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A piloted check valve includes a closure that is pressure balanced to relieve pressure on non-metallic seat when valve is closed against high pressure differential. The closure includes a disc having a stem moving in a sealed chamber communicating through the stem and disc with the interior of the v

A piloted check valve includes a closure that is pressure balanced to relieve pressure on non-metallic seat when valve is closed against high pressure differential. The closure includes a disc having a stem moving in a sealed chamber communicating through the stem and disc with the interior of the valve seat opening. The chamber is provided by a cylindrical wall received in a socket in the valve body. The closure disc has a lip engaging the seat, the lip I.D. being about equal to that of the seat opening and the valve stem.

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A pilot locked poppet check valve comprising: a valve body having a hollow interior and first and second flow ports extending from the hollow interior to the exterior of the body, forming with the hollow interior a flow passage through the body, a valve seat around said flow passage having an openin

A pilot locked poppet check valve comprising: a valve body having a hollow interior and first and second flow ports extending from the hollow interior to the exterior of the body, forming with the hollow interior a flow passage through the body, a valve seat around said flow passage having an opening therethrough communicating portions of said flow passage on opposite sides of said seat, a valve closure in said flow passage moveable between a closed position in which the closure is in engagement with said seat at one end of said opening through the seat to fully block flow through the flow passage and an open position in which the closure is away from said seat leaving the flow passage open for the flow of fluid therethrough from said first port through a first part of said flow passage to said seat and thence through said seat to said end of the opening therethrough into a second part of said flow passage and past said closure to said second port and vice versa, the cross sectional area of said closure perpendicular to the direction of movement of the closure toward the seat being larger than the cross-sectional area of the opening through the seat where the closure engages the seat, resilient means biasing said closure to closed position, valve closing means responsive to fluid pressure in said second part of the flow passage when the valve is closed for holding the valve closure in closed position, said valve closing means comprising surface on said closure exposed to fluid pressure in said second part of the flow passage, said valve closing means being effective when the closure is in closed position to assist said resilient means, the surface of said valve closure subject to fluid pressure in said second part of said flow passage when the valve is closed producing in response to the last said fluid pressure a resultant force in said direction tending to hold the valve closed, a rod extending in said passage in said valve body with clearance between the outer periphery of the rod and the inner periphery of said passage leaving room for fluid flow through said passage, said rod being separate from said closure and moveable between a position engaging said closure and a position out of engagement with said closure, hydraulic means connected to said rod for moving the rod, when the hydraulic means is actuated, to a position in engagement with said closure holding the closuire in open position and for allowing the rod, when the hydraulic means is unactuated, to move with the closure as the closure means moves to closed position under the force of said resilient means, balancing means which when the valve closure is in closed position, shields a first portion of the surface of said closure, other than the portion of the surface of the closure engaging the seat, from the fluid pressure in said second part of the flow passage and exposing said first portion to fluid pressure in said first part of the flow passage, and valve opening means responsive to fluid pressure in said first part of the flow passage when the valve is closed for moving the valve closure to open position, said valve opening means comprising surface on said closure exposed to fluid pressure in said first part of the flow passage, said valve opening means being effective to move said closure to open position upon occurrence of fluid pressure in said first part of the flow passage sufficient to overcome said resilient means and the effect of fluid pressure on surface of said closure subject to fluid pressure in said second part of the passage, said valve opening means being effective when said hydraulic means is unactuated and said rod is out of engagement with said closure.