All
areas of the building to be protected are covered by a grid of pipes
with sprinkler heads fitted into them at regular intervals. Water
from a tank via pumps or from the town main (if it can give enough
flow) fills the pipes.
Each sprinkler head will open when it reaches a specific temperature
and spray water on to a fire. The hot gases from a fire are usually
enough to make it operate. Only the sprinklers over the fire open.
The others remain closed. This limits any damage to areas where there
is no fire and reduces the amount of water needed.
The sprinkler heads are spaced, generally on the ceiling, so that
if one or more operate there is always enough to control a fire taking
into account the size and construction of the building and the goods
stored in it or its use.
Sprinkler heads can be placed in enclosed roof spaces and into floor
ducts to protect areas where a fire can start without being noticed.
In a large warehouse sprinklers may be placed in the storage racks
as well as at the roof.
At the point where the water enters the sprinkler system there is
a valve. This can be used to shut off the system for maintenance.
For safety reasons it is kept locked open and only authorised persons
should be able to close it. If a sprinkler opens and water flows through
the valve it lets water into another pipe that causes a bell to ring.
In this way the sprinkler system both controls the fire and gives
an alarm using water, not electricity.
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