_PTC_25-1998.pdf

Special AddendatoASME PTC 25-1994Pressure Relief DevicesThis 1998 Special Addenda to ASME PTC 25-1994,Pressure Relief Devices,is issued to reviseportions of this Code as it pertains to the performance testing of rupture disk devices.It reflects thecurrent industry-accepted terms and performance characteristics of these devices as used in ASMEaccreditation programs.The American National Standards Institute approved this document onMarch19,1998.Replace the pages listed.The pages not listed are the reverse sides of the listed pages and containno changes.PageLocationChangevi,vi进ContentsUpdated to reflect Addenda7-102.7Definition for flow resistance added2.8(1)Definitions for f and G revised(2)Definitions for HL Bc and Lex deleted(3)Definitions for Kc.p and KE-Fredesignated as Kac and KcD,respectively(4)Definitions for KpipeBC Kpipe B KRi,Kg-D,LB-D,PA-B,PB.CandPcDadded18Fig.4Revised19Fig.5RevisedFig 6Revised324.9Title revised4.9.1First paragraph revised33Fig.9Revised344.9.4(1)Title revised(2)Subparagraphs(a)and(b)revised(3)Subsubparagraphs(d)(1),(d)(2),and(d)(6)through(d)(9)revised4.9.5(1)Title revised(2)Subparagraphs(a)and(b)revised(3)Subsubparagraphs(d)(1),(d)(2),and(d)(5)through(d)(8)revised375.5.7(1)Title revised(2)Revised in its entirety47,48Form 5.5.7(1)Subtitle revised(2)Step(6)revised(3)Steps(13)through(17)revised(4)Steps(34)and(35)revised(5)Step(37)deletedCOPYRIGHT American Society of Mechanical EngineersLicensed by Information Handling ServicesCONTENTSForeward试Committee Roster.0Introduction11Object and Scope12Definitions and Description of Terms.3Part I-Flow Capacity Testing3Guiding Principles.114Instruments and Methods of Measurements155Computations of Results35Test Summary Report Form.49Part ll-In-Service and Bench Testing3Guiding Principles.554Instruments and Methods of Measurements57Computations of Results66Test Summary Report Form5Figures1Typical Curtain Areas of Pressure Relief Valves.Recommended Arrangements for Testing Devices With Atmospheric BackPressure-Flow-Meter Test Arrangement.173Recommended Arrangements for Testing Devices With Atmospheric BackPressure-Weighed-Condensate Test Arrangement.174Recommended Arrangements for Testing Devices With Atmospheric BackPressure-Weighed-Water Test Arrangement.185Recommended Discharge Arrangements for Testing Devices With Super-imposed Back Pressure196Recommended Discharge Arrangements for Testing Devices With Built-upBack Pressure197Recommended Internal Contours of Fittings,Adapter,and ReducersBetween Test Vessel and Test Device.208Recommended Arrangement for Testing Non-Reclosing Pressure ReliefDevices in Combination With Pressure Relief Valves.219Recommended Arrangements for Testing Rupture Disk Device FlowResistance3310Recommended Arrangement for Testing Valves With Compressible Fluids601Recommended Arrangement for Testing Valves With Incompressible Fluids611Pilot Operated Pressure Relief Valve Field Test Accessory.62viiCOPYRIGHTAmerican Society of Mechanical EngineersLicensed by Information Handling ServicesForms5.5.1 Pressure Relief Device Tested With Steam and Water-Observed Dataand Computed Results-Weighed-Water Method.385.5.2Pressure Relief Device Tested With Steam-Observed Data and Com-puted Results-Flow-Meter Method.*4395.5.3Pressure Relief Device Tested With Liquids-Observed Data andComputed Results-Flow-Meter Method.415.5.4 Pressure Relief Device Tested With Air or Gas-Observed Data andComputed Results-Flow-Meter Method.425.5.5Pressure Relief Device Tested With Air or Gas-Observed Data andComputed Results-Weighed-Water Method.445.5.6Pressure Relief Device Tested With Fuel Gas-Observed Data and Com-puted Results-Flow-Meter Method.455.5.7 Rupture Disk Device Tested With Air-Observed Data and ComputedResults-Flow Resistance.476.5.1Pressure and Relief Valve Performance Test Report-Steam.516.5.2Pressure and Relief Valve Performance Test Report-Liquids and Water526.5.3Pressure and Relief Valve Performance Test Report-Air,Gas,orFuel Gas.536.5.4Rupture Disk Device Performance Test Report-Air,Gas,or Fuel Gas.54Appendices1SI Metric)Units and Conversion Factors.671Examples of Determining Flow Rate Uncertainties.69AReferences.74TablesIAS Metric Units67IBCommonly Used Conversion Factors68ll-1 Table of Uncertainty Parameters71vi进COPYRIGHT American Society of Mechanical EngineersLicensed by Information Handling ServicesPRESSURE RELIEF DEVICESASME PTC 25-1994built-up back pressure-pressure existing at themarked relieving capacity-see rated relieving ca-outlet of a pressure relief device caused by the flowpacitythrough that particular device into a discharge sys-measured relieving capacity-the relieving capac-temity of a pressure relief device measured at the flow-burst pressure-the value of inlet static pressurerating pressure,expressed in gravimetric or volu-at which a rupture disk device functionsmetric unitschatter-abnormal rapid reciprocating motion ofopening pressure-the value of increasing inletthe movable parts of a pressure relief valve in whichstatic pressure of a pressure relief valve at whichthe disk contacts the seatthere is a measurable lift,or at which the dischargeclosing pressure-the value of decreasing inletbecomes continuous as determined by seeing,feel-static pressure at which the valve disk reestablishesing,or hearingcontact with the seat or at which lift becomes zerooverpressure-a pressure increase over the setcoefficient of discharge-the ratio of the measuredpressure of a pressure relief valve,usually expressedrelieving capacity to the theoretical relieving ca-as a percentage of set pressurepacitypopping pressure-the value of increasing inletcold differential test pressure-the inlet static pres-static pressure at which the disk moves in the open-sure at which a pressure relief valve is adjusted toing direction at a faster rate as compared with cor-open on the test stand.This test pressure includesresponding movement at higher or lower pressurescorrections for service conditions of superimposedprimary pressure-the pressure at the inlet in aback pressure and/or temperaturepressure relief deviceconstant back pressure-a superimposed backrated relieving capacity-that portion of the meas-pressure which is constant with timeured relieving capacity permitted by the applicablecracking pressure-see opening pressurecode or regulation to be used as a basis for theflow capacity-see measured relieving capacityapplication of a pressure relief devicereference conditions-those conditions of a testflow-rating pressure-the inlet static pressure atwhich the relieving capacity of a pressure relief de-medium which are specified by either an applicablevice is measuredstandard or an agreement between the parties tothe test,which may be used for uniform reportingflow resistance-a dimensionless term(such asof measured flow test resultsused in para.5.5.7)which expresses the number ofvelocity heads lost due to flow through a rupturerelieving pressure-set pressure plus overpressuredisk device(where velocity head is one-half the ve-resealing pressure-the value of decreasing inletlocity squared divided by the acceleration of grav-static pressure at which no further leakage is de-ity)tected after closing.The method of detection maybe a specified water seal on the outlet or otherflutter-abnormal,rapid reciprocating motion ofmeans appropriate for this application.the movable parts of a pressure relief valve in whichthe disk does not contact the seatreseating pressure-see closing pressureleak pressure-see start-to-leak pressureseal-off pressure-see resealing pressuresecondary pressure-the pressure existing in theleak test pressure-the specified inlet static pres-passage between the actual discharge area and thesure at which a quantitative seat leakage test isvalve outlet in a safety,safety relief,or relief valveperformed in accordance with a standard procedureset pressure-the value of increasing inlet staticmarked breaking pressure-the value of pressurepressure at which a pressure relief device displaysmarked on a breaking pin or a shear pin device orone of the operational characteristics as definedits nameplateunder opening pressure,popping pressure,start-to-marked burst pressure-the value of pressureleak pressure,burst pressure,or breaking pressure.marked on the rupture disk device or its nameplate(The applicable operating characteristic for a speor on the tag of the rupture disk and indicates thecific device design is specified by the device man-burst pressure at the coincident disk temperatureufacturer.)marked set pressure-the value or values of pres-simmer-the audible or visible escape of fluid besure marked on a pressure relief devicetween the seat and disk at an inlet static pressureCOPYRIGHTAmerican Society of Mechanical EngineersLicensed by Information Handling ServicesASME PTC 25-1994PRESSURE RELIEF DEVICESbelow the popping pressure and at no measurable/=Valve-disk lift,in.capacity.It applies to safety or safety relief valvesm=Mass flow rate,Ibm/hron compressible-fluid service.o=Volumetric rate at base condition atspecified burst pressure(of a rupture disk device)-the meter,cfmthe value of increasing inlet static pressure,at aq,=Valve capacity at reference inlet tem-specified temperature,at which a rupture disk isperature,cfmdesigned to functiont=Length of test,minstart-to-discharge pressure-see opening pressurev=Specific volume,ft/lbmstart-to-leak pressure-the value of increasing inletw=Mass of water or condensate.Ibm(w)static pressure at which the first bubble occurs whena pressure relief valve is tested by means of air underw=Valve-steam leakage,Ibm/hra specified water seal on the outletwel=Condenser leakage,Ibm/hrsuperimposed back pressure-the static pressurewdr Test-drum drainage,Ibm/hrexisting at the outlet of a pressure relief device atthe time the device is required to operate.It is theC=Valve inlet temperature correctionresult of pressure in the discharge system from otherC=Discharge coefficient,dimensionlesssources.Ctap=Sonic velocity at pressure tap,ft/sectest pressure-see relieving pressureD=Internal diameter of meter run pipe,theoretical relieving capacity-the computed ca-in.pacity expressed in gravimetric or volumetric unitsD=Test rig inside diameter,ftof a theoretically perfect nozzle having a minimumD=Internal diameter of meter run pipe,cross-sectional flow area equal to the actual dis-in.charge area of a pressure relief valve or relief areaE=Pipe roughness,in.of a non-reclosing pressure relief deviceFa=Thermal expansion number,dimen-vapor-tight pressure-see resealing pressuresionlessvariable back pressure-a superimposed backF=Area factor for thermal expansion,Fapressure that will vary with timeG=Mass velocity,Ibm/ft2-secwarn-see simmerG=Specific gravity with respect to dryyield(melt)temperature-the temperature at whichthe fusible material of a fusible plug device becomesMair,sufficiently soft to extrude from its holder and re-MaK=Flow coefficientlieve pressureKo=Trial flow coefficientKpipe Bc=Pipe resistance factor between pres-2.8 DESCRIPTION OF TERMSsure taps B and C without the rupturea=Actual discharge area,in.2disk devicea=Minimum net flow area in.2Kpipe Bp=Pipe resistance factor between pres-am=Meter-bore area,in.2sure taps B and D without the rupturedisk deviceP=Water density.Ibm per cu ftKgi=Individual flow resistanced=Meter-bore diameter,in.d=Meter-bore diameter squared,in.2Ktap=Total resistance factor to pressure tapKAB=Resistance factor between pressured=Minimum holder bore diameter,in.taps A and Bd=Bore diameter,in.Ksc=Resistance factor between pressuredo=Diameter of orifice plate,in.taps B and Cd,=Seat diameter,in.KB-p=Resistance factor between pressuref=Fanning friction factor,dimensionlesstaps B and Dh=Differential pressure at the meter,Kco=Resistance factor between pressureinches of watertaps C and Dk=Ratio of specific heatsLA-B=Length between tap A and B,ft8COPYRIGHT American Society of Mechanical EngineersLicensed by Information Handling Services