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Accel Fire Systems, Inc.
4510 Gambell Street
Anchorage, Alaska 99524
Phone: (907) 349-1490
Email: mike@accelfire.com
Accel Fire Systems, Inc.
915 30th Avenue, Suite 110
Fairbanks, Alaska 99701
Phone: (907) 456-3990
Email: brian@accelfire.com 
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  • What is a Sprinkler System?
  • How do Sprinkler Systems Operate?
  • What are the Benefits of a Sprinkler System?
  • What are the Common Types of Sprinkler Systems?
What is a Sprinkler System?

An automatic sprinkler system is a heat activated system of underground and overhead piping designed in accordance with the National Fire Protection Association (NFPA) and other relevant codes to save lives and limit property damage. This engineered network of piping includes one or more automatic water supplies, hydraulically calculated piping, and sprinkler heads spaced systematically to deliver the required water density to extinguish a fire or contain it to a limited area.

The “heart” of the sprinkler system is called the system riser and consists of a main control valve, main drain, gages, and a mechanism for activating an alarm when the system activates.

How do Sprinkler Systems Operate?

A fire sprinkler system is a network of pipes and sprinkler heads with water under pressure. When the individual sprinkler heads are activated by heat, they automatically extinguish or suppress a fire before it gets out of control, saving countless lives and immeasurable amounts of property. Located in every sprinkler head is an activating device, normally a solder link or glass bulb. When the temperature from a fire heats this activating device it is designed to melt or break at a specified temperature depending on the model of the head, most commonly 155 degrees Fahrenheit. Thusly, the water is released directly over the fire automatically limiting growth or extinguishing the fire, as well as sounding an alarm.
What are the Benefits of a Sprinkler System?

Aside from the fact that sprinkler systems save lives, there are several other benefits to having a sprinkler system. Due to their quick response time, the fire is contained to a small area or extinguished allowing occupants to evacuate. Additionally, since the sprinkler system controls or extinguishes the fire, limited damage is caused by firemen in an  attempt to control the fire. The amount of water needed to douse an unsprinklered building fire is usually tens to hundreds of times more than that which sprinklers would have discharged. Fire damage is also usually many times greater. It is proven that sprinkler systems limit property damage so much that discounted insurance may be offered to owners of sprinklered buildings.

Contrary to popular belief and what Hollywood portrays, accidental discharge of sprinklers is a
rarity with an average of only 1 in 16,000,000 defects detected per year. The media often exaggerates reports of water damage from sprinklers.

What are the Common Types of Sprinkler Systems?

Wet Pipe Sprinkler System:
An automatic system in which water is under pressure within the entire system and directly behind all the sprinkler heads, so that when the head is activated, water discharge is immediate. This is the most commonly used sprinkler system.

Dry Pipe Sprinkler System:
An automatic system in which air is under pressure within the entire system through the use of an air compressor. When the pressure is relieved, normally through an activated sprinkler head, loss of air allows water pressure to open a Dry Pipe Valve, allowing water to flow into the system and to the source of the fire. Dry pipe systems are installed when the system would be exposed to cold temperature, eliminating the possibility of freezing pipes. This is the second most commonly used sprinkler system.

Preaction Sprinkler System:
An automatic dry system with a supplemental detection system (smoke and/or heat detectors) installed in the same areas as the sprinkler heads. In a normal situation the preaction piping is filled with pressurized air. When a fire detector senses a fire, the alarm panel signals the preaction valve to open and water flows in the system pipes. There are three distinct  types of preaction systems:

  • NonInterlock Preaction: A noninterlock system admits water to sprinkler piping upon operation of either detection devices or opening of automatic sprinkler heads. This type of a preaction system is used much like a dry system to protect areas subject to seasonal cold weather, but where the delay required to fill the piping with water only after a sprinkler head activates could allow the fire to build to significantly. The detection system activates the preaction valve normally well before the fire would cause the sprinkler heads to open. By opening the preaction valve and filling the sprinkler pipe with water before the sprinkler head opens, the time elapsed before water is applied to a fire is greatly reduced to more closely imitate that of a wet pipe sprinkler system. This can apply water to the fire as much as 60 seconds sooner than a dry pipe system, reducing the opportunity for the fire to develop large enough to cause greater damage, or require a greater effort to be controlled.
  • Single Interlock Preaction: A single interlock system allows water to enter the sprinkler piping upon operation of detection devices. Water will still not discharge until one or more sprinkler heads have opened, presumably due to heat from a fire. The air pressure is used to monitor the integrity of the pipe in case of an accidental break to signify that repairs are needed to be made right away, so that when the detection system device activates the preaction valve and water enters the pipe, there won’t be water discharge until a fire opens the sprinkler heads. These are the systems typically used in computer rooms, archive rooms, or areas containing products or equipment that would be significantly damaged by accidental water discharge. These systems are also sometimes used as a back up to gaseous clean agent system.
  • Double Interlock Preaction: A double interlock system admits water to a sprinkler system only upon operation of both detection devices and automatic sprinkler heads. Requiring both the devices and the heads to activate provides the maximum assurance that the system will not accidentally fill with water. This system is most commonly used in commercial freezers where accidental water entry into the piping system could cause significant damage to the sprinkler system piping by freezing and busting it.
Deluge Sprinkler System:
An automatic system where all the heads are open and is activated by a detection system (smoke and/or heat detectors). When a fire is detected, the control panel signals the deluge valve to open, allowing water to enter the system piping. The water will then flow out ALL of the sprinklers or nozzles. Note that heat is not required to open the sprinklers (as in the
preaction system) since the heads are already open. Deluge systems are used in high hazard areas where a fire would tend to spread quickly. This system provides the advantage of applying water over a large area very quickly.
Foam Sprinkler System:
Any of the previously described systems connected to a special foam concentrate reservoir at the system riser that automatically delivers a combination of foam and water when the system is activated. This system is most commonly used in aircraft hangars, or facilities that handle products that are flammable liquids, or that become flammable liquids in a fire situation, such as petroleum, certain paints, solvents, fuels, etc.
Antifreeze Sprinkler System:
An automatic wet system in which the piping is filled with antifreeze, instead of water, to prevent freezing. When a head is activated by heat, the antifreeze solution is discharged, followed by water, operating the same as a wet system. Additionally, just a section of the system that is exposed to the cold can be designed to contain antifreeze and not the entire system. This is commonly used in overhangs, coolers, attics, etc.