Pneumatic shutoff valves are independent stop valves for water installations fitted with accumulators. These valves prevent air escaping from accumulators into the pipe network once a pump has failed owing to lack of water, power cut, pipe blockage etc. In this way dangerous water hammer in the pipe network and loss of compressed air is prevented.
The accumulator must be installed in a pipe spur. As long as the accumulator is filled with water up to the level of the lower connecting spigot, the float of the pneumatic shutoff valve keeps the valve open in both directions if there is a flow of water. As soon as air passes from the accumulator into the pneumatic shutoff valve the latter closes tightly preventing air entering the pipe network. When the pump starts delivering the pneumatic shutoff valve automatically opens again and allows water to flow into the accumulator. When the water level is rising the pneumatic shutoff valve will open only if the pressure inside and downstream of the valve is approximately zero. The water flow velocity in the valve must not exceed 1.5 m/s (1 m/s for valve size DN 200).
NV 80 is a pneumatic shutoff valve of angled design, whereas NV 82 is a straight valve. The valve body is of welded steel construction; the float is precisely guided in two bushes; the valve cone is fitted with a soft seal.