YOKOGAWA EJA210E - Impulse Piping Connection Examples

<4. Installing Impulse Piping>
37
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)