Limits of Bearing Housing Vibration

Limits of Bearing Housing Vibration

Question: Please explain the limits of bearing housing vibration.

Answer: The following limits of vibration pertain to uncoupled, resiliently mounted machines, running at no load. For machines tested with rigid mounting, the values given should be multiplied by 0.8. Vibration levels given here refer to internally excited vibration only. Motors as installed (in situ) may exhibit higher levels.

Figures 10a and 10b, taken from NEMA MG1-7.08, show limits for bearing housing vibration levels of machines resiliently mounted for both unfiltered and filtered measurements.

For unfiltered vibration, the measured velocity level shall not exceed the limit for the appropriate curve in figure 10a corresponding to the rotational frequency. For filtered vibration, the velocity level at each component frequency of the spectrum analysis shall not exceed the value for the appropriate curve in figure 10a at that frequency.

Figure 10: Machine Vibration Limits

Figure 10a

Figure 10b

Vibration Limit	Machine Type - General Examples
0.15	Standard industrial motors; motors for commercial or residential use
0.08	Machine tool motors; medium/large motors with special requirements
0.04	Grinding wheel motors; small motors with special requirements
0.02	Precision spindle and grinder motors
0.01	Precision motors with special requirements

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