consists of wooden posts and horizontal metal strands only, down conductors
consisting of No. 8 copper wire or equivalent shall be run from the ground
rod the full height of the fence and fastened to each wire, so as to be
electrically continuous.] The connection to ground shall be made from the
post where it is of metal and is electrically continuous with the fencing.
All metal fences shall be grounded at or near points crossed by overhead
lines in excess of 600 volts and at distances not exceeding 45 m 150 feet
on each side of line crossings.
3.6
EXTERIOR OVERHEAD PIPE LINES
Overhead pipes, conduits, and cable tray that enter a building containing
explosives shall be properly grounded on the exterior of the building,
preferably to the building grounds at points where the pipes enter the
building. Where a separate ground is used, the pipes shall also be bonded
to the building ground at points where the pipes are closest to the ground
connections. In addition, the pipes shall be bonded to any metallic masses
that are within 1.8 m 6 feet of the pipes.
3.7
SEPARATELY MOUNTED SHIELDING SYSTEM, MAST-TYPE
The mast-type protection shall consist of a pole, which, when of a
nonconducting material, shall be provided with an air terminal mounted to
the top, extending not less than 600 mm 2 feet nor more than 1.5 m 5 feet
above the top of the pole and a down conductor run down the side of the
pole and connected to the ground rod. When a metal pole is used, the pole
will act as a down conductor, and an air terminal need not be provided.
Where the resistance of the pole to ground is [_____] ohms or less,
additional grounding is unnecessary. Where the resistance exceeds [_____]
ohms, additional grounding shall be provided, and the ground connection
shall be fastened to the metal pole and the ground. When a ground rod is
necessary, the rod shall be driven approximately 1.8 m 6 feet from the base
of the pole. When the combined measured resistance to ground of the pole
and ground rod exceeds [_____] ohms, the Contracting Officer shall be
notified immediately. The grounding system at the base of the pole shall
be interconnected with any grounding system provided for the protected
structure.
3.8
SEPARATELY MOUNTED SHIELDING SYSTEM, OVERHEAD GROUND-WIRE TYPE
This type of protection shall consist of two or more poles electrically
connected to each other by overhead conductors. Where the poles are made
of a nonconducting material, an air terminal shall be mounted to the top of
each pole and shall extend not less than 600 mm 2 feet nor more than 1.5 m
5 feet above the top of the pole. Down conductors shall be run down the
side of the pole, or a guy wire may be used as a conductor. When the guy
wire is used, the guy wire and the overhead ground wire shall be dead-ended
at the pole. The overhead ground wire and the guy wire shall then be
connected to each other by a separate cable using standard cable clamps in
such manner that the discharge will not be reversed at any point. Guy
wires used as down conductors shall be grounded by means of separate ground
rods with cable connections clamped to the lower end of guy wire.
Resistance to ground shall not exceed [_____] ohms. Where metal poles are
used, air terminals are not required and if resistance of the poles to
ground is [_____] ohms or less, additional grounding is unnecessary. Where
the resistance to ground exceeds [_____] ohms, additional grounding shall
be provided and the ground connection shall be fastened to the metal pole
and the ground. The height of the poles shall be sufficient to provide a
clearance of not less than 1.8 m 6 feet between the overhead ground wire
SECTION 13100A
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