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We are finding a large amplitude of 0.4 inches/second @ 4300 cpm on a 3500 rpm pump.

We tried a bump test on the pump while it was not running (the operator couldn't switch it on at the time). Found a very low peak @ the same frequency as well as a much higher amplitude from the neighboring operating pump, will go back when they can switch over pumps.

Could this be resonation? If not what could it be?

(Sorry for the limited fft graph)

Approximately 4300cpm (3580 cpm = RPM)

Screenshot [9)

 

RHW2ND

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Original Post

We are finding a large amplitude of 0.4 inches/second @ 4300 cpm on a 3500 rpm pump.

Could this be resonation? If not what could it be?

(Sorry for the limited fft graph)

Approximately 4300cpm (3580 cpm = RPM)

 

 

Yes, it could be resonance but seriously, is more data available to support some possible causes.

I see a firm, same name, same zip code.  https://idssproactive.com/.  Is that your firm or employer?  I'd be somewhat embarrassed to present what you've done so far!

Bob,

Have you measured vibration on suction and discharge piping, especially if two or more pumps share the same header/manifold? Possible piping resonance.

Is the pump single stage or multiple stage like a boiler feed pump?

Does the pump run at constant speed?

Horizontal or vertical shaft orientation?

New problem on old machine, old problem on old machine, or new machine with this problem?

Walt

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