Minimum flow control valve.

[Indy]

Hi,
If a pump has a minimum flow control valve which is fail open and say for instance this valve fails (open) would it be over the top to also trip the pump ?

Thanks.

 

[LittleInch]

No.

If the valve is full open, you can't have much forward flow and could go off the end of curve so trip the pump

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[mk3223]

To trip the pump, it may need some sort of flow, pressure, or temperature switches to activate it. Right?

 

[LittleInch]

It all depends on details. If the max flow through the valve at 100%open is less than pump max flow then you don't NEED to trip the pump.

This fault is pretty rare.

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[bimr]

Selecting a pump and motor combination that will function under all system conditions is essential. It is typical to select a non-overloading motor. This usually means selecting a motor 20-30% larger than the power required at the design point. This means that one will pay a slight efficiency penalty for selecting a non-overloading motor and also a higher upfront cost. The operational problems and costs that are avoided, however, far offset the relatively minor upfront cost.

 

[georgeverghese]

Most installations dont have such a feature - pump may run to end of curve but is not an immediate risk to machine integrity or plant safety. Long term operation at end of curve may cause impeller damage due to insufficient NPSH, so a low pressure alarm at DCS should do.

 

[Indy]

Thanks for the replies.

 

[LittleInch]

So what are you planning to do?

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

 

[georgeverghese]

Am assuming you have motor overload-overcurrent protection when the pump goes to end of curve as discharge pressure collapses when this min flow CV fails open, hence no need for further instrumented trip protection.