Dear  all

i am dealing with a RAW mill simple supported  system fan 2500 kw motor with 990 r.p.m . The  spectrum in DE bearing showing 1X with an amplitude 3.8mm/s overall vibration is 4mm/s in DE bearing in horizontal direction.

vertical: 1.2 mm/s

Axial: 1.4 mm/s

but at NON DE side bearing we are having 5mm/s overall vibration in horizontal direction. the  spectrum in NDE bearing showing 1X with an amplitude 3.9mm/s .

vertical vibration is :1.8mm/s

Axial: 2.4 mm/s

by doing time wave form analysis we observed impacting in NDE bearing. but there is no impacting in DE bearing. 

NDE bearing is SKF CARB  bearing. So my question is can we perform Dynamic Balancing ??

if yes  will we get satisfactory results?

Alignment was verified with SKF laser tool-41.

Phase at DE side bearing is 110 degree.

Original Post

questions:

(1) Is it a centerhung or overhung fan?

(2) Can you show us the impacting waveform?

(3) Have you tried and failed with a single plane balance or are you planning on a single plane first or multi-plane balance first?

(4)The 110 degree phase on the DE, what is the 110 referenced to, a refelection "tape" position on the shaft or reference to the NDE bearing?

 

Thanks,

Ralph

"So my question is can we perform Dynamic Balancing ??"

Yes, if rotor is accessible to add/remove balance weights.

"if yes  will we get satisfactory results?"

Yes, if rotor is clean and no cracks or looseness and bearings are tight and in good condition.

You should also inspect bearing pedestals/housing for loose bolts and foundation (steel, concrete, grout) for significant cracks.

Walt

Ralph Stewart posted:

questions:

(1) Is it a centerhung or overhung fan?

(2) Can you show us the impacting waveform?

(3) Have you tried and failed with a single plane balance or are you planning on a single plane first or multi-plane balance first?

(4)The 110 degree phase on the DE, what is the 110 referenced to, a refelection "tape" position on the shaft or reference to the NDE bearing?

 

Thanks,

Ralph

1 it is centrehung fan

2. i am planning for single plane balancing but i have some doubt in fan NDE bearing.

3 phase reference 110 on DE side is w.r.t to reflection tape position on shaft.

 

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Photos (1)

Your waveform looks like there is a modulation (angelfish) pattern associated with 1x.

Gs are fairly low, but concern-able.

Also might have several (4 or 5) harmonics of 1x in the spectrum. There may be a problem with the inner race.

Can you post a few spectrums of both bearings, horizontal and vertical?

What is the phase relationship between the Horizontal DE and the Horizontal NDE (for balance reasons)?

Is the fan actually centered between the bearings or is the rotor offset more toward one bearing than the other?

Thanks and Have a Great Day,

Ralph

A center hung rotor with wheel between bearing can be symmetrical with double air inlets or asymmetrical with single air inlet. Single inlet fans can be balanced by single plane method with care. While it would be better to fix the bearing first, it may take less time to trim balance and extend the bearing life to a more convenient outage.

Walt

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