Because dry pipe sprinkler systems are installed in areas where temperatures are expected to drop below freezing, all parts of the system must be airtight and kept free of water. Complete drainage is essential.
Each fall, before freezing season comes, check the pitch of all piping carefully using a spurt level to detect dips and small pockets in the lines. Check for:
broken, loose, or missing hangers; and
water in low point drains.
Check air and water pressures weekly. If air pressure losses exceed 10 psi, check the entire system for tightness and eliminate air leaks. Principal checking methods are as follows:
Put a strong smelling oil, such as oil of peppermint, into the air supply. This will produce a strong odor at the point of leakage.
Paint fittings with a soapy water solution and watch for bubbles.
Check the temperature of valve enclosure and maintain a temperature above 42F.
Make certain that the valve between the intermediate chamber and the alarm devices is open on dry pipe valves.
Check drip valves at intermediate chambers, making certain that clappers or balls are in a position to allow drainage. This is done by lifting push rods or by inserting a pencil in the opening. Water leakage through this valve is an indication that the water clapper is not holding tightly to the seat.
Check the air pressure. The air pressure versus water pressure for differential dry pipe valves should be as outlined in table 8-3 unless otherwise specified by the manufacturer's operating instructions. Certain mechanical dry pipe valves are designed to trip at a fixed pressure of 10 to 15 psi. Maintain 30 psi air pressure on these valves.
Basic inspections for accelerators and exhausters include the following:
Check air pressure. The system and the quick-opening device air pressure should be the same.
Relieve excess pressure in the quick- opening device by opening bleeder valves or loosening air gauges.
If the system pressure is high, relieve the excess pressure through the priming water test valve. Close the valve as soon as pressures balance. To avoid the possibility of tripping the dry pipe valve, do not open the priming test valve more than one turn and keep the valve to the quick-opening device closed while the priming test valve is open.
To make sure that dry pipe valves will operate effectively in fire situations, they should be trip-tested annually as follows:
1. Close the main control valve.
2. Open the 2-inch drain.
3. Open the main control valve until 5 psi pressure shows on the water gauge.
4. Close the 2-inch drain valve slowly.
5. Open the inspector's test connection of the system. Where there is no test connection, use the most remote low point drain.
6. As soon as the dry pipe valve trips, close the main control valve and open the 2-inch drain. This is particularly important in permanently cold areas.
7. Record initial air and water pressures, air pressure at the trip point, and time required for tripping.
8. Examine and clean the dry pipe valve interior. Replace facings and gaskets if needed.
9. Reset the dry pipe valve and the open control valve.
10. When a dry pipe valve fails to trip or when a clapper fails to latch in the open position, notify the person responsible for fire protection so that a qualified sprinkler contractor may be contacted.
To test dry pipe valves you should do the following:
1. Close the main control valve and open the 2-inch drain valve and low point drain valves.
Table 8-3. - Differential Dry Pipe Valve Air Pressure Specifications
|MAXIMUM WATER PRESSURE psi||AIR PRESSURE RANGE psi|