DonPenn,PE,CGDImageEngineering Group,Ltd

dpenn@iegltd.comOfficeNumber817-410-2858CellNumber817-832-3224

DESIGNING FOR SUCCESSWHAT ABOUT PURGING AND

FLUSHING

Commercial Applications

Learning Objectives• Discuss the importance of proper piping

design to accommodate purging and flushing.

• Discuss design considerations to facilitate flushing and purging.

• Discuss the potential benefits of different design features.

• Introduce new IGSHPA Inspectors Course

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Outline/Agenda

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q ImproperFlushingandPurgingandpipedesign/sizingcanbreakanotherwisepotentiallysuccessfulproject……..

q Designphilosophyforflushingandpurging

q Pipesizingconsiderations.

q Valvelocationandlocationpreferencesandlimitations….

q Header/manifoldconsiderations

Protection/Purging of Piping

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• Duringallphasesoftheinstallationitiscriticalthatallpipingisprotectedfromdebrisandforeignobjectsenteringthepipe.

• Aftertheheatexchangeriscompletedthesystemshouldbepurgedofallairanddebris.

• Debriscanclogorfoultheheatexchanger• Entrainedaircancorrodemetalliccomponents,causenoise,andcanpossiblypreventflowinsectionsofthesystem.

• Trappedaircanbeseparatedfromwaterandthereforeremovedbypowerflushingthesystemataminimumflowvelocityof2feetpersecond(FPS).

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• Therearetwobasicflowregimesdefinedinfluidmechanicstodescribethenatureoffluidflowinanysituation:laminarandturbulent.Inthelow-velocitylaminarregime,fluidflowisstreamlinedandsmooth.Oncethefluidvelocityhasbeenincreasedaboveacriticalvalue,flowbecomeschaoticanddisorderedandentersintotheturbulentregime.

• Themixingoffluidinturbulentflowmaximizestheheattransfercapability.

• Ground-looppipingshouldbesizedsuchthatfluidflowthrougheachloopisturbulenttoensuremaximumheattransfer.

• Turbulentflowcanalsoproducehigherlevelsoffrictionbetweenthefluidandpipewalls,pressuredropneedstobeevaluatedtominimizepumpHP.

Sizing Considerations

FLUSHING, PURGING AND FLOW TESTING

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Ø Beforethesystemisplacedinoperation,flushingofallheatexchangerpipingshallbeperformedtoremovedebrisandair.

Ø Flushingshallbeperformedat135%ofdesignflow,butinnocaselessthan2FPS.

ØEachsubfieldshallbeseparatelyflushedandpurgedØLaststageofflushingandpurgingshouldbethrutheunitheatexchanger;heatexchangersshouldbebypasseduntilpipingsystemisflushedandpurged.

ØAclosedloop-flushingunitwithavolumetankfiltersshallbeutilized.ØTheflushingvolumeshallbeatleast3xthe systemvolume

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Questions?

Don Penn, PE, CGDdpenn@iegltd.com

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