Abstract: A gate valve for controlling fluid flow, with a valve body forming a cylindrical flowbore and a gate cavity intersecting the flowbore to provide opposed openings. Seat pockets formed in the opposed openings may optionally include a metal carrier ring. A non-metallic bridging seal formed as a face seal is provided between the first seal surface of the annular seat element and the seat pocket. The bridging seal bridges any gap formed at the first seal surface such that sealing engagement is maintained across the gap at all times as the gate moves between open and closed positions, while still permitting limited axial movement of the annular seat element. Preferred embodiments of the bridging seal include tongue and groove seals and bridge ring inserts. A secondary seal to the seat pocket may be included as a corner, periphery or face seal, for example as an O-ring, U-ring or wiper seal.

Abstract: A gate valve for controlling fluid flow, with a valve body forming a cylindrical flowbore and a gate cavity intersecting the flowbore to provide opposed openings. Seat pockets formed in the opposed openings may optionally include a metal carrier ring. A non-metallic bridging seal formed as a face seal is provided between the first seal surface of the annular seat element and the seat pocket. The bridging seal bridges any gap formed at the first seal surface such that sealing engagement is maintained across the gap at all times as the gate moves between open and closed positions, while still permitting limited axial movement of the annular seat element. Preferred embodiments of the bridging seal include tongue and groove seals and bridge ring inserts. A secondary seal to the seat pocket may be included as a corner, periphery or face seal, for example as an O-ring, U-ring or wiper seal.