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 MIL-HDBK-1008B
Table 3.2.3.2
Fire Protection for Outdoor Oil-Insulated Transformers
SIZE (EACH TRANSFORMER)
NUMBER
PROTECTION
Under 9,999 kVA
One or more
Portable Extinguishers
10,000 - 99,999 kVA 1
One only
Hydrant Protection
10,000 - 99,999 kVA 1
More than one
a. Provide a 25 ft (8 m)
minimum clear space
between units, or
b. Noncombustible barriers
between units, or
c. Fixed automatic water
spray 100,000 kVA and
above. One or more fixed
automatic water sprays
100,000 kVA and above
One or more
Fixed automatic water
spray
1 Where there are mission-essential bus structures exposed to possible
transformer oil fire, or electric service or production could be
interrupted for an extended period, a fixed automatic water spray system
shall be provided to minimize the physical damage from fire and reduce the
downtime for repairs.
(3) Window openings in second and third story walls directly
above the transformers shall be protected using either wired glass in steel
sash or glass block.
(4)
Overhanging eaves, where they exist, shall be
noncombustible.
c) Where transformers expose a building having walls other than
masonry or concrete, provide a masonry or concrete barrier between the
building and transformers, with wing walls at each end of the barrier. The
barrier shall extend at least 1 foot (0.3 m) above the top of transformer
bushings and pressure-relief vents. Wing walls shall be of the same height
and shall extend horizontally 2 to 3 feet (0.6 to 0.9 m) beyond the
transformers, including any radiators and tap-changer enclosures. At
multistory buildings, provide a fire resistive roof on this three-sided
transformer enclosure.
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