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Developing a Motor Bearing Regreasing Strategy
Jeff Stegemiller, Maintenance Planner/Scheduler,
Gallatin Steel
First, we will want to establish a way of tracking each motor
as an asset. Develop a PM program in your CMMS package to track
these motors. Now it is time to be a detective and find as much
information on each motor as possible. Date of installation, HP,
RPM, Bearing type, Type of duty, Volts, Frame size, who was the
last vendor to repair the motor? And what type of grease did they
use? What type of bearing did they use? Warranty, etc. This may
sound like a lot of work but it will pay off. Start with your
most critical motors and new replacements.
Now separate the sealed, shielded bearings into one group and
the open bearings into another group.
1. Do vibration analysis on the sealed and shielded motor bearings.
Trend the vibration until replacement. On motors of 15 Hp or less,
stay with the sealed bearings. We tend to replace the motors and
not repair. Use your own formula for replacement vs. rebuild.
On larger motors when vibration shows bearing near failure we
rebuild motor with open bearings and bring them into the grease
program.
2. PM practice for open motor bearings. It is best to develop
your PM frequency on runtime. 6500 Hrs. (9 months continuous duty)
is what we use. We like to re-lubricate the bearings with the
motor at operating temperature and running when possible.
1. Clean top grease fitting, remove the bottom grease relief
valve.
2. With a manual grease gun pump and listen to the bearing using
an acoustic grease gun adaptor. Following the manufactures directions.
AVM Technology 1-800-667-5325, they have an Ultrasonic Lube Training
CD-ROM Free.
3. Watch for grease coming out the bottom port. If you pump excessive
grease into the motor and none comes out the bottom port, stop
and check for hardened grease in the bottom passage.
4. Allow motor to run for 1 hour to expel any excess grease before
install the bottom grease relief valves.
5. Clean any excess grease from the exterior of motor.
6. You must know if the original grease is compatible with new
grease. We use Brooks EMG (Electric Motor Grease). We also supply
this grease to our rebuild vendors. On new motors you will need
to contact the manufacture.
When you send a motor out for repair then you will want to evaluate
the bearings, and determine how well your program is working.
Start with your more critical motors or your most frequent failures.
We also do vibration analysis on our critical motors. It all depends
on if you can run to failure and how much downtime your plant
can stomach.
Editors Note: We would add that for bearings 2 years or older
that have supply tubes where the grease fitting attaches to a
pipe or tube, that tube needs to be removed and swabbed out. Grease
could have become caked in these supply tubes over time. Be sure
to fill the supply tube with grease after cleaning.
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to this Readers Challenge.
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