Sprinkler systems

Automatic Sprinkler Systems

An automatic sprinkler system consists of a water source, distribution piping, and one or more individual sprinklers (Figure 10.11). Depending on the situation, either a wet system or a dry system may be installed.

Wet-pipe system. The piping is constantly full of water under pressure (Figure 10.12). Heat from a fire causes one or more sprinkler heads to activate at a specified temperature, allowing water to be discharged directly onto the fire. Wet-pipe systems can apply water onto a fire faster than dry systems, but the water in the piping is subject to freezing. Frozen distribution piping can burst, and the linkage in individual sprinklers can be broken. When frozen piping thaws, water flows through the open sprinklers and piping, causing water damage. In cold-storage units and occupancies in cold climates, dry sprinkler systems are required.

Dry-pipe systems. The distribution piping is filled with air and allows the system to remain functional during freezing temperatures (Figure 10.13, p. 280). However, it delays the application of water onto a fire. There are three types of dry sprinkler systems:

• Dry-pipe

- Consists of closed sprinklers attached to a piping system that contains air under pressure.

When a sprinkler activates, air is released, activating the water or foam control valve and filling the piping with extinguishing agent. Dry systems are often installed in areas subject to freezing.

• Preaction — Consists of closed sprinkler heads attached to a piping system that contains air under pressure and a secondary detection system. Both systems must operate before the extinguishing agent is released. Similar to a dry-pipe sprinkler system, preaction systems are installed in areas that are sensitive to accidental water discharge.

Deluge — Consists of piping and open sprinklers. A fire detection system is used to activate the water or foam control valve. When the system activates, the extinguishing agent expels from all sprinkler heads in the designated area.