Is a relief valve needed for centrifugal pump in this application? 1

[EngCutie]

Hi, I’m new to pump field, so please help me.

I attached a drawing just in case I can’t explain myself clear enough.

Anyway, I read that ‘A relief valve is only needed if no other measures are provided to detect low flow conditions and shut down the centrifugal pump to prevent damage’, well in my situation, there isn’t a flow measuring instrument installed upstream of the pump, but there is a (tank) top mounted level transmitter to detect the level, I suppose if the level is too low, then there won’t be enough flow, so the LT can in a way detect the low flow condition, am I right? If not, does it mean I need a relief valve for this pump?
Thank you


Cutie


Thank you, EngTips

 

[BigInch]

I don't know what you've been reading, but it certainly should not be used as a general guide to pump installations.

Always you must realize that, if a maximum allowed pipe or equipment pressure can be exceeded, safety must be provided.

The diagram indicates that the pump will discharge maximum pressure when the tank is full. Centrifugal pumps normally discharge maximum suction pressure when flow is low. That can happen during normal operation and during both startup and shutdown. So, assuming the tank is full and the pump is starting, you would have maximum suction pressure and the pump curve is at maximum discharge head, giving a combined total maximum discharge pressure.

If the pump maximum discharge pressure is greater than the pump's rated discharge pressure (for example if the suction pressure were to go very high), or if the discharge pressure could reach levels over the downstream piping's pressure rating, or any equipment downstream, you can have a dangerous condition and a relief valve should be provided somewhere. On, or very near, the pump's discharge would be the logical place to put one as that point would normally experience the highest pressures in a piping system.

A pump can also develop high pressures, if it is operating while any downstream valve is closed, due to fluid heating inside the pump. Another reason for a pump to have an integral relief valve.

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[EngCutie]

Thank you very much BigInch, it’s very helpful.

Cutie


Thank you, EngTips