Gate valve

1. A method for installing an annular seat ring into the body of a gate valve, the method comprising:

providing a valve body having a seat pocket, the seat pocket having an annular shoulder sealing face and a plurality of recesses defined at the seat pocket;

providing an annular seat ring comprising an annular seat face and an opposed annular flange sealing face and a plurality of recesses defined in the flange sealing face corresponding to and alignable with the plurality of recesses defined at the seat pocket;

locating a dynamically-energized seal in an annular groove, the annular groove provided in one of: the flange sealing face and the shoulder sealing face;

connecting a plurality of removable fasteners between the valve body and the seat ring, the fasteners located in the plurality of recesses in the seat pocket and the flange sealing face, to bring the flange sealing face of the seat ring to a mechanical stop on the shoulder sealing face of the seat pocket and to thereby provide a seating load which plastically and elastically compresses the dynamically-energized seal.

2. A method for replacing an annular seat ring in the body of a gate valve, the method comprising:

removing a bonnet from the gate valve;

removing an obturator from the gate valve through an aperture exposed by removing the bonnet;

removing a plurality of fasteners from in a plurality of recesses defined at a seat pocket in the annular seat ring, the plurality of fasteners connecting the annular seat ring to a plurality of recesses defined in a flange sealing face of a gate valve body corresponding to and alignable with the plurality of recesses defined at the seat pocket and the annular seat ring made accessible by the removal of the bonnet and the obturator;

extracting the annular seat ring from a seat ring location in the gate valve through the aperture removing a dynamically-energized seal from between the annular seat and the gate valve body and replacing the dynamically-energized seal with a replacement dynamically-energized seal by locating the replacement dynamically-energized seal in an annular groove provided in one of the annular seat ring and the valve body;

locating a replacement seat ring at the seat ring location;

connecting a plurality of replacement fasteners to the replacement seat ring;

providing a seating load which plastically and elastically compresses the replacement dynamically-energized seal; and

installing the obturator and bonnet in the gate valve.

3. A method according to claim 2 wherein the gate valve is maintained in an operating location throughout each step of the method.

4. A method according to claim 2 wherein the plurality of fasteners and the plurality of replacement fasteners are the same.

5. A gate valve for controlling flow of pressurized operating fluid, the gate valve comprising:

a valve body having a seat pocket, the seat pocket having an annular shoulder sealing face and a plurality of recesses defined at the seat pocket;

an annular seat ring comprising an annular seat face opposing an annular flange sealing face, the flange sealing face having an annular groove defined thereon and a plurality of recesses defined in the flange sealing face corresponding to and alignable with the plurality of recesses defined at the seat pocket;

a plurality of fasteners connectable between the valve body and the seat ring located in the plurality of recesses in the seat pocket and the flange sealing face and configured to bring the flange sealing face of the seat ring to a mechanical stop on the shoulder sealing face of the seat pocket; and

a dynamically-energized seal located in the annular groove, the dynamically-energized seal plastically and elastically compressible by a seating load between the seat ring and the valve body when the flange sealing face of the seat ring has reached a mechanical stop on the shoulder sealing face of the seat pocket.

6. A gate valve according to claim 5 wherein the dynamically-energized seal is elastically expandable under process pressure exerted by the pressurized operating fluid.

7. A gate valve according to claim 5 wherein the dynamically-energized seal has a free height greater than a depth of the annular groove.

8. A gate valve according to claim 5 wherein the flange sealing face is defined on an annular sealing flange.

9. A gate valve according to claim 8 wherein the plurality of recesses defined at the seat pocket are internally threaded, and the plurality of recesses defined in the sealing flange are a plurality of axial bores.

10. A gate valve according to claim 9 wherein the plurality of fasteners comprise externally threaded fasteners mateable with the plurality of internally threaded recesses.

11. A gate valve according to claim 5 wherein the seat pocket is located at an inlet port.

12. A gate valve according to claim 5 wherein the seat pocket is located at an outlet port.

13. A gate valve according to claim 5 wherein the dynamically-energized seal comprises a generally annular cross-section.

14. A gate valve according to claim 5 wherein the dynamically-energized seal comprises a generally C-shaped cross-section.

15. A gate valve according to claim 5 wherein the dynamically-energized seal comprises an E-shaped cross-section.

16. A gate valve according to claim 5 wherein the dynamically-energized seal comprises a vented seal.

17. A gate valve according to claim 16 wherein the vented seal comprises perforations for allowing pressurized operating fluid to flow through the perforations.

18. A gate valve according to claim 17 wherein the perforations are configured to allow pressurized operating fluid from an outside of the seal into an interior of the seal, thereby energizing the seal internally.

19. A gate valve according to claim 5 wherein the dynamically-energized seal comprises a spring-energized seal.

20. A gate valve according to claim 19 wherein the spring-energized seal comprises a C-shaped sealing ring and an internal spring.

21. A gate valve according to claim 5 wherein the annular groove is defined inside a periphery of the flange sealing face of the seat ring.

22. A gate valve according to claim 5 wherein the annular groove comprises a notch defined at or outside of the periphery of the flange sealing face of the seat ring.

23. A gate valve according to claim 5 wherein the plurality of fasteners have a diameter of less than ¾ of an inch.

24. A gate valve according to claim 23 wherein the plurality of fasteners have a diameter of less than ½ of an inch.

25. A gate valve according to claim 24 wherein the plurality of fasteners comprise at least 24 fasteners.