Clarification on static head in pumps

[mucour]

Hello guys,

Any time I read an article or text book on determining the measurement to take when referring to static head I get confused.

The text book definition is that it is the measurement from the free liquid surface in the vessel to the pump inlet eye (centre line).

My own opinion is that the static head should be the measurement from the vessel pipeline discharge point to the pump inlet eye (centre line). Or better still from the LZA(LL) switch of the vessel to the pump eye.

Please what is your opinion on this issue.

Thanks

 

[KenA]

Mucour,
The text book definition is correct (from free liquid surface to pump centre line), but the question is - what level do you assume for the free liquid surface? That can vary depending on why you are calculating the static head. Assuming that you require the static head for calculating the NPSHA for the pump, then the normal practice is to assume that the liquid in the vessel is at the lowest level that the pump is required to operate. This is usually the low low level trip point which you refer to.
k

 

[mucour]

Thanks KenA for the clarification.

I actually raised the thread wrt NPSHA as you correctly guessed.

You confirmed my thoughts also.