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Remember that electrical and electronic circuits often have more than one source of power. Take
time to study the schematics or wiring diagrams of the entire system to ensure that all sources of
power have been disconnected
If pertinent, inform the remote station regarding the circuit on which work will be performed.
Use one hand when turning switches on or off.
Safety devices, such as interlocks, overload relays, and fuses, should never be altered or
disconnected except for replacement. In addition, they should never be changed or modified in
any way without specific authorization.
Fuses should be removed and replaced only after the circuit has been de-energized. When a fuse
"blows," the replacement should be of the same type and have the same current and voltage
ratings. A fuse puller should be used to remove and replace cartridge fuses.
All circuit breakers and switches from which power could possibly be supplied should be secured
(locked if possible) in the OPEN or OFF (safe) position and danger tagged in accordance with
procedures in the Standard Organization and Regulations of the U.S. Navy, OPNAVINST
3120.32.
After the work has been completed, the tag (or tags) should be removed only by the same person
who signed it (them) when the work began.
Keep clothing, hands, and feet dry if at all possible. When you must work in wet or damp
locations, place a rubber mat or other nonconductive material on top of a dry, wooden platform or
stool; then use the platform or stool to sit and stand on. Use insulated tools and insulated
flashlights of the molded type when you are required to work on exposed parts.
GROUNDING OF POWER TOOLS AND EQUIPMENT
The possibility of electrical shock can be reduced by ensuring that all motor and generator frames,
metal bases, and other structural parts of electrical and electronic equipment are at ground potential.
Normally, on steel-hull vessels, such grounds are inherently provided because the metal cases or
frames of the equipment are in contact with one another and with the metal structure of the vessel. In
some instances where such inherent grounding is not provided by the mounting arrangements, such as
equipment supported on shock mounts, suitable ground connections must be provided.
The grounding wire used for this purpose is generally made of flexible material (copper or
aluminum) that provides sufficient current-carrying capacity to ensure an effective ground. In this
manner, equipment cases and frames that are not intended to be above ground potential are effectively
grounded; also, the possibility of electrical shock to personnel coming in contact with metal parts of the
equipment is minimized. The secondary purpose of grounding equipment is to improve the operation and
continuity of service of all equipments.
Paint, grease, or other foreign matter can interfere with the positive metal-to-metal contact at the
ground connection point. Therefore, all bonding surfaces (connection points or metallic junctions) must
be securely fastened and free of such matter. In all instances where equipment grounding is provided,
certain general precautions and preventive maintenance measures must be taken. A few of these
precautions are listed below:
