PREACTION SPRINKLER SYSTEM
Preaction systems are similar to dry systems in that the piping is filled with air instead of water. However, unlike a dry system this air is not used to hold back the water from entering the piping. The air contained in the system is for supervisory purposes only. Should a sprinkler head open due to fire or accident, air will escape from the piping triggering a low air alarm on the fire alarm panel-no water will enter the system. For water to actually fill the systems piping, the activation of a heat or smoke detector is required. Once activated, an electric signal is sent to the preaction systems solenoid valve, which then opens allowing the main deluge valve to trip and fill the piping with water. Preaction systems can also be tripped manually at the valve by a manual release pull station. These types of systems are typically installed in high value areas such as computer rooms.
Some of the components of this type of system include:
- Tamper switches on the control valves, which will provide a trouble signal to the fire alarm panel if the valve is closed.
- Pressure switches on the deluge valve trim to detect flow conditions, and then send an alarm signal to the fire alarm panel if the system should begin flowing water.
- Pressure switches on the system riser to send a trouble signal to the fire alarm panel if the systems air supply should drop below a preset level.
- The trim of the preaction valve provides for the testing of the actuation signal without filling the piping with water.
- Air and water pressure gauges on the system riser to check the system pressure.
- A main drain for allowing the system to be drained and allow for the replacement of sprinkler heads or repair of system piping.
- Auxiliary drains to drain “trapped” portions of pipe. These drains, drum drips, need to be monitored and maintained during colder months. maintenance schedule.