Testing a Turbine Pump

[safiamoiz]

My company has purchased a 10 stage Turbine pump, 10 HP. The pump manufacturer has provided the pump curve. Their persons visited our site for commissioning of this pump. The problem is that the data point of commission test comes a bit lower than the pump curve. Can any body suggest why this is happening. Else the pump is running smooth.

Moiz khan

 

[Artisi]

Wow, no need to calculate specific speed any more to decide what impeller profile we have - just look at the pump curve, if it doesn't extend to zero flow it must be mixed flow.

Actually if you would like to check the specific speed you will find it is probably in the Francis-vane range.

As the OP hasn't responded other than;

"safiamoiz (Mechanical) 4 May 10 5:13
Thanks to all. Now the pump is running smooth."

then discussion of the problem, if there was a problem will require a crystal-ball.

 

[QualityTime]

 

[dabluffrat]

You won't damage a small 10 HP mixed flow vertical taking it to shut off during testing... actually it's there that the open impeller to liner fit clearance is "rubbed in" to gain a point or two in efficiency at BEP (little trick).

I can tell you two things for certain working for OEM's for the past 10 years; 1.) No two pumps are exactly identical in performance and 2.) Even two tests on one pump will yield some variance. The combined tolerances allowed in test equipment and casting variations always yields some discrepancies in performance. Most published curves are conservative.

To your point #5... I have a dozen or so similar stories. more often then not, they are discovered during the preliminarily testing prior to the witness test. There's a BIG difference between a 10 HP pump and a 4000 HP pump, namely the size of the impeller... which goes back to my previous argument on casting variations on small sand castings vs. large ones. It's a fact, please take the time to go look this up... larger impeller pump performance is more predictable/repeatable then smaller impellers.

Artisi, I know we're arguing a moot point.


Did you know that 76.4% of all statistics are made up...

 

[dabluffrat]

And since when is a Francis-vane type impeller not considered a centrifugal pump??? did you mean a vertical tubine pump (enclosed impellers)??

Did you know that 76.4% of all statistics are made up...

 

[dabluffrat]

QT,

And to your point #3... I never said a blockage at the suction would not cause a similar curve characteristic.

I said for this small 5" bowl and impeller combination, you won't be able to look into anything. You cannot even run your finger thru the bowl diffusers to check for blockage it's so small.

Did you know that 76.4% of all statistics are made up...

 

[Artisi]

I don't reacall anyone saying that Francis vave impeller/s are not centrifugal or cannot be arranged as a vertical stack, further, vertical turbine is a generic name for any verticaly stacked impeller arrangement, either radial flow, any of the mixed or partialy mixed flow or axial flow impeller profiles.

After 30 years in the pump industry, nothing surprises me any more when it comes to performance testing, particularly site testing or what some belive is "testing" - especially when "ëxpert" consultants are involved. I once had a largish vertical pump rejected on test because the pump tested out at 95% efficient whereas the spec. sheet we tendered said 93% - the reason "not to specification" - a quick phone call to the idiots boss soon sorted that problem.