Owner manual

  <4.InstallingImpulsePiping>
25
IM01C25A01-01E
(4) TemperatureDifferenceBetweenImpulse
Piping(fordifferentialpressure
transmitters)
Ifthereisatemperaturedifferencebetweenthehigh
andlowimpulselines,thedensitydifferenceoftheuids
inthetwolineswillcauseanerrorinthemeasurement
pressure.Whenmeasuringow,impulselinesmustbe
routedtogethersothatthereisnotemperaturedifference
betweenthem.
(5) CondensatePotsforSteamFlow
Measurement(fordifferentialpressure
transmitters)
Iftheliquidintheimpulsepipingrepeatedlycondenses
orvaporizesasaresultofchangesintheambientor
processtemperature,thiswillcauseadifferenceinthe
uidheadbetweenthehighpressureandlowpressure
sides.Topreventmeasurementerrorsduetothesehead
differences,condensatepotsareusedwhenmeasuring
steamow.
(6) PreventingWindSpeedEffectsinVeryLow
DifferentialPressureMeasurement
(fordifferentialpressuretransmitters)
IMPORTANT
Whenusingadifferentialpressuretransmitterto
measureverylowpressures(draftpressure),thelow
pressureconnectionportisleftopentoatmospheric
pressure(thereferencepressure).
Anywindaroundthedifferentialpressuretransmitter
willthereforecauseerrorsinthemeasurement.To
preventthis,itwillbenecessaryeithertoenclosethe
transmitterinabox,ortoconnectaimpulselineto
thelowpressuresideandinsertitsendintoawind
excludingpot(cylindricalwithabaseplate).
(7) PreventingFreezing
Ifthereisanyriskthattheprocessuidintheimpulse
pipingortransmittercouldfreeze,useasteamjacketor
heatertomaintainthetemperatureoftheuid.
NOTE
Aftercompletingtheconnections,closethevalveson
theprocesspressuretaps(mainvalves),thevalvesat
thetransmitter(stopvalves),andtheimpulsepiping
drainvalves,sothatcondensate,sediment,dustand
otherextraneousmaterialcannotentertheimpulse
piping.
4.2 ImpulsePipingConnection
Examples
Figure4.6,4.7,and4.8showsexamplesoftypical
impulsepipingconnections.Beforeconnectingthe
transmittertotheprocess,studythetransmitter
installationlocation,theprocesspipinglayout,and
thecharacteristicsoftheprocessuid(corrosiveness,
toxicity,ammability,etc.),inordertomakeappropriate
changesandadditionstotheconnectioncongurations.
Notethefollowingpointswhenreferringtothesepiping
examples.
• Iftheimpulselineislong,bracingorsupportsshould
beprovidedtopreventvibration.
• Theimpulsepipingmaterialusedmustbecompatible
withtheprocesspressure,temperature,andother
conditions.
• Avarietyofprocesspressuretapvalves(mainvalves)
areavailableaccordingtothetypeofconnection
(anged,screwed,welded),construction(globe,gate,
orballvalve),temperatureandpressure.Selectthe
typeofvalvemostappropriatefortheapplication.
Tee
3-valve
manifold
Drain valve
Orifice
Drain plug
Tap valve
Union
or flange
Liguid Gas
Condensate pot
Steam
F0406.ai
Figure4.6 ImpulsePipingConnectionExamples
(fordifferentialpressuretransmitters)
F0407.ai
Pipe (opened to atmosphere
at low pressure side)
Open Tank
Closed Tank
Tap valve
Union or flange
Vent plug
Tee
Drain valve
Drain plug
Figure4.7 ImpulsePipingConnectionExamples
(EJ210)
InstallingImpulsePiping
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