Case study

Motor Bearing Failure

Abstract: An inner race fault was successfully detected in the bearing of a motor for a cooling water pump.

The following case study was taken from a regular survey of plant located at the site one of our customers.

Background: The aptGroup carries out regular vibration surveys at the customer's plant. The pump that is the subject of this study circulates cooling water to other machines.

Method: A portable data collector/analayser and accelerometer were used to take the vibration measurements. The accelerometer was attached to the machine using a magnet.

Measurements of velocity (0-600 Hz), acceleration (0-5000 Hz) and acceleration enveloping (5 - 40 kHz) were made.

Results: Following a survey, a fault was detected in the drive end bearing of the motor. The vibration spectrum (fig 1) indicated that an inner race fault was present in the bearing.

When the motor was overhauled, the inner race of the bearing was found to be damaged (fig 2), as indicated by the vibration data.

Figure 1: Vibration Spectrum from DE Bearing

Figure 2: Inner Race, showing damage

Conclusions: Vibration monitoring successfully detected a damaged bearing in this motor. Corrective action was undertaken well before a failure occurred.

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