Have any one seen similar behavior. This has been picked up from MOB wiht flow direction of Vertical Motor driving Pump.

What is the best way to dignose this beating?

The Beat frequency is 0.042Hz or 2.53 cpm. If the electrical frequency is 60 Hz, and Synchronous speed is 900 rpm, then the electrical pole-pass frequency is 0.71 Hz or 42.6 rpm. So there is no match to an electrical fault. Does the pump in question share a common foundation or pipes with another pump/machine that has a speed difference of 2.53 rpm?

Walt

Is it a beat or amplitude modulation? Can you take a high resolution spectrum? If there are 2 peaks, its a beat. Besides the phenomena Walt has mentioned above, this could be some kind of flow problem related to design of the inlet vortex, tank levels or process flow. A beat is very likely if there are 2 or more pumps operating at the same speed close by.

Any chance of you exporting the data so I could import it into my copy of Ascent?

Be interested in playing around with the data a little bit.

Marty

Hi All,

Thanks for sharing ideas, as requested by Marty, the file is attached.

This pump B is sharing another pump A in one tank and they are nearby. Another pump C is line with other two but it has its own tank.

First I suspected beating is being excited by some electrical problem, so I requested to replace the motor with a newly overhauled motor. Despite this, as Walt stated, this not an electrical fault but still worth a try.
As two pump must be running and one is standby, I requested to shutdown the pump A sharing this pump in the same tank. The output is the same. What I did not do is to shutdown the third pump C and to take my reading.

As I want to put a recommendation, what else can be done except shutting dow Pump C and see the result. As the field is far a way and I need to be will prepared.

Thanks.

XYZ,

Can you post very high resolution (12,800 lines), low Fmax (200 Hz) spectrums? Look for sidebands around 1x, 2x and 3 x which would be indicative of amplitude modulation, or most likely, 2 peaks near 1x which would be the beating frequencies.

Bill,

with thanks.

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