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slip in a cylindrical roller bearings
- Thread starter alexsurf
- Start date
electricpete
Electrical
Maybe you are talking about skidding? That can occur when there is not enough radial load (such as a motor designed for belt application run uncoupled without radial load).
It may or may not show up as a high-pitched squeal, or as a bearing fault in vib. (Or it may be intermittent and missed by vib).
It may be avoided by adding load (4% of static rating). Or also possibly by special lubrication preparation of the bearings.
It may or may not show up as a high-pitched squeal, or as a bearing fault in vib. (Or it may be intermittent and missed by vib).
It may be avoided by adding load (4% of static rating). Or also possibly by special lubrication preparation of the bearings.
electricpete
Electrical
... also ramping the motor up to speed with variable speed start is better than d.o.l. start to prevent skidding.
All of the above comes from a Toshiba article on this subject.
All of the above comes from a Toshiba article on this subject.
machinerys
Petroleum
A Defect Frequency at No of balls X Rpm can be an indication of Slip in the race ways.
electricpete
Electrical
Is the previous comment based upon experience or from physcial reasoning?
From physical reasoning I would expect that if the balls all skid at the same point in space, we would see BPFO=FTF*Number of balls. That's because the balls rotate around the bearing at FTF, not at 1x.
From physical reasoning I would expect that if the balls all skid at the same point in space, we would see BPFO=FTF*Number of balls. That's because the balls rotate around the bearing at FTF, not at 1x.
- Thread starter
- #6
MachineryWatch
Mechanical
alexsurf,
The terms rollers and balls are typically used interchangeably for the rolling elements in rolling element bearings and the formulae used for analysis. I wouldn't expect to see impacts spaced at any particular calculated frequency if light shaft loading is the cause of the skidding. It would be too random for that in my opinion. You may have success looking in higher frequency ranges for the excitation of individual bearing component natural frequencies.
As for number of rollers times RPM, I have never seen that frequency in 25 years of data collection and analysis. That doesn't mean that someone else hasn't seen it. But think about it. It almost requires that the rollers all be welded solid to the inner race in order to generate that frequency.
Skip Hartman
The terms rollers and balls are typically used interchangeably for the rolling elements in rolling element bearings and the formulae used for analysis. I wouldn't expect to see impacts spaced at any particular calculated frequency if light shaft loading is the cause of the skidding. It would be too random for that in my opinion. You may have success looking in higher frequency ranges for the excitation of individual bearing component natural frequencies.
As for number of rollers times RPM, I have never seen that frequency in 25 years of data collection and analysis. That doesn't mean that someone else hasn't seen it. But think about it. It almost requires that the rollers all be welded solid to the inner race in order to generate that frequency.
Skip Hartman
- Thread starter
- #8
I am agree with you Skip Hartman.
I think if there is only skidding without rolling defect, it is impossible to see some frequency.
But if there is any defect in the bearing conponents it is possible to diagnostic a skidding phenomena.
the caracteristic frequencies of bearing conponents will be lightly higher or slower.
Are you OK ?
I think if there is only skidding without rolling defect, it is impossible to see some frequency.
But if there is any defect in the bearing conponents it is possible to diagnostic a skidding phenomena.
the caracteristic frequencies of bearing conponents will be lightly higher or slower.
Are you OK ?
Here is my suggestion. It depends on wether you want an automated solution or a manual visual solution.
For a manual solution and assuming that the machine operates at a constant speed, I would mount either reflective tape and a photoelectric sensor or a stud/hole and a proximity sensor on the shaft. This will give a once per revolution pulse. Then you look at the pulse train in the time domain. If the time between pulses is constant, either there is no slipage or it is constant. If the time between pulses changes, then there is slippage.
For an automated soulution, you can mount a shaft encoder or position sensor to do the same thing, but have the computer calculate the time per revolution.
Other variations may be required if the speed is always changing, but you can handle most of that if the data is reviewed manually. C. Hugh
For a manual solution and assuming that the machine operates at a constant speed, I would mount either reflective tape and a photoelectric sensor or a stud/hole and a proximity sensor on the shaft. This will give a once per revolution pulse. Then you look at the pulse train in the time domain. If the time between pulses is constant, either there is no slipage or it is constant. If the time between pulses changes, then there is slippage.
For an automated soulution, you can mount a shaft encoder or position sensor to do the same thing, but have the computer calculate the time per revolution.
Other variations may be required if the speed is always changing, but you can handle most of that if the data is reviewed manually. C. Hugh
acmotorengineer
Electrical
for Alexsurf
If you have a vertical motor with spherical thrust bearings, you must have axial load, typically 2000 to 4000 pounds for successful operation.
no axial load, and the bearings skid - one skid and the bearing is damaged and will have short life.
If you have a vertical motor with spherical thrust bearings, you must have axial load, typically 2000 to 4000 pounds for successful operation.
no axial load, and the bearings skid - one skid and the bearing is damaged and will have short life.
electricpete
Electrical
Call me picky, but I'd like to respond
Hatch - maybe your technique may detect belt slip or other problems, but I don't think it will detect bearing skidding.
acmotorengineer - What you say is true, but we are talking about cylindrical roller bearings.
Hatch - maybe your technique may detect belt slip or other problems, but I don't think it will detect bearing skidding.
acmotorengineer - What you say is true, but we are talking about cylindrical roller bearings.
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