
BRONKHORST HIGH-TECH B.V.
9.17.057 page 10
2.13 Description
2.13.1 Introduction
FLOW‐SMSsystemsarecompactmountingrailassemblies,
containingoneormoremassfloworpressuresensor
modules,thatcanbecombinedwithcontrolvalves,
shut‐offvalves,mixingchambers,filtersoranyother
functionalmoduleaspercustomer'srequest.
Alsothemanifoldonwhichthefunctionalmodulesare
mountedconsistsofamodularassemblyofsupportrails,
basebodiesandadapterorblindplates.
2.13.2 Functional modules
Thepicturesontherightsideillustratethemodularconcept
oftheFLOW‐SMSsystem.Itoffersgreatflexibilityfortheend‐user
withrespecttomodificationsandserviceability.Thefunctional
modulesare‘top‐mount’,sotheycaneasilybeexchangedwithout
removingthetotalassembly.
Inthefollowingparagraphswehavelaiddowntheinstructions
forremovalandreplacementoffunctionalmodules.
BronkhorstHigh‐Techrecommendstocleanortoreplacegasketsandhexagonboltsbefore
reassemblingfunctionalmodules.
FLOW‐SMSmanifoldcomponents(basebodies,distributionand mixingchamber,etc.)shouldonlybe
removedorreplacedbyqualifiedpersonnel.
2.13.3 Flow modules
- Generalinformation
Thegasflowsensoroperatesonaprincipleofheattransferby
sensingthetemperaturedifferencealongaheatedsectionof
acapillarytube.Partofthetotalflowisforcedthrough the
capillarybymeansofalaminarflowelementinthemainstream
generatingapressuredifference.Thedesignofthelaminarflow
deviceissuchthatflowconditionsinboththecapillaryand
laminarflowdevicearecomparable,therebyresultingin
proportionalflowratesthroughthemeter.TheΔTsensedbythe
upstreamanddownstreamtemperaturesensorsonthecapillary
dependsontheamountofheatabsorbedbythegasflow.
Eachinstrumenthasbeencalibratedandadjustedforcustomerprocessconditions.Theperformance
andaccuracymaybeaffectedtremendouslyifphysicalfluidpropertiessuchasheatcapacityand
viscositychangeduetochangingprocessconditions.Foroperationonothergasesseeparagraph4.1.
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