Transcription

Corrugated Metal Gaskets for Superior Reliability

Garlock Sealing TechnologiesA century of excellence in fluidsealing technologyThe success of nearly every manufacturing andprocess facility in the world depends on the reliableoperation of countless pumps, valves, motors andpiping systems.Those vital pieces of equipment operate longer and more efficiently when running with GarlockSealing Technologies gaskets, packings, hydrauliccomponents, mechanical seals, oil seals, bearing protectors, and expansion joints.For more than a century, Garlock SealingTechnologies has designed, tested and manufacturedthe most innovative and high quality fluid sealingproducts available. As a result, industrial customersaround the globe have come to rely on Garlock products as a key to their profitability and success.Garlock Metallic Gaskets, a division of GarlockSealing Technologies, manufactures spiral wound,metal clad, and solid metal gaskets at its facility inHouston, Texas. This facility is registered to ISO9002.gaskets have a successful track record, showing costreductions through improved heat exchanger reliabilityand overall increased equipment productivity.This unique construction, utilizing corrugated metaland compressible sealing elements, provides for excellent performance in thermal cycling applications. Thisconfiguration provides a rigid gasket that easily sealsagainst flange seating surface imperfections.The GET , GRAPHONIC and TEPHONIC gaskets handle a wide variety of applications. This premium gasket has passed various industry standard firetests (API 607 4th ed. modified; FITT) and is suitablefor 150# and 300# ANSI sized piping and vessel applications.This catalog is provided for customer informationand convenience. However, Garlock Metallic Gasketsapplications engineers and customer service personnel are also on hand to assist you with your applicationrequirements and technical questions. Please give us acall at 800-972-7638. Weʼre here to serve you.In recent years, Garlock Metallic Gaskets hasintroduced some of the industryʼs most innovativeproduction methods and products. For example,CONTROLLED DENSITY winding for spiral woundgaskets provides a high tightness level with reducedgasket stress. The TANDEM SEAL combineschemical resistance and fire safety in a single gasket,while the Garlock EDGE gasket eliminates the costlyand potentially catastrophic problem of radial buckling.Joining this innovative family at the Metallic Gasket Division are the Garlock GRAPHONICSeries of Gaskets. This series of gaskets providesa full range of performance, designed to seal in themost severe and the most common applications.The GET , GRAPHONIC and TEPHONIC gaskets will save money and increase margins ofsafety. The new emission laws and the need tomake your plant run as efficiently as possible, makethe GRAPHONIC Series of Gaskets The RIGHTGASKET for your applications.Corrugated gasket metal technology has been aproven provider of sealing solutions for tough applications. The GET , GRAPHONIC and TEPHONIC CONTROLLED DENSITY, EDGE, GRAPHONIC,FLEXSEAL are registered trademarks of Garlock Inc.TEPHONIC, TANDEM SEAL, STABL-LOCK and GETare trademarks of Garlock Inc.

ContentsIntroduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2GET Gasket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3GRAPHONIC Gasket . . . . . . . . . . . . . . . . . . . . . . . . . . 4TEPHONIC Gasket . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Selection of Metals. . . . . . . . . . . . . . . . . . . . . . . . . . . 6Chemical Resistance of FlexibleGraphite and ePTFE . . . . . . . . . . . . . . . . . . . . . . . . . . 7Flange Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Definition of Gasket Stress . . . . . . . . . . . . . . . . . . . . 9Effective Gasket Seating Width. . . . . . . . . . . . . . . . . 10Gasket Factors “M” and “Y” . . . . . . . . . . . . . . . . . . . 11Test Results - OverviewROTT Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13Gasket Constants – Crush Test . . . . . . . . . . . . . . . . . . 14Gasket Leak Rate T3 vs Gasket Stress. . . . . . . . . . . . 15Gasket Stress vs Mass Leakage . . . . . . . . . . . . . . . . . 15Mass Leak Rate to VolumetricLeak Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Fire Integrity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Performance Comparison Load Charts . . . . . . . . . . 18Performance Comparison Unload Charts . . . . . . . . 19Gasket Constants. . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Glossary of Terms . . . . . . . . . . . . . . . . . . . . . . . . 21-25AppendixPVRC Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-29PVRC Method Notations . . . . . . . . . . . . . . . . . . . . 30, 31PVRC Flow Chart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Gasket Dimensions for Standard Flanges . . . . . . . . . . 33Heat Exchanger Gaskets . . . . . . . . . . . . . . . . . . . . . . . 34Heat Exchanger Gasket Shapes . . . . . . . . . . . . . . . . . 35Bolt Torque Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Application Data Form . . . . . . . . . . . . . . . . . . . . . . . . . 371

IntroductionThe selection of gaskets has become more criticalbecause of a number of factors: Standard FlangePipes and joints are now included in the pressurevessel codesTighter rules for emission controlAggressive effort to lower costs by reducing productloss and increasing margins of safetyThe international demand for standards forevaluating asbestos-free gasketsBecause of the tighter standards of emission controland restrictions on the use of gaskets containing asbestos,Garlock is committed to continuous development of bettersealing systems for bolted gasket flanges. Our impressivenew GRAPHONIC Series of Gaskets provides superior performance over other gaskets.GRAPHONIC SeriesAdvantagesThe GRAPHONIC * Series of Gaskets saves money andincreases margins of safety by: Better resistance against both chemicalattack and high temperatures Reducing product loss through leakage in pipeand heat exchanger flanges Eliminating monitoring due to excessive fugitiveemission levels Fewer industrial accidents caused by suddengasket failure Preventing costs associated with productionloss through plant shutdown and environmentalclean-up costs*Patent numbers 5,421,594 and 6,092,811WARNING:Properties/applications shown throughout this brochure are typical. Your specific application should not be under taken without independent study and evaluation for suitability.For specific application recommendations consult Garlock. Failure to select the propersealing products could result in property damage and/or serious personal injury.Performance data published in this brochure has been developed from fieldtesting, customer field reports and/or in-house testing.While the utmost care has been used in compiling this brochure, we assume no responsibility for errors. Specifications subject to change without notice. This edition cancels allprevious issues. Subject to change without notice.2Heat Exchanger

GET GasketAdvantagesGraphite and ePTFE Combination Chemical resistance and fire safetysimultaneouslyThe tightest seal of the GRAPHONIC Series ofGaskets (under 500 F/260 C).ConstructionWith or without metal ringsFigure 1:GETTM Gasketwithout Metal RingsCorrugated Metal Core Minimizes extrusionsRedirects compressible sealing element andblocks leak pathsAdds strength and rigidityIncreases sealability under low bolt loadsActively assists in thermal cycling applicationsBenefits Can be used in a wide variety of applicationsIs forgiving on worn and corroded flange surfacesPassed fire tests, API 607, 4 ed., modified andFITTʼs testsSeals under a wide range of loadsFigure 2:GETTM Gasketwith Outer MetalRingFigure 3:GETTM Gasketwith Inner Metal RingFigure 4:SpecificationsGETTM Gasketwith Outer and InnerMetal RingsCorrugated metal encapsulated with bondedflexible graphite and ePTFENominal thickness:1/8'' (3.2 mm)Graphite layers:2 layers, each flexible graphiteePTFE ID seal:Expanded Teflon envelope on ID of gasketMetal inset:Nominal thickness 0.024'' (0.6 mm) austeniticstainless steel with corrugations(Other types of metal are available)Gasket dimensions:Per ASME B 16.21Continuous operating temperature:Minimum:-350 F (-210 C)Max. in steam:600 F (314 C)Pressure, max.:2000 psig (140 bar)P x T, max.:1/8" thickness:300,000 (10,250)†Material:Note: When approaching maximum temperatures, consult the Garlock MetallicGasket Engineering Dept. at 1-800-972-7638 or 1-281-459-7200.† P x T max. psig x F (bar x C)Teflon is a registered trademark of DuPont.3

GRAPHONIC GasketAdvantagesFlexible Graphite Accommodates a wide range of temperaturesInherently resilientChemically resistantExcellent aging characteristicsIs forgiving on pitted or corroded flange surfacesConstructionWith or without metal ringsFigure 1:GRAPHONIC Gasket without MetalRingsCorrugated Metal Core Minimizes extrusionsRedirects compressible sealing element into the leak pathsAdds strength and rigidityIncreases sealability under low bolt loadsActively assist in thermal cycling applicationsBenefits Can be used in a wide variety of applicationsExcels in thermal cycling conditionsIncreases heat exchanger reliabilityPasses fire tests, API and FITTs testsIs forgiving on worn and corroded flange surfacesSeals under a wide range of loadsSpecificationsFigure 2:GRAPHONIC Gasket with OuterMetal RingFigure 3:GRAPHONIC Gasket with InnerMetal RingFigure 4:GRAPHONIC Gasket with Outerand Inner MetalRingsCorrugated metal encapsulated withbonded flexible graphiteNominal thickness:1/16'' (1.6 mm) and 1/8'' (3.2 mm)Graphite layers:2 layers, each flexible graphiteMetal inset:Nominal thickness 0.024'' (0.6 mm)austenitic stainless steel with corrugations(Other types of metal are available)Gasket dimensions:Per ASME B 16.21Continuous operating temperature:Minimum:-400 F (-240 C)Max. in steam:1200 F (650 C)Pressure, max.:2000 psig (140 bar)P x T, max.:1/16" thickness:700,000 (25,000)†1/8" thickness:400,000 (13,500)†Material:* Maximum temperatures of 975 F (525 C) can be allowed for flexible graphite with oxidation inhibitors.† P x T max. psig x F (bar x C)Note: When approaching maximum temperatures, consult the Garlock Metallic Gasket Engineering Dept. at 1-800-972-7638 or 1-281-459-7200.4

TEPHONIC GasketAdvantagesePTFE Compressible Sealing Element Chemically inertCreates an extremely tight sealA soft and deformable sealConstructionWith or without metal ringsFigure 1:TEPHONICTM Gasketwithout Metal RingsCorrugated Metal Core Minimizes extrusionsRedirects compressible sealing element andblocks leak pathsAdds strength and rigidityIncreases sealability under low bolt loadsActively assist in thermal cycling applicationsFigure 2:TEPHONICTM Gasketwith Outer MetalRingBenefits Offers superior chemical resistance (withcom patible metal core)Capable of sealing with low bolt loadsCan be used in a wide variety of applicationsIs forgiving on worn and corroded flangesurfacesFigure 3:TEPHONICTMGasket with InnerMetal RingFigure 4:TEPHONICTM Gasketwith Outer and InnerMetal RingsSpecificationsCorrugated metal encapsulated with bonded ePTFE1/8" (3.2 mm)2 layers, each ePTFENominal thickness 0.024" (0.6 mm) austeniticstainless steel with corrugations(Other types of metal are available)Gasket dimensions:Per ASME B 16.21Continuous operating temperature:Minimum:-350 F (-210 C)Max. in steam:500 F (260 C)Pressure, max.:2000 psig (140 bar)P x T, max.1/8" thickness:250,000 (8,500)†Material:Nominal thickness:ePTFE:Metal inset:† P x T max. psig x F (bar x C)Note: When approaching maximum temperatures, consult the Garlock Metallic Gasket Engineering Dept. at1-800-972-7638 or 1-281-459-7200.WARNING:Properties/applications shown throughout this brochure are typical. Your specific application should not be under taken without independent study and evaluation for suitability.For specific application recommendations consult Garlock. Failure to select the propersealing products could result in property damage and/or serious personal injury.Performance data published in this brochure has been developed from field testing, customer field reports and/or in-house testing.While the utmost care has been used in compiling this brochure, we assume no responsibility for errors. Specifications subject to change without notice. This edition cancels allprevious issues. Subject to change without notice.5

Selection of MetalsThe chemical resistance for the GRAPHONIC Series of Gaskets will be governed by their materials ofconstruction.The metal core of the GRAPHONIC Series ofGaskets can be selected from most types of sheetmetal. The selection is generally based on chemicalresistance, heat resistance and cost. The most popularmetals for the GRAPHONIC Series of Gaskets include: Mild steel HASTELLOY C 276† Stainless steel 304 MONEL 400‡ Stainless steel 316 INCONEL 625* INCONEL 600* INCOLOY 825*TemperatureBesides its effects upon the mechanical propertiesof the gasket, the temperature of the corrosive agentwill have a marked influence upon the rate of attack.Forms of Corrosion Nickel 200The selection of a metal to be used in a gasketthat is suitably resistant to corrosive media or to hightemperature involves many considerations. Garlock recommends that designers contact the manufacturers ofalloyed material, who conduct laboratory corrosive testsand in-plant corrosion testing.Concentration of CorrosiveAgentsDilute solutions are not necessarily less corrosivethan those of full strength, and the reverse is often thecase. Probably the most familiar example of this is theaction of sulfuric acid on iron; concentrations over 90%acid may be handled by iron without much difficulty, butbelow this concentration, the rate of attack will increaserapidly with an increase in dilution.General corrosionGalvanic corrosionConcentration cell or crevice corrosionChemical pittingIntergranular corrosionEffects of stress on corrosion– Corrosion fatigue– Stress corrosion crackingCorrosive Environments *†‡Atmospheric corrosionCorrosion by water, acidsCorrosion by alkalies, salts, fluorineCorrosion by chlorines and hydrogenCorrosion by chloridesINCONEL and INCOLOY are registered trademarks ofInco Alloys International, Inc.HASTELLOY C is a registered trademark of HaynesInternational.MONEL is a registered trademark of International Nickel.Purity of Corrosive AgentsPurity, in this instance, means the absence of contaminating amounts of other corrosive compounds.For example, the corrosive attack by compounds thatare derivatives of an acid: in the pure state these compounds may be relatively inert, but if contaminated byany carry-over of free acid they must be handled morecarefully.Chemical Resistance ofFlexible6

Acetic acid Acetone Acrylic acid ethyl ester Air ( 550 C)Aluminum (molten) Ammonia Ammonium hydroxide solution Aqua regia Boric acidBromine (dry) Bromine (room temperature) Calcium chloride (molten)Carbon dioxide ( 510 C) Carbon monoxide Carbon tetrachloride Chlorides (aqueous) Chlorine (dry) Chlorine dioxide ChloroformChromates ( 20%) (aqueous) Chromic acid ( 10%, 95 C) Citric acid Copper (molten) Diethyl ether Dimethyl sulfoxide Dioxane Ethanol Ethanolamine Ethylene Ethylene dichlorideEthylene glycol Formaldehyde Fluorine ( 150 C)Freon GasolineHeat transfer oilHydrochloric acidHydrofluoric acidHydrofluoric ( 60% atroom temperature)Hydrogen chlorideHydrogen fluorideHydrogen peroxide ( 85%)Iodine (room temperature)Iron (molten)Isopropyl alcoholMethanolMethyl ethyl ketoneMotor oilsNitrates (aqueous)Nitric acid ( 20%)Nitric acidNitric acid ( 20% atroom temperature)NitrobenzeneOleum (fuming sulfuric acid)Oxygen (260 C)PhenolPhosphates (aqueous)Phosphoric acidPotash (molten)Potassium ( 350 C) (molten)Potassium chlorate (molten)Potassium hydrogen sulfate GraphiteePTFEGraphiteePTFECompletely Resistant Moderately Resistant Not Resistant GraphiteePTFEChemical Resistance ofFlexible Graphite andePTFE(molten)Potassium hydroxide solution( 400 C)Potassium nitrate (molten)PropaneSiliconesSilver (molten)Soda (molten)Sodium ( 350 C) (molten)Sodium hydroxide solution( 400 C)Sodium peroxide (molten)Steam ( 750 C)Stearic acidSulfurSulfur dioxideSulfuric acid (93-96% at roomtemperature)Sulfuric acid (70%-100%,up to 100 C)Sulfuric acid ( 96%,over 100 C)Sulfur trioxideZinc (molten) WARNING:Properties/applications shown throughout this brochure are typical. Your specific application should not be under taken without independent study and evaluation for suitability.For specific application recommendations consult Garlock. Failure to select the propersealing products could result in property damage and/or serious personal injury.Performance data published in this brochure has been developed from fieldtesting, customer field reports and/or in-house testing.While the utmost care has been used in compiling this brochure, we assume no responsibility for errors. Specifications subject to change without notice. This edition cancels allprevious issues. Subject to change without notice.7

Flange RotationWhat is Flange Rotation?A common problem in the pressure vessel and pipingworld is the phenomenon called flange rotation. It is usuallyencountered under bolt tightening with a raised face flange.The outer edges of a raised face flange are pulled towardseach other when the bolts are tightened, and relieved towardsthe inside of the vessel or pipe. See illustration.How Much Flange Rotation?Petrochemical engineers who must cope with rotation saythat it can greatly increase the difficulties of sealing a joint.Some even say that rotations as small as 0.10 degrees canmake a tight seal almost impossible. This is quite a bit stifferthan the preliminary proposed ASME limit of a maximum 0.30degrees for integral type flanges or 0.20 degrees for loosetype flanges.Flange Rotation and theCodeFlange rotation is known to be important but there areno simple ways to estimate it. Section Vlll of the ASME Code,Table UA-49.2 Effective Gasket Width acknowledges rotationby introducing an effective width for a gasket, which is equalto or less than half the width of the gasket or joint-contactsurface seating width. This allowance leakage assumes thatat least half of the gasket will have been unloaded by rotation.But flanges often rotate more or less than this. Proper installation and bolt tightening procedures greatly reduce the chancefor flange rotation.Excessive Bolt LoadOne of the causes of flange rotation is excessive boltload. In fact, too much bolt load can rotate raised face flangesenough to open a leak path. The threat of rotation, therefore,can place an upper limit on planned or specific clamping force.WARNING:8Properties/applications shown throughout this brochure are typical. Your specific application should not be under taken without independent study and evaluation for suitability.For specific application recommendations consult Garlock. Failure to select the propersealing products could result in property damage and/or serious personal injury.Performance data published in this brochure has been developed from fieldtesting, customer field reports and/or in-house testing.While the utmost care has been used in compiling this brochure, we assume no responsibility for errors. Specifications subject to change without notice. This edition cancels allprevious issues. Subject to change without notice.

Definition of GasketStressGasket stress is the contact pressure between the flangeand gasket bearing surface. The definition of stress is the magnitude of the force applied to the area of the gasket on whichthe force acts. In a flange it is created by the applied forcefrom the tension in the bolts clamping the flanges.Gasket Contact Area Symbolsand UnitsGo OD ID N Ag The smaller of Gasket OD or flangesealing surface OD (inch)Outside diameter of sealing surface,gasket or flange face (inch)Inside diameter of sealing surface,gasket (inch)Width of full gasket contact sealingused to determine the basic gasketseating width (inch)Full gasket contact area based on thecontact width (in2)For initial seating, use the full contact area of the gasket. When the joint is pressurized, the PVRC introduces aneffective (roughly half) width (N) that is the same as (b) in theASME Code, Section VIII Table 2-5.2 to allow for flange rotation.1. Compute the full surface sealing area of thegasket, Ag (in2)Ag 0.7854*(OD2-ID2) or3.14*(Go-N)N Ag in2How to Find Gasket Stress atAssembly (Sya) Symbols andUnitsCArAb 0.0833; conversion Factor, Torque (ft-in to ft-lbs) Root cross-section area of a bolt (in 2) Ar* number of bolts, (n)Bolt Load1. Compute, the nominal bolt preload in each bolt at assembly(lbs.). For example, if preload is specified by torque (T; ft./lbs.)thenFp 12*T/*K*D lbs2. Compute, if preload is specified by the actual total crosssectional area of bolts at root of thread or section of leastdiameter under stress, (Ar), then multiply Ar by the bolt stress,Sa.Fp Ar*Sa lbsYou can convert the final nominal preload to nominal Torque:T K*D*Fp/12 Ft/lbs3. Compute the total, nominal clamping force on the gasket atassembly (FGA; lbs.), n number of bolts. Ab Ar* number ofbolts (n)FGA n*Fp lbs (or)FBA Ab*Sa lbsGasket Stress4. Compute the initial gasket stress (Sya)Sya FGA/Ag psiAfter the assembly, you then calculate the pressure load onthe joint, estimate how much the pressure load will partiallyrelieve the joint and compute the net clamping force on thejoint after the system has been pressurized. For reference, goto the pages titled PVRC Method.Sg The stress on the sealing area of thegasket (psi)Sya The PVRC uses this symbol for the design assembly seating stress or joint contact unit seating load(psi)Fp Bolt preload in each bolt at assembly (lbs)FGA Total nominal clamping force on the gasketat assembly (lbs)Sa bolt stress at ambient temperature (psi)K Nut factor (dimensionless)D nominal diameter of bolt (inch)12 Divide Torque by 12 to convert fromft-in to ft-lb9

Effective Gasket Seating WidthN Width of gasketW Width of contact area(raised face or serrations)T Thickness of gasketb0 Basic seating width of gasketb1 Effective seating width of gasketb1 b0 if b0 1/4";b1 ( b0)/2 if b0 1/4"* Where serrations do not exceed 1/64" in depthand 1/32" width spacing, choose 1b or 1d.WARNING:10Properties/applications shown throughout this brochure are typical. Your specific application should not be under taken without independent study and evaluation for suitability.For specific application recommendations consult Garlock. Failure to select the propersealing products could result in property damage and/or serious personal injury.Performance data published in this brochure has been developed from field testing, customer field reports and/or in-house testing.While the utmost care has been used in compiling this brochure, we assume no responsibility for errors. Specifications subject to change without notice. This edition cancels allprevious issues. Subject to change without notice.

Gasket Factors“M” & “Y”“M” and “Y” data are to be used for flange designs onlyas specified in the ASME Boiler and Pressure Vessel CodeDivision 1, Section VIII, Appendix 2. They are not meant to beused as gasket seating stress values in actual service. Ourbolt torque tables give that information and should be used assuch.“M” - Maintenance FactorA factor that provides the additional preload needed in theflange fasteners to maintain the compressive load on a gasketafter internal pressure is applied to a joint.M Where:W Total Fastener force (lb. or N)A Inside area of gasket (in.2 or mm2)2P Test pressure (psig or N/mm2)A Gasket area (in.2 or mm2)1“Y” - Minimum Design Seating Stressthe minimum compressive stress in pounds per square inch(or bar) on the contact area of the gasket that is required toprovide a seal at an internal pressure of 2 psig (0.14 bar).(W - A2P)/A1PY W/A1GasketFactor"M"Min. DesignSeating Stress"Y" (psi)Stainless steel or MONEL 3.0010,000Garlock CONTROLLED DENSITY flexible graphite-filled spiral woundStainless steel or MONEL 3.007,500Garlock EDGE Stainless steel or MONEL 2.005,0002.00 (1/16")9.00 (1/8")2.002,000 (1/16")3,000 (1/8")900Gasket DesignGasket MaterialSpiral wound metal,non-asbestos filledGarlock GRAPHONIC Stainless steel and Flexible GraphiteLiquid service:Corrugated metal,non-asbestosorCorrugated metal-jacketed,non-asbestos filledSoft aluminumSoft copper or brassIron or soft steelMONEL or 4%-6% chromeStainless Corrugated metalSoft aluminumSoft copper or brassIron or soft steelMONEL or 4%-6% chromeStainless Flat metal-jacketed,non-asbestos filledSoft aluminumSoft copper or brassIron or soft steelMONEL 4%-6% chromeStainless ,0009,000Grooved metalSoft aluminumSoft copper or brassIron or soft steelMONEL or 4%-6% chromeStainless 0Solid flat metalSoft aluminumSoft copper or brassIron or soft steelMONEL or 4%-6% chromeStainless ,000Ring jointIron or soft steelMONEL or 4%-6% chromeStainless steel5.506.006.5018,00021,80026,000This table lists many commonly used gasket materials and contact facings with suggested design values of "M" and "Y" that generallyhave proven satisfactory in actual service when using effective gasket seating width B1 described in the formula on page 10. The designvalues and other details given in this table are suggested only and are not mandatory.MONEL is a registered trademark ofInternational Nickel.11

Test Results OverviewRoom Temperature TightnessTest (ROTT)Garlock Sealing Technologies certifies the results of twoor more tests on 4-7/8" I.D. by 5-7/8" O.D. GRAPHONIC series of gaskets with helium as media, and conducted inaccordance with the Pressure Vessel Research Council RoomTemperature Tightness Test (ROTT) procedure. Standard testcriteria is represented below.Requirement GbTypical:aGsS100 S1,000 (1.2)315 0.36 1.855 1.6533,787Notes:1. The constants Gb, a and Gs shall be determined by theROTT test procedure (See Reference 1).2. S100 and S1000 are stresses (psi) respectively representing the values Gb(100)a and Gb(1000)a.SummaryRoom Temperature Tightness tests (ROTT) were performed on gasket specimens at the École PolytechniqueGasket Test Facility. The tests show excellent tightness. Ona range of loading and unloading stress levels, they are thetightest flexible graphite gaskets tested to date. By comparison to laminated graphite sheet, the initial leak rate of the gasket averaged about l00 times less at an initial gasket stress(Sg) of 8,000 psi.Constants, Gb, a, and Gs: These are the constants usedin formulas that give a design bolt load having the samemeanings as the larger of Wm1 or Wm2 of the ASME Code.Gb, a and Gs are obtained by interpretation of leakage testdata as plots of gasket stress (Sg) vs the tightness parameter,Tp on log-log paper. The values of Gb and Gs are determinedby the intercepts of the loading and unloading lines with theTp 1.Gb, a: What the gasket seating load should be, becauseGb and a are associated with the seating load sequence (PartA data) of a gasket test. Gb represents the loading of the gasket (Intercept of the loading curve on the gasket stress Axis) atTp 1. The slope of the line is represented by a.Gs: Gs is associated with the operating part of a gaskettest, known as Part B, where the gasket is unloaded andreloaded as leakage is measured. Gs Unloading intercept(intercept of the unloading curve on the gasket stress axis) atTp 1.Tightness Parameter, Tp: The investigators discoveredthat test data could be summarized by use of a dimensionless tightness parameter. It is represented by Tp, expressed interms of mass leak rate.12Tp is the pressure (in atmospheres) required to cause ahelium leak of 1 mg/sec for a 150 mm (5.9 in.) OD gasket ina joint. A tightness parameter of 100 would mean that it takesan internal pressure of 1,470 psi (10.1 MPa) to create a totalleak rate of about 1 mg/sec from a 6'' OD gasket (152 mm)gasket. A 100 times less leak rate of 0.01 mg/sec at 1,470 psiwould mean a tenfold increase in the tightness parameter to1,000 Tp. Tp is proportional to pressure and inversely pro-portional to the square root of the leak rate. A higher value of Tpindicates a tighter joint.Gb(Tp)a: The value of Gb(Tp)a compares seating proper-ties among gaskets when comparisons are made at representative values of Tp, such as 100 and 1,000. Such comparisonsshow the combined effect of Gb and a on the seating performance of a gasket. The new gasket constants will eventually replace the present ASME Code M and Y factors. Thenew constants, Gb, a and Gs help define the behavior of thegasket under all possible stress conditions. The only designguidance emerging from this work is the concept of “tightness”levels. Once the designer has learned how to convert Gb, a,Gs and selected tightness level to specific stress targets, hecan design better flanges. The installer of gaskets will find thenew gasket constants useful, since they genuinely define gasket behavior.

ROTT Test (cont’d)Gasket Constants -Low Stress Interpretation NPS 4" Corrugated GRAPHONICGasket- LowStyleGASKET CONSTANTSStress InterpretationM&P NPS 4" CORRUGATED GRAPHONIC GASKET STYLE100000Filled Markers : 400 psiUnfilled Markers : 8

gasket stress. The TANDEM SEAL combines chemical resistance and fire safety in a single gasket, while the Garlock EDGE gasket eliminates the costly and potentially catastrophic problem of radial buck-ling. Joining this innovative family at the Metallic Gasket Division are the Garlock GRAPHONI