Pump Curve - Centrifugal Vs Air Operated Diaphragm Pump

[chemks2012]

Hi all,

Need your help as bit confused..

Please let us know if my below understanding is correct.

Normally, the pump curve is plotted for HEAD vs FLOWRATE

1) For centrifugal pump, this HEAD is nothing but the TOTAL HEAD i.e. the difference in total discharge head required – NPSHa
2) For air operated diaphragm pump, this HEAD is nothing but the total discharged head required

I believe this is because, air operated diaphragm pump capacity depends on the air supply pressure and not the NPSHa.

Any pointers please.

Thanks in advance
KS

 

[sshep]

Centrifugal pump head has nothing to do with with NPSHa (except when the pump is cavitating).
Good luck!
SShep

 

[LittleInch]

For centrifugal pups the pump curve is the differential head, i.e. the outlet head minus the inlet head. If this is below atmospheric pressure then you might have worked it out as the NPSHa, but just think of it as head in plus the differential head from the pump curve equals head out.

An AODP provides the maximum head possible based on air pressure available. It is less sensitive to inlet pressure but then simply needs less air / less work to deliver a fixed outlet pressure if the inlet pressure rises.

I haven't had much experience of AODs, but see this which might be useful..

http://www.globalpumps.com.au/resou...to-read-an-air-operated-diaphragm-pump-curve/

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[chemks2012]

Thanks a lot both of you.

Regards,
KS