pump noise

[Giray Veli]

I have centrifugal pumps ın my company. We are usıng for transfer cooling tower water. these pumps are parallel. when we run only one pump ıt ıs creating noise like cavitation but we run other pump same time the noise is cut off. I dont want to run these pumps same time, one of must be spare. What can be the problem.

 

[pointsman]

Referring to the pump characteristic curve, running the second pump shifts the operating point to the left, and lowing your NPSHr and reducing tendency for cavitation.

Is this a new problem? Could it be that you have an obstruction in the suction line, like a partially closed valve or blocked strainer? We need more details in order to troubleshoot effectively.

 

[LittleInch]

Need more details for sure, but is this a new set up or something which has been there along time?

Basic sounds like either blogged or clogged suction or excess flow so operating on the RHS of the pump curve.

Or vortexing into the pump inlet.

Or if this is lifting liquid an air leak into the inlet line.

Many possibilities here.

 

[Artisi]

It's undoubtedly cavitation.
The reason why needs more info.
Check the reasons listed above by others

 

[goutam_freelance]

You did not mention vertical or horizontal pumps.
If vertical pump please check pump submergence. For high flow in any pump with inadequate submergence, vortices may form resulting in air entrainment. This may give rise to cavitation like noise.

 

[Giray Veli]

We have solved problem. We close the return lıne valve to %10 and the sound has cut. Our operation point has moved to right and we adjusted it. Thanks for your replies.

 

[LittleInch]

So in a few months time you'll be writing about how can you repair the return line valve ( I assume you mean on the discharge from the pump?).

On the pump curve, your operation will have moved left, not right.

But thanks for the update, even if this is clearly a temporary fix and could happen again if someone opens the valve a bit more.

 

[georgeverghese]

Sounds like that min flow / pressure recycle valve is not automated, and is set to suit 2 pumps in operation

 

[goutam_freelance]

Continuously recirculating the discharge flow to the inlet results in avoidable energy loss. If possible this should be prevented.

 

[LittleInch]

We don't really know what is meant by "return line valve". Could be a bypass/recirculation line or could be return to wherever the water came from in the first place.

 

[pierreick]

Hi,
A PID and isometric will help.
Is it happening with the same pump or both pumps ?
Pierre