Pressure relief valve

A pressure relief valve for relieving excess pressure in a fluid distribution system comprising:

• a valve body having an inlet port and an outlet port in communication with an interior of the valve body, the inlet port being connectable directly to the fluid distribution system;
• a valve member movable between a closed position to prevent fluid flow through the valve body and an open position to permit fluid flow through the valve body, the valve member being exposed to a first opening force exerted by the pressure in the fluid distribution system;
• a cylindrical auxiliary chamber in the valve body isolated from the interior of the valve body;
• a movable piston member slidable within the auxiliary chamber to divide the chamber into first and second regions and exposed to the pressure in the fluid distribution system, the movable piston member co-operating with the valve member to provide a second opening force for the valve member;
• and
• biasing apparatus to exert a default closing force to move the valve member to the closed position, the closing force being equivalent to a pre-selected pressure in the fluid distribution system whereby the first and second opening forces act to move the valve member to the open position whenever the pressure in the fluid distribution system exceeds the pre-selected pressure.

A pressure relief valve for relieving excess pressure in a fluid distribution system comprising:

• a valve body having an inlet port and an outlet port in communication with an interior of the valve body, the inlet port being connectable directly to the fluid distribution system;
• a valve member movable between a closed position to prevent fluid flow through the valve body and an open position to permit fluid flow through the valve body, the valve member being exposed to a first opening force exerted by the pressure in the fluid distribution system;
• an auxiliary chamber in the valve body isolated from the interior of the valve body;
• a movable member housed in the auxiliary chamber to divide the chamber into first and second regions and exposed to the pressure in the fluid distribution system, the movable member co-operating with the valve member;
• a conduit from the inlet port of the valve communicating the fluid of the fluid distribution systems to the first region of the auxiliary chamber to generate the second opening force at the movable member;
• a needle valve and a check valve connected in parallel in the conduit to allow unrestricted flow of fluid through the conduit into the first region of the auxiliary chamber and to limit the flow of fluid in the opposite direction from the first region to the inlet port;
• and
• biasing apparatus to exert a default closing move the valve member to the closed position, the closing force being equivalent to a pre-selected pressure in the fluid distribution system whereby the first and second opening forces act to move the valve member to the open position whenever the pressure in the fluid distribution system exceeds the pre-selected pressure.

A pressure relief valve for relieving excess pressure in a fluid distribution system comprising:

• a valve body having an inlet port and an outlet port in communication with an interior of the valve body, the inlet port being connectable directly to the fluid distribution system;
• a valve member movable between a closed position to prevent fluid flow through the valve body and an open position to permit fluid flow through the valve body, the valve member being exposed to a first opening force exerted by the pressure in the fluid distribution system;
• an auxiliary chamber in the valve body isolated from the interior of the valve body;
• a movable member housed in the auxiliary chamber to divide the chamber into first and second regions and exposed to the pressure in the fluid distribution system, the movable member co-operating with the valve member to provide a second opening force for the valve member with the second region of the auxiliary chamber being sealed;
• and
• a pressure source communicating with the second region to maintain the second region at a pressure to exert a default closing force to move the valve member to the closed position, the closing force being equivalent to a pre-selected pressure in the fluid distribution system whereby the first and second opening forces act to move the valve member to the open position whenever the pressure in the fluid distribution system exceeds the pre-selected pressure.