Non-floating seat structure for expanding gate valves

Claim 1

A gate valve structure comprising a valve body having a valve chamber therein and inlet and outlet flow passages communicating with the valve chamber, an expanding valve assembly including a gate element and segment slidably mounted within the valve chamber for movement between open and closed positions of the gate valve structure with said gate element and segment expanding away from each other at the fully open position, said valve body having an annular recessed portion about each flow passage and a circumferential groove in each of the recessed portions facing the valve chamber, generally cylindrical seats about said flow passages for engaging said gate element and segment in the open and closed positions of the gate element and segment, each seat having a circumferential groove in opposed relation to the groove in the adjacent flow passage and fitting within an associated recessed portion in face-to-face abutting contact with the associated recessed portion, and a deformable seal of an elongate cross section positioned within each pair of opposed grooves and filling between 80 and 100 percent of the total cross-sectional areas of the combined facing grooves when the seat is pressed within the associated recessed portion, said elongate seal having a width between around 105 and 130% of the total combined depth of the associated grooves and a thickness between around 70 and 90% of the total thickness of the associated grooves, said seal upon being inserted within the opposed pair of grooves being deformed when the seat is in abutting contact with the associated recessed portion to fill substantially the entire cross-sectional area of the combined grooves and permitting face-to-face abutting contact between the seat and valve body without any portion of the seal being gripped between the opposed faces of the seat and valve body.