Adjacent Installations

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.

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