WHAT IS HYDRANT : An upright water pipe, open in a street, with a nozzle to which a fire hose can be attached.
FIRE HYDRANT SYSTEM :
Large quantity of water require for quenching major fires in the industries Easy accessibility in the shortest possible time is of paramount importance in controlling and putting out these fires. Fire hydrant System is designed to serve these requirements.
Main components of a well designed hydrant system are as follows :
(a) Fire Water Reservoir :
Tanks of adequate capacity depending upon the risk to be covered. These should be located between 60 to 200 meters from the risk. Proper approach roads of at least 3.6 meter width should be provided.
Arrangement should be made to divide these tanks in two compartments such that one compartment is always available for service while the other can be taken out for cleaning or maintenance purposes.
(b) Main Pumps:
A minimum of two pumps one electric and the other diesel driven (stand by) should be installed to provide water to the installation at a required pressure. It is preferable to make them start automatically once the pressure drops, below the minimum required. Both pumps can be electrically driven provided the source of power supply is from different sources. The capacity of the pump shall be according to the nature of Hazard.
(c) Jockey Pump:
A pump of 500 litres/minute capacity is installed for maintaining pressure in the network. As and when the pressure drops this pump starts automatically to raise the pressure to preset pressure / cm2 and then stopping by itself. In case the pressure drops below the set pressure the main pump starts automatically.
(d) Ring Mains:
- It is net pipe work laid underground. Where it is not feasible, these can be laid above ground provided the pipes are sufficiently supported for its stability, at least one support every 10 feet. These are laid in ring pattern along the side of the roads / passages.
- The hydrants are located between 2 to 15 meters from the building to be protected in non hazardous areas and 30 meters from the edge of the building . accommodating hazardous stores.
- The size of mains is decided such that desired pressure is available at the hydraulically remotest point.
- Material of construction of mains is normally cast iron as this is anticorrosive and cheaper. However if MS is to be used this must be coated with good quality’ of anticorrosion point and suitably wrapped.
- Hydrants are installed in such a way that the risk is protected from two independent sources of water supply.
(e) Single Hydrants:
These are the points from where Fire hoses are connected for drawing water. Single^ oudet is fixed with 63 mm diameter instantaneous female coupling with a whea type control valve called the landing valve coupled to 80 mm diameter stand pipf through a bend. It is erected 1 meter above the ground level.
(f) Double hydrant :
in this case the stand post diameter is 100 mm provided with a “T” at the top. to each end a landing valve is fixed
(g) Riser Mains:
These are provided where the hydrants are provided on upper floors of the building. These have one main isolation valve at the ground level.
The diameter of such mains is 150 mm reduced to 100 mm at the top.