DRY SPRINKLER SYSTEM
Dry pipe systems are different from wet systems in that the piping is filled with air instead of water. This air pressure holds back the water from entering the system by using a special dry pipe valve. With the opening of a sprinkler head from heat, the pressure is decreased and the valve opens allowing the water to fill the piping and flow out the open head. Dry systems are typically installed where the piping is subject to freezing.
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 dry pipe 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 are also on the system riser to send a trouble signal to the fire alarm panel if the systems air supply should not be adequate to keep the dry pipe valve from tripping open.
- An inspector’s test and drain is located at the most remote location of the system to test the operation of the dry pipe valve, check the actuation of the pressure switch, and check the time it takes for water to reach the test location.
- Air and water pressure gauges are on the system riser to check the system pressure.
- A main drain is provided to drain the system 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.