This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be produced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

 API MANUAL OF PETROLEUM MEASUREMENT STANDARDS Chapter 7.5 Temperature Determination - Automatic Tank Temperature Measurement onboard Marine Vessels Carrying Refrigerated Hydrocarbon and Chemical Gas Fluids  

ANSI/API MPMS CHAPTER 7.5

First Edition 

ISO 8310:2012 (Identical) Refrigerated hydrocarbon and non-petroleum based liquefied gaseous fuels — General requirements for automatic tank thermometers on board marine carriers and floating storage

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

ii

API Foreword

Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent. This document was produced under API standardization procedures that ensure appropriate notification and participation in the developmental process and is designated as an API standard. Questions concerning the interpretation of the content of this publication or comments and questions concerning the procedures under which this publication was developed should be directed in writing to the Director of Standards, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005. Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the director. Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. A one-time extension of up to two years may be added to this review cycle. Status of the publication can be ascertained from the API Standards Department, telephone (202) 682-8000. A catalog of API publications and materials is published annually and updated quarterly by API, 1220 L Street, N.W., Washington, D.C. 20005. This standard shall become effective on the date printed on the cover but may be used voluntarily from the date of distribution. Standards referenced herein may be replaced by other international or national standards that can be shown to meet or exceed the requirements of the referenced standard. Suggested revisions are invited and should be submitted to the API, Standards Department, 1220 L Street, NW, Washington, DC 20005, or by email to standards@api.org. This American National Standard is under the jurisdiction of the API Subcommittee on Measurement Accountability. This standard is considered identical to the English version of ISO 8310. ISO 8310 was prepared by Technical Committee ISO/TC 28, Subcommittee 5, Measurement of refrigerated hydrocarbon and non-petroleum based liquefied gaseous fuels. .

All rights reserved. No part of this work may be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher.

Contact the Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C. 20005. Copyright © 2005 American Petroleum Institute

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be produced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

iv

Contents Page

Forward

Introduction

1  Scope................................................................................................................................................................1 

2  Normativereferences.................................................................................................................................1 

3  Termsanddefinitions................................................................................................................................1 

4  Safetyprecautions.......................................................................................................................................2 4.1  General............................................................................................................................................................2 4.2  Equipmentprecautions.............................................................................................................................3 4.2.1  General............................................................................................................................................................3 4.2.2  Mechanicalrigidity......................................................................................................................................3 4.2.3  Gastightdesign.............................................................................................................................................3 4.2.4  Compatibilitywithcargo...........................................................................................................................3 4.2.5  Toleranceagainstlowtemperatures....................................................................................................3 4.2.6  Typeapproval...............................................................................................................................................3 

5  Designrequirements..................................................................................................................................3 5.1  General............................................................................................................................................................3 5.2  Temperaturesensors.................................................................................................................................3 5.3  Indicatingdevice..........................................................................................................................................4 5.4  Installation.....................................................................................................................................................4 5.5  Provisionsforroutinemaintenanceandverification......................................................................4 5.6  Provisionagainstsuddenmalfunctions...............................................................................................4 5.7  Dynamicresponse.......................................................................................................................................4 5.8  Measurablerange........................................................................................................................................4 5.9  Dataprocessingandreporting................................................................................................................4 5.10  Compensationforvariationofcargotemperatures.........................................................................4 5.11  Sealing,securityandunsealing...............................................................................................................4 5.12  Redundancy...................................................................................................................................................4 5.13  Datacommunication...................................................................................................................................5 

6  Calibrationandaccuracyverification...................................................................................................5 6.1  General............................................................................................................................................................5 6.2  Calibrationreference.................................................................................................................................5 6.3  Calibrationandaccuracyverificationatfactory...............................................................................5 6.3.1  Calibrationatfactory..................................................................................................................................5 6.3.2  AccuracyofPRTs..........................................................................................................................................5 6.3.3  Factoryacceptancetest(FAT).................................................................................................................6 6.4  Calibrationandaccuracyverificationafterinstallation.................................................................6 6.4.1  Calibrationandinspectionafterinstallation......................................................................................6 6.4.2  Siteacceptancetest(SAT).........................................................................................................................6 6.4.3  Accuracyofindicatingdevice..................................................................................................................6 6.5  Periodicaccuracyverification.................................................................................................................8 6.5.1  General............................................................................................................................................................8 6.5.2  Methodofperiodicverification...............................................................................................................8 6.5.3  Frequencyofsubsequentcalibrationandrecertification..............................................................8 6.5.4  Customaryverification..............................................................................................................................8 

7  Accuracyrequirement...............................................................................................................................8 

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be produced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

7.1  Overallerror.................................................................................................................................................8 7.2  Resolution......................................................................................................................................................9 

8  ATTcalibrationrecords............................................................................................................................9 

AnnexA(informative)Informationonplatinumresistancethermometers......................................10 A.1  General..........................................................................................................................................................10 A.2  Characteristicsofplatinumresistancethermometers..................................................................10 A.3  Nominaltemperature/resistancerelationship...............................................................................10 Bibliography

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

vi

IntroductionLargequantitiesofliquefiednaturalgas(LNG),liquefiedpetroleumgas(LPG)andotherliquefiedgasesareusuallytransportedbymarinecarriersdedicatedfortheseapplicationsandtradedbasedonstaticmeasurementonboardbyautomatictankmeasurement.Suchanautomatictankmeasurementmaybeapartofthecustodytransfermeasurementsystem(CTMS)whichinvolvesdeterminationofliquid/vaporinterface,i.e.liquidlevel,averagetemperaturesofliquidandvapor,andvaporpressure.Thevolumetricquantityoftheliquidandgasisthencomputedwiththetankcapacitytablebasedonwhichthedeliveredquantityintermsofenergycontentormassiscalculated.Inmostcases,shoretankmeasurementisnotusedduetotheactiveanddynamicconditionsoftheshoretankoperations.Intheabsenceofothermeansofacceptablemeasurement,custodytransfermeasurementusuallytakesplaceonboardthecarrierorfloatingproductionstorageoffshore(FPSO)andfloatingstorageoffshore(FSO).Liquidcargodensityisverysensitivetotemperature;therefore,obtainingaccuratetemperaturereadingsisextremelyimportant.Forexample,achangeof0.2°C(0.36°F)forliquidmethanecargoresultsinachangeindensityofapproximately0.07%.ThisInternationalStandardalsodiscussesuseofautomatictankthermometersonboardmarinevesselsforothervolatile,non‐petroleumliquidsinfullyrefrigeratedconditions.Manyofthesenon‐petroleumliquids,suchasdi‐methylether(DME)aremeasuredinasimilarmannertothatusedforfullyrefrigeratedLPGs.ValuesoftemperatureinthisInternationalStandardareintermsoftheInternationalTemperatureScaleof1990,ITS‐90.TemperaturesindegreesCelsiusaredenotedbythesymbolt.

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

1

AutomaticTankTemperatureMeasurementonboardMarineVesselsCarryingRefrigeratedHydrocarbonandChemicalGasFluids

1 ScopeThisInternationalStandardspecifiestheessentialrequirementsandverificationproceduresforautomatictankthermometers(ATTs)consistingofplatinumresistancethermometers(PRT)andanindicatingdeviceusedforcustodytransfermeasurementofliquefiednaturalgas,liquefiedpetroleumandchemicalgasesonboardships.TemperaturedetectorsotherthanPRTareconsideredacceptableforuseinthecustodytransferserviceofliquefiedgasesiftheymeettheperformancerequirementsofthisInternationalStandardandareapprovedbynationalregulations.

2 NormativereferencesThefollowingdocuments,inwholeorinpart,arenormativelyreferencedinthisdocumentandareindispensableforitsapplication.Fordatedreferences,onlytheeditioncitedapplies.Forundatedreferences,thelatesteditionofthereferenceddocument(includinganyamendments)applies.IEC60751,IndustrialplatinumresistancethermometersandplatinumtemperaturesensorsASTME1137,StandardSpecificationforIndustrialPlatinumResistanceThermometers

3 TermsanddefinitionsForthepurposesofthisdocument,thefollowingtermsanddefinitionsapply.3.1automatictankgaugeATGautomaticlevelgaugeALGinstrumentthatautomaticallymeasuresanddisplaysliquidlevelsorullagesinoneormoretanks,eithercontinuously,periodicallyorondemand3.2automatictankgaugingsystemATGsystemsystemthatincludesATGsatthecargotanksandcontrol/displayunitthatprocessesanddisplaysoutputsignalsfromtheATGalongwithanyotherparametersrequiredtodeterminetheliquidlevel,i.e.liquid/vaporinterface3.3automatictankthermometerATTautomatictanktemperaturesysteminstrumentthatcontinuouslymeasurestemperatureincargotanksNOTE1 AnATTtypicallyincludestemperaturesensors,suchasPRTs,field‐mountedtransmittersforelectronicsignaltransmission,andindicatingdevice(s).

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

2

NOTE2 ATTsonliquefiedgascarriersareusuallymultiple‐pointATTswhichconsistofthreeormoretemperaturesensors,suchasPRTs,tomeasurethetemperaturesatselectedheightsinthecargotank.3.4custodytransfermeasurementsystemCTMSsystemthatprocessesinputsfromanATGsystem,anATT,pressuregauges,etc.andprovidescustodytransfermeasurementinformationonboard,generatingdocumentswithregardtocustodytransferofliquefiedgasesNOTE AnATTcanbeincorporatedaspartofaCTMS.3.5gasdangerousspaceorzonespaceorzonedefinedbytheInternationalCodefortheConstructionandEquipmentofShipsCarryingLiquefiedGasesinBulk(IGCCode)3.6indicatingdevicedisplayingdevicesetofcomponentsofameasuringinstrumentintendedtoindicatethemeasuredvalue3.7inherenterrorintrinsicerrorerrorofagaugewhenitistestedagainstareferencestandardundercontrolledconditionsasspecifiedbythemanufacturer3.8nominalresistanceexpectedresistanceR0ofaPRTat0°C(32°F),declaredbythemanufacturerandshowninthethermometermarking,usuallyroundedtothenearestohm3.9nominaltemperature/resistancerelationshiprelationshipbetweentemperatureandresistanceofanominalPRT3.10platinumresistancethermometerPRTresistancetemperaturedetectorRTDtemperature‐responsivedeviceconsistingofoneormoresensingplatinumresistorswithinaprotectivesheath,internalconnectingwiresandexternalterminalstopermitconnectionofelectricalmeasurementinstruments3.11uncertaintynon‐negativeparametercharacterizingthedispersionofthequantityvaluesbeingattributedtoameasurand,basedontheinformationused

4 Safetyprecautions4.1 GeneralNothingcontainedinthisInternationalStandardisintendedtosupersedeanyregulatoryrequirementsorrecommendedoperatingpracticesissuedbyorganizationssuchastheInternationalMaritimeOrganization(IMO),InternationalChamberofShipping(ICS),OilCompaniesInternationalMarineForum(OCIMF),InternationalAssociationofClassificationSocieties(IACS)andindividualoperating

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

3

companies,noristhisInternationalStandardintendedtoconflictwithanysafetyorenvironmentalconsiderations,localregulations,orthespecificprovisionsofanycontract.4.2 Equipmentprecautions4.2.1 GeneralAllelectriccomponentsofanATTforuseinelectricallyclassifiedareasshallmeettheelectricalareaclassification.Theyshallconformtoapplicablesectionsofthenationaland/orinternationalelectricalsafetystandards.AllATTsshallbemaintainedinasafeoperatingconditionandmanufacturers'maintenanceinstructionsshouldbecompliedwith.4.2.2 MechanicalrigidityAllATTsshallbecapableofwithstandingthepressure,temperature,dynamicloadsgeneratedfromrolling/pitching,andsloshingfromenvironmentalconditionslikelytobeencounteredintheservice.WhereaPRTisinstallednearasubmergedpumportheendofaloading/unloadinglineinacargotank,appropriatemeasuresshallbeappliedtopreventtheATTfrombeingaffectedbythevortexorvaporization,i.e.boiling,ofcargocausedbycargoloadingorcargounloadingoperations.Inaddition,allPRTsshallbemountedsuchthattheyarenotaffectedbythesprayofliquefiedgaswheneverthespraynozzlesareinoperation.4.2.3 GastightdesignAllpartsofATTsexposedtoagasdangerousspaceorzoneshallbeofgastightconstruction.4.2.4 CompatibilitywithcargoAllpartsoftheATTincontactwithliquefiedgasesortheirvaporshallbechemicallycompatiblewiththeproduct,toavoidbothproductcontaminationandcorrosionoftheATT.4.2.5 ToleranceagainstlowtemperaturesATTsshallbedesignedtomeasurethelowtemperaturesencounteredinrefrigeratedliquefiedgasservice.Theyshallalsobedesignedtowithstandthelow‐temperaturethermalcontractionoftheircomponentsandofthetanks.Additionally,changeintheheightofPRTinthetanksbysuchthermalcontractionshallbecompensatedforinanappropriatemanner.4.2.6 TypeapprovalThedesignandinstallationofATTsshallbesubjecttotheapprovalofanationalmetrologyinstitute(NMI)orclasssociety.Forelectricalconsiderations,refertoIACSUnifiedRequirementsE10[10].TypeapprovalisnormallyissuedafteranATThasbeensubjectedtoaspecificseriesoftests.

5 Designrequirements5.1 GeneralThefollowingdesignrequirementsapplytoalltypesofATTsonliquefiedgascarriers,FPSOsandFSOs.Theserequirements,whichmaybeinadditiontothetechnicalspecificationsbytheATTmanufacturer,shouldbemetwheretheyareapplicable.5.2 TemperaturesensorsTemperaturesensorsusedforcustodytransfermeasurementofliquefiedgasesonboardshipsshallbeeitherthree‐orfour‐wiretypePRTsasdescribedinIEC60751(whicharedescribedinASTME1137).TherelationshipoftemperatureandresistanceofthePRTsisdescribedbyatemperature/resistancerelationship(seeAnnexA).EachPRTshallbesubjecttothefollowingroutineproductiontests:a) insulationresistanceatambienttemperature;b) sheathintegritytest;c) dimensionaltest;d) toleranceacceptancetest.

NOTE:SeeIEC60751orASTME1137forthedetailsoftheroutineproductiontest.

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

4

ThemanufacturershallcalibrateeachPRTandestablishitsnominalresistance(R0)andconstantsA,BandCinthetemperature/resistancerelationship.IdentificationsuchastheserialnumbershouldbeclearlyandindeliblymarkedoneachPRT.5.3 IndicatingdeviceIndicatingdeviceswithanalogueinputsshallhaveahigh‐impedanceinputcircuitsoastominimizeerror.5.4 InstallationThenumberofPRTsinatankdependsonthecapacityandtheheightofthetank;however,IGCCoderequiresaminimumofthree.InthecaseoflargeLNGcarriers,theremaybefiveormorePRTsineachtankwitheachPRTsupportedbyasecondaryPRTmountedadjacenttotheprimaryPRT(see5.12).AtleastonePRTshallbelocatedabovethemaximumfillheightsoastoremaininthevaporspace.ThelowestPRTshallbelocatednearthebottomofthetanksoastomeasurethetemperatureoftheheel.TheindicatingdeviceofanATTshallbeinstalledinalocationfreefromtemperaturevariations,whichcancausemeasurementerrors.TheindicatingdevicemaybeintegratedintotheCTMS.5.5 ProvisionsforroutinemaintenanceandverificationExceptforthosecomponentswithinthecargotankitself,allpartsofanATTshallallowroutinemaintenancetobeperformedwithoutcompromisingtheintegrityofthetank.Thisincludesmeansofverificationwherebytheaccuracyofanindicatingdevicecanbechecked.5.6 ProvisionagainstsuddenmalfunctionsATTsshallbedesignedtominimizethefrequencyandseverityofanymalfunction.Electronicsessentialfortheproperfunctioningofthesystemshouldideallybeaccessiblefromthedeckandbeserviceablewithtanksinoperation.5.7 DynamicresponseATTsshallhavesufficientdynamicresponsetotrackthetemperatureofliquidandgasinthetanks.5.8 MeasurablerangeATTsshallhavesufficientmeasurablerangeinaccordancewiththeintendedcargoestobeloaded.5.9 DataprocessingandreportingAnATTorCTMSmaycalculateandreport:a) theaverageliquidtemperatureineachcargotank;b) theaveragevaportemperatureineachcargotank;c) theaverageliquidtemperaturethroughoutallcargotanks;d) theaveragevaportemperaturethroughoutallcargotanks.5.10 CompensationforvariationofcargotemperaturesToensureaccuratediscriminationoftheliquidandvaporphases,theheightofeachPRTshallbecompensatedforanyeffectofthermalcontraction/expansionofmaterialusedinathermowellorprotectingtube.ThecompensationmaybecarriedoutbytheelectronicsintheATTsystemormanually.5.11 Sealing,securityandunsealingTheATTsshallbeequippedwithameansofpreventingunauthorizedadjustmentortampering.Specifically,ATTsusedinfiscalorcustodytransferapplicationsshallprovidesecuritytoallowsealingofthecalibrationadjustment.Thesecuritymayincludeaphysicalsealand/orsoftwarepassword(s).OncetheATThasbeensealed,itshallnotbeunsealeduntilthenextscheduledinspection.Shouldunsealingbecomenecessaryforsomeunavoidablereason,theinspectionorganizationshallbeinformedofsuchactionpriortounsealing.5.12 RedundancyUsually,liquefiedpetroleumandchemicalgascarriersareequippedwithonesetofPRTspertank.

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

5

Whereahigherdegreeofreliabilityisdesired,itiscommonpracticetoinstalltwosetsofPRTsineachcargotank.OnesetshallbedesignatedastheprimaryPRTsandtheotherasthesecondaryPRTs.Insuchacase:a) eachPRTshallbesupportedbyasecondaryPRTmountedadjacenttotheprimaryPRT;b) failureofaprimaryPRTshallnotaffectthesecondaryPRT,orviceversa;c) secondaryPRTsshallalwaysbeinoperation;thisprovidesasecondaryPRTforcomparisontothe

primaryPRTandameansofmonitoringtheprimaryPRTformalfunction.5.13 DatacommunicationTheATTsystemshallbedesignedandinstalledsuchthatitsdatatransmissiondeviceandindicatingdevice:a) doesnotcompromisetheaccuracyofthemeasurement;b) providespropersecurityandprotectionofthemeasureddatatoensureitsintegrity;c) providesadequateupdatespeed.

6 Calibrationandaccuracyverification6.1 GeneralThemanufacturerofanATTshallcalibratetheATTtomeetthespecificationbeforeitisshippedfromthefactory(see6.3).TheATTisthencalibratedbythemanufactureroritsauthorizedservicerepresentativeafteritisinstalled(see6.4)andperiodically(see6.5),withtheresultsnormallyverifiedbyaqualifiedthirdparty.TheaccuracyoftemperaturemeasurementbyanATTisaffectedbytheinherenterroroftheATTequipment,theerrorduetoinstallation(e.g.stability,location,etc.)andtheeffectofchangesinoperatingconditions.Accuracyisalsosubjecttotheuncertaintyassociatedwiththecalibration.ChronologicalchangeofcharacteristicsofaPRTisnegligiblysmallinrelationtothelifeoftheship.6.2 CalibrationreferenceThecalibrationreferenceshallbetraceabletoanationalmetrologyinstitute(NMI).Theuncertaintyofthereferencestandardshallnotexceed±0.05°C(or0.1°F).TheATTmanufacturershallestablishthetotaluncertaintyassociatedwiththeaccuracyverificationoftheATT.6.3 Calibrationandaccuracyverificationatfactory6.3.1 CalibrationatfactoryOutputresistanceofallPRTsshallbecomparedagainstacalibrationreferenceundercontrolledconditions,e.g.inatemperaturebath.Typicalcalibrationpointsinclude:a) approximately−196°C(‐321°F)(boilingpointofnitrogen);b) approximately−75°C(‐103°F)(generatedbycontrolledbath);c) approximately0°C(32°F)(icepointofwater);d) approximately100°C(212°F)(boilingpointofwater).AtleastthreecalibrationpointsshallbeselectedtakingtheoperatingrangeoftheATTsintoaccount.Thetemperatureoftheroomshallbecontrolledatthetimeofcalibration.Theindicatingdeviceshallbecalibratedbythemanufacturer.6.3.2 AccuracyofPRTsThedifferencebetweentheoutputfromaPRTintermsoftemperature(°C)andthesolutionsofthenominaltemperature/resistancerelationship(seeA.3)shallberegardedasthePRTerroratthecalibrationpoint.ThemaximumPRTerrorshallbelessthana) ±(0.15+0.002|t|)forLNGapplications,orb) ±(0.3+0.005|t|)forotherapplications,where|t|istheabsolutevalueoftemperaturein°C.

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

6

WhereUSCustomaryUnitisused,thedifferencebetweentheoutputfromaPRTintermsoftemperature(°F)shallbelessthan

ThemaximumPRTerrorshallbelessthana) ±(0.27+0.0036|t|)forLNGapplications,orb) ±(0.54+0.009|t|)forotherapplications,where|t|istheabsolutevalueoftemperaturein°F.

Ateachcalibrationpoint,themaximumPRTerroramongallPRTstobeinstalledontheintendedship(Es)shallbedetermined.IftheoverallerrorofATT(E)isdefinedinaccordancewith7.1.1b),theresistance(R0)andconstantsA,BandCuniquetoeachPRTshallbecalculatedfromthecalibrationresults.6.3.3 Factoryacceptancetest(FAT)IfthemaximumPRTerror(Es)isverifiedbyaqualifiedthirdparty,atleast25%ofthetotalnumberofthePRTs,orstatisticallysufficientnumbers,shallberandomlychosenandrecalibratedwiththerepeatabilitylessthantheroot‐mean‐square(RMS)oftheuncertaintiesassociatingwiththecalibration.Calibrationofindicatingdevicesmaybeverifiedbyaqualifiedthirdpartybyapplyingtheproceduredescribedin6.4.2.6.4 Calibrationandaccuracyverificationafterinstallation6.4.1 CalibrationandinspectionafterinstallationTheinstallationofthePRTs,theirconnectingcablesandassociatedconnectionsshallbevisuallyinspected.PRTsdonothavetoberecalibratedafterinstallation.Calibrationoftheindicatingdevicesismadebythemanufactureroritsauthorizedserviceengineers.6.4.2 Siteacceptancetest(SAT)Thecalibrationresultsoftheindicatingdeviceshallbeverifiedbyfeedingsimulationresistancesfromaprecisiondecadeboxorotherdevices.Theaccuracyverificationiscarriedoutinthecargocontrolroomorondeckdependingonthelocationoftheanalogue/digitalconverter(seeFigure1).Ineithercase,impedanceofthecablefromPRTstotheindicatingdeviceshallbenegligiblysmall.Theresistancestobefedshallbedeterminedfromthenominaltemperature/resistancerelationship(seeA.3)orfromthetemperature/resistancerelationshipuniquetoeachPRT.Typicalsimulationpointsinclude:a) 0°C(32°F);b) −100°C(‐148°F)forLNGapplicationor−50°C(‐58°F)forotherapplications;c) temperatureclosetotheboilingpointoftheintendedcargo.Ateachsimulationpoint,themaximumindicatingdeviceerroroftheATT(Ed)shallbedetermined.6.4.3 AccuracyofindicatingdeviceThemaximumindicatingdeviceerroroftheATT(Ed)shallbelessthanthefollowingvalues:a) forLNGapplications:

1) 0.2°C(0.36°F)fortemperaturesbelow−145°C(‐229°F);2) 1.5°C(2.7°F)fortemperaturesabove−145°C(‐229°F);

b) forotherapplications:1) 0.5°C(0.9°F)throughoutthemeasurablerange.

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

7

Key

1 cargotank2 PRT

3 analogue/digitalconverter

4 decadebox

5 indicatingdevice6 cargocontrolroom

Figure1—Accuracytestofindicatingdevice

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

8

6.5 Periodicaccuracyverification6.5.1 GeneralAccuracyofanATTusedincustodytransfershallbeverifiedperiodically.ThisprocessnormallyinvolvesverifyingaccuracyoftheATTand,iffoundtobeneeded,resetting/adjustingtheATTsagainstacalibrationreference.Adjustmentorcalibrationshouldnormallybemadebyanauthorizedserviceengineerwithresultsverifiedbyaqualifiedthirdparty.WherethereareprimaryandsecondaryATTsinthecargotanks,comparisonoftheseATTsduringoperationsisnotconsideredanATTaccuracyverificationasdefinedinthisInternationalStandard.AnATTshouldnotbeadjustedsimplyduetoanobservationofadifferencebetweentheprimaryandsecondaryATT.PeriodicrecertificationofATTsincustodytransferapplicationisnormallyrequiredbylocalregulationsand/orthepartiestothesalesandpurchasecontractofliquefiedgases.6.5.2 MethodofperiodicverificationPeriodicaccuracyverificationshallbeperformedinaccordancewiththeSATproceduredescribedin6.4.2.Theprocedurestodeterminetheoverallerrordescribedin7.1shallalsobeappliedforthedeterminationoftheoverallerroratthetimeofperiodicaccuracyverification.NOTE TheaccuracyofPRTsdoesnothavetobetestedduringperiodicverificationunlesstheirtemperature/resistancerelationshipissuspect(see6.1).6.5.3 FrequencyofsubsequentcalibrationandrecertificationThefrequencyofperiodicaccuracyverificationissometimesagreedamongthepartiestothesalesandpurchasecontractofliquefiedgases,andmaybesubjecttonationalorlocalregulationsandInternationalStandards.Periodicverificationistypicallyscheduledtocoincidewithclassificationsocietyinspections.ThefrequencyshouldalsotakeintoconsiderationrecommendationsbytheATTmanufacturer.6.5.4 CustomaryverificationCross‐checkingoftheoutputsfromtheprimaryandsecondaryPRTsduringoperationortrackingofthehistorymayprovideanindicationoftheperformanceoftheATTs.However,itisrecognizedthatsuchverificationdoesnotconstituteameansofensuringthattheaccuracyoftheATTsmeetstheaccuracyrequirementsetforthin7.1.1.

7 Accuracyrequirement7.1 Overallerror7.1.1 TheoverallerrorofanATTatthetimeofSAT(6.4.2)orperiodicaccuracyverification(6.5)shallbedeterminedbyeitherofthefollowingprocedures:a) Theroot‐mean‐square(RMS)ofthemaximumPRTerror(Es)andthemaximumindicatingdevice

error(Ed)shallberegardedastheoverallerroroftheATT(E).Inthecaseofthree‐wiretypePRTs,theresistanceofthecableshallbeincludedinEsorEd(see6.4.2).

2 2s d( ) ( )E E E

b) IncaseswheretheerrorofeachPRTiscompensatedbytheATTorCTMSsoftware,theoverallerroroftheATT(E)mayberegardedasthemaximumindicatingdeviceerror(Ed)oftheATT.Insuchacase,theresistance(R0)andconstantsA,BandCuniquetoeachPRTstoredintheATTorCTMSsoftwareshallbeverified.

7.1.2 ThemaximumoverallerroroftheATT(E)shallbelessthanthefollowingvalues:a) forLNGapplications:

1) 0.2°C(0.5°F)fortemperaturesof−145°C(‐229°F)andbelow;2) 1.5°C(2.7°F)fortemperaturesabove−145°C(‐229°F);

b) forotherapplications:

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

9

1) 0.5°C(0.9°F)throughoutthemeasurablerange.NOTE MaximumoverallerroroftheATTincustodytransferapplicationsisnormallysubjecttolocalregulationsand/orrequirementsofthesalesandpurchasecontractofliquefiedgases.

7.2 ResolutionResolutionofATTsshallbe0.1°C(0.18°F)orbetterthroughoutthemeasurablerange.

8 ATTcalibrationrecordsAllATTcalibrationrecordsshallbedocumented.Calibrationandverificationrecordsshallbeavailableforinspectionbypartiesinvolvedincustodytransfer.AlladjustmentstotheATTsshallalsobedocumented.

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

10

AnnexA(informative)

Informationonplatinumresistancethermometers

A.1 GeneralTheplatinumresistancethermometeriswidelyusedforthecustodytransfermeasurementofliquefiedgasesasatemperaturesensorwithinanATT.IEC60751andASTME1137providethecharacteristicsofaplatinumresistancethermometer.

A.2 CharacteristicsofplatinumresistancethermometersIEC60751(andASTME1137)applietoplatinumresistorswhosetemperaturecoefficient,α,definedas

100 0

0 100 CR RR

isconventionallywrittenasα=3.851×10−3°C−1,whereR100istheresistanceatt=100°CandR0istheresistanceatt=0°C.

A.3 Nominaltemperature/resistancerelationshipIEC60751(andASTMD1137)givethefollowingrelationshipbetweentemperatureandresistanceofthenominalPRT.Fortherange−200°Cto0°C:

Rt=R0[1+At+Bt2+C(t−100°C)t3]

Fortherangeof0°Cto850°C:Rt=R0(1+At+Bt2)

where Rt istheresistanceattemperaturet,inohms(Ω); R0 istheresistanceatt=0°C,inohms(Ω).Theconstantsintheseformulaeare:

A=3.9083×10−3°C−1(7.0349×10−3°F−1)

B=−5.775×10−7°C−2(−10.395×10−7°F−2)

C=−4.183×10−12°C−4(−7.5294×10−12°F−4)

IEC60751:2008,Table1(andASTME1137)exhibittheresistancevaluesofthenominalPRTattemperaturetcalculatedfromtheaboveformulaeandconstants.

This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.

11

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