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LUBRICATION.-- Lubricate bearing points and
moistened, if required, with a small amount of
bearing surfaces, including latches, with a drop or two
inhibited methyl chloroform. Be sure that ample
of light machine oil. Wipe off excess oil.
ventilation is provided if inhibited methyl chloroform
is used. (Refer to NSTM, chapter 300, for information
FINAL INSPECTION AND INSULATION RE-
on the safety precautions to observe when inhibited
SISTANCE CHECK..-- Before returning a circuit
methyl chloroform (1,1,1 trichloroethane) is used.)
breaker to service, inspect all mechanical and electrical
Remove all traces of residue left by inhibited methyl
connections, including mounting bolts and screws, dra-
wout disconnect devices, and control wiring. Tighten
chloroform. Silver alloy contacts should not be filed
where necessary. Give final cleaning with a cloth or
or dressed unless sharp projections extend beyond the
compressed air. Operate manually to make sure that all
contact surface. Such projections should be filed or
moving parts function freely. Check insulation resis-
dressed only to the contact surface. When cleaning and
tance .
dressing contacts, maintain the original shape of the
contact surface and remove as little material as
SEALING SURFACE.-- Sealing surfaces of cir-
possible.
cuit breaker, contactor, and relay magnets should be
kept clean, and relay magnets should be kept clean and
C O N T A C T SURFACE INSPECTION.--
free from rust. Rust on the sealing surfaces decreases
Inspect the silver alloy contact surface for heavy
the contact force and may result in overheating of the
burning, erosion, or overheating. If any discrepancies
contact tips. Loud humming or chattering will fre-
are found, replace the contact. Slight burning, pitting,
quently warn of this condition. Light machine oil wiped
or erosion is acceptable. Carbon deposits should be
sparingly on the sealing surfaces of the contactor mag-
removed using a dry, lint-free cloth. Loosen deposits
net will aid in preventing rest.
according to the MRC. Do not use emery cloth, a file,
USE OF OIL.-- Oil should always be used spar-
or sandpaper. If the contacts have deep pitting that
ingly on circuit breakers, contractors, motor controllers,
penetrates through the contact surface or 50 percent of
relays, and other equipment, and should not be used at
the contact surface, replace the contact.
all unless there are specific instructions to do so or oil
CLEANING  BREAKER  MECHANISM
holes are provided. If working surfaces or bearings
show signs of rust, the device should be disassembled
SURFACES.-- Clean all circuit breaker mechanism
and the rusted surface carefully cleaned. Light oil may
surfaces, particularly insulation surfaces, with a dry
be wiped on sparingly to prevent further rusting. Oil has
cloth or air hose. Be sure that water is blown out of the
a tendency to accumulate dust and grit, which may
air hose, that the air is dry, and that the pressure is not
cause unsatisfactory operation of the device, particu-
over 30 lb/in2 before directing it on the breaker.
larly if the device is delicately balanced.
INSPECTION OF MOVING PARTS.-- Inspect
ARC CHUTE MAINTENANCE.-- Arc chutes
pins, bearings, latches, and contact and mechanism
should be cleaned by scraping with a file if wiping with
springs for excessive wear or corrosion and current-
a cloth is not sufficient. Replace or provide new linings
carrying parts for evidence of overheating. Bolt-on
when they are broken or burned too deeply. See that arc
parts/attachments and subassemblies may be replaced
chutes are securely fastened and that there is sufficient
by ship's force personnel. Replacement of parts that
clearance to ensure that no interference occurs when the
require major disassembly or subassembly teardown
switch or contactor is opened or closed.
must be accomplished by an overhaul facility or
FLEXIBLE PARTS.-- Shunts and flexible con-
shipyard with circuit breaker repair capability.
nectors that are flexed by the motion of moving parts
OPERATIONAL CHECK.-- Slowly open and
should be replaced when worn, broken, or frayed.
close circuit breakers a few times manually, See that
trip shafts, toggle linkages, latches, and all other
Adjacent Installations
mechanical parts operate freely and without binding.
Make sure that the arcing contacts meet before and
Inspections should not be confined to switchboard
break after the main contacts. If poor alignment,
and distribution panels, but should also include
sluggishness, or other abnormal condition is noted,
adjacent installations, which may cause serious
adjust according to the technical manual for the circuit
casualties. Rubber matting, located near switch-
boards, should be inspected for signs of deterioration,
breaker.
3-15

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