3.1.6
Igloo-Type Magazines
In earth-covered reinforced-concrete, igloo-type magazines, the reinforcing
steel shall be made electrically continuous. Electrical continuity may be
provided by clipping or brazing, unless a specific method is noted on the
drawings. The air terminals and roof conductors shall be securely
connected to, and made electrically continuous with, the reinforcing steel.
One air terminal shall be located on the top of the front wall and one on
or adjacent to the ventilator in the rear. The air terminals shall extend
vertically at least 600 mm 2 feet above the top of the front wall and the
highest point on the ventilator. Down conductors and grounding electrodes
shall be provided at diagonally opposite corners of the magazine and shall
be connected together. Grounding electrodes shall be connected to the
horizontal reinforcing rods below the floor line of the wall system. The
steel door frame shall be made electrically continuous with the reinforcing
steel. The steel door shall be connected to the steel frame by means of a
flexible copper strap or cable unless the steel hinges make the door and
frame electrically continuous.
3.1.7
Tanks and Towers
3.1.7.1
Wooden Tanks and Towers
The lightning protection system shall consist of air terminals, ridge
cables, down conductors, ground connections, and grounds, electrically
interconnected to form the shortest distance to ground. Where the roof of
the structure ends in a peak, a single air terminal not less than 600 mm 2
feet high will be regarded as sufficient. When the structure does not end
in a peak, air terminals not less than 600 mm 2 feet high shall be provided
at intervals not exceeding 7.5 m 25 feet along the perimeter of the
structure. When the tank or tower is an adjunct of a building, near or
touching the perimeter, one of the down conductors shall be extended
directly to a ground connection and the other shall be connected to the
lightning protection system of the building. When tank or tower is set
well within the perimeter of a building, both down conductors shall be
connected to the lightning protection system of the building. When the
height of the facility exceeds 18 meters 60 feet, the down conductors shall
be cross-connected at intermediate levels not exceeding 18 meters 60 feet.
Where buried metal pipes enter the tank or tower, one down connector shall
be connected to the pipes, approximately 300 mm 1 foot below grade. Metal
guy wires or cables 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.
3.1.7.2
Metal or Reinforced-Concrete Tanks and Towers
The metal or reinforcing steel shall be made electrically continuous.
Electrical continuity may be provided by bolting, riveting, or welding
metal and tying or clipping reinforcing bars, unless a specific method is
noted on the drawings. Air terminals and down conductors are required
except on bolted, riveted, or welded 4.8 mm 3/16-inch minimum, steel plate
tanks. Ground connections and grounding electrodes are not required on
metal tanks that are electrically continuous with a metallic underground
pipe system. On other structures, two ground connections shall be provided
approximately 180 degrees apart, at the base of the structure. Where
buried metal pipes enter the tank or tower, one ground connection shall be
connected to them, approximately 300 mm 1 foot below finished grade. Metal
guy wires on tanks and towers shall be grounded. Metal guy wires or cables
SECTION 13100A
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