Abstract: A valve seat structure adapted to be positioned within each annular seat pocket (37, 36) which is formed about the flow passage (12, 13) adjacent the valve chamber on both the upstream and downstream sides of the gate element of a gate valve. The valve seat structure comprises a metallic seat ring (40) which fits snugly within the seat pocket (36, 37) but has an axial dimension which exceeds the depth of the pocket. The seat ring is formed with an annular notch (49, 50) in the outer corner of the ring at its rear face (48) for accommodating a resilient O-ring (66) therein. In its front face (47) the seat ring is provided with an annular groove (51) coaxial with the ring axis and provided with serrated side walls (51a, 51b). A plurality of passages (55) are formed in the ring with equiangular spacing and extend from the face groove (51) to the corner notch (49, 50).

Abstract: A seat assembly for an expanding gate valve comprising an outer loose fitting main ring (31) with a resilient face seal (41) for sealing against an expanding gate assembly which is mounted in a valve chamber (11) and an inner auxiliary ring (44) fitting loosely in a counterbore recess in the main ring (31) for sealing against the rear wall (35) of a seat pocket (26). An O-ring (61) between opposed surfaces (51, 52) of the rings (31, 44) continuously urges the rings apart and their orientation such that when the gate assembly is expanded in its open and closed positions, the front face (38) of the main ring (31) is flush against the adjacent sealing surface (25) of the gate assembly and the rear face (46) of the auxiliary ring (44) is flush against the rear wall (35) of the seat pocket (26).

Abstract: A gate valve structure having a pair of opposed spacer carriers (72,74) fitting within the valve chamber in abutting relation to each other and spacing the floating upstream and downstream seats (60, 62) from each other a predetermined minimum distance. Each carrier (72, 74) has an annular base (76) adjacent one of the flow passages and a pair of spacers or guides (78, 80) secured to the base and extending from the base (76) in a direction axially of the flow passage. The spacers (78, 80) on opposed carriers are in abutting relation to each other and form a smooth continuation. An expanding gate assembly (28) fits between the spacers and moves between open and closed positions relative to the flow passages.