Counter weight on the foot valve

[Bultum]

HI,

I am currently working on a pump station that is struggling when the water level is below the pumps centre line. It has been suggested the foot valve located on the suction side is causing too much head loss since its fitted with a counter weight.

My understanding is the purpose of the counter weight is to generate a torque on the NRV and ensure its tightly shut. Besides ensuring the valve is tightly shut, does it serve another purpose? if i was to remove the counter weight, how would the operation of the foot valve change? Few of my reading seem to suggest, the disk will slam against the body when the pump is starting and stopping, therefore reducing the expected life of the foot valve.

Thanks for your help!

 

[Artisi]

If the pump is "struggling", what ever that means, when the level is below the pump centre line, you have more of a problem than the head loss thru' the foot valve, assuming the foot valve is correctly sized.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

A counter weight does what you suggest. However this is clearly something the designers thought was needed. If you remove the weight there may be more leakage and your pump may not work due to lack of water when you start it.

Is this something new?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[electricpete]

My two cents - I agree with LittleInch (whose two cents are worth 1,000 times mine).

I don’t know about foot valves, but that’s the way a typical check valve works: forward flow holds it open, gravity helps close it to prevent reverse flow.

If the counterweight assists gravity to keep it closed, then removing the counterweight may allow the pump to drain when not in service. That could result in priming problems or maybe water hammer during next start.


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(2B)+(2B)' ?

 

[LittleInch]

I wish they worth 1000 times yours....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

The main question is the counterweight causing excessive head loss (the OP's opinion), the OP's question of removing the counter-weight is secondary and in my opinion not a cause of the pump "struggling" what ever that means.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[georgeverghese]

For these and other reasons, foot valves at pump suction are considered to be unreliable. Preference is to enable self priming at the pump.