MIL-HDBK-1164
previous readings. Change taps or contact the power company if the voltage is more
than 5 percent high or low.
d)
Inspect contacts on switches, contactors, circuit breakers,
disconnects, and relays if the contacts are accessible. Dress or replace contacts if
they are pitted or burned. Replace contacts in pairs, not singly.
11.4.4
Electric Motors. Perform the following work items in accordance with the
manufacturer's instructions, but not less than once per year. Perform the work more
often if the equipment is exposed to excessive dirt or vibration. Additional information
on motor control equipment can be found in par. 2.1.4.
a)
Blow dirt from the windings. Clean out magnetic particles that may
be hanging on poles.
b)
Drain, wash, and renew oil in sleeve bearings. Clean and renew
grease in ball-and-roller bearings. Check air gaps. Inspect bearings for excessive
wear.
c)
Check end play. Under load, machines without thrust bearings
should have the rotor within the end play. That is, the rotor should not be riding against
the thrust collar of either bearing. This condition can cause heating and failure of the
bearing; it can be corrected by shifting the rotor on the shaft or by shifting the
laminations. Consult the manufacturer.
d)
On rotating equipment with commutators or slip rings, check brush
tension and brush wear. Make sure brushes are free in the brush holder. Replace
brushes as required. Sand-in new brushes. Check commutators and slip rings for
wear, scratches, or pitting. Dress as required.
e)
Megger low-voltage rotating equipment using a 500-volt megger.
Megger reading should be 1 megohm at minimum, but readings should be compared
with previous readings, since a decreasing megger reading indicates deteriorating
insulation or excessive dirt or moisture.
f)
journal set screws, and keys. Ensure that all covers and guards for pulleys and
couplings are in good condition and securely fastened. Observe operation during
starting and running.
11.4.5
Standby Power Generators. Operate emergency generators once a
week, if possible, to ensure they will work properly when needed. Operate the
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