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A
well-designed wet riser/hydrant systems is the backbone of
fire protection systems for modern buildings and is mandated
by the local Fire Brigade, insurance authorities and other
regulatory bodies. A typical building normally has two or
more shafts, which travel from the lowest level of the building
to its terrace. Such shafts are normally used to carry the
piping for the wet-riser systems. Hydrant outlets are provided
on every floor so that the entire floor area of the building
is adequately covered. Outlets are provided in the form of
double-outlet landing valves. Apart from a canvas hose for
the use of fire-fighting personnel in the event of fire, a
rubber hose of 20 mm diameter is also provided, mounted on
a hose-reel drum to enable volunteers from the general public
to help fight incipient fires.
All
wet-riser pipes remain charged with water at systems pressure.
The opening of a hydrant landing valve or hose reel on any
floor reduces the pressure in the pipeline and starts the
hydrant pump. Pump-sets of suitable capacity are provided
for this purpose. Because of the static pressure differential
caused by the change in floor height, a multi-stage pump is
employed so that different tapping can be taken from the output
of the pump. Each of these tapping can be used to serve more
than one floor. Pumps-sets should be fed with reliable electric
supply from a separate feeder and it is therefore also desirable
to have a stand-by diesel pump. Apart from the wet riser system,
hydrant points should also be provided at strategic locations
around the building at ground level. These 'yard hydrants'
are of immense use on fire fighting.
Water must be made available through reservoirs in adequate
quantities at convenient locations. Periodic drills should
be conducted by opening the hydrant valves to ensure proper
operation of the systems.
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