Lubrication Problem (Grease)

This was happened on 15 kW motor that drive three stages centrifugal compressor. During routine measurement there where no evidence of any problem on the motor (figure 1).

figure 1

22 July 2010, compressor was tripped because motor was overloaded, mechanical inspection found leaks at compressor cooler. During the inspection period, motor solo run test was done to make sure that there is nothing wrong with the motor.

Motor was noisy, like something was rubbing especially at NDE position. TWF show different pattern than routine measurement (figure 2).

Figure 2.

It was decided to open bearing cover and re-grease the bearing. We found that bearing housing cavity was filled with grease. We recommend to clean bearing cavity and re-grease the bearing. The vibration spectrum after re-greasing is shown on figure 3 below :

Figure 3. Vibration spectrum after re-greasing.