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Fire Sprinkler Types
January 15, 2010 - Contact FacilitiesNet Editorial Staff »
Properly maintaining a facility's sprinkler system starts with understanding which system is in place. Most sprinklers fall into one of four categories.
Wet sprinklers are the most common and simplest. When a fire occurs, the heat activates the system, allowing the water to flow. Because wet sprinklers are the simplest type, they require the least amount of inspection, maintenance and testing.
Dry sprinklers are designed for systems in which the pipes may be exposed to temperatures below 40 F. Pressurized air holds back the water at the main sprinkler valve. When a sprinkler is activated, the air discharges from the system, causing the air pressure to drop, and water to flow to the open sprinklers.
A third sprinkler type is pre-action. These typically are used in areas where the property being protected can be easily damaged by water. Pre-action systems are similar to dry systems, except that a lower level of air pressure is maintained within the network of pipes. The air is used to monitor the piping and sense pressure changes; it doesn't actually hold back the valve, as it does in a dry system. Instead, the valve is closed, and needs to be opened by a signal from a detection system, such as a heat or smoke detector. Once the system is activated, the valve opens and water flows into the pipes.
Finally, deluge systems are used in locations in which vast quantities of water would be needed to control a fire. While TV and movies make it seem like deluge systems are pretty common, they are actually rarely used in real life.