What is a Design System?
As defined by NFPA is an installation equipped with multiple open nozzles connected to a water supply by means of a deluge valve which allows water to flow from all nozzles simultaneously. This is like a water spray system but does not use directional water spray nozzles to achieve a specific water discharge and distribution. In the refining and petrochemical industries, the term deluge system is generally a system without nozzles in which all the water is applied from an open pipe. API 2510 and API 2510A describe such a system at the top of a vessel which allows water to run down the sides in a thin film, frequently using a weir to improve distribution and assist the even flow of water over the protected vessel.
A deluge system consists of a non-pressurized piping network using open sprinklers or nozzles that discharge water once the water control valve operates. These systems are somewhat more complex than wet pipe or dry pipe systems because they require a detection system or manual release to discharge water into the system. Once water is released into the system, all sprinklers or nozzles discharge simultaneously.
Design Systems
Deluge systems differ from wet or dry sprinkler systems in that they require the operation of a detection device or manual release for the sprinkler system to discharge. The detection system is the only mechanism required to flood the system piping with water. Detection systems can be hydraulic, pneumatic, or electric. Choosing the appropriate detection system is dependent upon the type of hazard and location of the hazard that is being protected.
Wet Pilot Detection
A wet pilot line is a non-electrical type of detection/release system that can be used in areas maintained at or above 40°F (4°C). Closed sprinklers or fixed-temperature-release pilot line detectors are installed throughout the protected area on small diameter piping that contains water under pressure.
Dry Pilot Detection
Where freezing conditions exist, or where height/distance limits of wet pilot lines are exceeded, a dry pilot line can be used. Closed sprinklers or fixed-temperature-release pilot line detectors are installed throughout the protected area on small diameter piping that contains pressurized air or nitrogen.
Electric Detection
Where electrical actuation of the system is preferred over wet or dry pilot lines, or where otherwise required by project specifications, electric detection can be provided. There are numerous types of electrical detectors used for the release of deluge systems including smoke, heat, and linear detection.
Releasing Devices
Releasing devices serve as the basis for the activation of all deluge systems. They are most often located on the valve trim and are used to vent hydraulic pressure from the water control valve allowing water to flow into the fire protection system. These devices can be manual or automatic. Automatic devices are triggered or released by detection devices located within the protected area and have been previously described. Manual devices are required by NFPA 13 to be located at the water control valve but can also be located remotely within the protected area.
Types and Uses of Deluge Valves
A deluge system consists of a non-pressurized piping network using open sprinklers or nozzles that discharge water once the water control valve operates. These systems are somewhat more complex than wet pipe or dry pipe systems because they require a detection system or manual release to discharge water into the system. Once water is released into the system, all sprinklers or nozzles discharge simultaneously.
Deluge systems are commonly used where large quantities of water must be applied quickly and consistently. In some cases, they are used to quickly extinguish a fire while in other cases they can be used to rapidly cool a structure or reduce increasing temperatures within tanks or process lines. Deluge systems are used to protect a wide variety of hazards including stage prosceniums, flammable storage tanks, tunnels, transformers, and processing equipment. Deluge systems can be supplemented with fire-fighting foam to smother the fire when protecting areas like aircraft hangars or flammable liquids.
