 Arc By-products

These solid fluorides are usually presentas a fine dust or powder on the walls andin the bottom of the unit. Theyreact rapidly with moisture to form amixture of metal oxides and metal fluo-rides. It is necessary to have a source ofwater, such as an emergency showerand/or eyewash equipment, availablefor immediate flushing of exposed skinor eyes, should contamination occur.

Effect of Moisture on SF6In the presence of an electrical dis-charge, moisture will react with SF6 orits decomposition products to form avariety of compounds. Many of thesecompounds, as well as the original decom-position products, are toxic and corro-sive. (See Chemical Properties section).

Safety Measures

If a unit is known or suspected to beleaking SF6 which might containdecomposition products, follow theprocedure outlined below:

Evacuate all personnel from the area.

Ventilate the area thoroughly.

Remove the gas and store in suitablecontainers (a gas cart equipped withfilters or scrubbers is highly recom-mended).

Lower fluorides of sulfur formedby the decomposition of SF6 maybe removed as described in the Chemical Properties - Treatment of Arced SF6 (page 17).

Safety Precautions

WARNING:

DO NOT open a unit filled withSF6 that has experienced arcingwithout taking adequate safetymeasures before attempting inspec-tion or repair. H2S and SO2 bothhave a characteristic acrid, rottenegg odor or taste and can easily bedetected. However, personnelshould NEVER test for possibleunit arcing by smelling the gas, sincethese and other impurities that maybe present are irritating and toxic.

CAUTION:

If personnel must remain near dam-aged units or if any odor is present,provide air masks or rescue breath-ing apparatus (preferably self-con-tained oxygen masks) for maximumsafety. Do not continue to inhaleany gas which has an odor.

18

Safe

ty P

reca

utio

ns

A S T M Honey well Method of Analysis

Water Content, max. Dew Point, C -62(a) -65(b) ASTM Method D-2029:Test for water vapor content ofelectrical insulating gases(c)

by measurement of dewpoint by capacitance method.

Hydrolyzable fluorides, expressed as 0.3 0.3 ASTM Method D-2284:Acidity, expressed as HF,according to ASTM test foracidity of sulfur hexafluoride.

Air expressed as N2, max. wt.% 0.05 0.04 ASTM Method D-2685:Amount of nitrogen, oxygen orany mixtures, expressed asnitrogen - determined by gaschromatographic analysis.

Carbon tetrafluoride, max. wt.% 0.05 0.04 ASTM Method D-2685:Determined by gaschromatographic analysis.

Assay, min. wt.% 99.8 99.9 Assay: Assay shall be bydifference after impuritycontent has been determined.

a Corresponds to a water content of 0.99 ppm by volume at 1.01135 x 105 Pa.

b Honeywell AccuDri SF6, a high purity, low moisture dielectric grade of sulfur hexafluoride, has amaximum dew point of -65C, which corresponds to a water content of less than 0.65 ppm by weightor 5.3 ppm by volume.

c Liquid Phase.

Specification

Sulfur hexafluoride is shipped in steel cylinders as a liquefied gas.

Product exceeds ASTM Specification D 2472-92, as determined by the methods given.

19

Specification

SF6 Cylinders

AccuDri SF6 is packaged in DOT3AA 2015 cylinders. The outercylinder diameter is approximately9 inches (23 cm) and the height ofthe cylinder, including the valve andprotective cap, is approximately57 inches (145 cm). The cylindervolume is a minimum of 2640 cubicinches, which corresponds to a watercapacity of 95 pounds (43 kg). Thenominal tare weight of the cylinder

is 110-117 pounds (50-52 kg) and itis filled with 115 pounds (52 kg) ofliquefied SF6.

Honeywell also provides smallercylinders containing 20 pounds (9kg) of SF6 as well as bulk shipmentsin tube trailers of approximately30,000 pounds (13,608 kg) capacity.For intermediate scale use, manifold-ed racks of 12 DOT 3AA cylindersare also available.

SF6 Valves

The SF6 cylinder is equipped with ahand wheel valve having a single out-let at a right angle to the brass body.The outlet is protected with a plasticplug, and the valve is fitted with afrangible safety disc which will burstin the pressure range of 3000-3600psi (211-253) kg/cm2). For domesticshipments, the outlet corresponds toCGA No. 590 and has a 0.965-inch 14NGO-LH-INT thread.

Packaging

AccuDri S F6 Packages: Specifications and Pertinent Data

SF6 Quantity 20 lb (9 kg) 115 lb (52 kg) 30,000 lb

DOT Designation 3AA 2015 3AA 2015 3T 29003T 27003T 2400

Cylinder Diameter 6.75 in (17.2 cm) 9.0 in (23 cm)Cylinder Height 29 in (59.7 cm) 57 in (145 cm)Cylinder Volume (nominal) 646 in3 (10.6 L) 2640 in3 (43.3L)Cylinder Tare Weight 33-37 lb (15-17 kg) 110-114 lb (50-52 kg)Trailer DimensionsLength 40 ftWidth 8 ftHeight 9ft

SF6 Transportation Inform ation

Chemical Formula SF6CAS Registry Number 2551-62-4US DOT Hazard Class Class 2.2 Nonflammable GasUN Number 1080Transport Canada Classification 2.2

20

Pack

agin

g

SF6 Cylinders

Certain auxiliary equipment may beneeded to transfer SF6 from the cylinderto the equipment. A list of recom-mended equipment follows:

Valve Adapter

Use a bullet-shaped coupling nipple,typically as used with a CGA connectionNo. 590, having a 0.965-inch, lefthand,external, male thread, 14 threads perinch.

Pressure Gauge

A pressure gauge of brass or stainlesssteel internal construction with a rangeof 0-500 psig (0-35 kg/cm2) will be sat-isfactory for most purposes. The gaugeshould be dry and free of oil.

Manual Control Valve

A brass or steel needle valve is satisfac-tory. If the valve is to be connecteddirectly to the cylinder, specify a CGA590 connection.

Pressure Regulator

A one-stage regulator, with a CGAconnection No. 590, is satisfactory.However, a two-stage regulator, with aCGA connection No. 590 or equiva-lent, can also be used. Sulfur hexaflu-oride is not a corrosive material and nospecial metals are required. The deliv-ery pressure range may vary with themodel chosen. Select the model tomeet your particular requirements. Incertain cases a heated regulator may berequired to prevent freezing of SF6 inthe gas delivery system.

Transfer Hoses and Lines

Gas Phase: Braided hydraulic hose of1/2 diameter or less is recommendedfor gas transfer. If high purity operationis required or where the avoidance ofmoisture contamination is a major fac-tor, electropolished stainless steel tubingshould be used.

Liquid Phase: Braided hydraulic hoseof various sizes (typically 3/4) is satis-factory for liquid SF6 transfer. The rec-ommended pressure rating is 5000 psigor greater.

Auxiliary Equipment

CAUTION:

When transferring liquid SF6,DO NOT trap liquid in any linewithout a relief device. Many thou-sands of pounds per square inch pres-sure can develop, creating the poten-tial for hydrostatic rupture of the line.

The main valve on 115-lb. cylinders is a CGA No. 590 and is fitted with afrangible safety disc.

21

Auxiliary E

quipment

Cylinder StorageStore cylinders in an appropriate loca-tion, out of direct sunlight, and at tem-peratures no greater than 125F (50C).Cylinders should be attached to a rackor support so they will not fall. Thevalve cap should always be in placewhen the cylinder is not in use or whenit is being moved.

Cylinder HandlingSF6 cylinders, when full, weigh approx-imately 230 pounds (104 kg). The useof a hand truck with pneumatic tires isrecommended, particularly if the cylin-der is to be transported by hand overrough terrain. In addition, the follow-ing warnings apply:

Filling Equipment With SF6Equipment should be clean, dry, andevacuated prior to filling to avoid con-tamination of the gas with moisture and

air. SF6 is introduced directly from thecylinder in the vapor phase, filling untilthe desired pressure is reached. Afterfilling, care must be taken to test theequipment for leaks that could cause gasloss and contamination. Portable SF6leak detectors for this purpose are avail-able from a number of manufacturers.Once the equipment is filled with SF6,the best equipment performance will beattained by maintaining the gas in acompletely dry condition.

Filling gas-insulated equipment canbe a slow process, due to the refrigera-tion effect of the evaporating liquid inthe cylinder. To decrease the timerequired to empty a cylinder, warm thecylinder or, since SF6 is packaged as aliquefied gas, withdraw it in the liquidstate:

1. Warming the CylinderWarming the cylinder during transferminimizes the refrigeration effectcaused by the evaporation of SF6 whileallowing its transfer in the vapor(gaseous) phase. Submerging the cylin-der to approximately one-third to one-half its height in warm (125F) water ina 55-gallon drum is an inexpensive andconvenient method. Alternatively, spe-cially-designed cylinder heating blan-kets may be used for this purpose. If aheating blanket is used, it must be con-trolled so that the temperature insidethe cylinder does not rise above 100F.Heat should be removed if the cylindervalve is to be closed or if the flow of SF6gas is to be stopped. The critical tem-perature of SF6 is approximately 114F,and at temperatures greater than thecritical temperature, cylinder pressurerises significantly. Heating tapes are notrecommended as they are difficult tocontrol and may cause local hot spots.

Since SF6 is packaged as a liquefiedgas, it is possible to withdraw it as a liq-uid to decrease the time required toempty a cylinder. There are two waysto accomplish this:

2. Withdrawing Liquid SF6a. Cylinders With Dip TubesThese cylinders allow the customer todischarge SF6 as liquid without theneed to invert the cylinder. Thesecylinders are specially stencilled to pre-vent confusing them with other SF6cylinders.

b. Cylinders Without Dip TubesCylinders not having dip tubes may beinverted so that the liquid will be at thevalve end of the cylinder. This may beaccomplished with a hand cart or witha commercially available cylinderinverter.

Storage & Handling

CAUTION:

While Honeywells SF6 meets orexceeds specifications, there is thepotential that the cylinder itself maycontain particulate metal oxides,commonly found in gas cylinders.For this reason, it is highly recom-mended that a 1 micron filter, madeof fiberglass or sintered metal, be usedto protect the equipment being filledany time SF6 is discharged from thecylinder as a liquid.

WARNING:

With any liquid phase transfer of SF6,great care should be taken to ensurethat the SF6 is completely vaporizedbefore it enters the equipment to pre-vent over-pressurization.

NOTE:

Do not store cylinders on dampground or in contact with moisture.

WARNING:

Do not move cylinders withoutthe valve cap in place.

Do not tamper with the valve orsafety device.

Do not add gas to the cylinder. Do not drop cylinders. Do not allow cylinders to slam

together. Do not allow cylinders to be

chilled below -29C (-20F). Do not apply direct heat to cylin-

ders. Do not allow cylinder temperature

to exceed 50C (125F).

22

Stor

age

& H

andl

ing

1. Moissan, H.; LeBeau, P. C., R. Acad. Sci.,130, 984-988, 1900.

2. Charlton, E. E.; Cooper, F. S. Gen. Electr.Rev., 40, 438, 1937.

3. Ryan, H. M.; Jones, G. R. SF6 Switchgear,Peter Peregrinus, New York, 1989.

4. Guaglione, G. P. Meier, H. G. A NewLine of Dead Tank SF6 High Voltage CircuitBreakers, IEEE Trans., PAS-89, No. 8, 2024,1970

5. Leeds, W. M.; Friedrich, R. E. RecentDevelopments in the Use of SF6 for PowerCircuit Breakers, Proc. Am. Power Conf.XXIV, 833, 1962.

6. Van Sickle, R. C. et al, 500 kV SF6 CBAdaptable to Many EHV Levels, ElectricalWorld, May 17, 1965.

7. Van Sickle, R. C. et al, A Modular SF6Circuit Breaker Design for EHV,Westinghouse Engineer, March, 1965.

8. Yeckly, R. N.; Cromer, C. F. New SF6EHV Circuit Breakers for 550 kV and 765kV, IEEE Trans., PAS-89, No. 8, 2615,1970.

9. Underground Power Lines - High CostSolution to Scenic Pollution, MachineDesign, April 1, 1970.

10. Pederson, B. O.; Doepken, H. C. Jr.;Bolin, P. C. Development of Compressed-Gas Insulated Transmission Lines, IEEETrans., PAS-90, No. 6, 2631, 1971.

11. Reason, J., Sr. Ed. Gas-InsulatedSubstations, Electrical World, 207, No. 9, 28-40, 9/1993.

12. Evans, F. E.; Mani, G. Sulfur Fluorides,Kirk-Othmer Encyclopedia of ChemicalTechnology, 4th ed., 11, 428, 1994.

13. Shugg, W. T. Handbook of Electrical andElectronic Insulating Materials, Van NostrandReinhold, New York, 1986.a Former name of Honeywell

14. Clark, F. M., Insulating Materials forDesign and Engineering Practice, John Wileyand Sons, New York, 1962.

15. Busk, R. S.; Jackson, R. B. Use of SF6 inthe Magnesium Industry, Proc. Int. Magn.Soc., June 1980.

16. Pennington, J. N. Mag Die CastingGrowing Again in North America, ModernMetals, January 1989.

17. MacNeal, J. R.; Rack, T. P.; Corns, R. R.U.S. Patent 4,959,101, September 25, 1990.

18. Niemeyer, L. E.; McCormick, R. A.Some Results of Multiple-Tracer DiffusionExperiments at Cincinnati, J. Air PollutionControl Assoc., 18, 403, 1968.

19. Wijaya, H.; Hughes, H. M. A ProposedProcedure for Qualifying Halogen LeakDetectors, presenterd at the InternationalConference on CFC and Halon Alternatives,Baltimore, MD, 1990.

20. Glass, I. I.; Hall, J. G. J. Chem Phys., 27,1223, 1957.

21. Champion, R. L. Gaseous Dielectrics 6,Proc. of Sixth Intl. Symp., 1-8, 1990.

22. Jackson, R. B. Properties of SulfurHexafluoride, presented at the PA Elec.Assoc. Spring Meeting, Skytop, PA, 1969.

23. Earwicker, G. A.; Fear, E. J. P., Chem. Ind.(London), 903, 1954.

24. Mannion, J. P.; Philosophos, J. A.; andRobinson, M. B. Arc Stability ofElectronegative Gases, IEEE Trans., EI-2, 1(1967).

25. Vanderkooi, N., The Solubility of SF6,C3F8, and N2 in Transformer Oil, PaperNo. CP 59-258 presented at Am. Inst. ofElec. Eng., February 1959.

26. Asthon, J. T., Chem. Soc., (A), 1793-6,1968.

27. Mears, W. H., Allied Chemical Corp.,a

private communications, 1970.

28. Rosenthal, E. Sulfur Hexafluoride -Thermodynamic Properties, SpecialtyChemicals Division, Allied Chemical Corp.,a

Unpublished Study, 1968.

29. Mears, W. H.; Rosenthal, E.; Sinka, J. V.Physical Properties and Virial Coefficients ofSulfur Hexafluoride, J. Phys. Chem., 73,2254, 1969.

30. AlliedSignal Material Safety Data Sheetfor Sulfur Hexafluoride, Nov. 1993.

31. American Conference of GovernmentalIndustrial Hygienists, Threshold Limit Valuesfor Chemical Substances and Physical Agentsand Biological Exposure Indices, Cincinnati,OH, 1994-1995.

32. Klemm, W.; Henkel, P. Z. Anorg. Allgem.Chem., 207, 73-86, 1932.

33. Handbook of Compressed Gases, 3rd Ed.,Compressed Gas Association, Inc., New York,1991.

34. Design Inst. for Phys. Prop. Data,University Park, PA. American Institute ofChemical Engineers (AIChE), 1993.

35. Eucken, A.; Schroder, E. Z. Phys. Chem.,B41, 307, 1938.

36. Unpublished Data, Allied ChemicalCorp.,a Morristown, New Jersey.

37. Trautz, Ehrman, J. Prakt, Chem., 142, 79,1935.

38. Makarevich, L. A.; Sokolova, E. S.;Sorena, G. A. Zh. Fiz. Khim., 42, 22, 1968.

39. JANAF Thermochemical Tables NSRDS-NBS 37 2nd ed., June, 1971.

40. Moissan, H.; Lebeau, P., Ann. Chim.Phys., 26, 145, 1902.

References

23

References

41. Mastroianni, M. J.; Mears, W. H., SF6Thermal Stability with Selected Metals,Specialty Chemicals Division, AlliedChemical Corporation,a Unpublished Study,1978.

42. Mastroianni, M. J.; Jackson, R. B. SF6Gas Analysis Service, presented at the DobleEngineering Client Conf., 1980.

43. Ushio, I.; Shinnura, I.; Tominga, S.Practical Problems of SF6 Gas CircuitBreakers, IEEE Trans., PAS-89, No. 5, 2166,1971.

44. Baker, A.; Dethlefsen, R.; Dodds, J.;Oswalt, N.; Vouros, P. Study of Arc By-Products in Gas-Insulated Equipment, EPRIEL-1646, 1980.

45. Boudene, C. et al Identification andStudy of Some Properties of CompoundsResulting from the Decomposition of SF6Under the Effect of Electrical Arcing inCircuit-Breakers, Rev. Gen. de lElectr., 45-78,June 1974.

46. Lester, D.; Greenberg, L. A. The Toxicityof Sulfur Hexafluoride, Arch. of Ind. Hyg.Occup. Med., 2, 348, 1950.

47. Occupational Safety and HealthAdministration (OSHA) 29 CFR 1910.146,Permit-Required Confined Spaces.

a Former name of Honeywell

Textbooks and General References(Uncited)

1) Ryan, H. M. and Jones, G. R. SF6Switchgear, published by Peter Peregrinus onbehalf of the Institution of ElectricalEngineers, London, 1989.

A monograph which discusses SF6 technolo-gy relating to transmissioin, distribution, andutility switchgear; regulations, testing andinstrumentation; design and characteristics.

2) Shugg, W. T. Handbook of Electrical andElectronic Insulating Materials. published byVan Nostrand Reinhold, New York, 1986.

Text describes a wide variety of electrical insu-lating materials; see especially Chapter 15 per-taining to dielectric gases.

3) Handbook of Compressed Gases.Third Edition, published by the CompressedGas Association (CGA), Van NostrandReinhold, New York, 1990.

A general reference relating to the propertiesand safe handling of industrial gases, contain-ers and equipment, regulations, with mono-graphs relating to each type of gas.

4) Evans, F. E., and Mani, G. SulfurFluorides, Kirk-Othmer Encyclopedia ofChemical Technology, 4th ed., 11, 428, 1994.

An introductory reference with extensive bib-liography and further references. See also pasteditions and supplements:

Elbeck, R. E.; Mears, W. H. SulfurFluorides, Kirk-Othmer, 3rd ed., 10, 779,1980.

Brown, J. A. Fluorine Compounds, Inorganic,Kirk-Othmer, 2nd ed., 9, 664, 1966.

Mears, W. H. Sulfur Hexafluoride, Kirk-Othmer, Second Supp., 2, 793, 1960.

Miller, H. C. Fluorine Compounds,Inorganic, Kirk-Othmer, 1st ed., 6, 732,1951.

5) McMaster, R. C., Ed. NondestructiveTesting Handbook, Vol. 1: Leak Testing, pub-lished by the American Society forNondestructive Testing, Inc., 1982.

Discusses theory, practice and application ofleak-testing technology, both vacuum andpressure-related. Contains sections regardingsafety and halogen tracer gases, among manyother topics.

References

24

Ref

eren

ces

Linear Measure1 in = 2.54 cm1 ft = 30.45 cm1 m = 39.37 in

Temperature, TCelsius to KelvinCelsius to FahrenheitFahrenheit to CelsiusRankine to Kelvin

Pressure, T1 atm = 14.6960 psia1 atm = 29.921 in Hg1 atm = 760 mm Hg1 atm = 1.01325 bar1 atm = 101.325 Pa

Density1 lb/ft3 = 0.133680 lb/gal1 lb/ft3 = 0.016018 g/cc1 lb/ft3 = 16.018463 kg/m3 or g/L

Specific Heat (Entropy, s)1 Btu/lb R = 1 cal/g K1 Btu/lb R = 4.184j/g K1 j/g K = 0.2390 Btu/lb R1 j/g K = 0.2390 cal/g K

Thermal Conductivity, k1 Btu/ft hr R = 4.1338 x 10-3 cal/cm sec K1 Btu/ft hr R = 0.017296 joule/com sec K1 Btu/ft hr R = 0.017296 watt/cm sec K1 Btu/ft hr R = 1.7296 watt/cm sec K

Viscosity, 1 poise= 1 dyne sec/cm2 = 1 g/cm sec1 poise= 0.1 newton sec/m2

1 poise= 0.01 centipoise1 poise= 2.0885 x 10-3 lbf sec/ft

2

1 poise= 0.01 kg/m sec

Mass1 lb = 454 g1 oz = 28.35 g1 kg = 2.2046 lb

TK = TC + 273.15

TF = (1.8 x TC) + 32

TC = (TF - 32)/1.8

TK = TR/1.8

Volume, V1 in3 = 16.39 mL or cc1 in3 = 0.0043 gal1 in3 = 5.787 x 10-4 ft3

1 in3 = 0.0163871 Liter1 cc = 1 mL = 0.06101 in3

1 gal= 3.785 L

Specific Volume1 ft3/lb = 7.48055 gal/lb1 ft3/lb = 62.4280 cc/g1 ft3/lb = 0.624280 m3/kg or L/g

Enthalpy, H1 Btu/lb = 0.55556 cal/g1 Btu/lb = 2.3244 j/b1 j/g = 0.43021 Btu/lb1 j/g = 0.2390 cal/g

Coefficient of Heat Transfer1 Btu/ft2 hr F = 1.3562 x 10-4 cal/cm2 sec C1 Btu/ft2 hr F = 5.6783 x 10-4 watt/cm2 C1 Btu/ft2 hr F = 4.8823 k cal/cm2 hr C1 Btu/ft2 hr F = 5.6783 watt/m2 sec K

These conversions factors have been adapted fromASHRAE Guide and Data Book, Am. Soc. ofHeating, Refrigeration and Air-Conditioning Eng., Inc.,New York, 1972.

ConversionsConversion Factors and Formulas

for Frequently Used Units

SF6 OrderingTo place an order, or to obtain pricing andavailability information from anywherewithin the continental United States,call our Customer Service System at

Telephone: 800-522-8001

618-524-6343

Technical Service/SalesFor additional information or TechnicalService on all phases of Sulfur Hexafluorideuse, contact:

Honeywell

Industrial Fluorines

101 Columbia Turnpike

P.O. Box 1053

Morristown, NJ 07962

Telephone: 800-622-5002

973-455-5233

Fax: 973-455-6141

All statements, information, and data given herein are believed to be accurate and reliable but are presentedwithout guaranty, warranty or responsibility of any kind, express or implied. Statements or suggestions con-cerning possible use of our products are made without representation or warranty that any such use is freeof patent infringement, and are not recommendations to infringe any patent. The user should not assumethat all safety measures are indicated or that other measures may not be required. Please note that all usersof SF6 are responsible for adherence to applicable instructions and regulations and for the observance of cur-rent laws.

2000 Honeywell 4-00 KAE Printed in the U.S.A.

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