attached to steel anchor rods set in earth will be considered as grounded.
Metal guy wires or cables set in concrete or attached to buildings or
nonconducting supports shall be grounded to a ground rod driven full length
into the ground.
3.1.8
Stacks
Metal guy wires for stacks shall be grounded. Metal guy wires or cables
attached to steel anchor rods set in the earth will be considered as
sufficiently well grounded. Metal guy wires or cables attached to anchor
rods set in concrete or attached to buildings or nonconducting supports
shall be grounded to a ground rod driven full length into the ground.
3.1.8.1
Metal Stacks
Metal smokestacks shall be electrically continuous and be grounded. Where
the construction of the foundation does not provide [_____] ohms maximum to
ground, the stack shall be grounded to two ground rods driven full length
into the earth. Ground rods shall be located approximately 180 degrees
apart and shall be set not less than 900 mm 3 feet from the nearest point
of the stack foundation.
3.1.8.2
Nonmetallic Stacks
On nonmetallic smokestacks constructed of brick, hollow tile, or concrete,
the air terminals shall be made of solid copper, copper alloy, stainless
steel or Monel metal. Air terminals shall be uniformly distributed about
the rim of the stack at intervals not exceeding 2.5 m 8 feet and shall
extend 450 to 750 mm 18 to 30 inches above the stack if side mounted or 450
mm 18 inches above the stack if top mounted. Air terminals shall be at
least 18 mm 5/8 inches in diameter, exclusive of the corrosion protection.
Top-mounted air terminals shall not extend more than 450 mm 18 inches above
the top of the stack. The air terminals shall be electrically connected
together by means of a metal band or ring to form a closed loop about 600
mm 2 feet below the top of the stack. Where the stack has a metal crown,
the air terminals shall be connected thereto. Where stacks have a metal
lining extending part way up, the lining shall be connected to the air
terminal at its upper end and grounded at the bottom. At least two down
conductors shall be provided on opposite sides of the stack leading from
the ring or crown at the top to the ground. When the stack is an adjunct
of a building near or touching the building perimeter, one of the down
conductors shall be extended directly to a ground connection while the
other may be connected to a lightning protection system on the building.
On stacks exceeding 50 m 160 feet in height, the down conductors shall be
cross-connected approximately midway between the top and the bottom.
Joints in conductors shall be as few as practicable and shall provide a
strength in tension equal to that of the conductor. Fasteners of copper or
copper-bronze alloy shall be spaced not over 900 mm 3 feet apart for
vertical conductors and not over 600 mm 2 feet apart for horizontal
conductors. To prevent corrosion by gases, copper air terminals,
conductors, and fasteners within 8 m 25 feet of the top of the stack shall
have a continuous covering of lead at least 1.6 mm 1/16-inch thick. Stacks
partly or wholly of reinforced concrete shall conform to the requirements
for nonmetallic stacks, and in addition, the reinforcing steel shall be
electrically connected to down conductors at the top and bottom of the
concrete.
SECTION 13100A
Page 13
Previous Page
