Wet-Pipe System

The wet pipe system is the most common type of fire protection system. The piping is filled with water under presser at all times. Once a sprinkler is activated, water is instantly discharged and continues to send water until the system is shut off. The wet system is the simplest and most reliable system.

Dry-Pipe System

The dry pipe system is used in areas that are not heated so that water does not freeze within the system. The system is filled with pressurized air or nitrogen that keeps the clapper within the system from closing, thus preventing water from initially entering the system. The system’s valve is kept in a heated area to keep the water below the clapper from freezing. When a sprinkler is activated, the air within the system is released, which then lower the presser in the system. After the air pressure drops low enough, the water pressure below the clapper is greater than that within the system, which pushes the clapper open. At this point, the water is released into the system and to the activated sprinkler. The dry system has an inherent delay time due to the time it takes the clapper valve to trip and fill up the sprinkler system. It is less reliable and requires more maintenance than a wet system due to its complexity.

Preaction System

A preaction system is similar to a dry pipe system. They are used in areas that are highly susceptible to damage from accidental sprinkler discharge from mechanical damage to sprinkler or piping. The preaction system can be used instead of a dry pipe system. Water is prevented from entering the system by a closed valve (preaction valve) that is controlled by a detection system. If a sprinkler or pipe is damaged, water does not enter the system. During a fire however, when a sprinkler is activated, the fire detection system is activated also. This opens the preaction valve and allows water to enter the system to the activated sprinkler. The preaction system partially reduces the water delay that exists in a dry system; however it is less reliable due to the necessity of operation of both the preaction valve and detection system. There is also additional maintenance required to service both the preaction valve and the detection system.

Deluge System

A deluge system is similar to a preaction system, except that the sprinklers are open, or specially designed nozzles are used. Water discharges from all sprinklers at the same time, dousing the entire protection area. This system is used in high-hazard occupancies where immediate discharge of large quantities of water is needed.

Clean Agent

A waterless gas based system that uses a highly sophisticated detection system. The Clean Agent is stored as a liquid in pressurized cylinders. When discharged, the liquid flows through a piping network into the protected area, where it vaporizes and extinguishes the flame. There are no sprinklers involved. The amount of gas delivered from each nozzle is carefully calculated to deliver the proper amount of agent to each protected area. These systems are used to protect areas that contain highly valuables such as art, computer servers, or history collections.

System Valves

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