Valve apparatus

A valve apparatus having a longitudinal axis therethrough, comprising:

• i) a valve seat member that comprises a hollow bore and a first frustoconical contact surface;
• ii) a valve closure member that comprises a body and a second frustoconical contact surface that is adapted to seal against the first frustoconical contact surface, the valve closure member being movable along the longitudinal axis of the valve apparatus;
• iii) a fluid flow path through the bore of the valve seat member and between the valve seat member and the valve closure member, the fluid flow path being closed when the second frustoconical contact surface is in contact with the first frustoconical contact surface;
• and
• iv) a reverse screening member that is attached to at least one of the valve closure member or the valve seat member and that screens particles from fluid passing through the fluid flow path in a reverse direction when the valve closure member approaches the valve seat member;
• and
• v) a means to delay the valve closure while the reverse screening member is within a range of screening distances from the opposing frustoconical contact surface
• wherein the means to delay valve closure is a resilient screening insert which allows the passage of screened fluid until differential pressure across the valve deforms the insert to seal the valve, further wherein the resilient screening insert comprises at least one protrusion from its contacting surface, and the one or more protrusions create a screening gap between the insert and the opposing frustoconical contacting surface when the valve closure member approaches the valve seat member, and further wherein the one or more protrusions are of resilient material and deform under forces caused by differential pressure to allow the screening gap to close.