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Air Ingress Into Surface Condensate Pump Lines

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#1 Venkat1989


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Posted 12 May 2019 - 07:59 AM

Dear all,


Recently our recycle gas compressor got tripped due to high level, we have got two surface condensate pumps, one is driven by steam and other is by electric driven. Steam driven condensate pump is on maintenance, blinding of the suction and discharge lines are done after closing suction valve.


After maintenance of steam driven condensate pump, lining up of it is planned, before opening the suction valve whose upstream pressure is around -0.4kgf/cm2 abs, the downstream line is primed through priming line available u/s of pump discharge check valve connected to surface condenser top whose pressure is -0.9kgf/cm2 abs.


After opening the suction valve, the other pump stopped developing pressure, the level in surface condenser  level raised in 3-4 minutes to 90% and RGC got tripped.



My 1st question is, what could go wrong in electric driven pump while opening the suction valve of standby pump??


Suppose if the trapped air in the downstream of suction valve due to improper priming is present, Is it possible to the trapped air to  travel to the suction line of other pump? Kindly help me in understanding this. thank you.







#2 thorium90


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Posted 12 May 2019 - 10:30 AM

Perhaps a simple sketch would be useful? Sometimes I find it hard to imagine pumps even though I see pumps all the time.

#3 Art Montemayor

Art Montemayor

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Posted 12 May 2019 - 03:33 PM



Thorium is correct in requesting more specific and detailed basic data - especially in the form of a detailed flow diagram showing all the piping around the two pumps.


Nothing else is as descriptive as a detailed flow diagram - no matter what language you write in or whether it is rhymed poetry or not.  Engineers express themselves in detailed drawings that reflect an international language understood by all involved.  For example, what does a “recycle compressor trip” have to do with the loss of prime in a pump?  After 55 years in the industry, I never heard the term “surface condensate pump”.  Is it on the ground surface?  Or is the condensation taking place on the surface of cooling tubes?  Are you pumping a saturated liquid at its boiling point?  What is the pump fluid and its temperature as well as its boiling point at the indicated suction pressure.


I personally don’t see the data importance of having a steam and an electric motor piped together.  It should not make any difference what the driver is (and its condition) when there is loss of prime in the pump.  What is an “RGC” - a recycle gas compressor?  If so, it should be identified if it plays a part in the pumping process.  If not, forget it.


Please submit a sketch and if entrained, trapped air is suspected in the piping, show an isometric view so our members can make a valued judgment.

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