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Measuring the temperature in steam pipelines in a chemical plant
•Securesupplyusingsteamasaheatingmedium•Continuousmonitoringofsteamtemperature•Reliablemeasurementdespitehighmechanicalloads
1. BackgroundInachemicalplant,processsteamisusedbothtoheatprocessesandasaheattransfermedium.Thesteamisgeneratedcentrallyandthetransportedandfurtherdistributedtovariouspartsoftheplantvialargepipelines.Tosafeguardtheprocessesandproductionswhichdependonthesteam,thesteamtemperatureismeasuredatseveralpointsinthenetwork.Bymeasuringthetemperatureofthesteaminthefeedandreturnlinesincombinationwithaflowmeasurementandacalculator,theenergyconsumptionofaplantcomponentorprocesscanbecalculated.
2. Measurement requirements
ItisnecessarytomeasurethetemperatureofthesteaminDN200pipelinesservingastransportlinestoplantcomponents.Theycarrymediumpressuresteamat26barand226°C.Thethermometersusedmustenablequickandaccuratetemperaturemeasurementataflowvelocityupto30m/sinthe100…300°Crange.Thepipelinesareforthemostpartcompletelyinsulated.Atthemeasuringpoints,thethermometerneckpipemustbeguidedthroughtheinsulationtotheoutside.Tominimiseongoingcosts,thegoalismaintenanceandfault-freeoperation.
3. KROHNE solution
Intheplant,atotalofover50weld-inOPTITEMPTRAT30(FormF)resistancethermometerswithOPTITEMPTT50Ctemperaturetransmittersareused.Thetransmitterisintegratedintotheheadofthethermometer(head-mounttransmitter).
APPLICATION NOTE Chemical
Application 253 EN.indd 1 20.05.2010 11:24:11 Uhr
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4. Customer benefits
Processconditionsplacehighdemandsonthemechanicalstrengthofthethermometer.OPTITEMPTRAT30devicesguaranteesafeandreliablemeasurementofthesteamtemperatureatthemeasuringpoints.Tomeetaccuracyrequirements,resistancethermometerswereselectedinsteadofthermocouples.Duetothehighpressureandtheflowvelocity,FormFweld-inthermometerswereused.Thisdesignkeepstheriskofthermowellbreakageasaresultofvibrationinducedbyvortexsheddingtoaminimum.Thesteel1.4571thermowellmaterialisresistantupto400°Cunderthegivenconditionsofuseandweldingsleevesforinstallationinpipelineswereincludedindelivery.Thethermometersareparticularlysturdytoensurefault-freeoperation.Maintenanceisnotrequired.
5. Product used
OPTITEMP TRA T30 weld-in thermometer with OPTITEMP TT 50 C head-mounted temperature transmitter• Speciallydesignedforsteammeasurements• Withstandshighflowvelocities• Weldingcoverswithparticularstrengthinavarietyofmaterials• OptionallyavailablewithaHARTcompatibletemperaturesignalconverter
APPLICATION NOTE
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Application 253 EN.indd 2 20.05.2010 11:24:14 Uhr