How does a centrifugal pump age?

I am involved with a project that has centrifugal pumps that have
been in service in a large municipal installation for about 40
years. No real possibility of running them off their curves...
but...
What is typical aging behavior for the impeller / volute over
time? Is it "predictable", or something you can't know without
(at least) 4 data points...
Anyone with experience in this area?
David A. Smith
Reply to
N:dlzc D:aol T:com (dlzc)
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Are you pumping abrasives or clear fluid?
C-pumps running abrasives degrade approximately linearly as long as the wear isn't drastic. I have a lot of experience with c-pumps running cement slurry. They're good for ~20-40 hours at max flowrate with the most agressive stuff before the slurry eats the ends off the impeller. Critical wear point was the trailing edge of the impeller vanes.
This doesn't significantly change the overall flow pattern in the pump, so the rate of material loss is approximately linear (at fixed flow rate) and you can predict when you'll hit a certain pressure point. Volute wear wasn't nearly as much a problem as impeller/seal wear.
Tom.
Reply to
Tom Sanderson
Dear Tom Sanderson:
Tom Sanders> > What is typical aging behavior for the impeller / volute over time? Is it
Canal water (slightly green, very little sand).
As to "prediction", does it follow simply making the impeller smaller diameter (for some range), or is it more complex than this?
And thanks for intuiting that I was interested in the flow vs. head / pressure curve! ;>)
David A. Smith
Reply to
dlzc
"N:dlzc D:aol T:com (dlzc)" wrote in message news:74ZYg.4746$v43.1904@fed1read02...
A pump that ages experiences wear at it's sealing surfaces. Power consumption can be considered nearly constant for a given flow and, due to recirculation, the output head will drop a few percent. Hydraulic losses due to changes in surface finish are negligible, particularly for medium sized and large pumps. The net effect of this will be lower efficiency for a given head/capacity. As you near end stage when the shaft starts slamming around in the bearings power consumption can be expected to change markedly, perhaps even climbing.
Reply to
Anthony Garcia

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