In a building, a fire hydrant system is a safety measure or emergency equipment required in some buildings that comprises a series of components that when assembled together provide a source of water to assist fire authorities in a fire.
Putting it another way, a fire hydrant system is a water supply with sufficient pressure and flow delivered through pipes throughout a building to strategically located network of valves for fire-fighting purposes.
In some circumstances, water from a reticulated fire hydrant system can also be shared with other safety measures such as automatic fire sprinkler systems or fire hose reels.
In Australia, the Building Code of Australia (BCA) sets out the Deemed-to-Satisfy (DtS) provisions for a fire hydrant system required in buildings to the degree necessary to facilitate the needs of the fire brigade for;
- fire-fighting operations; and
- the floor-area of the building; and
- the fire hazard.
Fire hydrant systems are designed and installed in accordance with Australian Standard AS2419 and comprise the following primary components;
- Water Supply & Water Storage
- Pipework & Valves
- Fire Brigade Booster
- Hydrant, Hydrant Valve or Landing Valve & Coupling
- Layflat Fire Hose
- Block Plan
When designing a fire hydrant system specific performance objectives must be satisfied. These performance objectives require a hydraulic analysis to demonstrate there is sufficient water pressure and flow at the most hydraulically disadvantaged hydrant.
The pressure and flow requirements vary according to the building classification, floor area and sprinkler protection.
Water Supply & Water Storage
A water supply for a fire hydrant system can be derived from a reliable source of water such as; street mains, static water supply such as a tank or dam. Water storage must also include a facility for automatic replenishment (make-up water) due to losses from evaporation, leakage, periodic testing, etc. The capacity or volume of the water supply or storage must also be taken into account as part of the hydraulic analysis.
Pipework & Valves
To direct the water from its point of origin (supply) to its destination (hydrant valve) requires a series of interconnected pipes at defined sizes. The dimensions of the pipe is determined by Australian Standard AS2419 and hydraulic analysis. The control valves are used in combination with the pipework to control a direct the flow of water.
Fire Brigade Booster
The booster assembly provides a point of attachment for the fire brigade to provide additional water to a fire hydrant system in the event of an emergency. The location of the fire brigade booster should be chosen to ensure that it is readily accessible and provide protection to fire-fighters. A booster is typically mounted in a cabinet that includes details of the pressure limitations and requirements for the fire hydrant system.
In some circumstances where the hydraulic analysis has determined that the water supply is insufficient for the building requirements, one or more booster pump sets may be required. A pumpset may comprise a combination of electric or compression ignition (diesel) motors.
Hydrant (also known as the Attack Hydrant)
The end-point of a fire hydrant system is the Hydrant (also known as a Hydrant Valve or Landing Valve) strategically located throughout a building in accordance with the provisions of AS2419. The nominal diameter for a hydrant valve connection is 65mm. The connection for a fire hose varies throughout Australia according to the local fire authority. In simple terms fire brigades throughout Australia use different hose connections. In these cases, the Hydrant must also be fitted with a connection or coupling compatible with the local fire brigade. Care must be taken to ensure each fire hydrant is readily accessible and has sufficient clearance to satisfy the requirements of the AS2419.
Layflat Fire Hose
Some buildings may also require as part of the approved design the installation of ancillary equipment such as a layflat fire hose. A layflat fire hose is manufactured in accordance with Australian Standard AS2792 is a flexible hose and nozzle that may be connected to a hydrant.
A fire hydrant system block plan is an indelible diagram mounted within the booster cabinet, pump room and fire control room that illustrates the primary features of the fire hydrant system including the water supply location & dimensions, location & capacity of each water storage or tank, location & quantity of each valve, location of each pump, pressure & flow rating of the pumps, location of the main electrical control room, location of all flammable storage areas, year of installation, installing contractors name, the height of the highest fire hydrant and the lowest booster connection.
Under normal circumstances, a fire hydrant system is pressurised with water ready for emergency use. When a hydrant valve is opened, the system experiences a drop in water pressure.
The drop in water pressure is detected by a pressure switch which in turn starts the booster pump(s), drawing water from the water supply to increase the water pressure of the system.
Water from the hydrant is then directed through the layflat fire hose to a nozzle which is then directed to the seat of a fire.
During a fire the fire brigade may provide additional water and boost the water pressure to satisfy the demands of the fire hydrant system. This is carried out by connecting a fire appliance (truck) between an alternate water supply and the booster connection.