ASTM F2836.28800

Designation: F2836 − 18Standard Practice forGasket Constants for Bolted Joint Design1This standard is issued under the fixed designation F2836; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice determines room temperature gasket tight-ness design constants for pressurized bolted flanged connec-tions such as those designed in accordance with the ASMEBoiler and Pressure Vessel Code.1.2 This practice applies mainly to all types of circulargasket products and facings typically used in process or powerplant pressure vessels, heat exchangers, and piping includingsolid metal, jacketed, spiral wound, and sheet-type gaskets. Asan optional extension of this practice, the maximum assemblystress for those gaskets may also be determined by thisprocedure.1.3 Units—The values stated in SI units are to be regardedas the standard, but other units may be included.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASME Standards:2ASME B16.5 Steel Pipe Flanges and Flanged FittingsASME B16.20 Metallic Gaskets for Pipe Flanges—Ring-Joint, Spiral-Wound, and JacketedASME B16.21 Nonmetallic Flat Gaskets for Pipe FlangesASME Boiler and Pressure Vessel Code Section VIII Divi-sion 1, Appendix 23. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 ASME Class 150, n—refers to the dimensions andpressure rating of Class 150 of standard flanges in ASMEStandard B16.5.3.1.2 flange rotation, n—rotation of the flange face surfacesso that the gasket outside diameter (OD) is compressed morethan the gasket inside diameter (ID) when the bolts aretightened to compress the gasket.3.1.3 gasket constants, n—if a log-log plot of gasket stressversus tightness (Sg-Tp graph) is made and an analysis of thedata is performed in accord with this practice, then (see Fig. 1):(1) The value, Gb, is the stress intercept (at Tp =1)associated with a regression of the Part A tightness data.(2) The value, a, is the slope associated with the PartAdataand combined values of Gb and a describe the seating orloading characteristic of a gasket and give an indication of thegasket capacity to develop tightness upon initial seating.(3) The value, Gs, is the stress intercept (at Tp =1)associated with Part B tightness data and values of Gs representthe gasket potential to maintain tightness after pressurizationand during operation and indicate the gasket’s sensitivity tounloading excursions or susceptibility to crushing.(4) The combined effect of constants Gb and a is bestrepresented by the value of STp= Gb × Tpacalculated fortypical values of Tp such as 100, 1000, or 10 000 where STptells us what the minimum gasket stress shall be to maintain aspecified level of minimum tightness.(5) The value, Gs, is an independent constant that repre-sents operation and it characterizes the gasket tightness sensi-tivity to operating bolt load reductions that occur duringpressurization or gasket creep or thermal disturbances.3.1.4 gasket contact area, Ag, n—initial (nominal) area ofthe gasket that is considered to be loaded by the flangesurfaces.3.1.5 gasket stress, Sg, n—gasket stress is the ratio of theapplied load by the fixture over the gasket contact area, Ag.3.1.6 gasket types, n—for this practice, it is convenient todifferentiate gasket styles as:(1) Sheet gasket materials typically from 0.5 to 5 mm thickcommonly in use and in which circular gasket samples are cut,1This practice is under the jurisdiction ofASTM Committee F03 on Gaskets andis the direct responsibility of Subcommittee F03.20 on Mechanical Test Methods.Current edition approved Aug. 1, 2018. Published November 2018. DOI:10.1520/F2836-18.2Available from American Society of Mechanical Engineers (ASME), ASMEInternational Headquarters, Two Park Ave., New York, NY 10016-5990, http://www.asme.org.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1Copyright by ASTM Int l (all rights reserved); Mon Jan 14 09:10:22 EST 2019Downloaded/printed byTexas Tech Univ (Texas Tech Univ) pursuant to License Agreement. No further reproductions authorized.such as compressed or beater-added fiber-reinforced, flexiblegraphite and polytetrafluoroethylene (PTFE)-based sheet prod-ucts;(2) Preformed gaskets with a flat seal element that contactsthe raised faced flange surfaces as intended by themanufacturer, such as solid flat metal gaskets with and withoutnubbin, spiral wound gaskets, flat metal jacketed with nonme-tallic filler gasket, and so on;(3) Preformed gaskets with one or several cambered sealelements in which the nominal contact area is not obvious suchas solid metal oval rings, hollow metal rings, elastomerO-rings, corrugated gaskets, and so on; and(4) Formed-in-place sealing products such as expandedPTFE rope and so on.3.1.7 known volumes, n—volume of the internal high-pressure chamber or volume of the external low-pressure leakcollection chamber used, respectively, in pressure decay orpressure rise methods to measure gasket specimen leaks.3.1.8 leakage rate, Lrm, n—total rate of internal fluidleakage around or through the gasket expressed as milligramsper second, Lrm, reduced to standard conditions.3.1.9 maximum assembly stress, Sc, n—maximum gasketstress found to achieve a minimum acceptable tightness whenthe gasket is unloaded to the minimum allowed stress level, S1,of the procedure (see Section 13).3.1.10 maximum and minimum tightness, Tpmax andTpmin, n—highest and lowest level of tightness, Tp, achieved,respectively, during Part A and Part B of the test procedure.3.1.11 nominal pipe size, NPS, “d,”, n—refers to the nomi-nal pipe size in which “d” is the nominal size in inches, forexample, NPS 12 refers to standard 305-mm pipe.3.1.12 pressure decay method, n—this method measures, atregular intervals of time, the helium pressure decay of theinternal high-pressure chamber of known volume upstream ofthe gasket.3.1.13 pressure rise method, n—this method measures, atregular intervals of time, the pressure rise of an externallow-pressure leak collection chamber of known volume built atthe external periphery of the gasket.3.1.14 range of gasket behavior possibilities, n—variousgasket behaviors ranging from tightness softening to extremetightness hardening are illustrated in Fig. 2(a-f).3.1.15 reference gasket diameter, n—outside gasketdiameter, 150 mm (~5.9 in.).3.1.16 reference mass leak, Lrm*, n—defined as 1.0 mg/s(0.008 lbm/h) for a gasket of 150 mm outside diameter.3.1.17 tightness hardening, n—refers to behavior in whichlarge increases of gasket stress (Sg) cause small or no increaseof tightness parameter (Tp).3.1.17.1 Discussion—There is typically an increasing slopein log-log Sg-Tp plots resulting in a reverse “knee” in the PartA curve [see Fig. 2(d-e)].3.1.18 tightness parameter, Tp, n—dimensionless sealabilitymeasure that is proportional to pressure and inversely propor-tional to the square root of leak rate.3.1.18.1 Discussion—More precisely, Tp is the pressurerelative to the atmospheric pressure required to cause a heliumleak of 1 mg/s for a 150 mm OD gasket. Since this is about thesame as the OD of an NPS 4 joint, the pressure to cause a leakof 1 mg/s of that joint is its tightness. (Tightness is a measureof the gasket’s ability to control the leak rate of the joint for aFIG. 1 Typical Representation of Gasket Constant Gb, a, and GsF2836 − 182Copyright by ASTM Int l (all rights reserved); Mon Jan 14 09:10:22 EST 2019Downloaded/printed byTexas Tech Univ (Texas Tech Univ) pursuant to License Agreement. No further reproductions authorized.given load. With all other variables equal, a tighter gasketrequires higher internal pressure to push the same rate of fluidthrough the joint. In other words, the tighter the seal, smallerthe leak).Tp 5PP*SLrm*LrmD0.5(1)where:P = fluid pressure (MPa),P* = reference pressure (0.1013 MPa), (14.69 psi),Lrm = mass leak rate (mg/s) of ROTT gasket specimens asdefined per 8.1, andLrm* = unit mass leak rate equal to1 mg/s for a 150 mm ODgasket in a joint.3.1.18.2 Discussion—The Tp equation can be rewritten asfollows:Tp 5P0.1013S1LrmD0.5~For P in MPa! (2)Tp 5P14.69S1LrmD0.5~For P in psi! (3)3.1.19 tightness softening, n—refers to behavior in whichsmall increases of gasket stress (Sg) cause large increases oftightness parameter (Tp).3.1.19.1 Discussion—There is typically a decreasing slopein log-log Sg-Tp plots resulting in a “knee” in the Part A curve(see Fig. 2a).3.2 Acronyms:3.2.1 AARH—arithmetic average roughness height in meters(m)3.2.2 Ag—nominal contact area of the gasket, mm23.2.3 Ai—pressurized area, mm23.2.4 Dg—gasket deflection, mm3.2.5 Extended LP—extended low-pressure test sequence3.2.6 HP—high-pressure test sequence. Part B of the testingsequenceFIG. 2 Range and Definition of Typical Behaviors from Softening to Extreme HardeningF2836 − 183Copyright by ASTM Int l (all rights reserved); Mon Jan 14 09:10:22 EST 2019Downloaded/printed byTexas Tech Univ (Texas Tech Univ) pursuant to License Agreement. No further reproductions authorized.3.2.7 ID—identification of gasket test specimen, mm3.2.8 LP—low-pressure test sequence. Part A of the testingsequence3.2.9 Lrm—mass leakage rate, mg/s3.2.10 Lrmin—minimum mass leakage rate of the system,mg/s3.2.11 Lrm*—unit mass leak defined as 1.0 mg/s for a 150mm outside gasket diameter3.2.12 NPS—nominal pipe size3.2.13 OD—outside diameter of gasket test specimen, mm3.2.14 P—internal fluid pressure, MPa3.2.15 P*—standard pressure, 0.1013 MPa3.2.16 ROTT—room temperature tightness test procedure3.2.17 RLM—ratio of mass leak rates, Lrm1 and Lrm2,measured at the same step of the ROTT test procedure (seeTables 1 and 2) in two different ROTT tests performed on agasket style3.2.18 S—level of gasket stress defined in Table 3, MPa3.2.19 Sc—the highest gasket stress of the optional extendedLP tests preceding the stress level that resulted in Tpc, MPa3.2.20 Sg—gasket stress calculated from the net appliedload and the nominal area, Ag, MPa3.2.21 slpm—standard litre per minute3.2.22 Ss—gasket stress developed when contact is initiatedwith a compression limiting device, or stop, such as a groovecontaining the gasket, a gage ring, or a stress associated with atightness limit such as Tpmax3.2.23 T—test fixture temperature in the vicinity of thetested gasket3.2.24 Tp—tightness parameter (dimensionless)3.2.25 Tpmax—average of highest two levels of tightnessobtained from each test3.2.26 Tpmin—lowest tightness value achieved during PartB of all HP tests3.2.27 Tpc—first tightness value of the optional extendedLP tests less than Tpmin4. Summary of Practice4.1 This test procedure consists of two parts (see Fig. 1):4.1.1 Part A—At the fluid test pressure, obtain gasket leakrate and deflection measurements for several levels of gasketstress, each stress level being higher than any previouslyTABLE 1 ROTT HP Test Sequence (with P = 6 MPa)Test Step Test Part“S” StressLevelGasketStressType ofMeasurementMPa(1) Leakage(2) Mechanical1 A S1 8 (1+2)2 A S2 20 (1+2)3 A S3 30 (1+2)4 A, B1 S4 40 (1+2)5 B1 S1 8 (1+2)6 A, B1 S5 50 (1+2)7 A, B2 S6 60 (1+2)8B 22 2)9 B2 S1 8 (1+2)10 A, B2 S7 70 (1+2)11 A, B3 S8 80 (1+2)12 B3 S3 30 (2)13 B3 S1 8 (1+2)14 A, B3 S9 90 (1+2)15 A, B4 S10 105 (1+2)16 B4 S4 40 (2)17 B4 S1 8 (1+2)18 A, B4 S11 120 (1+2)19 A S12 140 (1+2)20 A, B5 S13 160 (1+2)21 B5 S5 50 (2)22 B5 S1 8 (1+2)TABLE 2 ROTT LP and Extended LP Test Sequences (with P =2MPa)Test Step Test Part“S” StressLevelGasketStressType ofMeasurementMPa(1) Leakage(2) MechanicalOnlyLP Test Sequence1 A S1 8 (1+2)1a A S2 20 (1+2)2 A S3 30 (1+2)3 A S5 50 (1+2)4 A S7 70 (1+2)5 A S10 105 (1+2)6 A S12 140 (1+2)Extended LP Test Sequence7 A S14 170 (1+2)8 B S1 8 (1+2)9 A S15 190 (1+2)10 B S1 8 (1+2)11 A S16 210 (1+2)12 B S1 8 (1+2)13 A S17 230 (1+2)14 B S1 8 (1+2)15 A S18 250 (1+2)16 B S1 8 (1+2)17 A S19 270 (1+2)18 B S1 8 (1+2)TABLE 3 Nominal Values for Gasket Stress LevelsNOTE 1—Multiply the gasket stress values by Ag to obtain the total loadrequired for a particular gasket.NOTE 2—The nominal “S” load stresses correspond to a low to highrange of typical pipe fitter imposed bolting stresses. For example, S1 istypical of the low gasket stresses resulting from (69 MPa) bolt stresses ona NPS 12ASME/ANSI cl 68 kg joint and S10 is typical of high (414 MPa)bolt stresses on a NPS 12 ASME/ANSI cl 272 kg joint.(1) S Load ValueGasket StressMPaS1 8S2 20S3 30S4 40S5 50S6 60S7 70S8 80S9 90S10 105S11 120S12 140S13 160F2836 − 184Copyright by ASTM Int l (all rights reserved); Mon Jan 14 09:10:22 EST 2019Downloaded/printed byTexas Tech Univ (Texas Tech Univ) pursuant to License Agreement. No further reproductions authorized.applied stress. Part A may be interrupted to perform Part Bsequences (see 4.1.2). Part A provides information on initialloading known as gasket seating and yields the constants Gband a (see 3.1.3).4.1.2 Part B—Obtain gasket leak rate and deflection mea-surements under fluid pressure for five unload-reload stresscycles. Part B is performed by interrupting Part A at fivespecific stress levels as shown in Fig. 1. Part B providesinformation on the operating gasket performance including itssensitivity to load reductions after initial loading. Part B yieldsthe constant Gs (see 3.1.3(5)).5. Significance and Use5.1 This practice determines the room temperature gasketconstants Gb and a for initial seating and Gs for operatingconditions as related to the tightness behavior of pressurizedbolted flanged connections. These constants are used in deter-mining the design bolt load for gasketed bolted joints.5.2 This practice is suitable for all the types of gaskets andfacings as are considered by the ASME Division 1 Code. Thisincludes ASME B16.5 raised facings, nubbin-type facings,O-ring grooves, and a wide variety of gaskets including spiralwound, flat sheet, solid metal, jacketed, and other type