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marksl

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Hello All,

We recently collected routine vibration on a set of Vertical irrigation pumps while all three pumps where running. The results showed extreme run speed vibration (1x) in all three pumps which was dominate in the motor locations but still excessive in the pumps. We told the client to check the base/mounting for any broken welds or lose bolts as all three pumps where mounted on a common base. To cut a long story short the root cause turned out to be a faulty VSD drive on one of the motors which was causing varying amps across all three phases, has anyone seen this happen before?
John from PA

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Yes, but too long ago to remember the exact details except it was multiple small pumps in a pharmaceutical facility.  The facility was poorly equipped as far as electrical talent (not my talent either) so we had to call in an outside consultant electrician.  Not only was it an internal electrical issue with one controller (maybe a bad SCR) but there were some aggravating influences due to poor utility.  A search now comes up with a good article about the effects of poor power conditions on VFD’s.  See https://www.ecmweb.com/content/article/20892285/riding-through-unstable-power-conditions-with-vfds
Dave Reynolds

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Reply with quote  #3 
Was this the first time you collected data with all 3 pumps running, have they ever exhibited this type of vibration in the past?

Depending on discharge arrangement, you can only stuff so much water thru a certain size pipe. Hydraulic upset can also create high 1 x vibration. I would anticipate more noise than usual coming from pump/piping.

Pumps operating in parallel I assume? IF this is true, then all pumps must have same size impellers, must operate at the same speed whether it be 1 2 3 pumps operating, must run same speed. Pump that is not running correct speed can not overcome the "system" head from the other pump/s thus the water boils in the pump because it can not go anywhere.

IF they all share the same foundation, then one pump can literally shake anything connected to it or in close proximity, again depending on arrangement

Dave
Curran919

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Reply with quote  #4 
Mark, Im curious for more information on this case if you have it.
marksl

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Quote:
Originally Posted by Curran919
Mark, Im curious for more information on this case if you have it.


Hi Curran,

What additional information are you after. The customer was having trouble with the VSD while we were performing the testing so he decided to change it out and the 1x vibration problem disappeared.
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