Dear Experts 

what is the best way to detect the shaft wear under the bearing inner race or under the sleeve specially i face many problems like that but the only frequency shown in the spectrum is 1XTS.

Example 

Overhung Fan 

variable speed motor (rated speed 1485 rpm)

dominant frequency 1XTS (H=10 mm./sec....Vertical=6 mm./sec.....A=4 mm./sec)

after balancing the vibration dropped to 2 mm./sec  but in two days the vibration reached 36 mm./sec at horizontal direction 1XTS dominant

vertical 25 and axial 8 but dominant is 3XTS 

please take a look at the attachement 

Shaft photos and measurement points after symptom being very effective 

 

Attachments

Photos (2)
Files (1)
Original Post

I'd have to look carefully at the data to see if there are some subtle symptoms but if I have an undersize shaft ("looseness") that also means I have a shaft that can be eccentric in the bearing bore.  What does eccentricity cause?  Unbalance (1X).  But if the shaft is undersize to the point where it can randomly take a position within the bore, I would anticipate a different phase every time the machine is stopped/started.  In addition, attempts to balance might be unsuccessful.  

John from PA posted:

I'd have to look carefully at the data to see if there are some subtle symptoms but if I have an undersize shaft ("looseness") that also means I have a shaft that can be eccentric in the bearing bore.  What does eccentricity cause?  Unbalance (1X).  But if the shaft is undersize to the point where it can randomly take a position within the bore, I would anticipate a different phase every time the machine is stopped/started.  In addition, attempts to balance might be unsuccessful.  

i have already balanced the fan two days before exhibiting high vibration ,but how should i anticipate the shaft wear specially during balancing the phase was stable horizontal to horizontal 

is there a way to anticipate shaft wear , we found it 0.07 mm wear 

thanks 

I think something is wrong with your cascade plot. You measured the highest vel. in december right? But on your cascade you have the highest levels in june. The spectrum order in cascade is random which also isn't the best.

Can you sort these things above and also send cascade for Peakvue?

 

Becar posted:

I think something is wrong with your cascade plot. You measured the highest vel. in december right? But on your cascade you have the highest levels in june. The spectrum order in cascade is random which also isn't the best.

Can you sort these things above and also send cascade for Peakvue?

 

Based on date entries of "10/17/2019" and "10/27/2019" it appears as if the date format is month-day-year so the largest is December (12/6/2019).

Did you clean the fan rotor before balancing it?

Did you weld weights on rotor for balancing? If yes, then was the electric welder properly grounded to the fan rotor and not to the case?

I assume the bearing was destroyed to cause the inner race to drag over the shaft and cause all of the surface gouging; correct?

Did you use any other means of bearing fault detection; such as high frequency acceleration or demodulation?

Were the bearing housing grease seals in good condition and keeping contamination from the lubricant (grease or oil)?

Considering the trend of the spectra with no bearing fault frequencies present, it looks like the bearing damage occurred as a result of the balance job!

Walt

Walt Strong posted:

Did you clean the fan rotor before balancing it?

Did you weld weights on rotor for balancing? If yes, then was the electric welder properly grounded to the fan rotor and not to the case?

I assume the bearing was destroyed to cause the inner race to drag over the shaft and cause all of the surface gouging; correct?

Did you use any other means of bearing fault detection; such as high frequency acceleration or demodulation?

Were the bearing housing grease seals in good condition and keeping contamination from the lubricant (grease or oil)?

Considering the trend of the spectra with no bearing fault frequencies present, it looks like the bearing damage occurred as a result of the balance job!

Walt

thanks for your attention 

yes the welding machine was properly grounded and the procedure of balancing and welding was correct.

i used peakvue technique yes i always use peakvue using CSI 2140 

 

the bearing seal was replaced two days before balancing as it was damaged.

the balance job damage the bearing ??!!! i doubt.

Regards'

Attachments

Photos (1)

Thanks for confirming a good balancing procedure and results. You did not mention if the rotor was cleaning prior to balancing. A material loss after balancing could explain the very high 1xSS two days after balancing. You did not mention the bearing condition when it was removed. 

Walt

Walt Strong posted:

Thanks for confirming a good balancing procedure and results. You did not mention if the rotor was cleaning prior to balancing. A material loss after balancing could explain the very high 1xSS two days after balancing. You did not mention the bearing condition when it was removed. 

Walt

 

Attachments

Photos (1)

So the bearing and housing and shaft surface were destroyed in two days from the balancing job!

One of the early technical papers on CSI PeakVue presented in October 2001 stated, “the primary PeakVue parameter which should be used for trending PeakVue measurements is the parameter referred to as Peak-Peak Waveform”. I believe that the bearing was significantly damaged by contamination at the time of balancing and when the grease seal was replaced. The PeakVue waveform was already indicating nearly 8-G acceleration before/after balancing! The fan operates in a hostile environment, so consider better shaft seals and improved monitoring with PeakVue measurements.

Walt

Adding to previous comment:

The photos of shaft do not indicate spinning of inner race on shaft due to a loose fit. The surface gouges appear to be from Galling as a result of the inner race/ring being forced (tight/interference fit) to rotate on shaft when bearing locked up.

The presence of 1xSS and harmonics in the PeakVue indicate bearing looseness, and probably occurring within the damaged/worn rolling elements. The lack of bearing fault frequencies is probably the result of extremely worn ball/roller rolling elements and fully tracked inner and outer races. I recent had a bearing with same vibration symptoms and extensive damage, but action was take before consequential (shaft) damage occurred.

These comments are based on OP information, so as Ralph says "I could be totally wrong"! It is indeed unfortunate that bearing was not replaced at time of fan rotor balance!

Walt

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