Efficient Plant March 2021 - 23
A little preventive maintenance on motors that have been in storage
or returned from a repair shop will go a long way toward preventing
IT'S BOLD TO assume that motors that have been in storage for
a length of time or that have been repaired or replaced can be put
into service without some kind of inspection. It only requires a
short amount of time, and relatively minimal effort, to go through
a checklist before powering up a newly installed motor. Here are
some things to consider if a motor has been removed from longterm storage and/or received from a repair shop.
These tips are adapted from the EASA, St. Louis (easa.com)
publication, Getting the Most from Your Electric Motors.
Download the full e-booklet at go.easa.com/electricmotors.
BEFORE INSTALLING A MOTOR THAT HAS BEEN IN
STORAGE FOR MORE THAN A FEW WEEKS:
Thoroughly inspect and clean the motor to restore it to " as shipped "
If the motor has been subjected to vibration, disassemble it and check for
bearing damage, e.g., false brinelling and fluting.
Grease-lubricated motor bearing cavities should have been filled with
grease for storage. To protect the windings from contamination, remove
the drain plugs before adding the lubricant specified on the lubrication
plate. Then purge old or excess grease from the bearing cavity by running
the motor at no load for 10 to 20 min. and replace the drain plugs. If any
moisture is present in the purged grease, the bearings are probably rust
damaged and should be replaced.
If the motor has been stored for several years, the grease has likely dried
out or separated and the drainpipe is probably plugged. Disassemble the
motor, clean out the old grease, and repack the bearings.
To prevent winding contamination, drain oil-lubricated motors before
Test the winding's insulation resistance (IR) and dielectric absorption ratio
(DAR) and record the results. If the IR and DAR test results are satisfactory,
perform a no-load test operation.
BEFORE PUTTING A REPAIRED OR REPLACEMENT
MOTOR INTO SERVICE, BRIEFLY START IT TO CHECK
If the motor vibrates or emits unusual noises or odors, immediately
de-energize it and look for the cause.
Magnetic or electrical problems that exhibit as vibration or noise will
instantly improve when the power is off.
No improvement may indicate an anomaly such as rotor or driven-load
unbalance or misalignment.
If the motor operates normally, allow it to reach full speed before shutting
off the power.
Always lock out and tag out the motor before connecting the driven load.
Once the motor and driven load operate properly, record the full-load
voltage and current for all three phases on the motor data sheet for this
installation. If possible, also record the input power with load.
If the motor is so equipped, monitor the bearing and winding temperatures
until they reach a steady state. Document these values as well as the
ambient temperature and humidity.
For critical applications, record the initial vibration signature of the
complete machine as a baseline. EP
3/2/21 9:42 AM
Efficient Plant March 2021
Table of Contents for the Digital Edition of Efficient Plant March 2021
Efficient Plant March 2021 - Cover1
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Efficient Plant March 2021 - 1
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