Installation of Fire Pumps To Ensure Dependability
Industrial Fire Safety
Fire protection pumps should be installed in a manner to assure reliable and efficient operation in the event of a fire.
All equipment must be approved by Underwriters’ Laboratories or Factory Mutual and the installation plans must be approved by the familiar “authority having jurisdiction.” It is also usually necessary to have the pump manufacturer’s certified set of curves showing head delivery, efficiency and brake horsepower to obtain approval of an installation.
The provision of adequate water sources, such as ponds, lakes, rivers, tanks and wells, was mentioned in our March article and bears repeating because without a proper suction source, fire pumps are useless and provide a false sense of security.
Note: Booster pumps are connected to city mains to increase inadequate pressure to a usable level in the plant.
Suction cribs: For suction from ponds, lakes and similar bodies of water, properly screened and gated suction cribs, or intakes, must be installed. The screens have to be serviced to remove obstructions and maintain adequate suction.
Thought must be given to selecting the type of pump driver. In many cases, the maximum reliability can be built into your pump installation by using twin pumps, one driven by an electric motor and the other by a diesel engine. This is important in remote locations and places with histories of public power failures.
In many cases, reliability can be obtained from an electrically driven pump if two separate power supplies are available and neither power line crosses plant roofs, where it can be destroyed by fire. The lines also should be placed to be protected as much as possible from windstorms. Other types of drivers can be acceptable, but all the pros and cons of drive power should be fully explored before choosing pump drivers, particularly a single one.
Protection required: All pump installations in buildings should be in separate rooms of adequate size with standard cutoffs from the rest of the facility. The construction must be noncombustible and there must be adequate lighting, heat, humidity control, drainage and automatic sprinkler protection for the equipment.
Outside pump houses, we feel, should be of noncombustible construction, properly sprinklered, have the other safeguards just mentioned and be secured by locked doors or a locked fence—or both.
A jockey pump, with smaller capacity and higher pressure than the main pump, is an integral part of any pump installation that makes up for minor leakage in the system and maintains high pressure without running the main fire pump.
Control of drivers: Controllers for either electric motor or internal combustion engine pump drivers must be approved models. Automatic controllers are recommended only for pumps that take suction under positive head and are not recommended for suction lift pump installations. The automatic controllers start the pump driver as a result of a drop in water pressure or the tripping of a deluge or dry pipe sprinkler valve. Automatic controllers also must have a manual starting capability with the starting control at the panel.
The controller for an electric motor pump driver should: (a) be located within sight of the motor, (b) be placed so that any water entering the pump room will not damage the controller, (c) have its current-carrying parts at least 12 inches above the pump room floor, and (d) have a 3 1/2-foot clear space at the rear to facilitate inspection and servicing. Items (a) and (b) also apply to controllers for internal combustion engines. The clearance mentioned in (d) is defined as 2 1/2 feet in NFPA No. 20, “Standard for the Installation of Centrifugal Fire Pumps,” but the larger space is preferable. All controllers must be adequately labeled with the manufacturer’s name, identifying designation and complete electrical rating. Full operating instructions must be mounted on the controller to ensure proper installation, operation and maintenance.
Steam turbine drivers for fire pumps cannot be controlled by the controllers previously mentioned. If automatic starting of a turbine-driven pump is desired but there is no intent to have the turbine on pressure control after starting, the installation can have a quick-opening manual-rest valve in a bypass of the steam feeder line around the manual control valve.
Alternative setup: If the application calls for the pump to start automatically and to operate by means of a pressure signal after starting, it is recommended that a pilot-type pressure control valve be placed in the bypass around the manual control valve in the steam feeder line.
All fire pump installations should have an automatic trouble or running signal to a 24-hour supervised alarm center. Such a signal indicates that the pump is operating and there is either a fire or distribution pipe break, allowing water to flow beyond the capacity of the jockey pump.
All installations must pass an acceptance test that should be conducted in the presence of the insurance carrier, the contractor and any other party having an interest in the protection system.