A fire fighting pump provides extra hydraulic pressure to meet demand for systems such as sprinklers and standpipes. The selection and installation of fire pumps should be handled by a qualified fire safety professional.
An electrical motor or diesel engine powers the fire fighting pumps, turning the shaft that provides water to systems. The size of the driver is determined using either the Sprinkler Area Method or power sizing by head and flow curve.
Electric
Unlike diesel fire fighting pumps electric pumps use electricity to drive the pump. They require a continuous power source for operation during normal and emergency conditions, and the design of this power supply is an important consideration. Power requirements are addressed by standards and codes that govern these systems including NFPA 20.
Ideally, the Q-H curves for fire pumps are stable and continuously decreasing to provide stability in system pressure. The Q-H curves should be sized to allow for the maximum allowed locked rotor current during operation. This can be accomplished by sizing the generator to handle six times the full load current and careful selection of transformers for the emergency system that will allow for this lock-rotor current while maintaining a low voltage drop at the fire pump motor.
For most installations, it will be necessary to include a transfer switch between the fire pump controller and the generator. The fire pump controller should be able to sense the loss of power from the normal supply and automatically switch to backup power provided by the generator.
Diesel
Fire pumps can be powered by electric motors, diesel engines or steam drives. Depending on the situation, a client may require either an electric motor-driven or a diesel engine-driven system. In cases where the electrical supply is unreliable or the system is located in a seismic zone, a diesel engine is required.
The fuel storage tank for the diesel engine must be located in a pump room that complies with the local building codes and NFPA 20. The tank must have a dedicated fill, vent(s), and a visual fuel level gauge installed.
The diesel engine must be able to produce the maximum volume and pressure of the fire pump curve. This pressure is based on the churn pressure of the pump and the static water pressure from the connecting source. This pressure is combined with the rated capacity of the pump to create the total system piping pressure. The churn pressure also includes the pressure needed to keep the fuel pump running.
Portable
Fire fighting pumps are designed to be either transportable (on fire-fighting vehicles as integrated or front-mounted pumps or as portable fire pumps) or stationary. Pumps that are intended for transportable use feature a pump end that is flanged to the motor and are mounted on a protective frame.
Fire fighting water pumps increase the pressure (measured in psi and bar) of a fire protection system water supply. They can be used to overcome the hydraulic design resistance of long hose lays or high elevation areas where the water pressure may be too low for the system to operate.
The Angus Fire range of portable fire pumps includes petrol and diesel powered models that are suitable for any application. They are all capable of achieving high levels of pressure and flow. Developed using the latest advancements in air-cooled engines, materials and pump technology, they are highly reliable and easy to use. They also meet world wide regulations on exhaust emissions and sound levels.
Stationary
Many large insurance companies require two fire pumps especially in high risk environments. This is based on the TIV or MFL/PML of the building and its contents. This is a critical requirement to ensure that the fire department will be able to effectively fight the fire and control the loss.
These are typically single-stage volute casing pumps, double-suction radial flow pumps or deep-well turbine pumps that extract water from a fire water pond, river or lake and provide it to the system under pressure. The fire pump must start reliably for testing and in the case of an actual fire.
In addition, the fire pump must be sized to accommodate the most demanding area of the fire protection system. In a high-rise building, this may be the automatic fire standpipe demand requiring 500 gallons per minute at 100 pounds per square inch. In low-rise buildings, it could be an occupied floor with a manual fire standpipe that requires the same water supply.