Wet Sprinkler Systems
The sprinklers in these systems are attached to pipes containing pressurized water at all times. Individual sprinklers in the vicinity of a fire are set off by heat, allowing water to flow through them immediately.
Wet-pipe systems are used wherever temperatures are high enough to prevent freezing.
Water expands when it freezes, this causes water filled pipes to burst and become ineffective. Burst pipes decrease your fire suppression capabilities and can cause significant water damage.
Sometimes, an antifreeze solution or additive is added to certain pipes in a wet-pipe system
Dry Sprinkler Systems
In a dry-pipe system, sprinklers are attached to pipes that contain pressurized air. When heat activates the sprinklers to open, the air pressure is reduced, allowing the dry pipe valve to open and water to flow from the sprinkler.
Dry-pipe systems are usually used only when temperatures are not high enough to prevent freezing (Below 40 deg. F).
Since they have a slower response time, they should be converted to wet-pipe systems as soon as sufficient heat becomes available.
In situations where only a few sections lack heat, it is recommended to use a combination of dry and wet-pipe systems.
Antifreeze loops protect areas in a building that are prone to freezing. A check valve isolates the antifreeze loop from the rest of the sprinkler system. There is also a main drain and a fill cup to assist in the draining and refilling of the loop. Antifreeze loops are filled with a variety of different liquids the most common being: propylene glycol, glycerin and ethylene glycol. If the sprinkler system is connected to a public water supply ethylene glycol should not be used because it is considered poisonous. Also, systems that are constructed out of CPVC plastic pipe should only be filled with glycerine. Absolute Protective Systems, Inc. has a policy only to use glycerine due to environmental and practical concerns. NFPA requires the testing of antifreeze loops on an annual basis.
Pre-Action Sprinkler Systems
These systems contain an additional fire-detection device that will recognize a fire before the sprinklers are activated. The sprinklers are attached to a pipe containing air that may or may not be pressurized.
When the detection device senses a fire, it opens the main valve, allowing water to flow through the pipes before the sprinklers are set off. When the heat activates the sprinklers, water flows through immediately, as in a wet-pipe system.
Pre-action systems are usually employed in areas that are at risk for serious water damage due to damaged sprinkles and/or piping.
They operate faster than dry systems, but tend to be significantly more expensive.
Deluge Sprinkler System
In these systems, sprinklers are open at all times. They are connected to a dry pipe that is connected to a main water supply.
A fire detection device controls the main valve. When it is activated, the valve opens, allowing large amounts of water to flow through all of the sprinklers.
The purpose of a deluge system is to quickly wet down an entire hazardous area to prevent a fire from spreading. They are usually used in facilities that contain high or extra hazard materials such as: flammable liquids, chemicals, and explosives. Rooms with high ceilings sometimes use deluge systems, as it is difficult to direct water over the burning area from such a distance.
A foam fire protection system should be used to protect buildings that contain combustible materials and other hazards that a normal water based fire protection system could not supress in the event of a fire. The foam system supresses the fire by separating the fuel from the air. These systems typically inject a concentrated foam mixture into a water based deluge system.
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