A fire pump is any kind of pump that is part of a fire protection system's water supply. It is important to know that a fire pump does not create water, it takes water that is given to it from a water supply and increases the pressure (energy) of the water. A fire pump can be powered by electric, diesel or steam and can supply fire sprinklers, standpipes, foam systems, water spray/mist systems or any combination of these systems. The fire pump's intake is usually connected to the external water supply, although in some cases it may be connected to a local water source such as a well, tank, or body of water.
Fire pumps are needed when the water supply cannot provide sufficient pressure to meet the hydraulic design requirements of the fire protection system. This usually occurs if the building is very tall, such as in high-rise buildings, or in systems which require a relatively high terminal pressure at the fire sprinkler in order to flow a large volume of water, such as in storage warehouses. Fire pumps are also needed if the water supply is provided from a ground level water storage tank.
Types of pumps used for fire service include: horizontal split case, vertical split case, vertical inline, vertical turbine, and end suction.
The fire-pump delivers the water via the pipe-system to suppress the fire. Fire pumps are powered either by an electric motor or a diesel engine or sometimes by a steam turbine. The number of fire-pumps installed depends on the occupancy hazard (LH, OH or HH) and specific fire installation standard.
Where twin electric fire pumps are installed, there is a requirement for a secondary power source. This can be from a separate feed to the nearest electricity sub-station, or from a generator located on site. A mains changeover facility should be incorporated into the design to allow for switching to this alternate power source in the event of a mains supply failure.
The fire pump starts when the pressure in the fire sprinkler system drops below a certain set-point. If one or more fire sprinklers are exposed to heat above their design temperature, and opens, the sprinkler system pressure drops and the pressure switches gives a signal and the duty pump starts. If the duty-pump, for any reason, does not start, the standby pump will start, usually from a secondary pressure switch.