Off-design Pump Performance Testing

[BobThomasson]

We've placed an order for some large 50 Hz vertical can pumps with a major US pump manufacturer. The contract and PO was poorly written concerning factory performance testing. The factory says they do not have the ability to test the pumps at the design 50Hz and have proposed testing at 60Hz, evidently using affinity laws to correct back to 50Hz. (Attempts to get them to run the motors at reduced frequency and voltage have proven futile).

Can anyone tell me if performance testing of pumps at an off design speed and correcting back to design is an accepted practice and is there a published off-design protocol? My concern is that affinity laws are theoretical and there are real world conditions that may affect the corrections.

Thank you,

Bob

 

[smckennz]

Hi Bob
yes, testing is often done at different speeds to the specified speed. Most test codes permit a test/spec speed variation of around +/- 20%. The pump laws are used to correct the curve. However the efficiency is usually taken as constant. Testing at a higher speed may cause the efficiency to be slightly overstated, but the effect is normally not that great. You can see this by looking at the calculated pump efficiency curves, if you have them.
Have a look at the specified test standard. If one is not specified get a suitable one agreed with the manufacturer.


Cheers

Steve

 

[BobThomasson]

Steve,

Thanks for your reply, it was very helpful.

Bob