Anti-pollution valve for potable water - has spring loaded non-return valve with screw down security fitting

摘要

The valve (10) is fitted in, for example, a fire-main pipeline supplied with drinking water. The valve is designed to prevent back flow and consists of a normal screw down stop valve with a hand-wheel (26) and threaded spindle (27) forcing the valve (31,32,33) onto the seat (16). When the spindle is unscrewed the valve remains closed by virtue of the spring (34) and the fact that the valve (33) and guide ring (31) slide on the spindle. Excess pressure upstream (12) will lift the valve off its seat but a reverse differential pressure will close the valve.