Interstate Bank Building Fire;
SPRINKLERS AND STANDPIPE SYSTEM
The building was served by a single zone combination standpipe
system with four risers, one in each stairway. The standpipe
risers provided a 2 l/2 inch outlet in each stairway at
each floor and also supplied 1 l/2 inch hose cabinets in
the occupied areas of each floor. At the time the fire broke
out the building's fire pumps had been shut down, and the
risers had been drained down below the 58th floor to allow
a sprinkler line to be connected to a standpipe riser. This
job took only a few minutes and the jockey pump was in operation
to refill the system when the sprinkler crews noted smoke
rapidly filling the stairway. Being only four floors from
the roof, the workers went up to the helipad to await rescue.
The sprinkler system was virtually complete on the floors
that burned, but the valves were closed between the standpipe
riser and the sprinkler system on each floor. During the
fire a Battalion Chief was assigned to confer with the sprinkler
installation supervisor to explore the possibility of opening
these valves to control the fire. It was determined that
the fire on the involved floors would probably overwhelm
the sprinklers and deprive the handlines of needed water.
Eventually, the systems on floors 17, 18, and 19 above the
fire were activated, in case the fire extended past the
16th floor.
The four standpipes are supplied by two stationary fire
pumps, one diesel and one electric, each rated at 750 gpm
at 600 psi pressure. The standpipe system operates with
a single vertical zone, depending on the pressure reducing
valves at each outlet to control the pressure.
With the main fire pumps shut down, the only water pressure
available for the first hoselines was the static head in
the risers, and crews reported poor water pressure for the
first few minutes. This condition was rapidly corrected
when the combination of both building pumps and three Fire
Department pumpers were placed in operation.
The building pumps were started manually by the sprinkler
installation supervisor who had been rescued from the rooftop
by a Police helicopter, taken to a Police facility, and
transported back to the scene in a Police car. He arrived
at the Fire Department Command Post and informed the Incident
Commander of the situation. An engine company was assigned
to drive him into the basement loading dock area in a car,
to avoid the falling glass, and to assist him in starting
the pumps.
The building's two 750 gpm fire pumps drew water from an
85,000 gallon reservoir in the sub-basement. The resupply
from the public water supply system was unable to keep pace
with the outflow, estimated at over 2,000 gallons per minute,
and there were fears that the tank would be emptied.The
tank was down to less than one-third of its capacity when
the fire was controlled. If the tank had emptied, only fire
department pumpers would have been left to supply the standpipes.
The single zone riser system was designed to operate at
585 pounds per square inch (at basement pump discharge)
and relied upon the pressure reducing valves to limit the
discharge pressure at each outlet on each landing. Problems
were encountered with several of these valves allowing excess
pressure to be discharged, including one that provided over
400 pounds per square inch. The overpressure caused several
hose ruptures and made handlines difficult to control. The
heat of the fire caused several aluminum alloy valves in
the occupant hose cabinets to fail, creating high pressure
water leaks. These leaks took water from the supply that
was available for handlines and caused additional water
damage on floors below the fire.
It was estimated that a total flow of 4,000 gallons per
minute was delivered by the standpipe risers. The total
effective fire flow, provided by hoselines attacking the
fire, was approximately 2,400 gpm. The attack lines included
1 3/4, 2, and 2 l/2 inch handlines. No exterior streams
or master stream appliances were used.
Return to Interstate Bank
Fire Main Page
|
