An extensive range of low pressure Safety Valves, Vacuum Relief Valves, Combined Pressure and Vacuum Relief Valves, Pressure Relief Valves and Tank Blanketing Valves to guarantee the protection of tanks and vessels by relieving the overpressure caused by the thermal effects and the filling and emptying of storage tanks and vessels.
Main Valve Closed
As the top of the piston “A” has a bigger area than the seat area “a”,then the downward acting force is the greater, hence the main valve remains closed and leak tight.
Main Valve Open
When the system pressure “P” reaches the set pressure “SP”,the pilot seat lifts slightly and creates a flow in the “Feeding” sense line.The variable orifice restricts this flow to the top of the blow-down diaphragm, creating a low pressure above it and a high pressure below. This in turn gives a boost to the pilot lift. The dome pressure is released via the drain to the atmosphere and the main valve responds by lifting fully at the set pressure.