painfully loud motor
painfully loud motor
(OP)
Is there any electrical mechanism that I'm just not able to figure out that would cause a motor running under typical conditions to make an exceptionally loud noise under load? I'm fairly certain it's mechanical, but I'm being told it could be electrical and I just want to rule out anything wierd. It is a pump motor and the pump and motor have both been replaced seperately and together and the noise continues. I'm told it's coming from the motor/pump assy.





RE: painfully loud motor
Motors on adjustable freq drive can produce some interesting noises.
"An 'expert' is someone who has made every possible mistake in a very narrow field of study." -- Edward Teller
RE: painfully loud motor
RE: painfully loud motor
When you cut the power does the noise cease immediately or does it continue as the motor coasts down? Generally, if the noise is electrical it will quit as soon as the power is cut. Thanks
RE: painfully loud motor
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If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: painfully loud motor
RE: painfully loud motor
What does the noise sound like?
Got a recording?
Keith Cress
kcress - http://www.flaminsystems.com
RE: painfully loud motor
Run motor light (split coupling) to determine motor or pump. Maybe rotating unit bearings are U/S? Is the wear plate rubbing on the impellor?
Turn pump and motor by hand if you can to get a feel for the bearings.
Check non return valves/autovalves if any.
Does it have a spider coupling? Check spider. This can be done on the run with a strobe. Check tyre if it's a tyre type.
Sorry if I'm over simplifying. I am just a lowly shift electrical tech in a paper mill.
Has vibro analysis picked up that it is an electrical problem? Quite often I am handed jobs from the VA department saying that there is a problem with a motor electricaly only to find there isn't!
I would bet it is a process or mechanical problem. If your work is like mine, that makes it your problem.
RE: painfully loud motor
You may have a "forbidden frequency" at of near line frequency.
I remember a 4 inch diameter hole blown in the side of a pump casing by a VFD that had not been programmed for the forbidden frequency properly. The sad part was that it happened twice before it was corrected.
A long straight pipe run downstream of the pump is conducive to this problem.
There are the basic solutions.
Change the frequency.
Change the number of impeller blades.
Change (usually shorten)the length of straight discharge piping.
Is this a new or a changed installation? Did the noise start following some change?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: painfully loud motor
There is no vibration measuring equipment available to my knowledge.
I've heard several descriptions of what it sounds like, and I heard it over the phone....kind of like a boeing 747 coming to a stop on a runway - upside down. Can't really remember the other descriptions, all similar though :)
The coupling is a lovejoy. I think that was inspected, but not sure if they replaced it.
I'll see if the discharge pipe has a different configuration than usual, however, I'm fairly certain is a configuration we use regularly as far as plumbing the pump in. The longest run of pipe (tubing in this case) would be no more than a couple feet if that...
We ran the thing here and did not experience the noise...apparently it began on site. Another thing we've considered is a damaged diaphragm in the pressure vessel. Pretty much all other parts have been swapped.
I should know in a few days what they find and I'll post it...
RE: painfully loud motor
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RE: painfully loud motor
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RE: painfully loud motor
Typically the frequency of electromagnetic noise would be a pattern of 2*LF sidebands around/including rotor bar pass frequency.
For example if LF = 60hz, speed= 30hz and you have 40 bars, the frequencies would likely be:
30 * 40 = 1200hz
30 * 40 -120 = 1080hz
30 * 40 +120 = 1320hz
You might also have pattern of 2*LF sidebands near 2*RBPF, 3*RBPF etc.
Even if the noise didn't turn out electromagnetic, the spectrum may provide some clues as to the source.
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RE: painfully loud motor
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Eng-tips forums: The best place on the web for engineering discussions.
RE: painfully loud motor
Keith Cress
kcress - http://www.flaminsystems.com
RE: painfully loud motor
Has anybody checked the bypass valve. Hydraulic pumps are usually positive displacement. If the pressure gets too high on the outlet, a bypass valve opens and runs the overpressure back around to the suction side. On some pumps this is very noisy.
These are usually spring-loaded relief valves and a broken or weak spring will let it start 'bypassing' at a lower pressure.
old field guy
RE: painfully loud motor
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: painfully loud motor
RE: painfully loud motor
Why? Was that before the noise started or after? It may be that they may have removed a check valve that may have kept the fluid coming back to the pump from the vessel??
RE: painfully loud motor
If so, I will pretty much guarantee that electromagnetic noise is exactly what you're seeing.
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RE: painfully loud motor
At this moment I tend to agree with 1000V.
RE: painfully loud motor
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: painfully loud motor
I have a hydraulic pump which gets noisy when loaded at the workshop before. We singled-out the noise coming from the pump, the motor seems to run well. Turned-out to be an overload on the system and pressure relief partially bypasses and chatters causing the noise.
RE: painfully loud motor
Thanks for all the input....
RE: painfully loud motor
Keith Cress
kcress - http://www.flaminsystems.com