using non-dimentional pump curves to detect wear

[BobMaron]

Does anyone have experience detecting pump wear by looking for changes in non-dimentional pump curves (H-Q) produced from field data on variable speed pumps? I'm thinking of comparing a curve from a new as-installed pump, with one taken at a later time on the same pump

 

[MikeHalloran]

To do that, you need to have a flowmeter and pressure transducers installed.

Having done that, you could just tell the system controller to occasionally compare the operating point with the curve for a new pump, and phone you when the pump goes away.



Mike Halloran
Pembroke Pines, FL, USA

 

[Artisi]

Probably only useful if on a fixed duty instalation, in this case see post from Mike (above).

 

[BigInch]

The problem with "comparing curves" is complicated with variable speed, as you effectively have an infinite number of curves. You'd have to calculate efficiency from power consumption measured at a given HQ & Speed and compare that to the system-corrected efficiency map of the pump.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[BobMaron]

Thanks Mike. As you point out, flowmeter and pressure transducer are installed, in addition to pump speed sensor which permits non-dimensionalizing based on pump speed (variable) and impeller diamter (obviously a constant). And on line density measurment accounts for change in that variable. So it seems relatively straight forward, but I havent't been able to find reference to any application where this is used in 'real-time'. This is slurry pumping application with high abrasive wear, so this type of monitoring would be valuable. Have you ever seen this type of non-dimensional H-Q monitoring used in practice?

 

[BobMaron]

Thanks 'BigInch'. There is a pump speed sensor installed which makes it possible to non-dimensionalize and thus produce one non-dimensionalized pump curve that is speed independant. Do you agree? Have you seen this used in practice?

 

[MikeHalloran]

Most condition reports I've seen from pump "controls" amount to, "She don't work so good no' mo'.", or words to that effect, in some approximation of English, from an actual person.

If you're running lean and mean, and can't afford a person to grow old with the pump, then, yes, you need the controller to do it, and I concur that it should be possible.



Mike Halloran
Pembroke Pines, FL, USA

 

[Artisi]

I think this is a pretty basic investigation.
At x speed with y inlet head -- any change to head, flow, and power while factoring in the de-rating for any slurry variables in real time will give you an indication of drooping performance (wear of components). To correlate this into something meaningful might be an other story (other than the pump is now losing performance) but I guess overtime, reduced performance in conjunction with visual inspection of the wear components should be able to give you an indication of the amount of wear measured against any speed increase to maintain output.

 

[BigInch]

If you mean use a given operating point data H,Q,S you measure and convert that to H & Q at rated speed, you could do that as long as the affinity relationships remain valid.

The general method is used by the more advanced pipeline SCADA systems in order to predict for example, what the flowrate should be at any given setting, and to warn operators when some parameters are seen to be deviating from previous history, possibly as an indication that maintenance is required, or when other hydraulic parameters are not consistant, as evidence of pipeline leaks, etc.


**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/