effect of restricted suction upon pump amps (high speed multi-stage centrifugal pump) 5

[electricpete]

The pump in question is 10 stage horizontal 7300rpm centrifugal pump.

It is driven through gearbox by a 600hp motor.

For some context, the pump was operating in steady state at 70% motor load (approx 400hp), when suddenly the current began to increase, speed began to decrease, indicated flow went down.

We are investigating a variety of scenarios to explain that (and there's a lot more info not shared), but here for purposes of this thread I'm not concerned with any scenario other than sudden restriction of the suction path.

Would you expect that to cause the amps to increase or decrease? (my uninformed vote is decrease, similar to effect of throttling the dischrage path in radial flow pump, but I'm interested in firming that up or knocking it down).


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(2B)+(2B)' ?

 

[electricpete]

> I have two experimental gearboxes in my fleet right now and it has accelerometers mounted on the casing near every accessable bearing. The manufacturer is remote monitoring to develop a condition based maintenance approach but I don't have access to any information beyond that.

> This vibration sensor that has picked up high vibration "on the gearbox casing" needs clarification - it cannot be on the casing;

It should not be there but it is. We have only one sensor on the gearbox. It is not well situated. It is neither near a bull gear bearing nor a pinion bearing. We just call it casing. That is the data we have to work with.

> What is the bearing type/material in the pump.

Babbit lined tilting pad radial and thrust bearings.









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(2B)+(2B)' ?

 

[TugboatEng]

In my experience with centrifuges there will be an acceleration switch mounted on the machine. The machine is resilient mounted and acceleration exceeding a certain value will trip the unit. The mounting location isn't specific.

With that said, acceleration on a gearbox can be exaggerated by features. A lifting eye may resonate with more displacements than a bearing housing and may be a better indication of trouble when mounting an accelerometer.

Accelerometer diagnostics rely heavily on baseline measurements. There aren't strong correlations dictating position or nominal readings.