Gate valve

1 . A slab gate valve assembly comprising a housing comprising an inlet, an outlet, and a gated fluid passage between the inlet and the outlet, at least one valve seat disposed in a seat pocket of the housing, a gate-carrying shaft, and a slab gate plate arrangement in slidable engagement with the at least one valve seat and to be operated via the gate-carrying shaft between an open condition and a shut condition, wherein the at least one valve seat is threadedly disposed in the seat pocket, wherein the at least one valve seat comprises a seating surface and a radially extending peripheral seal integral with the at least one valve seat, the peripheral seal permitting splaying, and wherein the seat pocket comprises a radially extending abutment surface for the seating surface and a radially extending seal seat for the peripheral seal, axially spaced such that the seating surface comes into abutment with the abutment surface no sooner than the peripheral seal with the seal seat, whereby splaying of the peripheral seal is limited by abutment of the seating surface against the abutment surface and the degree of splaying of the peripheral seal is relative to the axial distance that the valve seat moves from where the peripheral seal abuts the seal seat until the abutment of the seating surface against the abutment surface.

2 . The gate valve assembly according to claim 1 , wherein at least one valve seat is threadedly engageable from within the housing.

3 . The gate valve assembly according to claim 1 , configured such that the peripheral seal contacts the seal seat before the seating surface abuts against the abutment surface.

4 . The gate valve assembly according claim 1 , wherein the housing comprises a port for the gate-carrying shaft, the at least one valve seat being sized to fit through the port for assembly within the housing.

5 . The gate valve assembly according to claim 1 , wherein the valve seat comprises a crown configuration for engagement by a torque-applying tool.

6 . The gate valve assembly according to claim 1 , wherein the at least one valve seat comprises one of at least 10, at least 12, at least 14, at least 16, and at least 18 threads per inch.

7 . The gate valve assembly according to claim 1 , wherein the peripheral seal of the valve seat is arranged at an oblique angle with reference to an axis of the valve seat.

8 . The gate valve assembly according to claim 1 , wherein the integral peripheral seal is angled in the direction of the seating surface.

9 . The gate valve assembly according to claim 7 , wherein a thread is located axially between the seating surface and the peripheral seal.

10 . A slab gate valve assembly comprising a housing comprising an inlet, an outlet, and a gated fluid passage between the inlet and the outlet, at least one valve seat threadedly disposed in a seat pocket of the housing, a gate-carrying shaft, and a slab gate plate arrangement in slidable engagement with the at least one valve seat and to be operated via the gate-carrying shaft between an open condition and a shut condition, wherein the at least one valve seat comprises a seating surface and a peripheral seal integral with the at least one valve seat, and wherein the seal pocket comprises an abutment surface for the seating surface and a seal seat for the peripheral seal, axially spaced such that the seating surface comes into abutment no sooner than the peripheral seal, wherein the peripheral seal is a lip seal angled to provide a ring contact for abutment in an axial direction against the seal seat, whereby splaying of the peripheral seal is permitted and limited by abutment of the seating surface against the abutment surface.

11 . The gate valve assembly according to claim 10 , wherein at least one valve seat is threadedly engageable from within the housing.

12 . The gate valve assembly according claim 10 , wherein the housing comprises a port for the gate-carrying shaft, the at least one valve seat being sized to fit through the port for assembly within the housing.

13 . The gate valve assembly according to claim 10 , wherein the valve seat comprises a crown configuration for engagement by a torque-applying tool.

14 . The gate valve assembly according to claim 10 , wherein the at least one valve seat comprises one of at least 10, at least 12, at least 14, at least 16, and at least 18 threads per inch.

15 . The gate valve assembly according to claim 10 , wherein the peripheral seal of the valve seat is arranged at an oblique angle with reference to an axis of the valve seat.

16 . The gate valve assembly according to claim 15 , wherein a thread is located axially between the seating surface and the peripheral seal.

17 . The gate valve assembly according to claim 10 , wherein the integral peripheral seal is angled in the direction of the seating surface.