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发表于 2017-1-10 08:32
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Inadeauate Lubrication
One of the most important diagnoses that can be made in antifriction bearings is
inadequate lubrication. When properly diagnosed, simply adding proper lubrication often
prevents a catastrophic failure and increases equipment life.
Considerable time and effort have been spent in developing a technique to accurately
diagnosis inadequate lubrication. Empirical measurements of lubrication problems
indicate the following:
1. When the lubrication in a bearing becomes marginal, the lubrication may break
down once each revolution. An example is when the heavy spot (caused by the
residual imbalance, loading, etc.) passes through the load zone each revolution.
When this occurs, the pulse or impact of the balls excites the natural frequency
of the installed inner race assembly. The source of excitation is the BPFI. The oil
film may be thinner on the inner race because of rotation, and the curvature of
the inner race is more acute.
2. The frequencies generated by these events produce a series of spectral lines
around the natural frequency. This natural frequency has sidebands or
modulation equal to the BPFI.
3. The result is about four spectral lines somewhere between about 500 to 2500 Hz
or more. The spectral line with the highest amplitude may be the natural
frequency, and the difference may be equal to BPFI. Normally the natural
frequency is not evenly divisible by BPFI.
4. When lubrication is added, the spectral lines either disappear or the amplitude
decreases significantly.
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发表于 2017-1-9 21:13
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