Valves, Risers, Alarm and Control Devices
What the exam tests
This domain covers the riser assembly and its control and alarm devices: main control valves, check valves, alarm check valves, dry pipe and preaction valves, flow and pressure switches, gauges, drains, FDCs and inspector's test connections.
Core rules and concepts
- Main control valve. Use an OS&Y or listed indicating valve, supervise it open, and secure it after every test. A closed main valve is one of the most common causes of a failed system.
- Check valves. Prevent backflow and nuisance alarms. Alarm check valves have a retard chamber and water motor gong on wet systems.
- Dry pipe and preaction valves. These valves require specific air pressure, priming water and trip settings. Preaction systems use detection and may require cross-zoning.
- Flow and pressure switches. Flow switches detect water movement and must alarm within the time allowed by the standard, commonly 90 seconds. Pressure switches monitor air or water pressure.
- Gauges and drains. Supply and system gauges, main drain and auxiliary drains must be accessible and functional. Main drain tests verify the supply.
- Inspector's test connection. It simulates the flow of a single sprinkler, usually through a smooth-bore orifice matching the smallest sprinkler, and confirms that the alarm operates.
- FDC. Fire department connections must be accessible, labeled and fitted with the correct clappers and caps.
Worked example
A wet-pipe system has a 6 in riser, an OS&Y main valve, an alarm check valve, a water motor gong and a flow switch. To test the alarm, open the inspector's test valve fully and time the response. Water should flow, the flow switch should operate and the gong should sound within 90 seconds. Record the time and pressures. Close the test valve, confirm the system returns to normal, and verify that the main control valve is still open and supervised.
Traps that cost marks
- Leaving the main control valve partly closed after a test.
- Using a gauge with the wrong range, making normal pressure hard to read.
- Plugging or removing the inspector's test orifice.
- Forgetting to record the test result and reset the valve.