Protect irreplaceable assets with a pre-action fire sprinkler. Standard water-based fire protection systems stand between you and major tragedies, including loss of life and destruction of your property. Yet, these same systems also pose the risk of accidental discharge that can damage valuable works of art, documents, computer systems and other important, even irreplaceable assets. The result? Severe disruption to operations; loss of systems, data, inventory or other valuable assets, like data centers, trading floors and storage facilities. Valley Fire Protection Systems offers pre-action fire sprinkler systems to our customers to protect valuable assets. Pre-action sprinklers provide extra insurance against the accidents mentioned, while maintaining a ready response against fire,

What is a pre-action sprinkler system?

A pre-action sprinkler system is typically a modified version of a “dry” system. Standard sprinkler systems always contain water in the pipes, just behind the sprinkler heads. A dry system only contains air until conditions indicating the presence of fire are met, at which point water is quickly pumped into the system to suppress the fire. A pre-action sprinkler system utilizes an electrically operated valve — the pre-action valve — to hold back water until flames, heat or smoke from a fire are detected.

How does a pre-action sprinkler system work?

A pre-action sprinkler system prepares to act when a fire detection system identifies a developing fire inside a facility. It electrically opens the pre-action valve through the use of a solenoid switch, which allows water to flow into the piping system. (In freezer warehouses and other below-freezing situations, the pipes must be kept dry unless fire suppression is definitively called for. Here, a specific type of system known as a double interlocked pre-action system is typically employed to mitigate against accidental tripping of the fire detection system. This is detailed in the “Types of Pre-Action Sprinkler Systems” section of this article.)

The types of fire detection systems that trigger the pre-action valve include:

• Thermal detectors, which react to temperature increases
• Smoke detectors, which react to combustion products or flaming/smoldering fire conditions
• Flame detectors, which react to a fire’s infrared radiation and/or ultraviolet light

Once the pre-action valve has opened, the pre-action sprinkler system acts much like a typical sprinkler system. When the temperature-sensitive solution contained within any individual sprinkler head detects heat at a predetermined temperature the glass bulb bursts and water flows to extinguish the fire.

Types of pre-action sprinkler systems

In order to deliver the optimal performance, there are several types of pre-action systems available, including non-interlock systems, single interlock systems and double interlock systems.

The non-interlock pre-action system acts as a typical pre-action system when a fire detection system reacts before a sprinkler head does. When a sprinkler operates first, the system responds like a dry pipe system to fill the pipes with water that then exits through the activated sprinkler. Because the water valve opens the moment that the detection system is tripped, a non-interlock system allows for very rapid response to fire. The moment that the sprinkler head reacts, water flows. The chief drawback of the non-interlock system is if a sprinkler head is activated due to damage, the safeguard feature offered by a pre-action system is nullified.

A single interlock pre-action system centers around a deluge valve that is tripped by a fire detection system. Water then fills the piping that discharges through any activated sprinklers. This system introduces some protection against accidental discharge, as a broken sprinkler or pipe will not cause the valve to open. Only the fire detection system can open the deluge valve and start the flow of water.

The most sophisticated pre-action sprinkler system is the double interlock pre-action system. In this type of system, which also uses a deluge valve, pressurized air or gas is kept within the piping until a sprinkler is activated. If this pressure drop is accompanied by a tripping of the fire detection system, then the valve will open to deliver water through the piping to the activated sprinkler or sprinklers. Should only one of these conditions be met, the valve will remain closed to prevent accidental tripping. The pressurized system offers the additional benefit of providing a warning about any leaks in the piping.

Typical applications of pre-action sprinkler systems to protect valuable assets

Pre-action systems are best suited to protect valuable assets or areas at risk for serious water damage due to damaged sprinklers and/or piping. Computer rooms, data centers, cell tower stations, telephone switching stations, server farms, telecommunications equipment and high-voltage electrical components must be protected from accidental water discharge. Similarly, artworks, libraries and archived paper records call for this additional protection.

In cold or frozen storage facilities, a double interlock pre-action system is a must to guard against accidental discharge of water and to ensure that water will flow in the event of a fire. While this type of system can be relatively costly, the price is still significantly lower than that which will be incurred through any accidental water discharge!

Additional advantages

Pre-action sprinkler systems offer protections not afforded by a typical dry system, which will quickly release water should a sprinkler head accidentally open. This factor alone should give any facility designer or manager pause.

An additional, oft-overlooked advantage of pre-action systems is that they ensure protection against the dangers posed by pipes going out of pitch. No one ever sets out to put a pipe off of its pitch. This prevents it from draining properly after testing (trapping water that can freeze and expand inside the pipe). However, there are many situations in which this happens by accident. A construction worker or pest control specialist may sit on what appears to be a unmovable section of pipe while engaged in a task.

An electrician may stand on a pipe to gain access to a higher area or hang components from it. Someone installing a security camera may place a ladder against a pipe. Even foundation shifting, due to a building settling or seismic activity, can affect pipe pitch. We have seen this type of incident occur time and again. When wintry conditions set in and freeze the standing water, it expands and bursts through the pipe.

Conclusion

In both my own as well as Valley Fire Protection Systems’ experience, pre-action systems more than justify their costs. Their unparalleled ability to prevent accidental water discharge can prevent damages to facilities like libraries, cultural institutions, cold storage warehouses, high-tech and financial businesses. As part of our ongoing mission to inform and protect our customers, I thank you for reading this piece and welcome your questions or feedback.

Related Topics: Fire Protection \/\/ Pre-Action Sprinkler