Water Based Suppression
As water based fire suppression systems continue to evolve, facilities now have more targeted and effective options for specific hazards. While high-risk areas with flammable liquids can benefit from the intensity of a deluge system, delicate electronic areas require a more specialized solution, such as a water mist system. F.E. Moran Special Hazard Systems has unparalleled experience employing every type of sprinkler system, giving them the ability to determine the appropriate solution to safeguard a plant's valuable assets.
Wet Pipe Sprinkler Systems
Because the piping in a wet pipe sprinkler system is continuously filled with water, these systems can only be used in environments that are not subject to freezing. Areas that require instant protection in the event of a fire can benefit from wet pipe sprinkler systems.
Pressurized water resides in the pipe until a fire is detected by a heat-sensitive automatic sprinkler, which allows water to flow from the targeted sprinkler. Water is expelled from sprinklers within the direct vicinity of the fire, minimizing water damage. Alarms are activated as water flows through the system, which provides notification that the system is operating. Alarms sound until the water flow is manually interrupted.
Wet pipe sprinklers are not appropriate for areas that are prone to freezing temperatures. In addition, if a wet pipe sprinkler sustains substantial impact it could result in damaging leaks.
Dry Pipe Sprinkler Systems
In conditions where wet pipe sprinkler systems could potentially freeze, dry pipe systems are a suitable option.
Dry pipe sprinklers are pressurized with air, which is released upon actuation of the sprinkler. There is a delay in the discharge of water while the pressurized air escapes from the system, upon which water flows into the piping system through the dry pipe valve. The air supply can be provided from a plant air system, approved air compressor or nitrogen.
Air escaping from the pipe causes a time delay for water to reach sprinklers, which allows the fire to grow larger than it would with a wet pipe system of similar design. To compensate for the delay, more sprinklers in the fire area actuate in response to expanding fires. When it is critical to speed operation of the dry pipe valve, a quick opening device can be used to rapidly remove air from the system.
Environments such as computer rooms and areas that contain equipment that is sensitive to water may be best suited for a preaction sprinkler system. The extra measures of detection help eliminate accidental discharge, making preaction systems a prudent choice for areas with delicate equipment.
Preaction systems are dry pipe sprinkler systems with pressurized air in their pipes and closed sprinkler heads. The occurrence of accidental discharge is vastly eliminated since the system can be configured to prevent discharge in the event of a false detection alarm or damage to the sprinkler.
There are three types of preaction systems:
- Non-Interlock - A deluge valve is tripped and water is introduced into the piping system by either the activation of the detection system or the actuation of the heat-responsive sprinkler
- Single Interlock - The activation of fire detector trips a deluge valve, introducing water into the piping system to await the actuation of a sprinkler (a sprinkler fusing will provide a supervisory signal due to loss of air in the piping system)
- Double Interlock - Water is only introduced into the piping system when both a sprinkler fuses and the detection system is actuated
There are defined size limitations to preaction systems, which can inhibit scalability. Future alterations to these systems must also include modifications to the fire detection and control system to ensure functionality.
Areas that house high-risk equipment and hazardous materials such as oil and other flammable liquids are prime candidates for deluge systems. In applications where fire could spread quickly over a large area, high velocity deluge systems are effective in controlling fires.
The deluge valve in a deluge system is tripped by the actuation of a detection system, which introduces water into the piping system. Deluge systems do not have pressurized air in the piping system and sprinkler heads are continuously open, subsequently allowing water to discharge through all of the sprinkler heads in the system.
Because sprinkler heads are perpetually in an open state, the risk for accidental discharge is elevated. Deluge systems should only be used in areas that are not susceptible to water damage.
Water Mist Systems
In areas that have equipment that is sensitive to water but are frequently occupied, water mist systems are a safe alternative to carbon dioxide systems. Areas that are susceptible to water damage can also benefit from water mist systems because only a nominal amount of water is required to control fires, minimizing cleanup. Water mist systems are commonly used to help protect combustion turbines.
Water is converted into steam, which cools, wets and moves oxygen away from flames. The mist water droplets deplete the oxygen on the flame front, which in turn extinguishes the fire. By cooling the fuel, water mist also prevents fires from reigniting. Water mist systems can be deluge, wet pipe, preaction or dry pipe systems.
When designing a system, it must be considered that water mist systems are most effective when the spray is applied directly to the fire. Additionally, in the case of smaller or slow-burning fires, water mist systems may not be as effective because heat is required to vaporize water mist.
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