CA2613896C

CA2613896C - Gate valve with tongue and groove or bridging seal to annular seat elements

Info

Publication number: CA2613896C
Application number: CA2613896A
Authority: CA
Inventors: Tony M. Lam; Andrew F. Masson; Tianle Guo; Glen M. Eleniak
Original assignee: Stream Flo Industries Ltd
Current assignee: Stream Flo Industries Ltd
Priority date: 2007-12-10
Filing date: 2007-12-10
Publication date: 2013-05-28
Anticipated expiration: 2027-12-10
Also published as: CA2613896A1

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 into the flowbore. Seat pockets formed in the opposed openings, each with a radial base and a side wall, may optionally include a metal carrier ring. The gate is slidably movable within the valve body between open and closed positions. Annular seat elements in each seat pocket allow for limited axial movement on opposite sides of the gate, with a first seal surface for sealing against the seat pocket or optional carrier ring, and a second seal surface for sealing against the gate. 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 (or optional carrier ring). The bridging seal bridges any gap formed at the first seal surface of the annular seat element such that sealing engagement is maintained across the gap at all times as the gate moves between open and closed positions, while still permitting the 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.

Description

4 This invention relates to a gate valve with improved seals to the annular seat elements.

7 Gate valves of slab gate valve type typically include floating annular seat 8 elements sealed in counterbores or seat pockets in the flowbore of the valve body on 9 either side of the slab gate. The annular seat elements are mounted for "floating" or limited axial movement toward and away from the slab gate. Gate valves of this 11 nature, the problems inherent with fines entering the sealing areas, and the prior art 12 efforts to solve these problems are well reviewed in prior art patents, see for example 13 U.S. Patents 4,645,179; 5,029,812; 5,727,775; 6,279,875; 6,664,572; and 7,004,452.
14 Gate valves of the expanding gate valve type are distinctly different from slab gate valves in that they typically include an expanding or split gate and fixed valve seats 16 which have an interference fit relative with the seat pockets. The expanding gate is 17 typically formed from wedge shaped gate members which slide against each other to 18 "expand" the width of the gate as the gate is opened and closed.
Alternatively, the 19 gate might be split to accommodate springs. This expanding action seals the gate against the fixed seats. Fixed seats of this type suffer problems in that, despite the 21 interference fit with their seat pocket, they are not positively held in place and can work 22 their way out of the seat pockets, especially after the valve has been cycled repeatedly.
23 Many locking and sealing mechanisms have been proposed to solve the problems of 24 fixed seats of expanding gate valves. However, these problems are generally not faced by gate valves with floating seats, where the annular seat elements are designed to 26 move (float) upstream and/or downstream with the opening and closing of the slab gate 1 member, such that the opposing seal surfaces (or faces) of the annular seat elements 2 seal to the gate on one seal surface and to the seat pocket on the opposing seal 3 surface. In the slab gate valve designs, carrier rings having an interference fit to the 4 seat pockets might be used, in which case the annular seat elements seal against the gate on one side, and the carrier ring on the other side. Gate valves are also known 6 which have expanding or split gate, but which also use floating annular seat elements, 7 although these are less common.

8 In the slab gate valve design with floating seat elements, tight clearances and 9 metal-to-metal sealing surfaces are maintained between the valve body (i.e., seat pockets with optional metal carrier rings), the annular seat element and the gate.
11 Despite the tight clearances, gaps exist between all surfaces. The upstream annular 12 seat element (generally at the inlet) and the gate float downstream (generally toward 13 the outlet) with the pressure to seal against the downstream annular seat element.
14 Particles smaller than the gap between the sealing surfaces may enter the gap. Flow through a gate valve is usually in one direction, with the gate valve holding pressure in 16 the opposite direction. With a slab gate valve type having floating annular seat 17 elements, the flow and sealing can occur from either direction, to be a bi-directional 18 valve. Over time, fine particles can get in between all surfaces, preventing the metal-to-19 metal seal from forming, and eventually produce leakage.

SUMMARY OF THE INVENTION

21 This application relates to improvements to applicant's Canadian Patent 22 Application No. 2,515,906, filed August 12, 2005.

23 The seat seal arrangement of the gate valve of the present invention is designed 24 to provide a non-metallic bridging seal which is formed as a face seal which bridges any gap between the annular seat elements and either the radial base of the seat pocket, or 26 an optional metal carrier ring which might be sealed in the seat pocket.
The bridging 1 seal is adapted such that sealing engagement is maintained across this gap at all 2 times, including as the gate is moved between the open and closed positions, while still 3 permitting the limited axial movement (i.e. floating) of the annular seat element.

In some embodiments, this bridging seal takes the form of a tongue and groove 6 seal. The tongue may be formed by machining the face of the seat pocket or an 7 optional metal carrier ring seated in the seat pocket, to provide an annular lip.
8 Alternatively, the tongue may be formed as an annular lip on the seal surface of the 9 annular seat elements facing the seat pocket. Still alternatively, the tongue may be provided as an annular lip on a tongue-forming ring insert installed in the radial base of 11 the seat pocket, the carrier ring if present, or by the annular seat elements. A generally 12 U-shaped non-metallic ring seal is tightly engaged with the tongue, the U-shaped ring 13 seal being installed in an annular groove in the member opposite the tongue. This 14 tongue and groove sealing engagement is maintained even as the annular seat element and the gate move from side to side (i.e., along the linear axis of the annular 16 seat elements) under pressure as the gate is opened or closed. In preferred 17 embodiments, each tongue of the one or more tongue and groove seals extends into 18 the annular groove with a depth that is greater than the limited axial movement 19 permitted by the sum of all the gaps along the flowbore axis of the annular seat elements between the gate, the annular seat elements, the seat pockets and the carrier 21 metal rings, if present.
22 In other embodiments, the non-metallic bridging seal is provided as a non-23 metallic bridge ring insert held in grooves between the first seal surface of each annular 24 seat element and, either the radial base of the seat pocket, or the carrier ring if present.
More particularly, this type of bridging seal includes a) a first annular groove formed 26 either on the first seal surface of the annular seat member or, on the radial base or 27 carrier ring if present, b) a second annular groove formed in the member opposite the 28 first annular groove, the second annular groove being aligned with the first annular 29 groove, and c) a non-metallic bridge ring insert held in each of the first and second 1 annular grooves so as to bridge a gap at the first seal surface such that sealing 2 engagement is maintained across said gap at all times as the gate is moved between 3 the open and closed positions. In a preferred embodiment, the bridge ring insert is 4 formed from a pair of opposing, aligned, non-metallic, U-shaped ring inserts held between and in the first and second annular grooves, the U-shaped ring inserts having 6 leg portions which face each other in abutting relationship to form a rectangular space 7 therebetween; and a rectangular ring insert held in tight fitting relationship enclosed in 8 the rectangular space.

9 Preferably, a secondary non-metallic ring seal to the annular seat elements is provided. This secondary seal is located in an annular groove formed in the annular 11 seat element, or in the seat pocket or the carrier ring if present. This secondary seal is 12 advantageous in preventing fines from entering and building up in the sealing surfaces 13 in the seat pocket, particularly on either side of the bridging seal. This secondary seal 14 thus assists in preserving an area adjacent the bridging seal (between the bridging seal and the secondary seal) for formation of the needed metal-to-metal seal during opening 16 and closing of the gate. Thus, the secondary seal may be located at one or more of the 17 following positions:
18 i) along the first seal surface of the annular seat element on either or both sides 19 of the bridging seal to seal against the radial base of the seat pocket or against the carrier ring if present (i.e., as a face seal):
21 ii) at or adjacent the periphery edge of the annular seat element located within 22 the seat pocket (i.e., as a corner seal), or 23 iii) at the outside diameter of the annular seat element (i.e., as an outside 24 diameter seal).

Particularly preferred embodiments of the secondary seal include a U-ring, a 26 wiper seal or an 0-ring. This secondary seal may be weakened, for example by 27 forming cut-away portions or scoring of the secondary seal, or by shaping the ring seal 28 for venting so as to allow pressure build up between the bridging seal and the 1 secondary seal to dissipate more quickly.

2 When the secondary seal is the U-ring seal, it may be formed with a generally 3 rectangular base portion and leg portions opening in a generally U-shaped manner from 4 the base portion. This U-ring seal is preferably oriented within its annular groove such that the leg portions face away from the bridging seal, and with one or both of the leg 6 portions forming the seal. In this manner, the U-ring seal has been found to best 7 withstand extrusion during repeated use, particularly in high pressure environments.
8 This has also been found to avoid the need for spring biasing the U-ring, as shown in 9 U.S. Patent No. 6,279,875.

It has also been found that locating the secondary seal as a face seal on the 11 flowbore side of the bridging seal is advantageous in preventing fines from entering the 12 gap between the annular seat elements and the radial base of the seat pocket or the 13 carrier ring if present. This assists in preserving the face seal area between the 14 bridging seal and the secondary seal without fines buildup, thus allowing this area to 15, form the metal-to-metal seal required during the opening and closing of the gate valve.
16 The secondary seal formed on the flowbore side of the bridging seal may take a wide 17 number of forms, including preferred embodiments of a U-ring seal, an 0-ring seal or a 18 wiper seal.

FIG. 1 is a side sectional view of the gate valve of the present invention, showing 21 the annular seat elements sealed in seat pockets of the valve body.

22 FIG. 2 is a side sectional schematic view showing details of the area marked 2 in 23 FIG. 1 to illustrate one embodiment of the tongue and groove sealing feature forming a 24 face seal. In this embodiment, the tongue is formed on a metal carrier ring, while the groove is formed by a generally U-shaped ring seal installed in the annular seat 1 element. A secondary seal is provided by an 0-ring seal located at the periphery of the 2 annular seat element so as to form a corner seal.

3 FIG. 3 is a side sectional schematic view of the same area as FIG.2, wherein the 4 secondary seal is provided by a second tongue and groove seal located on the face of the annular seat element so as to form a second face seal.

6 FIG. 4 is a side section schematic view of the same area as FIG. 2, but without 7 the optional metal carrier ring of FIG. 2, such that the tongue is formed by the radial 8 base of the seat pockets.

9 FIG. 5 is a side section schematic view of the same area as FIG. 2, wherein the secondary seal is provided by a tongue and groove seal located at the periphery of the 11 annular seat elements to provide a corner seal with a generally U-shaped ring seal.

12 FIG. 6 is a side section schematic view of the same area as FIG. 2, wherein the 13 secondary seal is provided by a tongue and groove seal located at the periphery of the 14 annular seat element, with a generally L-shaped ring seal.

FIG. 7 is a side sectional schematic view of the same area as FIG. 2, with 16 features similar to those in FIG. 5, but wherein the leg portions of the generally U-17 shaped ring seals of both of the tongue and groove seals extend into grooves in the 18 metal carrier ring.

19 FIG. 8 is a side section schematic view of the same area as FIG. 2, wherein the secondary seal is an outside diameter seal provided by an 0-ring seal located on the 21 outside diameter of the annular seat element to seal against the side wall of the seat 22 pocket.

23 FIG. 9 is a side sectional view of the same area as FIG. 2, wherein a non-1 metallic bridging seal is provided as a face seal between the annular seat element and 2 the carrier ring.

3 FIG. 10 is a side section view of the same area as FIG. 2, wherein a non-metallic 4 bridging seal is provided as a face seal between the annular seat element and the carrier ring, but differing from FIG. 9 in that one of the annular grooves is radially larger 6 than the other, with the bridge ring insert being likewise radially larger.

7 FIG. 11 is a side section view of the same area as FIG. 2, wherein the carrier 8 ring is right cylindrical in its cross section for a tight interference fit within the right 9 angled cylindrical counterbore (seat pocket) of the valve body, and wherein the secondary seal is an outside diameter seal to the side wall of the carrier ring.

11 FIG. 12 is a side section view of the same area as FIG. 2, showing features 12 similar to those shown in FIG. 2, but wherein the generally U-shaped ring seal provides 13 multiple grooves (here a double U-shaped ring seal) to accept multiple tongues on the 14 adjacent carrier ring and thus provide multiple tongue and groove seals.

FIG. 13 is a side section view of the same area as FIG. 2, showing features 16 similar to those shown in FIG. 5, but wherein an 0-ring seal to the seat pocket is added 17 and wherein the second tongue and groove seal located as a corner seal has a cut-18 away portion of one of the legs to assist in pressure equalization in this area during any 19 sudden pressure drop across the valve.

FIG. 14 is a side sectional view of the same area as FIG. 2, showing features 21 similar to those of FIG. 11, but wherein the secondary seal is a U-ring seal located on 22 the outside diameter of the annular seat elements to seal against the side wall of the 23 seat pocket.

24 FIG. 15 is a side sectional view of the same area as FIG. 2, showing features 1 similar to FIG. 2, but wherein the secondary seal is a U-ring seal located at the 2 periphery of the annular seat element so as to form a corner seal.

3 FIG. 16 is a side sectional view of the same area as FIG. 2, showing features 4 similar to FIG. 15, but showing the tongue and groove face seal in the reverse mode from FIG. 15, wherein the tongue is formed on the annular seat element and the groove 6 is formed by a generally U-shaped ring seal installed in the metal carrier ring. The 7 secondary seal, as for FIG. 15 is shown to be a U-ring seal so as to form a corner seal.

8 FIG 17 is a side sectional view of the same area as FIG. 2, showing features 9 similar to FIG. 3, but wherein an 0-ring seal to the seat pocket is added.
The secondary seal is provided by a U-ring seal installed in the annular seat element so as to form a 11 second face seal.

12 FIG. 18 is a side sectional view of the same area as FIG. 2, showing the tongue 13 and groove face seal in the reverse mode, wherein the tongue is formed on the annular 14 seat element and the groove is formed by a generally U-shaped ring seal installed in the metal carrier ring. The secondary seal is provided by a U-ring seal installed in the 16 annular seat element so as to form a second face seal.

17 FIG. 19 is a side sectional view of the same area as FIG. 2, showing features 18 similar to other figures, but showing the secondary seal as an 0-ring seal installed in 19 the annular seat element to form a face seal on the flowbore side of the tongue and groove seal.

21 FIG. 20 is a side sectional view of the same area as FIG. 2, showing tongue and 22 groove features in reverse mode to FIG. 19, and showing the secondary seal as an 0-23 ring seal installed in the carrier ring to form a face seal on the outside of the tongue and 24 groove seal.

1 FIG. 21 is a side sectional view of the same area as FIG. 2, showing tongue and 2 groove features in reverse mode to FIG. 19, and showing the secondary seal as an 0-3 ring seal installed in the carrier ring to form a face seal pn the flowbore side of the 4 tongue and groove.

FIG. 22 is a side sectional view of the same area as FIG. 2, showing features 6 similar to FIG. 14, but showing the tongue and groove face seal being formed with a 7 tongue-forming ring insert installed in the carrier rings, with the tongue portion of the 8 seal being formed by an annular lip on the ring insert.

9 FIG. 23 is a side sectional view of the same area as FIG. 2, showing features similar to FIG. 15, but showing the tongue and groove face seal being formed with a 11 tongue-forming ring insert installed in the carrier rings, with the tongue portion of the 12 seal being formed by an annular lip on the ring insert.

13 FIG. 24 is a side sectional view of the same area as FIG. 2, showing features 14 similar to FIG. 16, but showing the tongue and groove face seal being formed with a tongue-forming ring insert installed in the annular seat elements, with the tongue portion 16 of the seal being formed by an annular lip on the ring insert.

17 FIG. 25 is a side sectional view of the same area as FIG. 2, showing features 18 similar to FIG. 18, but showing the tongue and groove face seal being formed with a 19 tongue-forming ring insert installed in the annular seat elements, with the tongue portion of the seal being formed by an annular lip on the ring insert.

21 FIG. 26 is a side sectional view of the same area as FIG. 2, showing features 22 similar to FIG. 14, but showing a non-metallic bridging seal formed as a face seal 23 between the annular seat element and the carrier ring, the bridging seal comprising 24 opposing, aligned U-shaped non metallic ring seals installed in both the annular seat elements and the carrier rings, and a rectangular ring insert held in the aligned grooves 1 of the U-shaped ring seals.

2 FIG. 27 is a side sectional view of the same area as FIG. 2, showing features 3 similar to FIG. 15, but showing a non-metallic bridging seal as shown in FIG. 26.

4 FIG. 28 is a sectional view showing a preferred shape of the secondary U-ring seals for venting purposes.

7 As used herein and in the claims, the word "comprising" is used in its non-limiting 8 sense to mean that items following the word in the sentence are included and that items 9 not specifically mentioned are not excluded. The use of the indefinite article "a" in the claims before an element means that one of the elements is specified, but does not 11 specifically exclude others of the elements being present, unless the context clearly 12 requires that there be one and only one of the elements. Thus, for example, the terms 13 "a tongue" and "a groove" are intended to include embodiments with multiple tongue 14 and grooves.

As used herein and in the claims, the terms "side to side"; "side";
"upstream";
16 and "downstream" and other like terms indicating relative positions above or below or to 17 the side of a given point or element are used in this description or figures to more 18 clearly describe some embodiments of the invention. However, when applied to 19 apparatus and methods for use in wellheads, such terms may refer to a left to right, right to left, up or down or other relationship as appropriate.

21 As used herein and in the claims, the terms "generally U-shaped ring seal" or "U-22 ring" are meant to include ring seals which are generally U-shaped in cross section, with 23 generally U-shaped including not only the strict U-shaped ring seals shown in the 24 Figures, wherein both the outer and inner surfaces of the ring seal have general right 1 angled U-shaped profile, but also ring seals having more generally rounded or tapered 2 outer and/or inner surfaces. In general the outer surface of the ring seal is shaped to 3 form a close fit with the particular geometry of the annular groove formed to retain it.
4 For the tongue and groove seal, the inner surface of the U-shaped ring seal is shaped to form a close fit with the particular geometry of the tongue member so as to create a 6 tongue and groove sealing relationship between the U-shaped ring seal and the tongue 7 member. With respect to the tongue and groove U-shaped ring seal, the term "U-8 shaped ring seal" also extends to ring seals which provide multiple generally U-shaped 9 grooves, such as a double U-shaped ring seal, adapted to receive multiple tongue members.

11 "Limited axial movement" when used herein and in the claims refers to the 12 amount of movement that is permitted along the linear axis (flowbore axis) of the 13 annular seat elements as the upstream annular seat element and the gate float 14 downstream to seal the downstream annular seat element in its seat pocket.
This limited amount of movement is the sum of all the "gap" or "clearance" along this axis 16 between the valve body seat pocket (or carrier metal rings if present), the annular seat 17 elements and the gate.

18 "Face seal" when used herein and in the claims refers to a seal formed only 19 between two parallel planar facing surfaces, for instance between the first seal surface of the annular seat elements and the radial base of the seat pockets. A "face seal"
21 when used herein and in the claims is not meant to include an edge or corner sealing 22 function to another non-parallel surface, rather a "face seal" is formed only to a facing 23 and parallel surface.

24 "Corner seal" when used herein and in the claims refers to a seal to the perpendicular surfaces forming the corner being sealed.

26 "Outside diameter seal" when used herein and in the claims refers to a seal 1 formed between the outside diameter of the annular seat element either against the 2 side wall of the seat pocket or against the side wall of the carrier ring.
An outside 3 diameter seal is sometimes also referred to as a "radial seal".

4 Having reference to FIG. 1, the gate valve of this invention is shown generally at 10 to include a pressure-containing valve body 12, which is flanged for connection with 6 pressure tight seals to other wellhead components (not shown). Alternate connections 7 apart from flange connections may be used as is known in the art. The valve body 12 8 forms a central, generally cylindrical flowbore 14 which extends there through. A gate 9 cavity 16 which intersects the flowbore 14, is also formed in the valve body 12. One end of the gate cavity 16 is closed by the wall of the valve body 12, while the other end 11 is open to the exterior. A slab gate 18 is mounted for sliding movement across the 12 flowbore 14 between an open and closed position. At each of the opposing openings 13 into the flowbore 14, the valve body 12 forms a preferably right cylindrical counterbore, 14 (termed seat pocket) 20, 21. The seat pockets 20, 21 each have a radial base 22 and a side wall 23 (see FIG. 2). A pair of annular seat elements 24, 25 are mounted within 16 the seat pockets 20, 21 for limited axial movement therein, such that each of the 17 annular seat element 24 or 25 maintains sealing engagement between the gate 18 and 18 the seat pocket 20 or 21 as the gate 18 is moved between its open and closed 19 positions. Optional carrier rings 32, 33 (see FIG. 2) may be used, each having an interference fit with the seat pockets 20, 21. In Figures 2-27, seat pockets 20, 21, 21 annular seat elements 24, 25 and carrier rings 32, 33 are symmetrical, so are shown 22 interchangeable side for side.

23 While the gate 18 is shown as a slab gate in the Figures, the invention may 24 extend to expanding gates or split gates, as known in the art, as may be used with floating annular seat elements.

26 Attached in sealing relationship to the valve body 12 at the open end of the gate 27 cavity 16 is a bonnet 26. A gate stem 28 is fastened at one end to the gate 18 and at 1 its other end to a valve operator, such as a manual crank 30 for moving the gate 18 2 between its open and closed positions. Alternatively stem attachments may be used, 3 for example the gate 18 could be fastened to the stem through a gate nut (not shown).
4 The gate stem 28 is sealed within the bonnet 26, in a manner as is well known in the art.

6 The non-metallic bridging seals of the present invention are shown in multiple 7 embodiments in FIGS. 2 - 27, with FIGS. 2-8 and 11-25 showing the bridging seal 8 formed with rings and grooves to form a tongue and groove seal (tongue on one side 9 sealing in groove formed opposite), and FIGS. 9, 10, 26, and 27 showing the bridging seal formed as a bridge ring insert held within grooves formed on both sides.
The 11 bridging seals are preferably symmetric on both sides of the gate 18.
In all cases, the 12 bridging seals of the present invention are formed as face seals such that there are 13 bridge elements (ex. tongue or bridge ring insert) which extend across (i.e., bridge) and 14 seal any gap between the sealing faces of the annular seat elements 24, 25 and the seat pockets 20, 21 (or the carrier rings 32, 33 if present). This bridging of this gap . 16 allows the annular seat elements 24, 25 to maintain sealing engagement between the 17 gate 18 and the seat pockets 20, 21 (or carrier rings 32, 33 if present) at all times as the 18 gate 18 and the annular seat elements 24, 25 move side-to-side (i.e., float upstream or 19 downstream) as the gate 18 is moved between its open and closed positions. In this manner, the bridging seals of this invention accommodate the limited axial movement 21 needed for the floating annular seat elements 24, 25 and gate 18, while bridging the 22 gap and maintaining the seals at all times (open, closed and during opening and 23 closing). In the tongue and groove embodiments, the tongue and groove portions of 24 the seal are sized to ensure the tongue is retained in the groove throughout the limited axial movement, and thus bridges the gap at all times. Likewise, in the bridge ring 26 insert embodiments, the bridge seal insert and any groove(s) into which it is fit are sized 27 to ensure the bridge seal insert is retained in the grooves throughout the limited axial 28 movement, and thus bridges the gap and maintains the seals at all times. An 29 interference fit for the bridge ring inserts is preferred to ensure a tight fitting relationship.

1 As well, a convenient way to achieve tight fitting relationship between the tongue and 2 groove portions of the seal is to use the tongue to form the groove into which it is to fit.

3 In FIGS. 2-21, the gap formed between the annular seat elements 24, 25 and the 4 seat pockets 20, 21 (or the carrier rings 32, 33 if present), is shown with gap on both sides of the gate 18. This exemplifies the sealing positions of the bridging seals in a 6 neutral position (pressure equalized), after the gate is opened. In FIGS.
22 - 27, the 7 gap is shown only on one side of the gate 18, to exemplify the sealing positions of the 8 bridging seals during the closing action as the gate 18 and annular seat elements 24, 9 25 move (float) in a downstream direction.

It will be evident from the figures that the tongue and groove or bridge seals of 11 this invention are designed to bridge the gap at the face between the annular seat 12 elements 24, 25 and the radial base 22 of the seat pockets 20, 21 (or the carrier rings 13 32, 33 if present). Thus the tongue and groove or bridge seals of this invention extend 14 perpendicularly across the face which is being sealed. The tongue and groove or bridge seals of this invention are particularly advantageous in keeping fines out of the 16 sealing areas and for maintaining a seal even in low pressure environments.

17 Turning to the annular seat elements 24, 25, FIGS. 2 - 8, 11 - 25 show multiple 18 preferred embodiments of the invention wherein at least two non-metallic seals are 19 provided for the annular seat elements 24, 25. The first seal is a bridging seal shown as a tongue and groove seal (single or multiple) formed as a face seal on the seat 21 pocket facing surface of the annular seat elements 24, 25. The secondary seal 22 (second seal) for the annular seat elements 24, 25 is optional, but preferred.

23 The secondary seal may be formed in one or more of the following locations, as 24 shown in FIGS. 2 - 25:
i) at the periphery 44 (outside facing edge facing toward the corner of the seat 26 pockets 20, 21, i.e., opposite the flowbore edge) of the annular seat elements 24, 25 so 1 as to form a corner seal (see FIGS. 2, 4-7, 12, 13, 15, 16, 23, 24 and 27);
2 ii) as a face seal on either side of the tongue and groove seal (see FIGS. 3, 17 -3 21 and 25) to seal the annular seat elements 24, 25 to the radial base of the seat 4 pocket or to the carrier rings; or iii) as an outside diameter seal to seal the annular seat elements 24, 25 to the 6 side wall of the seat pocket or carrier ring if right cylindrical shaped (see FIGS. 8 -7 11,14, 22 and 26).

8 Multiple embodiments of the secondary seal are possible, as is known in the art 9 to seal a face or corner, for example ring seals with shapes (in section) including 0-rings seals, wiper seals, U-rings, C-rings, V-rings, rectangular or square ring seals etc.
11 The figures show examples of several of these embodiments, but others will be evident 12 to those skilled in the art, within the scope of the present invention. It should be 13 understood that the shapes of these secondary ring seals may vary from a strict 0-, U-, 14 C- or V-cross section, these terms merely denoting the general shape of the cross section. Alternatively, the secondary seal might take the form of a second bridging or 16 tongue and groove seal according the present invention when the secondary seal is 17 located as a face seal.

18 FIGS. 9, and 10 illustrate the first seal (bridging seal) as a non-metallic bridge 19 ring insert 64 for the annular seat elements 24, 25 in place of the tongue and groove seal shown in the other Figures. These embodiments are shown with a secondary seal 21 formed as an outside diameter seal. Alternate embodiments of this bridging seal are 22 shown in Figures 26 and 27, although the secondary seal in FIG. 27 is shown as a 23 corner seal. Any of the above-described alternate locations for one or more secondary 24 seals may be used.

FIGS. 2 - 28 are generally schematic in detail to illustrate the tongue and groove, 26 bridge seal and optional secondary seal features of the present invention, other 27 features of the gate valve of this invention being well understood and variable by 1 persons skilled in the art. In FIGS. 2-27, the valve components are shown as preferably 2 symmetrical, so that the valve is bidirectional, i.e., it will seal in both the upstream and 3 the downstream directions. The annular seat elements 24, 25 are generally formed 4 from a suitable metal such as carbon or alloy steels, or corrosion resistant alloys. Wear resistant coatings may be formed thereon as is known in the art. The annular seat 6 elements 24, 25 are formed with a central bore 31 which is generally aligned with the 7 flowbore 14.

8 In FIGS. 2, 3, and 5 - 27 optional metal carrier rings 32, 33 are mounted 9 (interference fit) in the seat pockets 20, 21 respectively, for sealing relationship with the valve body 12. A metal-to-metal seal is provided by virtue of an interference fit between 11 the metal carrier ring 32, 33, the radial base 22 and the side walls 23 of the seat 12 pockets 20, 21. As seen in the Figures, the flowbore 14 is generally aligned through 13 both the annular seat elements 24, 25 and the metal carrier rings 32, 33 as is known in 14 the art. The metal carrier rings 32, 33 may be formed from suitable metals such as carbon, low alloy steels or corrosion resistant materials, as is known in the art. In FIGS.

16 2, 3, 5 - 10, 12 - 13, 15 - 21, 23 - 25 and 27, the carrier rings 32, 33 are shown to be 17 annular shaped rings, while in FIGS. 11, 14, 22, and 26 the carrier rings (labeled as 32a 18 and 33a) are shown to be right cylindrical (in cross section), having an annular base 19 32b, 33b and a side wall 32c, 33c for a tight interference fit in the right cylindrical seat pockets 20, 21 respectively. In the description below, and in the claims, the reference 21 to the carrier rings 32, 33 applies equally to carrier rings 32a, 33a. In FIGS. 13 and 17, 22 an optional ring seal 66 is shown between the carrier rings 32, 33 and the radial base 23 22 of the side walls 23 of the seat pockets 20, 21. This ring seal 66 is shown as an 0-24 ring 67 held within an annular groove 68 formed in the carrier rings 32, 33. However, other ring seal types may be used, as is known in the art. This ring seal 66 prevents 26 the carrier rings 32, 33 from being displaced from the seat pockets 20, 21. This ring 27 seal 66 might be used in any of the illustrated embodiments with a carrier ring.

1 The Tongue and Groove Seal 2 In accordance with the present invention, one or more tongue and groove seals, 3 described more fully hereinbelow, is formed between the annular seat elements 24, 25 4 and either the radial base 22 of the seat pocket 20, 21, or the metal carrier ring 32, 33 if present. In each of FIGS. 2 - 8, 11 - 15, 17, and 19 the tongue (annular lip 34) of each 6 tongue and groove seal is formed either on the radial base 22, or on the metal carrier 7 ring 32, 33, if present. However, it should be understood that this feature can be 8 reversed, such that the tongue (annular lip 34) can be formed by the annular seat 9 elements 24, 25, as shown in FIGS. 16, 18, 20 and 21, without departing from the present invention. Still alternatively, the tongue (annular lip 34) may be formed on a 11 tongue-forming ring insert 75, installed in either the carrier rings 32, 33 (FIGS. 22, 23) 12 or the annular seat elements 24, 25 (FIGS. 24, 25). If the carrier rings are not present, 13 the tongue-forming insert ring 75 might be installed in the radial base 22 of the seat 14 pockets 20, 21 (this embodiment not shown).

The gate valve 10 of the present invention preferably includes a secondary seal 16 (i.e., in addition to the tongue and groove seal), described more fully hereinbelow.

17 In FIGS. 2 - 8, 11 - 15, 17, and 19, the radial base 22 of the seat pocket 20, 21, 18 or the gate-facing surface of the metal carrier ring 32, 33 if present, is formed with a 19 gate-facing annular lip 34 which serves as the tongue in the tongue and groove sealing arrangement of this invention. The seat pocket-facing surface 36 of the annular seat 21 elements 24, 25, also termed the first seal surface, seats and seals against the radial 22 base 22 of the seat pockets 20, 21, or against the carrier metal ring 32, 33, if present.
23 The gate-facing surface 38 of the annular seat elements 24, 25 forms a second seal 24 surface (opposing the first seal surface) for sealing against the gate 18.
The first seal surface 36 of the annular seat elements 24, 25 is formed with an annular groove 40, 26 sized to accept and retain a generally U-shaped non-metallic ring seal 42.
The leg 27 portions of the ring seal 42 extends beyond the annular groove 40, so as to protect the 1 radial base 22 and first seal surface 36 when the annular seat element 24 or 25 is 2 forced with pressure against the radial base 22, or the carrier metal ring 32 or 33 if 3 present. The groove 40 and ring seal 42 are located to mate in tongue and groove 4 sealing arrangement with the annular lip 34. An interference fit is preferred.

In FIGS. 16, 18, 20 and 21, the tongue and groove seal is shown in reverse, with 6 the tongue being formed by a seat pocket-facing annular lip 34b on the annular seat 7 elements, and the annular groove 40b being formed on the radial base 22 of the seat 8 pockets 20, 21 (or on the carrier rings 32, 33, if present). A generally U-shaped non-9 metallic ring seal 42b, as described above for ring seal 42, is held and retained in the annular groove 40b. The groove 40b and ring seal 42b are located to mate in tongue 11 and groove sealing arrangement with the annular lip 34b.

12 FIG. 7 shows a further embodiment of the double tongue and groove seals of 13 FIG. 5, in which the gate-facing surface of the metal carrier rings 32, 33 are formed with 14 secondary annular grooves 56, positioned to accept the leg portions 58 of the generally U-shaped ring seals 42, 50. This preferred embodiment further enhances the exclusion 16 of fines from the tongue and groove seals, and enhances the protection of the first seal 17 surface 36 of the annular seat elements 24, 25. This embodiment ensures that the 18 annular seat elements 24, 25 always remain in engagement with the tongue member of 19 any of the tongue and groove seals to exclude fines and to protect the first seal surface 36. Stated in another way, this embodiment ensures that any gap to the annular seat 21 elements 24, 25 is always bridged to exclude fines as the gate is opened or closed.

22 In FIG. 12, a multiple tongue and groove seal is shown with the generally U-23 shaped ring seal 42a including multiple grooves (shown as a double U-shaped ring seal 24 in the figure) to accept multiple tongues of annular lips 34, 34a. As described more fully below, the secondary seal may be a tongue and groove seal. In FIGS. 3, 5, 7, 13, a 26 secondary tongue and groove seal is formed with annular lip 47, annular groove 49 and 27 U-shaped ring seal 50. In FIG. 6, a secondary tongue and groove seal is formed with 1 annular lip 47, annular groove 52 and L-shaped ring seal 54.

2 In FIGS. 22 - 25, the tongue of the tongue and groove seal is formed on a 3 tongue-forming ring insert 75. In FIGS. 22, 23, the tongue-forming ring insert 75 is 4 installed in ring insert grooves 76 formed in the carrier rings 32, 33 (or 32a, 33a). In FIGS. 24, 25, the tongue-forming ring insert 75 is installed in ring insert grooves 77 6 formed in the annular seat elements 24, 25. The ring insert grooves 76, 77 are formed 7 to accommodate the tongue-forming ring inserts 75 in tight fitting relationship 8 (interference fit preferred). The tongue-forming ring inserts 75 might be made from 9 metallic or non-metallic materials (see below). The tongue of the ring inserts 75 is formed as an annular lip 34 or 34b, as described above. The annular lip 34 or 34b is 11 accommodated in the non-metallic U-shaped ring seals 42 or 42b, in the manner 12 described above for other embodiments.

13 To maintain the tongue and groove sealing arrangement of the present invention 14 in a manner to exclude fines from entering therein, and to protect the first seal surface 36 of the annular seat elements 24, 25, the depth of the annular lips 34, 34a, 34b, 47 16 (i.e., the depth that the lip or tongue extends into any of the ring seals 42, 42a, 42b, 50 17 and 54), is greater than the axial movement that is permitted by the annular seat 18 elements 24, 25, which equates to the sum of all gaps in this axis, as described above.
19 As well, as noted above, the leg portions of the ring seals 42, 42a or 42b extend beyond the annular groove 40, 40b, 49 or 52, so as to protect the radial base 22 or 21 carrier ring 32, 33 (32a, 33a) if present, and first seal surface 36 when the annular seat 22 element 24 or 25 is forced with pressure against the radial base 22, or the carrier metal 23 ring 32, 33 (32a, 33a) if present. As well, as shown in all of the Figures, the tongue is 24 tight fitting in the generally U-shaped or L-shaped ring seals 42, 42a, 42b, 50 or 54.

The Secondary Ring Seal 26 A secondary non-metallic seal is preferably provided for the annular seat 1 elements 24, 25. In general, any ring seal known in the art may be used, for example 2 an 0-ring seal, a U-ring seal, C-ring seal, a V-ring, rectangular or square ring seal, or a 3 wiper seal. Exemplary and preferred embodiments of 0-ring and U-ring seals are 4 shown in the Figures, although the invention is not limited to these embodiments.
Wiper seals are well known in the art, and may take a wide variety of shapes (see for 6 example a variety of wiper seals available from Parker Seal Group, Irvine, California).
7 This secondary seal is termed a face seal if it is located between the tongue and groove 8 seal and the periphery edge 44 of the annular seat elements 24, 25, or on the opposite 9 side of the tongue and groove seal (i.e., on the flowbore side of the tongue and groove seal). This secondary seal may alternately be a corner seal if located at or adjacent the 11 periphery edge 44. This secondary seal may still alternatively be an outside diameter 12 seal if located on the outside diameter of the annular seat elements 24, 25 for sealing 13 against the side wall 23 of the seat pockets 20, 21, as in FIGS. 8 - 10 (or against the 14 side wall 32c, 33c of the right cylindrical carrier rings 32a, 33a in FIGS. 11, 14, 22 and 26). The secondary seal is formed by providing an annular recess or groove 45 in the 16 annular seat elements 24, 25 at one of these locations, appropriately shaped to accept 17 and retain a secondary ring seal such as shown in the Figures. This secondary seal 18 may alternatively be formed by providing an annular recess 45a in the radial base 22 of 19 the seat pockets 20, 21 (or in the carrier rings 32, 33, if present), particularly for the reverse tongue and groove design as shown in FIGS. 20, 21.

21 In the Figures, this secondary seal is shown in multiple embodiments to provide:
22 a) a face seal (see a secondary tongue and groove seal in FIG. 3, U-ring seal of FIGS.
23 17, 18, and 25, and 0-ring seal of FIGS. 19, 20, 21);
24 b) a corner seal (see FIGS. 2, 4 - 7, 12, 13, 15, 16, 23, 24, and 27 for a corner secondary tongue and groove seal, a corner 0-ring seal, or a corner U-ring seal); or 26 c) an outside diameter seal (see FIGS. 8 - 11 for an 0-ring seal held on the outside 27 diameter of the annular seat elements, and FIG. 14, 22 and 26 for a U-ring seal as an 28 outside diameter seal).

1 A wiper seal might alternatively be located in any of these locations, although if 2 used is most preferably located as a corner or outside diameter seal. In general, an 0-3 ring corner seal such as shown in FIGS. 2 or 4 might be best suited for relatively low 4 pressure environments, say less than 10,000 psi, while a secondary tongue and groove seal such as shown in FIGS. 3 and 5, or the secondary U-ring seal of FIGS. 18, 24, 25 6 might be best suited for higher pressure environments, say greater than 15,000 psi.

7 FIGS. 2, 4 and 12 show the corner seal to include an 0-ring 46 located in 8 annular recess or groove 45 at the periphery edge 44 of the annular seat elements 24, 9 25. To provide a secondary tongue and groove seal in other embodiments, this secondary seal is formed by providing a second, gate-facing annular lip 47 on the radial 11 base 22 of the seat pockets 20, 21, or on the carrier rings 32, 33 if present. This 12 second annular lip 47 may be located at the periphery edge 48 of the metal carrier rings 13 32, 33 to provide a corner seal as shown in FIGS. 5 and 6, or it may be located 14 between the first tongue and groove seal and the periphery edge 48, as shown in FIG.
3. In the embodiments shown in FIG. 3, the annular recess 45 takes the form of a 16 second annular groove 49 which is generally U-shaped, formed on the first seal surface 17 36. A second generally U-shaped ring seal 50 is provided in the second annular groove 18 49, the ring seal 50 being sized and located to accept the second annular lip 47 in a 19 tongue and groove sealing arrangement. In the embodiments shown in FIGS. 5 and 6, the annular recess 45 takes the form of a generally L-shaped (in cross section) annular 21 groove 52 at its periphery edge 44. A generally U-shaped ring seal 50 is provided in 22 the groove 52 in FIG. 5, while a generally L-shaped (in cross section) ring seal 54 is 23 provided in the groove 52, the ring seal 54 being sized and located to accept the 24 second annular lip 47 so as to provide a corner seal. In FIGS. 8- 11, the secondary seal is provided by forming the annular recess 45 in the outside diameter of the annular 26 seat elements 24, 25, and locating the 0-ring seal 46 therein. This forms an outside 27 diameter or radial seal between the annular seat elements 24, 25 and the side wall 23 28 of the seat pockets 20, 21, or the side wall 32c, 33c of the right cylindrical carriers 32a, 29 33a.

1 In FIG. 13, the secondary seal is shown to take the form of a corner tongue and 2 groove seal as described above for FIG. 5. In the embodiment shown in FIG.
13, this 3 secondary seal is weakened slightly or shaped for venting,- as compared to the first 4 tongue and groove face seal. One way to weaken is with a cut away portion 69 from one of the legs 58 of the U-shaped ring seal 50. This cut away feature 69 is provided to 6 allow pressure build up at the metal-to-metal seal surfaces between the two seals to 7 dissipate more quickly, for instance in the event of a sudden pressure drop across the 8 valve. This has the effect of lowering the operating torque on the gate valve. This 9 secondary seal will preferably be weakened in this way at a location closest to the periphery 44 of the annular seat elements 24, 25.

11 In the embodiments described above, when the secondary seal takes the form of 12 an 0-ring seal, this seal may be weakened by scoring or notching the ring on its outside 13 sealing surface. To prevent fines from entering the metal-to-metal sealing surface 14 between the first and secondary seals, it is preferable to weaken only the secondary seal, and at a location closest to the periphery 44 of the seat elements 24, 25. This 16 feature of weakening the secondary ring seal is more important on larger valves, where 17 pressure build ups at the metal-to-metal sealing surfaces become larger due to the 18 greater friction between the surfaces.

19 In FIGS. 14- 18 and 22 -27, the secondary seal is formed from a U-ring seal 70 held in an annular groove 71, located as an outside diameter seal in FIGS. 14, 22 and 21 26, a corner seal in FIGS. 15, 16, 23, 24 and 27, or a face seal in FIGS.
17, 18 and 25.
22 The U-ring 70 may be formed of any non-metallic sealing material, but will most 23 preferably be formed of a thermoplastic material such as a polytetrafluoroethylene 24 (PTFE) based material such as Teflon ), or a polyetheretherketone (PEEK) based material. While the U-rings might be spring biased, when oriented as described below, 26 and when made of these thermoplastic materials, it has been found that the spring 27 biasing is not needed. The U-rings are shown to include a generally rectangular base 28 portion 72, and leg portions 73. In order to prevent collapse or extrusion of the U-rings 1 70 under pressure, the U-rings 70 are oriented in the grooves 71 so as to face away or 2 open away (i.e., with the leg portions 73 opening and facing away) from the tongue and 3 groove seal,-with one or both of the leg portions 73 (i.e., either or both of the sides or 4 ends of the leg portions 73) making the seal to the adjacent sealing surface. Thus, in the outside diameter seal location of FIGS. 14, 22 and 26, the leg portions 73 are most 6 preferably gate-facing (although they may less preferably be oriented to face against 7 the side wall 23 of the seat pocket 20, 21 (or carrier ring 32, 33, if present)). In the 8 corner seal locations of FIGS. 15, 16, 23, 24 and 27 the leg portions 73 are also most 9 preferably oriented to be gate-facing (or they may less preferably be oriented to face the side wall 23 of the seat pocket (or carrier ring 32, 33, if present), or against the 11 radial base 22 of the seat pocket (or carrier ring 32, 33 if present)). In the face seal 12 locations of FIGS. 17, 18, and 25, the leg portions 73 are preferably oriented toward the 13 side wall 23 of the seat pocket (or carrier ring, if present), or they may less preferably 14 be oriented to face the radial base 22 of the seat pocket (or carrier ring 32, 33 if present). To assist in releasing pressure that may build up between the tongue and 16 groove seal and the secondary seal, the secondary seal may be weakened or vented, 17 as noted above. For the U-rings 70, these may be shaped for venting, for example as 18 shown in FIG. 28, with a shape to allow one or both of the legs 73 to bend in order to 19 vent pressure build up. In FIG. 28, the base 72 is machined away at a corner to allow the leg 73 most proximate that corner to bend for venting. This assists in pressure 21 release. Alternatively, the leg portion(s) 73 may be formed with a cut away portion (not 22 shown). Similar to FIG. 13, an additional 0-ring seal 67 may be formed between the 23 seat pockets 20, 21 and the carrier rings 32, 33, as shown in FIG. 17.

24 In FIGS. 19 - 21, the secondary seal may be a face seal formed from an 0-ring seal 46, located and retained in an annular recess or groove 45 or 45a, located on 26 either (or both) sides of the first tongue and groove seal. The 0-ring 46 and recess 45 27 or 45a may be located in either the annular seat elements 24, 25, or in the radial base 28 22 of the seat pockets 20, 21 (or carrier rings 32, 33 if present). To assist in pressure 29 release, as noted above, the secondary 0-ring seal 46 may be weakened, for example 1 by scoring. The 0-ring seals 46 and 67 described above may be made of any non-2 metallic sealing material including elastomeric materials or thermoplastic materials.

3 As shown in FIGS. 19- 21, the 0-ring secondary seal might be provided on 4 either side of the tongue and groove seal, although any of the alternate secondary seals might be substituted.

6 While the above embodiments illustrate only one secondary seal, in addition to 7 the bridging seal (bridge seal or tongue and groove), it will be understood that multiple 8 secondary ring seals to the annular seat elements 24, 25 may be included, at one or 9 more of the locations described above.

The Bridge Ring Insert Seal 11 FIG. 9 and 10 show an alternate non-metallic bridging seal embodiment of this 12 invention for use instead of the tongue and groove seal described above. In this 13 embodiment, aligned annular grooves 60, 62 are formed in the carrier rings 32, 33 and 14 in the first seal surface 36 of the annular seat elements 24, 25. A non-metallic bridge ring insert 64 is located in these grooves 60, 62 for sealing engagement across the gap 16 between the carrier rings 32, 33 and the annular seat elements 24, 25. In a manner 17 similar to that described above for the tongue and groove seal, the insert 64 is held with 18 a sufficient depth within the grooves 60, 62 such that this bridging seal maintains the 19 sealing engagement across this gap at all times as the gate 18 is moved between its open and closed positions, while still permitting the limited axial movement of the 21 annular seat elements 24, 25. This prevents fines from building up in this gap and 22 ensures low pressure sealing.

23 In FIG. 10, the annular groove 62 in the annular seat elements 24, 25 is shown 24 to be radially larger than the opposing groove 60 in the carrier rings 32, 33. Likewise, the bridge ring insert 64 is radially larger in the portion 65 which is inserted in the 1 groove 62. In this embodiment, this radially larger portion 65 of the insert 64 provides a 2 non-metallic sealing surface to the portion of the metal carrier ring 32, 33 directly 3 opposed. This radially larger portion 65 of the insert 64 could be provided in the groove 4 60 on the carrier rings 32, 33 if desired.

The embodiments of FIGS. 9 and 10 are illustrated with the carrier rings 32, 6 present. However, the invention also extends to embodiments with carrier rings are as 7 shown FIG. 11, and to embodiments in which the carrier rings are omitted.
In the latter 8 case, the annular groove 60 would be formed in the radial base 22 of the seat pockets 9 20,21.

In FIGS. 26 and 27 the bridge ring insert 64 is formed from opposing, aligned U-11 shaped non-metallic ring seals 78 installed in both the annular seat elements 24, 25 12 and the carrier rings 32, 33 (or 32a, 33a). The U-shaped ring seals 78 are oriented and 13 sized such that their leg portions 79 align and touch each other. In this manner, the 14 grooves 80 formed within the leg portions 79 are also aligned to enclose a rectangular space into which a rectangular ring insert 81 is held in a tight fitting manner. In order to 16 ensure a tight fitting relationship, the ring insert 81 might be used to form the grooves 17 80. The U-shaped ring seals 78 are held within grooves 60, 62 in the annular seat 18 elements and carrier rings, in tight fitting relationship, with an interference fit being 19 preferred. While the U-shaped ring seals 78 are non-metallic, the rectangular ring insert 81 may be metallic or non-metallic (if non-metallic, it is of a sturdy materials such 21 as a thermoplastic). As for the above-noted embodiments, this multi-part bridge ring 22 insert 64 is held with a sufficient depth within the grooves 60, 62 such that this bridging 23 seal maintains the sealing engagement across this gap at all times as the gate 18 is 24 moved between its open and closed positions, while still permitting the limited axial movement of the annular seat elements 24, 25. This prevents fines from building up in 26 this gap and ensures low pressure sealing.

27 A secondary ring seal may be used with the bridging seal of this invention. Any 1 ring seal known in the art may be used, or any of the embodiments as described above 2 for the tongue and groove seal may be used. As above described for the tongue and 3.- groove embodiments, this secondary seal may be located as a face seal if it is located 4 between the bridging seal the periphery edge of the annular seat elements 24, 25, or on the other side of the bridging seal (flowbore side). This secondary seal may alternately 6 be a corner seal if located at or adjacent the periphery edge. This secondary seal may 7 still alternatively be an outside diameter seal if located on the outside diameter of the 8 annular seat elements 24, 25 for sealing against the side wall 23 of the seat pockets 20, 9 21 (or the carrier rings 32a, 33a, if present). The secondary seal is formed by providing an annular recess 45 in the annular seat elements 24, 25 (or in the seat pockets or 11 carrier rings) at one or more of these locations, appropriately shaped to accept a 12 secondary ring seal. In FIGS. 9 and 10, the secondary seal is shown to include an 0-13 ring seal 46 located as an outside diameter seal in an annular recess 45 formed in the 14 outside diameter of the annular seat elements 24, 25 to seal to the side wall 23 of the seat pocket 20, 21. In FIG. 26, the secondary seal is shown to be a U-ring 70, located 16 as an outside diameter seal, as described above for the tongue and groove 17 embodiments. In FIG. 27, the secondary seal is shown to be a U-ring 70, located as a 18 corner seal, also as described above. Alternate secondary ring seals may be used, as 19 described above for other embodiments shown in the Figures, or as will be apparent to one skilled in the art.

21 The ring seals 42, 42a, 42b, 46, 50 and 54 and the bridge ring inserts 64 (or U-22 shaped ring inserts 78) are non-metallic, generally made of suitable non-metallic seal 23 materials such as elastomeric materials or thermoplastic materials. The tongue-forming 24 ring inserts 75 are non-metallic or metallic. If non-metallic, the inserts 75 are generally made from a thermoplastic material such as polyetheretherketone (PEEK), with the 26 opposing female member being made of a polytetrafluoroethylene (PTFE) based 27 material. Most preferably, all of these seals are made from a thermoplastic material 28 such as a PTFE based material (Teflon being an example) or a PEEK based material.
29 For the bridge ring seals of FIGS. 26 and 27, the U-shaped ring seals 78 may be of a 1 non-metallic, preferably thermoplastic material, as above, and the rectangular ring 2 insert 81 may be metallic or non-metallic of the materials noted above for inserts 75.

3 In the claims which follow, it should be appreciated that each of the above 4 described tongue and groove seals, and the bridging seals function as a non-metallic bridging seal formed as a face seal between the first seal surface of each annular seat 6 element and, either the radial base of the seat pocket, or the carrier ring if present.
7 Each such bridging seal is adapted to bridge any gap formed at the first seal surface of 8 the annular seat element such that sealing engagement is maintained across said gap 9 at all times as the gate is moved between the open and closed positions, while still permitting the limited axial movement of the annular seat element.

11 All references mentioned in this specification are indicative of the level of skill in 12 the art of this invention. Some references provided herein provide details concerning 13 the state of the art prior to the filing of this application, other references may be cited to 14 provide additional or alternative device elements, additional or alternative materials, additional or alternative methods of analysis or application of the invention.

16 The terms and expressions used are, unless otherwise defined herein, used as 17 terms of description and not limitation. There is no intention, in using such terms and 18 expressions, of excluding equivalents of the features illustrated and described, it being 19 recognized that the scope of the invention is defined and limited only by the claims which follow. Although the description herein contains many specifics, these should not 21 be construed as limiting the scope of the invention, but as merely providing illustrations 22 of some of the embodiments of the invention.

1 One of ordinary skill in the art will appreciate that elements and materials other 2 than those specifically exemplified can be employed in the practice of the invention 3 without resort to undue experimentation. All art-known functional equivalents, of any 4 such elements and materials are intended to be included in this invention.
The invention illustratively described herein suitably may be practiced in the absence of any element 6 or elements, limitation or limitations which is not specifically disclosed herein.

Claims

1. A gate valve for controlling fluid flow, comprising:
a valve body forming a cylindrical flowbore extending through the body and a gate cavity intersecting the flowbore to provide opposed openings into the flowbore, the valve body forming a seat pocket in each of the opposed openings, each of the seat pockets having a radial base and a side wall;
an optional metal carrier ring mounted in sealing relationship to the valve body in each of the seat pockets;
a gate slidably movable across the flowbore within the valve body between an open and closed position, and having a planar face on each side;
a floating annular seat element mounted in each of the seat pockets for limited axial movement therein on opposite sides of the gate, each of the annular seat elements forming opposing seal surfaces, including a first seal surface for sealing against the radial base of the seat pocket or against the carrier ring if present, and a second seal surface for sealing against the planar face of the gate, the annular seat element maintaining sealing engagement between the gate and the seat pocket, or the carrier ring if present, as the gate is moved between the open and closed positions; and a non-metallic bridging seal formed as a face seal between the first seal surface of each of the annular seat elements and, either the radial base of the seat pocket, or the carrier ring if present, said bridging seal being adapted to bridge any gap formed at the first seal surface of the annular seat element such that sealing engagement is maintained across said gap at all times as the gate is moved between the open and closed positions, while still permitting the limited axial movement of the annular seat element, and said bridging seal comprising:
a first annular groove formed either on the first seal surface of the annular seat member or, on the radial base or carrier ring if present;
a second annular groove formed in the member opposite the first annular groove, said second annular groove being aligned with the first annular groove;
a pair of opposing, aligned, non-metallic, U-shaped ring inserts held between and in the first and second annular grooves, the U-shaped ring inserts having leg29 portions which face each other in abutting relationship to form a generally rectangular space therebetween; and a generally rectangular ring insert held in tight fitting relationship enclosed in the rectangular space.

2. The gate valve as set forth in claim 1, wherein the carrier rings, if present, may include a ring seal to the radial base of the seat pocket.

3. The gate valve as set forth in claim 2, wherein each of the annular seat elements is formed with a central bore aligned with the flowbore of the valve body such that the first seal surface of the annular seat element has a periphery edge opposite its flowbore edge, and wherein the gate valve further comprises a secondary ring seal formed as a) a corner seal at or adjacent the periphery edge of each of the annular seat elements, b) a face seal on the first seal surface of the annular seat element, or c) an outside diameter seal at the outside diameter of the annular seat element.

4. The gate valve as set forth in claim 3, wherein the secondary ring seal comprises an O-ring seal formed as a corner, face or outside diameter seal.

5. The gate valve as set forth in claim 3, wherein the secondary ring seal comprises an O-ring or a U-ring seal formed as a corner, face or outside diameter seal.

6. The gate valve as set forth in claim 5, wherein the bridge ring insert extends into the first and second annular grooves with a depth that is greater than the limited axial movement permitted by the sum of all the gaps along the flowbore axis of the annular seat elements between the gate, the annular seat elements, the seat pockets and the carrier rings, if present.

7. The gate valve as set forth in claim 6, wherein the U-shaped ring inserts are formed of a thermoplastic material, and the rectangular ring insert is formed of a30 metallic or thermoplastic material.

8. A gate valve for controlling fluid flow, comprising:
a valve body forming a cylindrical flowbore extending through the body and a gate cavity intersecting the flowbore to provide opposed openings into the flowbore, the valve body forming a seat pocket in each of the opposed openings, each of the seat pockets having a radial base and a side wall;
an optional metal carrier ring mounted in sealing relationship to the valve body in each of the seat pockets;
a gate slidably movable across the flowbore within the valve body between an open and closed position, and having a planar face on each side;
a floating annular seat element mounted in each of the seat pockets for limited axial movement therein on opposite sides of the gate, each of the annular seat elements forming opposing seal surfaces, including a first seal surface for sealing against the radial base of the seat pocket or against the carrier ring if present, and a second seal surface for sealing against the planar face of the gate, the annular seat element maintaining sealing engagement between the gate and the seat pocket, or the carrier ring if present, as the gate is moved between the open and closed positions;
a non-metallic bridging seal formed as a face seal between the first seal surface of each of the annular seat elements and, either the radial base of the seat pocket, or the carrier ring if present, said bridging seal being adapted to bridge any gap formed at the first seal surface of the annular seat element such that sealing engagement is maintained across said gap at all times as the gate is moved between the open and closed positions, while still permitting the limited axial movement of the annular seat element; and a secondary non-metallic ring seal in the form of a U-ring located in an annular groove formed in the annular seat element, or in the seat pocket or in the carrier ring if present, the secondary ring seal being formed as one or more of:
i) a corner seal at or adjacent the periphery edge of each of the annular seat elements;

ii) a face seal on the first seal surface of the annular seat element located on either or both sides of the non-metallic bridging seal; or iii) an outside diameter seal at the outside diameter of the annular seat element.

9. The gate valve as set forth in claim 8, wherein the bridging seal is a tongue and groove seal formed between the first seal surface of each of the annular seat elements and, either the radial base of the seat pocket, or the carrier ring if present, the tongue and groove seal maintaining sealing engagement within the seat pocket while still permitting the limited axial movement of the annular seat element.

10. The gate valve as set forth in claim 9, wherein:
a) the tongue of the tongue and groove seal is provided by an annular lip formed on either the radial base of the seat pocket, or the carrier ring if present, and the groove is provided by a non-metallic generally U-shaped ring seal seated in a first annular groove provided in the first seal surface of the annular seat element opposite the annular lip; or b) the tongue of the tongue and groove seal is provided by an annular lip formed on the first seal face of the annular seat element, and the groove is provided by a non-metallic generally U-shaped ring seal seated in a first annular groove provided in either the radial base of the seat pocket, or the carrier ring, if present, opposite the annular lip;
or c) the tongue of the tongue and groove seal is provided by an annular lip formed on a metallic or non-metallic tongue-forming ring insert installed in the radial base of the seat pocket, or the carrier ring if present, and the groove is provided by a non-metallic generally U-shaped ring seal seated in a first annular groove provided in the first seal surface of the annular seat element opposite the annular lip; or d) the tongue of the tongue and groove seal is provided by an annular lip formed on a metallic or non-metallic tongue-forming ring insert installed in the annular seat element, and the groove is provided by a non-metallic generally U-shaped ring seal seated in a first annular groove provided in either the radial base of the seat pocket, or the carrier ring, if present, opposite the annular lip.

11. The gate valve as set forth in claim 10, wherein each of the annular seat elements is formed with a central bore aligned with the flowbore of the valve body.

12. The gate valve as set forth in claim 11, wherein the tongue of the tongue and groove seal extends into the groove with a depth that is greater than the limited axial movement permitted by the sum of all the gaps along the flowbore axis of the annular seat elements between the gate, the annular seat elements, the seat pockets and the carrier rings, if present.

13. The gate valve as set forth in claim 12, wherein the radial base, or the carrier ring if present, is formed with secondary annular grooves to accept the leg portions of the generally U-shaped ring seals.

14. The gate valve as set forth in claim 12, wherein the secondary ring seal U-ring has a base portion and leg portions, and wherein the U-ring is oriented in the annular groove such that the leg portions open away from the tongue and groove seal.

15. The gate valve as set forth in claim 14, wherein the secondary ring seal U-ring is shaped so as to vent pressure build up between the tongue and groove seal and the U-ring.

16. The gate valve as set forth in claim 15, wherein the U-shaped ring seals of the tongue and groove seal and the secondary ring seal U-rings are formed of a thermoplastic material.

17. The gate valve as set forth in claim 15, wherein the U-shaped ring seals of the tongue and groove seal and the secondary ring seal U-rings are formed of a polytetrafluoroethylene based material or a polyetheretherketone based material.

18. The gate valve as set forth in claim 12, wherein the carrier rings are present, and wherein the gate valve further comprises a ring seal between the carrier ring and the radial base of the seat pocket.

19. The gate valve as set forth in claim 17, wherein the carrier rings are present, and the gate valve further comprises a ring seal between the carrier ring and the radial base of the seat pocket.

20. A gate valve for controlling fluid flow, comprising:
a valve body forming a cylindrical flowbore extending through the body and a gate cavity intersecting the flowbore to provide opposed openings into the flowbore, the valve body forming a seat pocket in each of the opposed openings, each of the seat pockets having a radial base and a side wall;
an optional metal carrier ring mounted in sealing relationship to the valve body in each of the seat pockets;
a gate slidably movable across the flowbore within the valve body between an open and closed position, and having a planar face on each side;
a floating annular seat element mounted in each of the seat pockets for limited axial movement therein on opposite sides of the gate, each of the annular seat elements forming opposing seal surfaces, including a first seal surface for sealing against the radial base of the seat pocket or against the carrier ring if present, and a second seal surface for sealing against the planar face of the gate, the annular seat element maintaining sealing engagement between the gate and the seat pocket, or the carrier ring if present, as the gate is moved between the open and closed positions;
a non-metallic bridging seal formed as a face seal between the first seal surface of each of the annular seat elements and, either the radial base of the seat pocket, or the carrier ring if present, said bridging seal being adapted to bridge any gap formed at the first seal surface of the annular seat element such that sealing engagement is maintained across said gap at all times as the gate is moved between the open and closed positions, while still permitting the limited axial movement of the annular seat34 element, the bridging seal being a tongue and groove seal formed between the first seal surface of each of the annular seat elements and, either the radial base of the seat pocket, or the carrier ring if present, the tongue and groove seal maintaining sealing engagement within the seat pocket while still permitting the limited axial movement of the annular seat element; and wherein:
a) the tongue of the tongue and groove seal is provided by an annular lip formed on a metallic or non-metallic tongue-forming ring insert installed in the radial base of the seat pocket, or the carrier ring if present, and the groove is provided by a non-metallic generally U-shaped ring seal seated in a first annular groove provided in the first seal surface of the annular seat element opposite the annular lip; or b) the tongue of the tongue and groove seal is provided by an annular lip formed on a metallic or non-metallic tongue-forming ring insert installed in the annular seat element, and the groove is provided by a non-metallic generally U-shaped ring seal seated in a first annular groove provided in either the radial base of the seat pocket, or the carrier ring, if present, opposite the annular lip.

21. The gate valve of claim 20, wherein the tongue-forming ring inserts are held an interference fit with an annular groove formed in the radial base of the seat pocket, or the carrier ring if present.

22. The gate valve of claim 21, wherein the tongue-forming ring inserts are metallic.

23. The gate valve of claim 22, which further comprises:
a secondary non-metallic ring seal in the form of a U-ring located in an annular groove formed in the annular seat element, or in the seat pocket or in the carrier ring if present, the secondary ring seal being formed as one or more of:
i) a corner seal at or adjacent the periphery edge of each of the annular seat elements;
ii) a face seal on the first seal surface of the annular seat element located on either or both sides of the non-metallic bridging seal; or iii) an outside diameter seal at the outside diameter of the annular seat element.

24. The gate valve as set forth in claim 23, wherein each of the annular seat elements is formed with a central bore aligned with the flowbore of the valve body.

25. The gate valve as set forth in claim 24, wherein the tongue of the tongue and groove seal extends into the groove with a depth that is greater than the limited axial movement permitted by the sum of all the gaps along the flowbore axis of the annular seat elements between the gate, the annular seat elements, the seat pockets and the carrier rings, if present.

26. The gate valve as set forth in claim 25, wherein the secondary ring seal U-ring has a base portion and leg portions, and wherein the U-ring is oriented in the annular groove such that the leg portions open away from the tongue and groove seal.

27. The gate valve as set forth in claim 26, wherein the secondary ring seal U-ring is shaped so as to vent pressure build up between the tongue and groove seal and the U-ring.

28. The gate valve as set forth in claim 27, wherein the U-shaped ring seals of the tongue and groove seal and the secondary ring seal U-rings are formed of a thermoplastic material.

29. The gate valve as set forth in claim 27, wherein the U-shaped ring seals of the tongue and groove seal and the secondary ring seal U-rings are formed of a polytetrafluoroethylene based material or a polyetheretherketone based material.

30. The gate valve as set forth in claim 25, wherein the carrier rings are present, and wherein the gate valve further comprises a ring seal between the carrier ring and the radial base of the seat pocket.36

31. The gate valve as set forth in claim 29, wherein the carrier rings are present, and the gate valve further comprises a ring seal between the carrier ring and the radial base of the seat pocket.

32. A gate valve for controlling fluid flow, comprising:
a valve body forming a cylindrical flowbore extending through the body and a gate cavity intersecting the flowbore to provide opposed openings into the flowbore, the valve body forming a seat pocket in each of the opposed openings, each of the seat pockets having a radial base and a side wall;
an optional metal carrier ring mounted in sealing relationship to the valve body in each of the seat pockets;
a gate slidably movable across the flowbore within the valve body between an open and closed position, and having a planar face on each side;
a floating annular seat element mounted in each of the seat pockets for limited axial movement therein on opposite sides of the gate, each of the annular seat elements forming opposing seal surfaces, including a first seal surface for sealing against the radial base of the seat pocket or against the carrier ring if present, and a second seal surface for sealing against the planar face of the gate, the annular seat element maintaining sealing engagement between the gate and the seat pocket, or the carrier ring if present, as the gate is moved between the open and closed positions;
a non-metallic bridging seal formed as a face seal between the first seal surface of each of the annular seat elements and, either the radial base of the seat pocket, or the carrier ring if present, said bridging seal being adapted to bridge any gap formed at the first seal surface of the annular seat element such that sealing engagement is maintained across said gap at all times as the gate is moved between the open and closed positions, while still permitting the limited axial movement of the annular seat element; and a secondary non-metallic seal located in an annular groove formed in the annular seat element, or in the seat pocket or the carrier ring if present, the secondary seal being formed as a face seal on the first seal surface of the annular seat element, and37 being located on the flowbore side of the bridging seal.

33. The gate valve as set forth in claim 32, wherein the bridging seal is a tongue and groove seal formed between the first seal surface of each of the annular seat elements and, either the radial base of the seat pocket, or the carrier ring if present, the tongue and groove seal maintaining sealing engagement within the seat pocket while still permitting the limited axial movement of the annular seat element.

34. The gate valve as set forth in claim 33, wherein:
a) the tongue of the tongue and groove seal is provided by an annular lip formed on either the radial base of the seat pocket, or the carrier ring if present, and the groove is provided by a non-metallic generally U-shaped ring seal seated in a first annular groove provided in the first seal surface of the annular seat element opposite the annular lip; or b) the tongue of the tongue and groove seal is provided by an annular lip formed on the first seal face of the annular seat element, and the groove is provided by a non-metallic generally U-shaped ring seal seated in a first annular groove provided in either the radial base of the seat pocket, or the carrier ring, if present, opposite the annular lip;
or c) the tongue of the tongue and groove seal is provided by an annular lip formed on a metallic or non-metallic tongue-forming ring insert installed in the radial base of the seat pocket, or the carrier ring if present, and the groove is provided by a non-metallic generally U-shaped ring seal seated in a first annular groove provided in the first seal surface of the annular seat element opposite the annular lip; or d) the tongue of the tongue and groove seal is provided by an annular lip formed on a metallic or non-metallic tongue-forming ring insert installed in the annular seat element, and the groove is provided by a non-metallic generally U-shaped ring seal seated in a first annular groove provided in either the radial base of the seat pocket, or the carrier ring, if present, opposite the annular lip.

35. The gate valve as set forth in claim 34, wherein each of the annular seat elements is formed with a central bore aligned with the flowbore of the valve body.

36. The gate valve as set forth in claim 35, wherein the tongue of the tongue and groove seal extends into the groove with a depth that is greater than the limited axial movement permitted by the sum of all the gaps along the flowbore axis of the annular seat elements between the gate, the annular seat elements, the seat pockets and the carrier rings, if present.

37. The gate valve as set forth in claim 36, wherein the radial base, or the carrier ring if present, is formed with secondary annular grooves to accept the leg portions of the generally U-shaped ring seals.

38. The gate valve as set forth in claim 36, wherein the secondary seal is one or more of an O-ring seal, a U-ring seal, or a wiper seal.

39. The gate valve as set forth in claim 36, wherein the secondary seal is a U-ring seal.

40. The gate valve as set forth in claim 39, wherein the secondary U-ring seal is shaped to vent pressure build up between the tongue and groove seal and the secondary seal.

41. The gate valve as set forth in claim 40, wherein the U-shaped ring seals of the tongue and groove seal are formed of a thermoplastic material.

42. The gate valve as set forth in claim 40, wherein the U-shaped ring seals of the tongue and groove seal are formed of a polytetrafluoroethylene based material or a polyetheretherketone based material.

43. The gate valve as set forth in claim 32, wherein the carrier rings are present, and wherein the gate valve further comprises a ring seal between the carrier ring and the radial base of the seat pocket.

44. The gate valve as set forth in claim 42. wherein the carrier rings are present, and wherein the gate valve further comprises a ring seal between the carrier ring and the radial base of the seat pocket.