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Each
sprinkler head is held closed independently by heat-sensitive seals.
These seals prevent water flow until a design temperature is
exceeded at the individual sprinkler heads.
Each
sprinkler activates independently when the predetermined heat level
is reached. The design intention is to limit the total number of
sprinklers that operate, thereby providing the maximum water supply
available from the water source to the point of fire origin.
Typical
"wet" systems are simple and passive. They have water
already pressurized in the pipes held back by the sprinkler head.
These systems require no manual controls to activate, so long as
adequate water supplies are provided.
Specialty
systems called "dry" systems, designed for unheated
spaces, have a low "maintenance" air pressure in the
pipes. Water is fed into the system when the sprinkler
"fuses" allowing the maintenance air pressure to reach the
minimum pressure point. "Pre-action" systems are highly
specialized for locations where accidental activation is
unacceptable such as museums with rare art works, manuscripts, or
books. Pre-action valves are connected to fire alarm initiating
devices such as smoke detectors or heat detectors and virtually
eliminate the possibility of accidental water flow.
"Deluge"
systems are "pre-action" systems that have open
sprinklers, i.e. the fusible link is removed, so that every
sprinkler served by the system will discharge water. This ensures a
large and simultaneous application of water over the entire hazard.
These systems are used for special hazards where rapid fire spread
is a concern.
Other
specialty systems may have foam instead of water suppression agents
for fire protection in occupancies with flammable liquids, such as
airport hangars. "Clean agent" gaseous systems, such as
Argon/CO2/Nitrogen mixtures can be used in very small spaces where
water cannot be used for suppression.
A
sprinkler activation will do less damage than a fire department
hose, as the fire department's hose streams provide around 15.0
Litre/Second (200 gallons per minute) whereas an activated sprinkler head
generally discharges around 90 Litres per minute (20 gpm).
To
view a short movie on 'How Sprinklers Work' click on the button
below.
(.rm 2.86mb)
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