module 7 - gas measurement (v.01)

7/31/2019 Module 7 - Gas Measurement (v.01)

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PRODUCTIONOPERATIONSCOMPETENCYLEARNINGMODULE

Module7:

GasMeasurement

No. #:

Category: Operations Production

Version: 01

Date: February 2009

Initial Writing by: Sardjono

Review by: Kodeco Operations Team

Copyright to: KODECOENERGYCO.,LTD.


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GASMEASUREMENT

ORIFICEMETERMEASUREMENT

Tomeasure volume of vapor/gas or liquid commonly use differentialmeasurement device, orifice

meter.

Definitions:

DifferentialTaps:Formeterusingflangetapsthecenteroftheupstreampressuretapisplacedoneinchfromtheupstreamfaceoftheorificeplate.Thecenterofthedownstreampressuretap isplacedone inch from the downstream face of the orifice plate. Formeters using pipe tap the upstream

pressuretapisplacedtwoandonehalftimestheactualinsidepipediameterfromtheupstreamfaceof

theorificeplateandthedownstreampressuretapisplacedeighttimestheactualinsidepipediameter

fromthedownstreamfaceoftheorificeplate.

DifferentialPressure :Differentialpressure is thedifferencebetween twopressures.Thedifferentialpressureacrossandorificeinametertubeisthedifferencebetweenthepressureattheupstreamtap

before thegaspasses through theorificeand thepressureat thedownstream tapafter ithaspasses

throughtheorifice.

StaticorLinePressure :StaticPressure isusuallymeasuredbyacoiledmetal tubewitha flattenedcrosssection(apressurespring).Thepressureofthegasinthelineisadmittedtoandactsontheinside

of the tubeand theatmosphericpressureactsupon theoutsideof the tube.Therefore thepressure

springmeasures thedifferencebetween thepressure in the line and the atmosphericpressure.The

pressure inthe linemaybegreateror lessthantheatmosphericpressure.Thestaticpressuremaybe

takenfromeithertheupstreamorthedownstreampressuretap.

AbsolutePressure :AbsolutePressure is thepressure above the absolute zero,or aboveaperfectvacuum.Theatmosphericpressure isalwaysexpressedasanabsolutepressure. Ifthepressureofthe

gasinalineisgreaterthantheatmosphericpressure,theatmosphericpressureinpsiaisaddedtothe

gagepressureinpsigtoobtaintheabsolutepressureofthegasintheline.Ifthegagepressureis40psig

(aboveatmosphericpressure)and theatmosphericpressure is14.4psia, theabsolutepressurePf, is

54.4psia.

Tomeasurepressurebelowatmosphericpressurewithgagescalibratedininchesofmercuryvacuum.

Insuchcases it isnecessary toconvert thevacuum from inchesofmercury intopoundspersquare


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inchbymultiplyingbytheconversionfactor0.491;forexample,10inchesofmercuryvacuum=4.91

psig(10x0.491)belowtheabsolutepressureoftheatmosphere.

PressureBase:Thepressurebaseisthepressureatwhichthecubicfootistheunitofmeasurementaccordingtothecontract.Thebasicorificeflowfactorsinthispublicationwerecalculatedforapressure

baseof14.73psia.

AbsoluteTemperature :On theFahrenheit thermometerscale the temperature isexpressed in thedegreesaboveorbelowanarbitraryzero,which is32degreesbelowthefreezingpointofwater.The

absolute zero is 460 degrees below the zero of the Fahrenheit thermometer scale. The absolute

temperatureisthetemperatureabovetheabsolutezeroandisobtainedbyadding460degreestothe

readingof the thermometer. If the readingof theFahrenheit thermometer is60, thecorresponding

absolute temperature is60 added to460 or520 Fabsolute. If the reading is 20 F, theabsolute

temperatureis 20 F+460 For440 Fabsolute.

TemperatureBase :The temperaturebase is the temperatureatwhich thecubic foot is theunitofmeasurementaccordingtothecontact.Theorificeflowfactorsinthispublicationwerecalculatedfora

temperaturebaseconditionof520 Fabsolute(60 F).

SpecificGravity:Therealspecificgravityofagasistheweightofacubicfootofgascomparedtotheweightofa cubic footofdryairunder the samepressureand temperature condition. If the specific

gravityof gasis2.0,itistwiceas heavyasair,orifthespecificgravityofagasis0.6,itissixtenthsas

heavyasair.

Acorrectlyinstalledorificecanprovideanoverallaccuracywithinplusorminus2%.

Theorificemeterconsistsof staticpressureanddifferentialpressure recording gauges connected to

anorificeflangeororificefitting.

Theorificemetertube(meterrun)consistsofupstreamanddownstreamsectionofpipe.

Theorificeplateisheldperpendiculartoflowbyflangesorfitting.Borecircumference,edgesharpness.


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ORIFICEFITTING

(3TypesofOrificeFitting)

StandardOrificeFlange. Requirethatthelineneedtobeshut down and depressurized inordertoinspectorchangetheorificeplate.

Single Chamber Orifice Fitting. This fitting also requires that the line be shut down anddepressurizedinordertoinspectorchangethe orificeplate.

SeniorOrificeFitting.Thisfittingallowstheremovalandinspectionofanorificeplatewhilethelineremainsunderpressure.


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ORIFICEPLATE

Thethicknessoftheorificeplatefor2 inchthrough10 inchnominaldiameterpipeshallbeat

least0.115in.,for12inpipeshallbeatleast0.175in.

Theupstreamfaceoftheorificeplateshallbeflatandperpendiculartotheaxisofthemeter

tube,wheninposition betweentheorificeflangesorintheorificefitting,squareand sharp,

shallnothaveaburredorfeatherededgeandshallbe maintainedinthisconditionatalltimes.

Thethicknessoftheorificeplateattheorificeedgeshallnot exceedthesmallerof:

a.1/50ofthepipediameterD

b.1/8oftheorificediameterd


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BETARATIO (d/D).

Theorificetometertubediameterratio, ,beta=d/D,shouldbelimitedasfollows:

a.Withmetersusingflangetaps,betashallbebetween0.15and0.70

b.Withmetersusingpipetaps,betashallbebetween0.20and0.67

Whenusingtheabovebetaratio,thetoleranceoftheorificecoefficient(Fbfactors)isplusor

minus0.5%forflangetapsandplusorminus0.75%forpipetaps.Betaratiosdownto0.10andupto0.75maybeusedforflangetapsbutthecoefficienttoleranceincreases.Betaratiosdown

to0.10andupto0.70maybeusedforpipetapsbutthecoefficienttoleranceincreases.


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METERTUBE

TheMeterTubemean thestraightupstreampipeof thesamediameter (of lengthAandA)

betweentheorificeflangesorfittings,andthesimilardownstreampipe( lengthBbeyondthe

orifice).

Thesectionofpipetowhichtheorificeflangesareattachedshallcomplywiththefollowing:

a. Seamless pipe , the pipewallsmay be honed,machined, or ground. Thewall finish

shouldsimulatethatofnewsmoothpipe.

b. Grooves,scoring,pits,raisedridgesresultingfromseams,distortioncausedbywelding

whichaffecttheinsidediametershallnotbepermitted.


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STRAIGHTENINGVANES

Thepurposeofstraighteningvanes istoeliminateswirlsandcrosscurrentssetupbythepipe

fittingsandvalvesupstreamofthemetertube.

Theconstructionofvanesthemaximumtransversedimensionaofanypassagethroughthe

vanesshallnotexceedthe insidediameter,Dof thepipe.ThecrosssectionalareaAof

anypassagewithintheassembledvanesshallnotexceed1/16 of the crosssectional area of

thecontainingpipe.ThelengthLofthevanesshallbeatleast10timesthelargesinsideadimension.Allthe vanespassagesisnotnecessarythesame sizebutshouldbesymmetrical.

Thevanestubeshouldbesecurelyweldedtogetherateachtangentpoint.Allweldmetalshould

begroundoffsmoothtopreventdisturbancestotheflowandshouldbesecurelyanchored in

themetertubebyuseof aflangeringorsetscrews.


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GASMEASUREMENT.

Inthemeasurementofgasbyorificemeter,thechartcontainsrecordsofthedifferentialandthestatic

pressure.Fromtheserecordsthequantityofgasmeasuredisdeterminedbytheuseoftheformula:

Qh = C ,inwhich

Qh = rateofflowatbaseconditionincu.Ft.perhr.

C = orificeflowconstant.Itistherateofflowincu.Ft.perhr.atbaseconditionwhenthe

Pressureextension =1.000

hw = differentialininchesofwater.

Pf = staticpressureinpsia.

= pressureextension

C=FbxFrxYxFpbxFtbxFtfxFgxFpvxFmxFaxF

Fb : basicorificeflowfactor

Fr : Reynoldsnumberfactor

Y : expansionfactor

Fpb : pressurebasefactor

Ftf : flowingtemperaturefactor

Fg : specificgravityfactor

Fpv : supercompressibilityfactor

Fm :manometerfactor(formercurytypemetersonly)

Fa : orificethermalexpansionfactor

F : gagelocationfactor


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Note :Fororificeconstantfactor,pleaseseetableonpage1through62oforificeconstant

factor.

BasicOrificeFlowfactor,Fb :Theorifice factor isbasedupon theconditions :pressurebase,Pb=14.73 psia; temperature base, Tb = 60F (520 F absolute); specific gravity, G = 1.000; flowing

temperature,Tf=60F.(520Fabsolute);andunderconditionswheretheReynoldsnumberisinfinite

andexpansionfactorisunity.Thevalueofthisfactordependsonupon:thelocationofdifferentialtaps;

thediameteroftheorifice,d;andupontheinternaldiameterofthepipe,D.

TableofFbareshownonpage2through4forflangetaps.

ReynoldsNumberfactor,Fr:TheReynoldsnumberfactortakes intoaccountthevariationsofthedischarge coefficient of an orifice with Reynolds number. The discharge coefficient of the orifice

decreasesas theReynoldsnumber increasesuntil theReynoldsnumber infinite,when thedischarge

coefficientwillhavethe leastpossiblevalueforthatparticular installation.Dischargecoefficientsvary

considerablywithReynoldsnumber inthemeasurementofviscousliquids;theytendtobecomemore

constant as the viscosity of the liquid decreases, and as the Reynolds number correspondingly

increases.Withinthelimitsofcommercialmeasurementofgases,thedischargecoefficientispractically

constant, varying only slightly with Reynolds number. The variation is sufficiently slight, and the

viscositiesofcommercialgasesaresufficientlyconstant towarrantarbitrarilyusing theaveragevalue

forthegasviscosity incomputingReynoldsnumberfactors.Forallpracticalpurposes,this leavesthe

Reynoldsnumber factorasa functionof theorificeandmeter tubedimensions, the locationof the

differentialpressuretaps,andtherateofflow afunctionofthepressureextension, .

When gaseswith other characteristics are to bemeasured, the ReynoldsNumber factor should be

adjustedasfollows:

(Fc), Fc=5124 ,whereistheabsolutevicosityinlb/ftsec

TablesofbvaluesfromwhichtheReynoldsnumberfactorcanbereadilyobtainedareshownonpage

10through15forflangetaps,andpages32through37forpipetaps.

ExpansionFactor,Y:Whenagasflowsthroughanorifice,thechangeinvelocityandpresureisaccompaniedbyachangein

specificweightandafactormustbeappliedtothecoefficienttoallowforthischange.Theexpansion

factordependsupon the locationof thedifferentialpressure taps, the locationof thestaticpressure

tap,andtheratiooftheorificediametertothediameterofthemetertube.Itisalsodependentupon

theratioofdifferentialpressuretostaticpressureanduponofspecificheatsfortheflowinggas.The


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variationofthefactorisslightandtheratioofspecificheatsforcommercialgasesissufficientlyconstant

towarrantusinganassumedconstantratioofspecificheats.Anassumedratioofspecificheatsofk=1.3wasused incalculating theexpansionfactors inA.G.AReportno.3andthispublication (SingerOrifice

MeterConstantHandbook).Thispermits tabulationof the factorsaccording to thediameter ratio,,

andtheratioofdifferentialpressuretostaticpressure,hw/pf.Inthetablespfisindicatedaspforpf

dependinguponwhetherthestaticpressureisobtainedfromtheupstreamtaporfromthedownstream

tap.

Whengasesbeingmeasuredhaveasignificantlydifferentratioofspecificheats thanthevalueof1.3

assumed inReportNo.31969, thedesirabilityofusingadjustedYvaluescanbedetermined from the

following:

AdjustedvalueofY = )

AdjustedvalueofY =Y )

Tablesofexpansionfactorsareshownonpages17through20forflangetaps.

Pressure Base Factor, Fpb : The orifice factorswere calculated to give gas volumes at a basepressure,pb,of14.73psia. Ifthemeasurementatanyotherbasepressure isdesired,thenapressure

basefactormustbeapplied. Thesefactors,andtheequationrepresentingthefactors,areindicatedon

page16.(Fpb=14.73basepressure,psia.).

TemperatureBaseFactor,F tb :Theorifice factorswere calculated togivegasvolumesatabasetemperature,Tb,of60F.(520F.absolute). Ifmeasurementatanyothertemperaturebaseisdesired,

then a temperature base factormust be applied. These factors, and the equation representing the

factors,areindicatedonpage16.(Ftb= )

Flowing Temperature Factor, Ftf : The orifice factorswere calculated, assuming that the gas isflowingthroughthemetertubeatatemperature,Tf,of60F.(520F.absolute).Ifmeasurementistobe

made at any other flowing temperature, then a flowing temperature factormust be applied. These

factors,andtheequationrepresentingthefactor,areindicatedonpage21.

Ftf =

SpecificGravityfactor,Fg: Theorificefactorswerecalculatedtogivegasvolumesbasedupontheflowinggashavingaspecificgravity,G,of1.000.Forgaseshavingaspecificgravityotherthan1.000a


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specificgravity factormustbeapplied.These factors,and theequation representing the factors,are

indicatedonpage16.Fg =

SupercompressibilityFactor,Fpv:Thesupercompressibilityfactoraccountsfordeviationfromidealgaslaw.Inthebasicflowequations,gasvolumesareassumedtovarywithpressureandtemperature

in accordancewith Boyles andCharles laws ( the ideal gas laws).Actually the volume occupiedby

individualgasesdeviate,byaslightdegree,fromthevolumeswhichtheidealgas laws indicate.The

amountofdeviationisafunctionofthecompositionofthegasandvariesprimarilywithstaticpressure

andtemperature.Theactualdeviationmaybeobtainedbyalaboratorytestconductedonasampleof

thegas,carefullytakenatlineconditionsofpressureandtemperature.

Practicalrelationshipshavebeenestablishedbywhichthisdeviationcanbecalculatedandtabulatedfor

natural gases containing normalmixtures of hydrocarbon components, considering the presence of

smallquantitiedofcarbondioxideandnitrogenandalsorelatingthedeviationtotheheatingvalueof

thegas.

TheA.G.AmanualfortheDeterminationofSupercompressibilityFactorsforNaturalGasshouldbeused

fordeterminationofthefactorFpv.ThevalueofthesupercompressibilityfactorFpvcanbedetermined

fromtablesonpages44through58. Illustrativeexamplesare includedwiththesetablestoclarifythe

methodbywhichthesefactorsareobtained.

ManometerFactor,Fm : Themanometerfactor isusedwith themercurytypedifferentialgagetocorrecttheslighterror inmeasurementcausedbytheweightoftheunbalancedcolumnofdensegas

above the mercury. This factor is not applicable where measurement is made with bellowstype

differentialgagessincethereisnounbalancedcolumnofdensegasinamanometerofthattype.Atable

ofmanometerfactorsisshownonpage21.

Orifice Thermal Expansion Fator, F a : The thermal expansion factor is used to adjust for thedeviationoforificediameter,fromthatofitsmanufacture,withextremetemperaturechange.Withina

temperature rangeof0Fto120F, thisdeviationordinarily isnogreater than tolerancesassigned to

orifice platemanufacture. Therefore, it is recommended that thisfactor be ignored in natural gas

measurement. The thermal expansionfactor is usually appied to steam and high temperature liquid

measurement.A tableof thermalexpansion factors forstainlesssteelandmonelorifices isshownon

page22.

GageLocationFactor,F l: Thegagelocationfactoris included inordertoadjustforlocationotherthan45latitudeandsealevel.Atableoflocationfactorsisshownonpage22.


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EXAMPLES

DETERMINATIONOFTHEORIFICEFACTOR,FbThevalueoftheorificefactor,Fb,isexpressedbytheformula:

Fb=338.17Kod,inwhich

338.17 = constant formeasurementwhen the pressure base is 14.73 psia, the temperature

basis60F,theflowingtemperatureis60F,andthespecificgravityis1.000.

Ko =dischargecoefficientwhentheReynoldsnumberisinfinite.

d =diameteroforificeininches.

When theorifice factor is tobe determined for ameter tube of standard internal diameter and an

orificeofevensizethevalueofthebasicfactorcanbefoundfromtablescontainedonpages2through

4forflangetaps,andonpage24through26forpipetaps.

Example:Ifa2.375inchorificeisusedwithflangetapsina9.564inchI.D.line,theorificefactor,Fbis

foundfromthetableonpage3 tobe1140.1.

Intheformula,Fb=338.17Kod,thedischargecoefficientKoforanygivenvaluefor,variesslightly

withthesizeoftheline.Theorificefactorforvarioussizesoforificesandforthelinesizesnotgivenin

thetablescanbecomputedbytheuseofthetablesonpages5through9forflangetaps,andonpages27through31forpipetaps.

Thebasic empirical equations fromwhich valuesof Ko are calculated arequite complex. Itwas felt

desirable todevelopamethodbywhichorifice factorscouldbedeterminedwithout resorting to the

basicequations.

Inordertodothis,theformulafortheorificefactorisconvertedto:

Fb=FFddinwhich

F =338.17Kofor4.026inchline.

Fd =factorforconvertingKofor4.026inchlineforacertainvalueof,intoKofor the

samevalueof,forothersizeoflines.

d =diameteroftheorificeininches.


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Fb=FxFdDinwhich

Fx =338.17Ko fora4.026inchlineorFx= F

Fd =factorforconvertingKofor4.026inchlineforacertainvalueof,intoKofor the

samevalueof,forothersizeoflines.

D =internaldiameterofthepipeininches.

Example : Ifa3.800inchorifice isusedwithpipe taps ina line7.981 inches indiameter,=3.800

7.981=0.47613.Refferingtopage31,

For=0.477, Fx=54.994

For=0.476, Fx=54.713

Byinterpolation,for=0.47613;Fx=54.749

Seepage29,for =0.476andD=7.981;Fd=0.9999

ThenFb=54.749x0.9999x7.981=3487.0

DETERMINATIONOFPRESSUREBASEFACTOR,FpbUsing the table on page 16 for apressurebase of 14.65psia thepressure base factor, Fpb,willbe

1.0055.Tocomputeapressurebasefactor,Fpb,foranyvalueofpressurebasenotshown,thefollowing

relationshipcanbeused:

Fpb= ,where: Pb=therequiredcontractpressurebaseinpsia.

Ifthecontractpressurebaseis14.65psiathenthepressurebasefactorequal

Fpb= =1.0055

DETERMINATIONOFTEMPERATUREBASEFACTOR,FtbTochangetoanybasetemperatureotherthan60 F,thetableonpage16maybeused.Iftherequired

contracttemperaturebaseis70 F,thenfromthetablethetemperaturebasefactorFtb=1.0192.Ifthe

contracttemperaturebaseisnotshowninthetablethefactorcanbedeterminedfromtheexpression:

Ftb= ,where: Tb=theabsolutetemperaturebasespecifiedbythecontract,(460+ F).


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Using70Fasrequiredcontracttemperaturebase,thetemperature basefactor,

Ftb= ,=1.0192

DETERMINATIONOFSPECIFICGRAVITYFACTOR,FgThespecificgravityfactor,Fg,canbedeterminedfromthetableonpage16.Ifthespecificgravityisnot

foundinthistablethenthefactorcanbedeterminedfromtheexpression:

Fg = ,where:G=specificgravityoftheflowinggas,air=1.000

Example: Ifthespecificgravityoftheflowinggasis0.450,thenthespecificgravityfactor,

Fg = =1.4907

DETERMINATIONOFFLOWINGTEMPERATUREFACTOR,FtfWhen the flowing temperature of the gas beingmeasured is something other than 60 F a flowing

temperaturefactor,Ftf,mustbeapplied.Foraflowingtemperatureof146 Fafactorof0.9263canbeobtainedfromthetableonpage21.Ifthetemperatureoftheflowingfluidisnotshowninthetablethe

factorcanbedeterminedfromtheexpression:

Ftf = ,where: Tf=actualflowingtemperatureindegreesFabsolute,(460+ F).

Iftheactualflowingtemperatureis146 FthenFtf = =0.9263

DETERMINATIONOFREYNOLDSNUMBER FACTOR,FrWhentheReynoldsnumberfactor,Fr, isrequiredusingastandardsizepipeandanevensizeorifice,

thisfactorcanbedeterminedusingthebfactorsonpages10through12forflangetaps,andpage32

through34forpipetaps.

Example : If an 8.000inch orifice is used in a 19.000inchmeter tube, and the average extension,

, is 115, using flange taps, the Reynolds number factor, = =

1.0001.


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DETERMINATIONOFEXPANSION FACTOR,YValuesofexpansionfactor,Y,arecontainedinthetablesonpages17through20forflangetapsandon

pages38through41forpipetaps.Sincetheexpansionfactordependsuponthepointwherethestatic

pressuretapsislocated,twotablesofexpansionfactorsforflangetapsarerequired:Y,forupstream

static pressure and Y, for downstream static pressure. For expansion factor using pipe taps, two

additionaltablesareprovided:Y,forupstreamstaticpressure,andY,fordownstreamstaticpressure.

Example:Usingflangetaps,withadifferentialof53inchesandwithastaticpressureof264.4psia(250

psig)observedatthedownstreamtap;= = =0.20.Ifthevalueof is0.40,thepropervalueof

theexpansionfactorcanbeobtainedfromthetableonpage19.Y=1.0013

DETERMINATIONOFSUPERCOMPRESSIBILITY FACTOR,FpvThevalueofthisfactorcanbeevaluatedfromthetableslistedanddescribedonpages44through58.

It is recommended that theappropriatealternatemethoddeterminingadjusting factorFpandFT,be

usedforgasmixturesexceedingaspecific gravityof0.75.Forgasmixturesexceedingaspecificgravity

of1.00,itisrecommendedthatcompressibilitytestsberuntodeterminethesuitabilityofapplyingthe

standardoranalternatemethod.Thediluentcontentofanygasmixturetowhichthemethodistobe

appliedshouldbe limitedto15mol.percentcarbondioxideand15mol.percentnitrogen,andactual

testsarerecommendedfordiluentcontentexceedingthesequantities.

Thespecificgravity,carbondioxideandnitrogencontents,inconjunctionwiththeflowingpressureand

temperature,areusedtodeterminetheadjustingpressureandtemperaturenecessaryforrelatingany

gas to the supercompressibility data of the 0.600 specific gravity, hydrocarbon gas. The adjusted

pressureisobtainedbymultiplyingthegagepressureoftheflowinggasbythepressureadjustingfactor

Fp,and theadjusted temperature isobtainedbymultiplying theabsolute temperatureof the flowing

gasbythetemperatureadjustingfactorFTandsubtracting460fromthisproduct.AdjustingfactorFp

andFTarecalculatedasfollows:

WhereKpisthediluentpressureconstant,Kp=Mc0.392Mnand

WhereKTisthediluenttemperatureconstant,KT=Mc+1.681Mnand

G=specificgravity;Mc=Mol.Percentcarbondioxide;Mn=Mol.Percentnitrogen.

Adjustedpressure=PfFppsig;adjustedtemperature=TfFT 460 F


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After the adjusted pressure and the adjusted temperature are determined, the supercompressibility

factorFpvcanbefoundintableA(page44through58)usingtheadjustedvalues.

TablesB (page59 through 60) andC (page 61 through62) give the valuesof Fpand FT for specific

gravities between 0.550 and 1.000 and appropriate ranges of the diluent constants. In the ranges

coveredbythesetables,conditionsmaybeindicatedwhichwouldneverexist;however,incommercial

measurementtheuseoftheseareaswillseldomoccur.

ThefollowingexampleillustratestheAGAspecificgravitymethodofcalculatingthesupercompressibility

factorFpv.

Example :Assumeagashavinga specificgravityof0.570, zeropercent carbondioxideand1.1mol.

Percentnitrogen,atapressureof370psigand65 F.

Pressureconstant:Kp=00.392(1.1)= 0.431

Referring to Table B, the pressure adjusting factor, Fp, for G = 0.570 and Kp = 0.431 is found by

interpolationas:Fp=1.0014.

Temperatureconstant:KT=0+1.681(1.1)=1.849

ReferringtoTableC,thetemperaturearenowcalculatedfrom:

Adjustedpressure=PfFp=370(1.0014)=370.5psig

Adjustedtemperature=TfFT460=525(1.0376)460=84.7 F

ReferringtoTableAandusingtheadjustedpressure (370.5psig)andadjustedtemperature (84.7 F),

thesupercompressibilityfactor,Fpvisfoundbyinterpolationas:Fpv=1.0254

DETERMINATIONOFTHEMANOMETER FACTOR,FmThis factor isusedwithmercurytypemeterswhere thegas comes in contactwithmercury surfaces.

Thisfactorcanbeobtainedfromthetableonpage21.

DETERMINATIONOFTHETHERMALEXPANSION FACTOR,FaThisfactormaybeusedwhenflowingtemperatureareoutsidethelimitsof0 Fto120 Fandcanbe

obtainedfromthetableonpage22.

DETERMINATIONOFTHEGAGELOCATION FACTOR,FlThisfactor isspecificallyapplicabletothemanometer.Thisfactor isrepresentedbythetableonpage

22.


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CALCULATIONOFORIFICECONSTANT,CThevalueoftheorificeconstant,C,correspondstotheexpression:

C=FbxFrxYxFpbxFtbxFtfxFgxFpvxFmxFaxFl

In the following examples the conditions ofmeasurement and some of the calculations are

givenontheleft.Thefactorsrequiredtoobtaintheorificeconstant,withcorrespondingpage

references,aregivenontheright.

Example1.

ConditionAtMeter ValueOffactor

MeterequippedwithPipeTaps AndReferencePage

d=diameteroforifice=3.000inches

D=internaldiameterofmetertube=7.981inches.. Fb=2012.7 24

Staticpressureobtainedatupstreampipetap

Averagedifferential=64.5inches

Averagestaticpressure=539.4psia(525psig)

=3.0007.981=0.38

=pressureextension(average)=187.

Seepage36.For =0.38 andD=7.981;b=0.0214

Fr=1+(0.0214187)Fr=1.0001 36

Differentialratio,hwPf=64.5539.4=0.12

Seepage38.For=0.38andhwPf=0.12.. Y =0.9983 38


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Pb=pressurebase,4oz,above14.4=14.65psia. Fpb=1.0055 16

Tb=temperaturebase=60 F. Ftb=1.0000 16

Tf=flowingtemperature=60 F Ftf=1.0000 21

G=specificgravity=0.64. Fg=1.2500 16

Itisassumedinthisexamplethatthesupercompressibility factor

isnotused,bytermsofcontract.

Manometerfactor. Fm=0.9989 21

ThenC=2012.7x1.0001x0.9983x1.0055x1.0000x1.0000x1.2500x0.9989=2522.9

Foranaveragepressureextension, = =186.52,theflowratewouldbe

Qh=C =2522.9x186.52=470,570cu.Ft.perhr.

Example2.

ConditionAtMeter

ValueOffactor

MeterequippedwithFlangeTaps AndReferencePage


D=internaldiameterofmetertube=9.800inches

=4.2009.800=0.42857;interpolatingforFfromthetable,

page5,F=206.87

Interpolatingfromthetable,page7,Fd=0.9992

Fb=FxFdxd=206.87x0.9992x4.200. Fb=3646.3

Staticpressureobtainedatdownstreamflangetap

Averagedifferential,hw=55.0inches


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Averagestaticpressure,Pf=1523psia(1510psig)

=pressureextension(average)=290.

Seepage14,interpolatingfor =0.43andD=9.800,b=0.0227

=1+0.0227290 Fr=1.0001 14

Differentialratio,hwPf=0.04

Seepage19,interpolatingforhwPf=0.04and=0.43.. Y =1.0002 19

Pb=pressurebase,10oz,above13.0=13.625psia

Fpb=14.7313.625 . Fpb=1.0811 16



G=specificgravity=0.68.. Fg=1.2127 16

Supercompressibility,asdeterminedbyanactualtestfactor

Onasampleofgas .. Fpv=1.1130

Manometerfactor... Fm=0.9957 21

ThenC=3646.3x1.0001x1.0002x1.0811x0.9808x0.9905x1.2127x1.1130x0.9957=5148.3


Qh=C =5148.3x289.42=1,490,000cu.Ft.perhr.

Example3.

ConditionAtMeter ValueOffactor

MeterequippedwithFlangeTaps AndReferencePage



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D=internaldiameterofmetertube=6.065inches.. Fb=2654.9 2

Staticpressureobtainedatdownstreamflangetap

Averagedifferential=52.5inches

Averagestaticpressure=562.7psia(548psig)

=3.5006.065=0.577

=pressureextension(average)=171.877

Seepage10.For =0.577 andD=6.065;b=0.0426

Fr=1+(0.0426171.877) Fr=1.0002 10

Differentialratio,hwPf=52.5562.7=0.093

Seepage19.For=0.577andhwPf=0.093. Y =1.0006 19

Pb=pressurebase,14.7psia.. Fpb=1.0020 16



G=specificgravity=0.74. Fg=1.1625 16

Supercompressibilityfactor,N2=0.0856Mol.%,CO2=0.6087Mol.%

Thisfactorwouldbecalculatedinaccordancewiththeformulabelow:

Kp=Mc0.392Mn=0.60870.392(0.0856)=0.60870.03355=0.57515

=1.0102

KT=Mc+1.681Mn=0.6087+1.681x0.0856=0.7526

=0.8867

Adjustedpressure=PfFp=562.7x1.0102=568.43psig.

AdjustedTemperature=TfFT460=580(0.8867)460=514.286460=54.286 F


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ReferringtoTableAandusingtheadjustedpressure(568.43psig)andadjustedtemperature(54.286

F),thesupercompressibilityfactor byinterpolationas:. Fpv=1.04948 44

ManometerfactorFmandFl isneglected(notmercurytypemeter)

Areafactor,Fa(flowingtemperature120 F):.. Fa =1.0010 22

ThenC=2654.9x1.0002x1.0006x1.0020x1.0000x0.9469x1.1625x1.04948x1.0010=3078.7084


Qh=C =3078.7084x171.877=529,159.1636cu.Ft.perhr.(12,699,819.9280cu.Ft.perday).


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ExampleofGasAnalyzeReport:

INSTITUT TEKNOLOGI SEPULUH NOPEMBER SURABAYALEMBAGA PENELITAN DAN PENGABDIAN PADAMASYARAKAT

GAS COMPOSITION ANALYSIS

SPESIFIC GRAVITY AND CALORIFIC VALUE CALCULATIONS

Sample : BW

Date of Sampling : July 28, 2008 at 17.00 Opening Condition :

Pressure : 548 Psig - Opening Press : 548 psig

Temperatur : - Opening Temp : 120oF


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module 7 - gas measurement (v.01)

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