Bottom valves is a kind of mechanical emergency valve The seat is located inside of the ... valves is a kind of mechanical emergency foot valve.(Emergency foot valve,or emergency shut-off valve)1) Emergency Valves now ... who require a tough, reliable, high flow emergency valve.6)Specifications:a.Diameter: 3",4"b.Working pressure ... Alloye:Open manner:Pneumatic(Q), Manual(S) Mechanical Emergency Valve