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Rheostats and Resistors
else that will reduce downtime. Remember, you are only
looking for a temporary replacement.
Be certain the ventilation of rheostats and resistors
is not obstructed. Replace broken or burned-out
SWITCHBOARD MAINTENANCE
resistors. Temporary repairs of rheostats can be made by
bridging burned-out sections when replacements are not
Another duty of an IC Electrician is the maintenance
available. Apply a light coat of petrolatum to the
of the power distribution systems assigned to your
faceplate contacts of rheostats to reduce friction and
division. Normally, the required inspections and
wear. Be certain no petrolatum is left in the spaces
cleanings are outlined on maintenance requirement
between the contact buttons, as this may cause burning
cards (MRCs). When the inspection and cleaning is due,
or arcing. Check all electrical connections for tightness
you often think only of the main IC switchboard. The
and wiring for frayed or broken leads.
small local IC switchboards located in the engineering
spaces and remote sections of the ship are forgotten.
Instruments
Auxiliary IC panels may have their own MRCs. You, as
a supervisor, should make sure all power panels receive
The pointer of each switchboard instrument should
the attention needed.
read zero when the instrument is disconnected from the
circuit. The pointer may be brought to zero by external
INSPECTION AND CLEANING
screwdriver adjustment.
At least once a year and during overhaul, each
CAUTION: This should not be done unless proper
switchboard propulsion control cubicle, distribution
authorization is given. Repairs to the switchboard
panel, and motor controller should be de-energized and
instruments should be made only by the manufacturers,
tagged out for a complete inspection and cleaning of all
shore-repair activities, or tenders.
bus equipment. Inspection of the de-energized
equipment should not be limited to visual examination
Fuses
but should include grasping and shaking electrical
connections and mechanical parts to be certain that all
Be certain fuses are the right size; clips make firm
connections are tight and that mechanical parts are free
contact with the times; lock-in devices (if provided) are
to function. Be certain no loose tools or articles are left
properly fitted; and all connections in the wiring to the
in or around switchboards or distribution panels.
fuses are tight.
Check the supports of bus work to be certain the
Control Circuits
supports will prevent contact between bus bars of
opposite polarity or contact between bus bars and
grounded parts during periods of mechanical shock.
Control circuits should be checked to ensure circuit
continuity and proper relay and contactor operation.
Clean the bus work and the creepage surfaces of
insulating material; be certain creepage distances
Because of the numerous types of control circuits
installed in naval ships, it is impractical to set up any
(across which leakage currents can flow) are ample to
prevent arcing. Bus bars and insulating materials can be
definite operating test procedures in this training
manual. In general, certain control circuits, such as those
cleaned with dry wiping clothes and a vacuum cleaner.
Make sure the switchboard or distribution panel is
for starting motors or motor-generator sets, or voltmeter
switching circuits are best tested by using the circuits as
completely de-energized and will remain so until the
work is completed; avoid cleaning live parts because of
they are intended to operate under service conditions.
the danger to personnel and equipment.
Protective circuits, such as overcurrent, reverse
power, or reverse current circuits, usually cannot be
The insulated front panels of switchboards can be
cleaned without de-energizing the switchboard. These
tested by actual operation because of the danger
panels can usually be cleaned by wiping with a dry cloth.
involved to the equipment. These circuits should be
However, a damp, soapy cloth can be used to remove
visually checked and, when possibe, relays should be
grease and fingerprints. Then wipe the surface with a
operated manually to be certain the rest of the protective
cloth dampened in clear water to remove all soap and
circuit performs its intended functions. Exercise
dry with a clean, dry cloth. Cleaning cloths must be rung
extreme care not to disrupt vital power service or
out thoroughly so no water runs down the panel. Clean
damage electrical equipment. Normally these checks
a small section at a time and then wipe dry.
and inspections are outlined on MRCs.
4-21

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