Low pressure diaphragm valve for town gas - has two diaphragms forming three chambers fitted with manual override system

摘要

The lower part (1) of the valve has a central inlet (4) and a side outlet (6). On this is fixed a ring (2), a diaphragm (7) being sealed between them. A similar diaphragm (8) is sealed between the ring (2) and the top cover (3). A valve plug (11) passes through the both diaphragms, its lower end (12) forming a seal (6) for the gas inlet. An axial hole (18) permits gas pressure to enter the top chamber, this being assisted by a coil spring (19). The middle chamber is open to atmospheric pressure and contains a lever fork (20, 25, 26) actuated manually from outside the valve, which can selectively open or close the valve.