Fire Hydrant Systems - Principle of Operation

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 a sufficient pressure and flow delivered through pipes throughout a building to strategically located network of valves for fire-fighting purposes.

Fire HydrantIn 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 & Storage
  • Pipework & Valves
  • Fire Brigade Booster
  • Pumpset
  • 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.

System Components

Water Supply & 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 the Control valves are used in combination with the pipework to control an 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 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.
Booster Pumpset
In some circumstances where the a hydraulic analysis has determined that the water supply is insufficient for the building requirements, one or more booster pumpsets may be required. A pumpset may comprise a combination of electric or compression ignition (diesel) motors.
Hydrant
The end-point of a fire hydrant system is the Hydrant (also known as a Hydrant Valve, Landing Valve or Millcock) 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.
Block Plan
A fire hydrant system block plan is a 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.

Typical Operation

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.

Maintenance

Fire hydrant systems require periodic inspections, tests and survey to determine the system is operating and is maintained in a state that enables it to fulfil its purpose. Australian Standard AS1851 sets out the requirements for the maintenance and Australian Standard AS2419 sets out the minimum requirements for the operation of the operation of the system.

Fire hydrant systems are an active fire protection system that is installed as part of an overall strategy for the protection of life within a building. The Building Code of Australia sets out the deemed-to-satisfy requirements for safety measures (including fire hydrant systems) that in buildings. Other active fire protection systems include automatic fire sprinkler systems, fire hose reels, fire detection & alarm systems, and the smoke and heat control measures of mechanical ventilation systems.

References

Building Code of Australia

  • Specification E1.3 Fire Hydrants
  • Specification E1.5 Combined Fire Sprinkler & Fire Hydrant Systems

Australian Standards

  • AS2419 - Fire Hydrant Systems, Part 1 System design, installation & commissioning
  • AS2719 - Fire Hose - Delivery layflat
  • AS1851 - Maintenance of Fire Protection Systems & Equipment

More articles in this series

About the author

Russ Porteous is the CEO and one of the founders of Maintenance Essentials, he has over 22 years experience in the installation and maintenance of fire and essential safety measures. Russ is an active contributor to a variety of Australian Standards including AS1851 for the Maintenance of Fire Protection Systems and Equipment. Russ speaks regularly at conferences and trade shows as a subject matter expert. You can follow Russ online via Twitter @rport or his popular fire safety blog.

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Comments

 
WOW! I was amazed of this
Submitted by fire fighting pump (not verified) on July 26, 2012 - 17:58.

WOW!
I was amazed of this post. Thanks for this helpful and informative post. If I'm not mistaken, this is just an improvised fire hydrant system.