Table 1-1.--Rubber Gloves

Interlocks and other safety devices must NOT be

and artificial ventilation instructions posted in their

altered or disconnected, except for replacement, and

vicinity. Switchboards, switchgears, and their access

must NOT be modified without specific authority

doors must also have DANGER HIGH VOLTAGE

from the cognizant systems command. Periodic tests

signs posted.

and inspections must be made to ensure the devices

When removing or installing switchboard and

are functioning properly.

control panel meters and instrument transformers, you

must be extremely careful to avoid electrical shock to

SAFETY SHORTING PROBE

yourself and damage to the transformers and meters.

The secondary of a current transformer MUST be

Before you start working on de-energized circuits

short-circuited before you disconnect the meter. An

that have capacitors installed, you must discharge

extremely high voltage buildup could be fatal to

them with a safety shorting probe. When using a safety

unwary maintenance personnel and it could damage

shorting probe, first connect the test clip to a good

the current transformer.

ground to make contact. If necessary, scrape the paint

off the metal surface. Then, hold the safety shorting

The primary of a potential transformer must be

probe by the handle and touch the probe end of the

opened before you remove the meter to prevent

shorting rod to the points to be shorted. The probe end

damage to the primary circuit due to high circulating

can be hooked over the part or terminal to provide for

currents.

a constant connection to ground. Never touch any

In most installations, potential transformer

metal parts of the shorting probe while grounding

primaries are fused, and the transformer and

circuits or components. It pays to be safe--use the

associated meter cart be removed after you pull the

safety shorting probe with care.

fuses for the transformer concerned. When dis-

connecting the transformer and meter leads, you

should avoid contact with nearby energized leads and

NOTE

terminals.

Capacitors not electrically connected to

INTERLOCKS

the chassis ground must have their terminals

shorted together to discharge than by the

use of a shorting probe.

Many modern electronic equipments are provided

with various built-in safety devices, such as interlock

switches, to prevent technical and maintenance

RUBBER GLOVES

personnel from coming into contact with electrical

potentials in excess of 70 volts rms or dc. However,

There are four classes of rubber insulating

some of these protective devices are removed or

gloves--class 0, class I, class II, and class III. The

destroyed by personnel who tamper with, block open,

or otherwise "override" them. The foregoing practices

primary feature of each class is the wall thickness of

the gloves and the maximum safe voltage. These

must NOT be performed unless authorized by the

features are identified by a color label on the glove

commanding officer for operational reasons. Then the

sleeve. Only use rubber insulating gloves that are

equipment must be properly tagged to notify

marked with a color label. Table 1-1 contains the

personnel of this condition.

Table 1-1.--Rubber Gloves

LABEL COLOR

MAXIMUM SAFE VOLTAGE

CLASS

Red

1,000

volts

White

7,500

volts

Yellow

17,000

volts

Green

26,500

volts

III

1-15