MIL-HDBK-1025/10
a stumbling hazard or come in contact with energized conductors or equipment. Do not throw
tools or materials into or out of manholes. Use canvas buckets or hand lines for lowering tools or
equipment into and removing them from manholes. Warn workers before lowering tools. Always
provide a windless handcrank subsurface worker rescue or an approved retracting lifeline system.
f. Before starting work, an inspection should be made to determine if there are any
dangerous conditions such as burnt or cut cables or loose or defective ladders. Use of portable
ladders is preferred. Ladders in manholes, if provided, may have rusted and become unsafe.
Before using open flames in manholes or excavations where combustible gases or liquids may be
present, such as near gasoline service stations, the atmosphere should be again retested and found
safe or cleared of the combustible gases or liquids. When open flames need to be used in
manholes, extra precautions should be taken to provide adequate ventilation.
g. Low-voltage (less than 600 volts) equipment is especially hazardous in or around
subsurface structures. Motor frames and equipment cases may be energized by electrical
conductors with frayed or damaged insulation. The faults may occur only momentarily or may be
prolonged through high-resistance grounding paths. Contact with energized equipment surfaces
and the damp and well-grounded floors and walls often results in electrocution. It is
recommended that only pneumatic tools and low-voltage (24-volt) lighting systems be used in
maintaining subsurface vaults and facilities.
Precautions Before De-energizing Underground Lines
8.6.2
WARNING
The worker should be familiar with the system before proceeding to any
necessary tagging of cable and equipment. Every possible precaution
will be exercised to correct identity (voltage, circuit, and phase) of cable
or apparatus to be worked upon.
a. Be sure cables are properly identified before beginning any work. All cables should be
tagged, but in the event that they are not or that tags have become illegible or lost, obtain specific
instructions rather than take a chance. Retagging is required before work can begin.
b. The external appearance of medium-voltage and low-voltage cables is often similar.
For this reason, a very careful check should be made of duct locations and tag numbers before
starting work. Any errors found in the tagging of cables or in the manhole records or maps
should be immediately reported to the supervisor. Work should not continue until permission is
given by the supervisor. Under no circumstances should an identification tag be removed or
placed on a circuit without direct permission from the supervisor.
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