Affinity laws applied to pump performance test ISO9906

[pumpmanpl]

Pump gurus
Can the affinity laws be applied to a pump performance test to ISO 9906.
We have a workshop pump test rig
and want to test a water centrifugal pump at 100 l/s at 35 meters head.
However our test rig can only handle 50 l/s so, is it acceptable to test it at 50 l/s and apply the affinity laws.
Is this acceptable under the ISO 9906 pump performance test as we are not testing the pump at its actual service flow and head condition.

 

[1503-44]

Affinity laws are not especially accurate and should only be used for relatively small changes in any given variable. That's why actual testing is needed.

A black swan to a turkey is a white swan to the butcher ... and to Boeing.

 

[LittleInch]

No because the affinity laws are relative either to impellor speed or impellor diameter, not flow rate through the pump.

You will only get duty points from 0-50 l/s and then you want to try and extrapolate the curve to 100l/s plus??

I wouldn't accept that as a client.
Pretty sure in ISO a test is a test, not an extrapolation of a curve with only half the points you need....

Need to find a bigger rig....

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

 

[pumpmanpl]

sound advise...yes its unlikely customer will accept
a pump performance tested at a lower speed.

 

[LittleInch]

You didn't say anything about speed, only flow.

So was the idea to reduce speed with 50l/sec?? Your head would be very low....

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

 

[pumpmanpl]

Correct Littleinch...

we have a VSD and can run the pump at a lower speed.

we can't run the pump at its service speed of 1450 rpm
on our pump test rig because it is not big enough to
handle the high flow.

but as you had mentioned best to test it on a pump test rig
so we will probably outsource it to someone with a bigger
pump test rig that can test the pump at its service duty
of 100 L/s @ 35 m head.

 

[LittleInch]

It's also very difficult to extrapolate NPSH.

That sounds like a good way forward. At 50% speed your head would only be about 8m. Too low to measure properly.

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

 

[pumpmanpl]

what velocity limits would you say we should keep
within on the our pump test rig pump discharge
pipe side.

would a max limit of 5 meters/sec be too high
or
the rule of thumb is about 3.5 m/s

avoiding the unwanted tuirbulence, noise, high friction,
cavitation.

 

[LittleInch]

If you've got elbows, valves etc in line then 5 is pushing it to avoid this issue you mention. You can see it in short sections but not generally the whole thing.

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

 

[pierreick]

Hi ,
When you purchase a pump from reputable vendor it's a good habit to purchase the test certificate .
note : Third party dealing with calibration can also offer this kind of service .
My 2 cents
Pierre

 

[SB1976]

Affinity laws break down at flows/speed away from the actual ones at site. API 610 stipulates test speed to be no more than 3% of the actual pump operating speed.
Hence, your test rig cannot be applied. Sorry.