Vibration Example

Vibration is considered to be the most difficult to understand of all of the predictive maintenance tools. Using it though as a trending tool and also using some simple troubleshooting techniques; vibration can reveal things about the equipment's operation without even being a vibration analyst.

Many times the graphs themselves cause confusion because of the shear amount of information the contain. Especially confusing is the waveform or time domain graph. By using the characteristics of the graphs and the level of vibration though one can determine a good condition from a bad condition.

For example here a waveform graphs taken from a motor. Initially this graph may not look like much. Taking into account though a few simple characteristics of how machine operating we can shed some light on what the graph is telling us. By knowing that the impacting in a waveform for a motor really should not exceed +2 to -2 g's of acceleration; a technician can view the impacting level of +8 to -8 and know something is not right. By then looking at the characteristics of the impacting we see it is erractic and without a pattern we can determine that the movement of this bearing is erractic. If we think about how a metal to metal contact would occur on a microscopic level; both of these indications are characteristic of an under lubricated bearing.

By then adding grease to the motor bearing and rechecking it we can determine the proper amount of grease to give the bearing to "quiet" it down as shown by the graph below that was taken after 12 shots of grease had been added.

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