Fire protection systems are those systems put in place to prevent or mitigate the unwanted effects of fire. According to the National Fire Protection Association (NFPA) about 3,000 people die in the United States from home fires every year. Most of these deaths could be prevented if the proper fire protection systems were put in place. Not only do fire protection systems save lives, they also safeguard property.
Wet Fire Sprinkler System
This is the fire protection system that is most often installed. The wet fire sprinkler system is very simple; it has a sprinkler and some have an automatic alarm check valve. When the wet fire sprinkler is exposed to heat beyond a certain degree, the built-in heat sensitive element will retract, allowing water to flow from the sprinkler. There are two basic types of fire sprinkler systems: one supplies water when needed, while the other is continuously pressurized. The system with pressurized water has distinct disadvantages. The water inside the pipes can quickly become stagnant, and a breeding ground for bacteria and mold. The water can also freeze and break the pipes; this is why regular draining and refilling of the pipes is necessary.
Dry Pipe Systems
Dry pipe systems are used in areas where cold is a factor. This system eliminates the storage of water, such as in a wet pipe system, in order to prevent the water from freezing. This is necessary in places that do not have heating, such as parking garages, attics and temporary out-buildings. Water is only supplied to the pipes when the system kicks into operation in the event of a fire. Dry pipe systems are also used in places where there are valuables that will be damaged by water, such as a library. In the dry pipe system, pressurized oxygen or nitrogen is stored in the piping system instead of water. This will be released when the sprinklers are turned on, permitting the water pressure to open a valve known as a dry pipe valve in order to flow through the piping system and out of the sprinklers. The main disadvantage of a dry pipe system is the increase in the response time when there is a fire.
There are three types of preaction systems: the Single-Interlocked Preaction system allows water to flow into the the closed sprinkler system upon the activation of of a detection system. In the case of the preaction system, it is the preaction valve which keeps the water out of the pipes. The preaction valve is held closed electrically to be released only when the detection system is activated. The detection system could be a heat or smoke detection system. When this happens, water fills the pipes to be released by the sprinkler. The Double-Interlocked preaction system does not allow water to flow into the pipes until the detection system and the sprinkler system are both activated. This is to prevent the accidental discharge of water. The Non-Interlocked preaction system will allow water to flow into the pipes when either the detection system or sprinkler system are activated.