A well-designed
wet riser/hydrant system 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 system. 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 system 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. Pump-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 in 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 system.
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