Dear everybody,

In our plant, there was a motor drive a centrifugal pump. Motor has 30kW, 2 pole, 50 Hz. We took last data on February 6, 2006 and all everything was normal. Today, on February 13 2006, motor vibration increase up mainly at 2V and 1V. We found overall vibration is 6.746 mm/s rms at 2V and 1V is around 4.7528 mm/s rms.
Frequency dominant is 338.75 Hz. 1xRS is 49.375 Hz. Could everybody give suggestion about this problem?

Looks like 6.8X modulated on the lowend by 1X sidebands, but really need more data to see what is going on. Does the 6.8X have harmonics? What are the other peaks in this spectrum?

Can you provide an acceleration spectrum to 2 kHz along w/TWF?

No real problem apparent or a developing problem that hasn't blossumed to full bloom.

I'm like Ralph; need more!

I agree 0-2khz may tell more if it's a bearing problem. Also the bearing p/n if you have it so we can find the fault frequencies.

Is see this is a farily small machine. Is there a monitoring point on the pump? Did it not show these frequencies?

Have you gone back to take another look to see if that pattern is stable?

To. Mr. Ralph, No, It doesn't, 6.8x has not harmonics, and there are not the others peak in this spectrum.

To Mr. Sam,
I'm sorry , my data collector could not TWF and herewith, I attach acceleration spectrum to 2kHz

To Mr. Pete,
Bearing number is 6212 C3 from SKF, I saw these frequencies are appear in 3V and 4V but amplitudo was lower than 0.512 mm/s RMS. This frequency increase up on February 13, 2006. Before that, there was no peak on 338.75 Hz. Everything is normal.

I hope these data more sufficient as your request. I'm waiting your response for this matter.

Regards,
Puji

Is that an acceleration spectrum or a demodulated acceleration spectrum?

I ask the same as Pete, this looks like a demodulation spectrum. May not be, but sure looks like one.

I think what Sam was wanting was a normal non enveloped spectrum displayed in acceleration units out to an Fmax of 2000 Hz.

If this does happen to be a demodulation spectrum, there doesn't look like much is going on in the high frequency range or the band width range chosen.