GB2100843A - Gate valve - Google Patents

Abstract

Disclosed is a gate valve including a pair of seat rings 192 operable under fluid pressure as pistons in sealing against the valve element 180. In one embodiment arcuate retainer plates 187 provide lateral support for the seat rings. <IMAGE>

Description

SPECIFICATION Gate valve 1. Field of the Invention: The present invention pertains to valves for control of fluid communication. More particularly, the present invention is related to gate valves, and to techniques for providing sealing between gate valve elements and valve bodies.

2. Description of Prior Art: Gate valves are known employing various structures to facilitate operation of the valve element and maintain sealing integrity between the valve element and the valve body, for example.

A basic gate design may be considered to include a gate valve element movable within a chamber intersecting a flow path through the valve body so that, in one configuration, the valve element blocks the flow path and, in a second configuration, the valve element is positioned to align a bore through the element with the flow path permitting fluid communication along the flow path. Such a valve element is illustrated in United States Patent No. 3,053,269. Generally, the chamber containing the valve element is rectangular in cross section, and may include rings positioned to either side of the valve element to facilitate sealing between the slidable valve element and the valve body. Such a construction may be found in United States Patent No, 2,977,975, for example.Valve element chambers of circular cross section are also known, as in one version of the type "F" gate valve of Cameron Iron Works, Inc.

Generally, as components in addition to a valve element are included within the valve body chamber, particularly where the chamber is of circular cross section, the complexity of the valve assembly may be expected to increase. The expense in construction and maintenance of such complex valve assemblies may be relatively large.

Available valves may be limited in the range of fluid pressures over which they are operable without employment of special techniques to maintain the sealing integrity between the valve element and the valve body, such as continually applying fluid pressure to restore lost sealing pressure as the valve is operated. Finally, the production of a chamber of rectangular cross section within the valve body may be considerable more expensive than the boring of a cylindrical chamber.

A gate valve assembly, utilizing a cylindrical valve element chamber and employing a sealing technique for maintaining sealing integrity between the valve element and the valve body over a wide range of fluid pressure without the requirements of special techniques is desired and may be expected to be relatively inexpensive to construct and maintain.

Summary of the Invention The present invention provides a gate valve having a generally cylindrical bore intersecting a flow passage through a valve body. A first seat ring is mounted for sliding, sealing engagement with the valve body, with a passage through the seat ring generally aligned with the body flow passage. A second seat ring is also mounted for sliding, sealing engagement with the valve body, a passage through the second seat ring being generally aligned with the flow passage of the valve body. Each of the seat rings features an annular seating surface, and the two seat rings are disposed about the valve body bore so that the seating surfaces of the first and second seat rings engage first an second sealing surfaces, respectively, carried on opposite sides of a gate valve element.The valve element is selectively movable along the body bore between a first position, in which the valve element closes off the body flow passage and the passages through the seat rings, and a second position in which the body passage is open for fluid communication through the seat rings and by the valve element.

Each seat ring is sealed to the valve body by at least one annular seal member carried by the respective seat ring to provide sliding, sealing engagement with the body. Thus, each seat ring may respond to fluid pressure within the body flow passage as a piston, and be urged by such fluid pressure to move longitudinally toward the valve element, enhancing the sealing engagement between the corresponding annular seating surface and the adjacent valve element sealing surface.

A gate valve according to the present invention may include first and second retainer plates, with each retainer plate including an arcuate surface generally complementary to the interior surface of the bore of the valve body. Each retainer plate further includes a bore for receiving one of the seat rings. The retainer plates are disposed within the body bore on opposite sides of the valve element, to maintain the corresponding seat rings in configuration for sealing engagement with the valve element.

The present invention provides a valve assembly which is relatively inexpensive to produce, particularly in view of the use of a generally cylindrical bore for receiving the valve element as opposed to a bore of generally rectangular cross section. Additionally, since the seat rings of the present invention maintain sealing engagement with the valve body as the seat rings are urged buy fluid pressure against the valve element, a valve assembly according to the present invention may be utilized to control fluid flow over a wide range of fluid pressure conditions. Furthermore, the present invention provides a valve assembly which can be maintained functional after extensive use by merely replacing the seat rings, for example.

Brief Description of the Drawings Fig. 1 is a side elevation in partial section of a gate valve having a cylindrical body chamber and seat rings according to the present invention; Fig. 2 is a fragmentary end elevation of the gate valve element included in Fig. 1; Fig. 3 is a fragmentary horizontal cross section taken along line 3-3 of Fig. 1 and further illustrating the valve element; Fig. 4 is a view in perspective of a seat ring included in the valve of Fig. 1; Fig. 5 is a fragmentary side elevation in partial section showing the lower portion of a gate valve including arcuate retainer plates according to the present invention; Fig. 6 is a fragmentary horizontal cross section taken along line 6-6 of Fig. 5 and further illustrating the arcuate retainer plates and the gate valve element of the valve of Fig. 5; and Fig. 7 is an end elevation of an arcuate retainer plate.

Description of Preferred Embodiments In Fig. 1 a gate valve incorporating the present invention is shown generally at 10, and includes a valve body 12 having a generally cylindrical, elongate flow passage 14 extending the length of the body to accommodate fluid flow therethrough.

Flange connectors 1 6 are positioned at opposite ends of the valve body 12, and are equipped with holes 18 for receiving bolts whereby the valve may be connected inline with tubular members for communication of fluid. Each flange 16 is faced with a seating surface 20 broken by an annular groove 22 for receiving an annular seal, such as an O-ring seal or a gasket, whereby the valve body may be sealed to adjacent tubular members.

The valve body 1 2 is further broken by a transverse, generally cylindrical bore or chamber 25 intersecting the passage 14. A bonnet 26, including a shank 26a and a flange fitting 26b, is held to the body 12 by bolts 28 passing through appropriate holes in the bonnet flange and extending into threaded bores in the body. The bonnet 26 is sealed to the body 12 by an annular seal 30, which may be an O-ring or metal gasket, residing in appropriate grooves in adjacent faces of the body, and the bonnet.

The bonnet 26 features a generally cylindrical central passage 32 extending through the shank 26a and the flange 26b and aligned with the bore 24 of the body 12. The passage 32 is divided into an upper segment and a lower segment, of lesser diameter than the upper segment, by a stepped, inwardly-extending annular shoulder 34 featuring a first, downwardly-facing frustoconical surface 36. A second, downwardly-facing, frustoconical surface 38 as part of the shoulder 34 is separated from the first surface 36 by a relatively short cylindrical section.

An elongate stem 40 is positioned within the passage 32 and extends into the bore 24 of the body 1 2. The stem 40 is divided into an upper smooth shank 42 and a lower, threaded screw 44 by an outwardly-extending flange 46 featuring an upwardly-facing frustoconical surface 48. The surface 48, which is generally complementary to the surface 36, extends within the diameter of the stem shank 42 as shown in Fig. 1. Abutment of the stem surface 48 against the bonnet surface 36 limits upward movement of the stem 40 relative to the bonnet 26 and the valve body 12.

An annular stem packing 50, of appropriate sealing material, surrounds the stem shaft 42 within the passage 32 above the annular shoulder 34. The packing 50, which may be constructed from the polymer material known by the registered trademark TEFLON, is longitudinally compressed between the ter of the shoulder 34 and the bottom cylindrical extension of a nut 52 threadedly engaged v:ith the Interior of the bonnet shank 26a. A flange 52a of the nut 52 abuts the end of the bonnet shank 26a to limit movement of the nut within the passage 32.The compression of the stem packing 50 between the shoulder 38 and the nut 52 extends the radial thickness of the wall of the packing to maintain sealing engagement between the interior surface of the bonnet shank 26a and the exterior surface of the stem 40, even while the stem is rotated relative to the bonnet 26.

The annular, top surface of the shoulder 34 is formed as a concave, frustoconical surface to wedge the packing 50 radially inwardly into tight, fluid sealing with the stem 40.

A bonnet cap 54 circumscribes the stem 40 and is threadedly engaged with the exterior end of the bonnet shank 26a. A downwardly-facing, internal annular shoulder 54a of the bonnet cap 54 abuts the nut flange 52a to lock the nut against rotational movement relative to the bonnet shank 26a, further insuring the integrity of the fluid seal between the stem 40 and the bonnet 26 provided by the stem packing 50.

A stem bushing 56 receives the upper end of the stem 40 within a downwardly facing recess 58. The stem 40 is locked to the bushing 56 in that configuration by a pin 60 passing through appropriate holes in both the bushing and the stem. A combination 62 including an annular thrust bearing assembly positioned between two annular races resides in an annular recess at the lower, outer edge of the bushing 56 to provide relatively friction-free engagement between the bushing and the nut 52. A similar assembly 64 of thrust bearings and races resides in a second annular recess in the bushing 56 to provide relatively friction-free contact between the bushing and an inwardly-extending annular shoulder 54b of the bonnet cap 54. An O-ring seal 66, residing in an appropriate annular groove in the neck of the bushing 56, seals the bushing to the radially interior surface of the shoulder 54b.

An otherwise-plugged lateral passage 68 extends through the side wall of the bonnet cap 54 to provide a means for inserting lubricating fluid into the interior of the cap to lubricate the bearing assemblies 62 and 64. The bushing 56 rises beyond the cap 54 in a rectangular extension 70, which is received within a generally complementary hole in the shaft of a handwheel 72, and held to the wheel by a pin 74 passing through appropriate holes in the handwheel shaft and the bushing extension. Rotation of the handwheel 72 results in rotation of the bushing 56 and the stem 40 pinned thereto, with the bushing riding on the bearing assemblies 62 and 64, and the packing 50 maintaining sealing integrity between the stem and the interior of the bonnet 26.

The engagement of the stem surface 48 with the shoulder surface 36 prevents upward movement of the stem 40 relative to the bonnet 26; the pin 60 prevents downward movement of the stem relative to the bushing 56 and, therefore, to the bonnet.

The screw portion 44 of the stem 40 is threadedly engaged within a longitudinallyextending threaded bore 78 of a gate valve element 80. The threaded bore 78 is continued in an elongate tubular neck 82 forming an upward extension of the valve element 80 to provide an extended thread array for maintaining threaded connection between the stem 40 and the valve element over a range of longitudinal positions of the valve element.

As shown in Figs. 2 and 3, a lateral bore 84 communicates with the threaded bore 78 within the valve element 80. The edges of the valve element 80 are beveled. As may be appreciated by reference to Fig. 3, the valve element 80 fits within the cylindrical bore 24 of the body 12 relatively closely along the beveled valve element edges. The valve element 80 may be maintained submerged in fluid lubricant within the cylindrical bore 24. The lubricant may be introduced within the valve 10 by means of interconnecting passages 86 and 88 within the bonnet 26, the latter passage 88 counterbored with a threaded hole 90 to receive a plug.The lubricant is communicated by means of the passages 86, 88 and 90 to the bonnet passage 32 just below the packing 50, and may thereby communicate throughout the stem screw 44, the valve element bores 78 and 84, and the body bore 24 exterior to the valve element 80. The valve element bore 84 insures that, as the valve element 80 is raised or lowered along the stem screw 84, fluid lubricant may flow accordingly into and out of the gate valve element to avoid pressure or vacuum locks from impeding such movement of the valve element. The beveling of the valve element edges facilitates the flow of fluid lubricant as the valve element 80 is so operated, while the relatively close fit of the valve element within the bore 24 avoids wobbling of the valve element during its longitudinal movement.

A pair of seat rings 92 is received within two cylindrical recesses 1 2a in the body adjacent the bore 24 and generally circumscribing the body passage 14. Each of the seat rings 92 carries, in an appropriate annular recess at the inner end of the seat ring, an O-ring seal 94. A second O-ring seal 96 is carried by each seat ring 92 in an appropriate groove breaking the outer cylindrical surface of the seat ring axially spaced from the first ring seal 94. Each pair of ring seals 94 and 96, which may be of resilient material, provides fluid-tight sealing between the corresponding seat ring 92 and the body 12.

Each of the generally tubular seat rings 92 features a central passage 92a which is aligned with the body passage 14 and is generally of the same transverse dimension. Each seat ring 92 extends longitudinally within the radial extent of the body bore 24 and ends in a planar, annular seating surface 92b which fits against the adjacent flat sealing surface of the gate valve element 80. Thus, a lubricated, metal-to-metal seal is maintained between each seat ring 92 and the valve element 80. The gate valve element 80 features a throughbore 98 of radial extent generally equal to that of the body passage 14 and the seat ring passages 92a. The valve 10 is operated by rotation of the hand wheel 72 to accordingly rotate the stem 40 in one rotational sense or the other as desired.As the stem screw 44 is thus rotated, the threaded engagement between the screw 44 and the threaded bore 78 of the gate valve element 80 drives the gate valve element upwardly or downwardly as viewed in Fig.

1, depending on the sense of rotation of the screw, with the engagement between the seat ring surfaces 92b and the surfaces of the gate valve element preventing rotation of the gate valve element relative to the rotating screw 44.

Thus, the gate valve element 80 is generally movable between a first configuration as illustrated in Fig.1, wherein the surfaces of the gate valve element completely close across the seat ring passages 92a to block the body flow passage 14, and a second position in which the gate valve element is raised to piace the throughbore 98 aligned in whole or in part with the seat ring passages 92a to thereby open the seat ring passages and the body passage 1 4 for fluid communication through the valve body 12.

The O-ring seals 94 and 96 may be initially lubricated with the fluid lubricant maintained in the bore 24, for example. The presence of fluid in the valve body passage 1 4 acts on the O-rings 94 to urge the seat rings 92 longitudinally toward the valve element 80, thereby insuring sealing integrity between the seating surfaces 92b and the valve element sealing surfaces. Thus, with the valve element 80 in the closed configuration of Fig. 1 for example, increased fluid pressure in the flow passages 14 acts on the corresponding seat ring 92 as a piston, driving the seat ring into tighter sealing engagement with the valve element.The lubricated metal-to-metal seals between the seat rings 92 and the valve element 80 provide sufficient sealing capability against low fluid pressure in the valve flow path 14 without the seat rings being driven against the valve element.

Another version of a gate valve including the present invention is illustrated in part in Fig. 5 generally at 110. A valve body 112 includes an elongate flow passage 1 for fluid communication therethrough. A transverse cylindrical bore or chamber 124 intersects the flow passage 114 and continues upwardly to a bonnet 126 held to the body by bolts 1 28 and sealed thereto by an appropriate annular seal member 130.A passage 132 extends through the bonnet 126 to communicate with the bore, and contains an elongate stem having a threaded screw end 144 which is threadedly engaged with a threaded bore 1 78 within a gate valve element 1 80. The threaded bore 1 78 is continued in an elongate tubular neck 182 forming an upward extension of the valve element 1 80. A lateral passage 1 84 communicates with the bore 1 78 to permit flow of fluid lubricant between the bore and the area exterior to the valve element 1 80 and within the cylindrical bore 124, as may be further appreciated by reference to Fig. 6.As may also be noted in Fig. 6, the longitudinal side faces of the gate valve element 1 80 feature elongate recesses 185 to facilitate the flow of fluid lubricant about the valve element. Further, the bottom edges of the valve element 180 are beveled (Fig. 5) after the nature of the valve element of Figs. 1-3.

A pair of arcuate, elongate retainer plates 1 87 is positioned within the bore 1 24 so that the gate valve element 180 will slide between facing flat surfaces 1 87a of the two retainer plates as the stem screw 144 is rotated about its longitudinal axis as in the case of the stem screw 44 of the valve of Fig. 1. The elongate, arcuate surface 1 87b of each retainer plate 1 87 features generally the same radius of curvature as the radius of the longitudinal bore 124.An arcuate groove 1 87c breaks the surface 1 87b toward the bottom of each retainer plate 187, and a passage 1 87d communicates between each groove 1 87c and the interior region defined in part by the flat surfaces 1 87a to further facilitate movement of fluid lubricant within the bore 124. Further, the bottom edges of each retainer plate 1 87 are also beveled for this purpose.

Two seat rings 1 92 are received within cylindrical recesses 11 2a in the body 112 adjacent the bore 124, and generally circumscribe the flow passage 114. Each of the seat rings 1 92 carries, in an appropriate annular recess at the inner end of the seat ring, a resilient O-ring seal 194 which provides fluid sealing between the corresponding seat ring and the valve body 112.

Each of the generally tubular seat rings 192 features a central passage 1 92a which is aligned with the body passage 114 and is generally of the same transverse dimension. Each seat ring 1 92 extends longitudinally through a bore 1 95 in the corresponding retainer plate 187, and ends in a planar, annular seating surface 1 92b which fits against the adjacent flat sealing surface of the valve element 1 80. Thus, a lubricated, metal-to metal seal is maintained between each seat ring 1 92 and the gate valve element 1 80. The gate valve element 1 80 features a throughbore 198 of radial extent generally equal to that of the body passage 114 and the seat ring passages 192a.

The valve 110 is operated by rotation of a hand wheel (not shown) to accordingly rotate the stem screw 144 in one rotational sense or the other as desired. As the stem screw 144 is thus rotated, the threaded engagement between the screw and the threaded bore 1 78 of the gate valve element 1 80 drives the gate valve element upwardly or downwardly as viewed in Fig. 5, depending on the sense of rotation of the screw, with the engagement between the seat ring surfaces 1 92b and the flat retainer plate surfaces 1 87a with the surfaces of the gate valve element preventing rotation of the gate vclve element relative to the rotating screw 44.Thus, the gate valve element 80 is generally movable between a first configuration as illustrated in Fig. 5, wherein the surfaces of the gate valve element completely close across the seat ring passages 1 92a to block the body flow passage 114, and a second position in which the gate valve element is raised to place the throughbore 1 98 aligned in whole or in part with the seat ring passages 1 92a to thereby open the seat ring passages and the body passage 114 for fluid communication through the valve body 112.

The O-ring seals 1 94 may be lubricated by the fluid lubricant from the bore 124, and provide sliding sealing between the valve body 112 and the corresponding seat rings 1 92 as the latter are urged by the fluid pressure in the flow passage 114 against the valve element 1 80. Then, as in the case of the seat rings 92 illustrated in Fig. 1, the seat rings 1 92 of the valve of Fig. 5 act as pistons for movement in response to fluid pressure to further press the seating surfaces 1 92b against the valve element sealing surfaces to insure increased sealing capability in the presence of increased fluid pressure in the valve flow passage 114.The lubricated metal-to-metal seals between the seat rings 1 92 and the valve element 1 80 provide sufficient sealing capability against low fluid pressure in the valve flow path 114 without the seat rings being driven against the valve body.

The present invention provides a gate valve having a valve body with a generally cylindrical bore within which the gate valve element is operated, and a pair of seat rings by which the valve element is sealed to the valve body. In the closed configuration, the valve element/seat ring assembly provides fluid-tight sealing between the valve element and the valve body over a large range of pressure values of the fluid whose communication through the valve body passage is to be controlled by the valve system. In low pressure, closed-valve circumstances, the lubricated metal-to-metal seal between the valve element and the upstream seat ring face, coupled with the seating of the O-ring or rings within the valve body recess, provides the necessary sealing integrity with no requirement for the fluid whose flow is to be controlled to provide fluid pressure to maintain the sealing in effect. In high pressure circumstances, the seat ring may act as a piston, with the high pressure of the fluid to be controlled acting on the O-ring seal or seals and tending to drive the seat ring against the valve element into tighter sealing engagement therewith, while maintaining the O-ring or rings under pressure to retain their sealing capabilities.

The present invention provides a gate valve design which is relatively inexpensive to construct and maintain. The valve body with a cylindrical bore to receive the valve element may be expected to be less expensive to manufacture than a valve body with a square or rectangular bore. Further, a valve according to the present invention may be maintained functional after extensive use by, for example, replacing the relatively inexpensive seat rings and/or valve element to maintain the sealing capabilities of the valve assembly. Additionally, valves of the prior art may be converted to use of the present invention by boring a cylindrical bore if none exists, and counterboring the valve body recesses to receive seat rings according to the present invention. Where the valve body bore is of relatively large transverse dimension, for example, arcuate retainer plates may be utilized to support, in part, the seat rings as disclosed. Although a non-rising stem is illustrated and described herein, it will be appreciated that the present invention may be readily employed with a rising stem assembly.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof, and various changes in the size, shape and materials as well as in the details of the illustrated construction may be made within the spirit of the appended claims without departing from the spirit of the invention.

Claims (4)

1. A gate valve comprising: a. a valve body including a passage for fluid communications therethrough, and a generally cylindrical bore laterally disposed relative to, and intersecting, said passage; b. a gate valve element selectively movable along said bore between a first position and a second position, and including first and second sealing surfaces disposed on opposite sides of said valve element; c. a first seat ring including a passage therethrough, a first annular seating surface, and first seal means for sealing said seat ring to said valve body; d. a second seat ring including a passage therethrough, a second annular seating surface, and second seal means for sealing said seat ring to said valve body;; e. wherein said first seat ring is mounted with its passage generally aligned with said body passage, and said first sealing means maintains sealing engagement between said valve body and said first seat ring for limited longitudinal movement of said first seat ring toward said valve element; f. wherein said second seat ring is mounted with its passage generally aligned with said body passage, and said second sealing means maintains sealing engagement between said valve body and said second seat ring for limited longitudinal movement of said second seat ring toward said valve element; and g. wherein said first and second annular seating surfaces sealingly engage said first and second sealing surfaces, respectively, of said valve element whereby, with said valve element in said first position, said body passage is blocked against fluid flow therethrough and, with said valve body in said second position, said body passage is open for fluid communication through said seat rings and by said valve element.

2. A gate valve as defined in Claim 1 wherein said first sealing means comprises at least one annular seal member carried by said first seat ring and providing sliding, sealing engagement with said body, and said second sealing means comprises at least one annular seal member carried by said second seat ring and providing sliding, sealing engagement with said body.

3. A gate valve as defined in Claim 1 further comprising: a. first retainer means, including an arcuate surface, generally complementary to said lateral bore of said body, and a bore for receiving said first seat ring; b. second retainer means, including an arcuate surface, generally complementary to said lateral bore of said body, and a bore for receiving said second seat ring; and c. wherein said first and second retainer means are disposed within said lateral bore of said body on opposite sides of said valve element to maintain said first and second seat rings, respectively, in configuration for said first and second seating surfaces to so sealingly engage said first and second sealing surfaces, respectively, of said valve element.

4. A gate valve substantially as hereinbefore described with reference to the accompanying drawings.