1. Type of automatic sprinkler system
a. Wet-pipe system
i. The wet-pipe sprinkler system has sealed sprinklers attached to piping that contains water under pressure at all times.
ii. When fire occurs, sprinklers are actuated by the heat, and water flows immediately.
iii. System is generally used whenever there is no danger of the water in the pipes freezing.
b. Dry-pipe system
i. A system with heat operated automatic sprinklers attached to piping containing air under pressure.
ii. When sprinkler operates, the air pressure is reduced, a “dry-pipe” valve is opened by water pressure and water flows to any opened sprinklers.
c. Pre-action system.
i. A system employing automatic sprinklers attached to a piping system containing air that is under pressure, with a supplemental fire detection system installed in the same area as the sprinklers. Actuation of the fire detection system by a fire opens a valve which permits water to flow into the sprinkler system piping and to be discharged from any sprinklers that are opened by the heat from the fire.
ii. May be used in areas subject to freezing. System minimizes the accidental discharge of water due to mechanical damage to sprinklers or piping, and thus is useful for the protection of the valuable or irreplaceable articles that are susceptible to damage or destruction by water.
d. Deluge system
i. The Deluge sprinkler system is equipped with open sprinklers and is installed in heated or unheated extra-hazard occupancies where an instantaneous discharge of water from all sprinklers is necessary. Piping contains air at atmospheric pressure.
ii. Deluge systems are used for fast, total application of water in extra-hazardous areas and in water-spray systems.
iii. The purpose of a deluge system is to deliver water to the entire area of a fire in the least amount of time possible through sprinklers or spray nozzles that are open all times.
iv. Deluge systems are suitable for extra-hazard occupancies in which flammable liquids are handled or stored, and where there is a possibility that fire may flash ahead of the operation of ordinary automatic sprinklers.
e. Combined dry-pipe and pre-action system
i. A combined dry-pipe and pre-action sprinkler system is one that employs automatic sprinklers attached to a piping system containing air under pressure and has a supplemental fire-detection system installed in the same areas as the sprinklers.
