Pump surging

[Charlesi]

Hi gents,

I have a problem relating to two pumps (both centrifugal). Both pumps pump the same distance have the same head requirments (on paper) and all have the same parts. Only one pump is ever running at a time. The problem is that when one pump is running all is well. When we change to the other pump (exactly the same fluid, head requirments ect...) the pump starts to surge. Why would this be? Is it possible that there is some minute change in the piping or impeller that could cause this? This has been an ongoing issue nobody has bothered to figure it out so I eliminated any recent changes that have occured.

Any ideas...

 

[ccfowler]

Charlesi,

Is there a time during the change from one pump to the other when both are running?

 

[cponnu]

You can check the performance curves of the pumps. If one pump has a 'droop' this problem can occur during changeover if most of the system resistance is fixed.

 

[25362]

Are the pumps equal ? Is the effect reciprocal, or it refers to only one pump ? Does it continue after start-up of the suffering pump or does it stop after a while ? How quick is the pump switching operation ? Is one pump stopped before the other is commissioned ?

Can you expand on the fluid handled ?

 

[mk2000]

Charlesi
During the change over. do you have any isolating valves for each pumps. I have to agree with 25362 we need a bit more info on you situation.

 

[JJPellin]

If it is a situation where pump "A" always pumps well and pump "B" always surges, I would suspect an issue with the suction piping. If the piping is assymetric one pump could be going into intermittent cavitation. If the suction is under vacuum during operation, one pump could have an air leak resulting in ingested air. Are there strainers in the suction lines, perhaps?