Constant pressure valve and method

A flow control valve for positioning in a fluid system between a high pressure pump and a fluid gun, the valve comprising:

• a valve body having a first flow path therein extending between a fluid inlet port and a fluid outlet port, and a second flow path therein hydraulically in parallel with at least a portion of the first flow path;
• a first valve member movable within the valve body between a closed position for blocking fluid flow through the first flow path and an opened position for permitting fluid flow through the first flow path, such that when the first valve member is opened, substantially all fluid flow through the valve passes through the first flow path;
• a first seat within the valve body along the first flow path for sealing engagement with the first valve member, the first flow path having an upstream portion between the fluid inlet port and the first seat, and a downstream portion between the first seat and the fluid outlet port;
• the first valve member being profiled such that pressure within the upstream portion of the first flow path exerts no axial force on the valve element when in sealing engagement with the first seat;
• a biasing member for biasing the first valve member toward engagement with the first seat;
• and
• a second valve member movable within the valve body for substantially restricting fluid flow through the second flow path, such that when the first valve member is closed, fluid passes by the second valve member to the output port so as to maintain a high pressure level upstream from the valve.

A flow control valve for positioning in a fluid system between a high pressure pump and a fluid gun, the valve comprising:

• a valve body having a first flow path therein extending between a fluid inlet port and a fluid outlet port, and a second flow path therein hydraulically in parallel with at least a portion of the first flow path;
• a first valve member movable within the valve body between a closed position for blocking fluid flow through the first flow path and an opened position for permitting fluid flow through the first flow path, such that when the first valve member is opened, substantially all fluid flow through the valve passes through the first flow path;
• a first seat within the valve body along the first flow path for sealing engagement with the first valve member, the first flow path having an upstream portion between the fluid inlet port and the first seat, and a downstream portion between the first seat and the fluid outlet port;
• the first valve member having first end with an enlarged diameter for sealing engagement with the valve body, and an opposing second end having a reduced diameter less than the enlarged diameter for sealing engagement with the first seat within the valve body, such that first valve member may be removed from the valve body without disassembling the first valve member;
• a first seal for sealing engagement between the first end of the valve member and the valve body, the first seal being continually exposed to the upstream portion of the first flow path during movement of the first valve member within the valve body;
• a biasing member for biasing the first valve member toward engagement with the first seat;
• and
• a second valve member movable within the valve body for substantially restricting fluid flow through the second flow path, such that when the first valve member is closed, fluid passes by the second valve member to the output port so as to maintain a high pressure level upstream from the valve.

A flow control valve for positioning in a fluid system between a high pressure pump and a fluid gun, the valve comprising:

• a valve body having a first flow path therein extending between a fluid inlet port and a fluid outlet port, and a second flow path therein hydraulically in parallel with at least a portion of the first flow path;
• a first valve member movable within the valve body between a closed position for blocking fluid flow through the first flow path and an opened position for permitting fluid flow through the first flow path, such that when the first valve member is opened, substantially all fluid flow through the valve passes through the first flow path;
• a first seat within the valve body along the first flow path for sealing engagement with the first valve member, the first flow path having an upstream portion between the fluid inlet port and the first seat, and a downstream portion between the first seat and the fluid outlet port;
• the first valve member when in sealed engagement with the first seat including a face exposed to the downstream portion of the first flow path for moving the first valve member off the first seat in response to increased pressure in the downstream portion of the first flow path;
• a biasing member for biasing the first valve member toward engagement with the first seat;
• a second valve member movable within the valve body for substantially restricting fluid flow through the second flow path, such that when the first valve member is closed, fluid passes by the second valve member to the output port so as to maintain a high pressure level upstream from the valve;
• a second seat within the valve body for cooperation with the second valve member for substantially restricting fluid flow through the second flow path;
• an access port within the valve body spaced from both the fluid inlet port and the fluid outlet port for removal and insertion of the second seat within the valve body;
• and
• a removable plug member for normally blocking the access port, the plug member having a stop surface for engagement with the second seat, such that the plug member can be removed and the second seat removed from the valve body through the access port.