Thrust Chamber Test Bench

[BoomerSooner7]

Hey guys,

I will give some background info. followed by my question.

We manufacture horizontal mounted, multi-stage centrifugal pumps with a thrust chamber between the pump and motor. We want to build a reliability test bench to artificially load the thrust chamber with axial force applied to the shaft.

Question: Since down thrust is a by-product of a given pump flowing a certain flowrate at a certain head, and that's the only thing the motor "sees" is the frictional forces between the thrust bearings, is it not a safe assumption that it will require the same BHP to operate the artificially loaded thrust chamber vs. the pump coupled to the motor under the same thrust load. I have been told otherwise. What am I missing?

Thanks in advance.

 

[scott1971]

BoomerSooner7:

You said...

...down thrust is a by-product of a given pump flowing a certain flowrate at a certain head, and that's the only thing the motor "sees"...

Unless I'm missing something, I disagree with that statement. The motor also "sees" the torque required to rotate the impellers that pump the fluid. As you increase the flow rate and/or TDH, the required BHP also increases.

I'm guessing that the purpose of your test bench is to allow testing without the pump in place, since running the pump dry would damage the seals and running it wet may be impractical. If you can simultaneously impart a known rotational resistance, maybe with a magnetic brake of some kind (I'm thinking of what they use for a bicycle trainer), that might be a more realistic set-up.

Scott
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[BoomerSooner7]

Agreed. I wasn't taking into account the additional torque required due to the centrifugal force imparted while pumping the water. Duh!

 

[Enkidu]

I'm kind of curious what the test set up looks like, and what you are trying to duplicate and measure.
gotta go - wife kicking me off ;-)