3.1.9
Post Tensioning Systems
On construction utilizing post tensioning systems to secure precast
concrete sections, the post tension rods shall not be used as a path for
lightning to ground. Down conductors shall be provided on structures using
post tensioning systems; down conductors shall have sufficient separation
from post tension rods to prevent side-flashing. Post tension rods shall
be bonded to the lightning protection and grounding systems only at the
base of the structure; this bonding shall be performed in strict accordance
with the recommendations of the post tension rod manufacturer, and shall be
done by, or in the presence of, a representative of the manufacturer.
3.2
RAILROADS
Rails that are not electrically continuous and rail switches shall be
bonded together by means of flexible copper cable or straps for a distance
of at least 30 m 100 feet on each side of structures in which explosives,
ammunition, or explosive ingredients are stored, handled, manufactured, or
processed. These rails shall also be grounded. Rails shall be grounded at
points 45 m 150 feet on each side of overhead line crossings in excess of
600 volts and rails shall be bonded between grounds. At points where the
tracks come within 7.5 m 25 feet of structures provided with a grounding
system, such grounds shall be interconnected to the nearest rail. The
cable used for the interconnection shall be at least 9.5 mm 3/8 inch
diameter or the same size as the conductors used on the structure.
Isolation joints shall be installed in metal rails outside of hazardous
areas to avoid stray currents being conducted into the bonded or grounded
area.
3.3
PIERS AND WHARVES
Lightning protection systems for piers and wharves shall conform to the
requirements specified for the type of construction involved.
3.4
INTERCONNECTION OF METAL BODIES
Metal bodies of conductance shall be protected if not within the zone of
protection of an air terminal. Metal bodies of conductance having an area
of 0.258 square meters 400 square inches or greater or a volume of 0.0164
cubic meters 1000 cubic inches or greater shall be bonded to the lightning
protection system using main size conductors and a bonding plate having a
surface contact area of not less than 1935.5 square mm 3 square inches.
Provisions shall be made to guard against the corrosive effect of bonding
dissimilar metals. Metal bodies of inductance shall be bonded at their
closest point to the lightning protection system using secondary bonding
conductors and fittings. A metal body that exceeds 1.5 m 5 feet in any
dimension, that is situated wholly within a building, and that does not at
any point come within 1.8 m 6 feet of a lightning conductor or metal
connected thereto shall be independently grounded.
3.5
FENCES
Except as indicated below, metal fences that are electrically continuous
with metal posts extending at least 600 mm 2 feet into the ground require
no additional grounding. Other fences shall be grounded on each side of
every gate. Fences shall be grounded by means of ground rods every 300 to
450 m 1000 to 1500 feet of length when fences are located in isolated
places, and every 150 to 225 m 500 to 750 feet when in proximity (30 m 100
feet or less) to public roads, highways, and buildings. [Where the fence
SECTION 13100A
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