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RGf

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Reply with quote  #1 
We just got done putting one off our condenser circulating water pumps back in the hole after the 2nd rebuild since the summer of 2013. Come to find out the baseplate was off level in more than a few places by almost 1/4" and wasn't found back in 2013 (not on my watch BTW). So in 2013 they put a perfectly good pump back in the hole and found out it went south again just as the original one did. Has anyone come across this situation where 2 of 3 pumps run warm and fuzzy forever but the third is a train wreck? Should I attribute it to a bad original baseplate install or is there something else I should be looking at? (See attached field machining data sheet and photo) the one on the right is the evil one.

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Dave Reynolds

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Reply with quote  #2 
Depends on the failure mode. If the impellers, bowls, shaft are being damaged is it because there is high vibration? Do the other 2 pumps run smoother have less vibration than pump 3?
Agree that out of level is a big deal, poor base plate contact to grout/concrete/anchors is also a major contributor.
Start with the pump is designed to deliver x flow @ x psi/tdh, does the pump meet this criteria? When it "fails" what is failing? Is a mechanical failure or performance/hydraulic failure?
What about the wet well design, is it prone to dirt buildup in the sump which would affect the pumps performance by restricting inlet to pump?
Need more data to better understand your problem
Dave
Curran919

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Reply with quote  #3 
This happens in almost all VS installations from my experience. At least from a vibration standpoint. I'm working on a site in Pakistan where they have five identical side by side verts. Four have vibration under 2 mm/s, the fifth has vibration over 8 mm/s. There is your difference between warm and fuzzy and a train wreck. I expect to see a poorly mounted base plate or a damaged foundation.

If you've really had two pumps in the same hole both have problems, its bound to either be vibe related with the baseplate foundation, or to be sump related (if wet pit).

In these situations, we like to start playing musical chairs with the pumps (or parts thereof) to confirm.
RGf

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Reply with quote  #4 
After a good machining of the baseplate and a precision alignment/lift adjustment the pump was placed in service and the MOH is less than 1 IPS (previous 0.75IPS) which is exceptional for this type of machine. As our inspections did not discover any issues with the pump pedestal and absent of any other known issues I'm going to assume (for now) that the issue was the baseplate. A tough lesson learned here as when all is said and done this exercise cost us almost $400K.

The pump rebuild report showed a very directional wear pattern that mimicked the 2013 failure. Worn wear rings and cutlass bearings. Motor checked out good during solo run.
Curran919

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Reply with quote  #5 
Quote:
Originally Posted by RGf
After a good machining of the baseplate and a precision alignment/lift adjustment the pump was placed in service and the MOH is less than 1 IPS (previous 0.75IPS) which is exceptional for this type of machine. As our inspections did not discover any issues with the pump pedestal and absent of any other known issues I'm going to assume (for now) that the issue was the baseplate.


Less than 0.1 IPS, you mean?
RGf

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Reply with quote  #6 
yes-0.073 IPS to be exact.
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