GB2070203A - A gate valve - Google Patents

Abstract

A gate valve is provided with an annular metallic sealing member (72) disposed between a bonnet (40) and a valve body (11) of the valve, a stem (52) extending through the bonnet and the sealing member (72) and secured to the valve gate, and two annular seat portions (82, 84) on the stem on opposite sides of the sealing member each of which is movable by movement of the stem into sealing engagement with the sealing member, one in the valve-open and the other in the valve-closed position of the stem. <IMAGE>

Description

SPECIFICATION A gate valve This invention relates to gate valves for use in both normal and relatively high temperature and/or high pressure environments.

According to the present invention there is provided a gate valve comprising a valve body, a bonnet mounted on the valve body, a valve member mounted within the body, a valve stem connected to the valve member and slidable longitudinally within the bonnet, an annular metallic sealing member surrounding the stem and fixed relative to the bonnet, the stem having seat portions at spaced apart positions thereon on opposite sides of the sealing member, the stem being movable in one direction to bring one seat portion into sealing engagement with the sealing member and in the opposite direction to bring the other seat portion into sealing engagement with the sealing member.

The present invention also provides a gate valve comprising a valve body having a fluid flow passage therethrough, a gate chamber extending through a portion of said body at right angles to and intersecting said fluid flow passage, a valve gate having a port therethrough and slidably mounted in said valve body to open the flow passage when said valve gate is in a first position, said valve gate blocking the flow of fluid through said passage when said valve gate is in a second position, a bonnet mounted on said valve body to close one end of said gate chamber, said bonnet having a bore therethrough, an annular metallic sealing member mounted between said body and said bonnet, a gate stem mounted within said bore in said bonnet and connected to the valve gate, said gate stem extending through the annular sealing member and having first and second seat portions, said first seat portion forming a fluid-tight seal with said sealing member when said stem is in a fully extended position and said second seat portion forming a fluid-tight seal with said sealing member when said stem is in a fully retracted position.

The invention will now be particularly described by way of example with reference to the accompanying drawings in which: Figure 1 is a central vertical section of a gate valve according to the present invention with the valve in a closed position and with the gate stem in a fully extended position; Figure 2 is an enlarged vertical section of a portion of the valve of Fig. 1 with the valve stem in a fully retracted position, and Figure 3 is a central vertical section of a portion of another embodiment of the gate valve of Fig. 1 illustrating the positions of the valve which differ from those of the valve of Fig. 1.

As illustrated in Fig. 1, a gate valve 10 for controlling fluid flow in either direction includes a generally annular body 11 defining a fluid flow passage 12, the illustrated body being adapted for insertion between two opposed standard pipe flanges (not shown). A gate chamber 1 6 extends through a portion of the body 11 at right angles to and'intersecting the fluid flow passage 12, with the passage 1 2 including a pair of enlarged portions 17, 18 adjacent the chamber 1 6. Fitted into the enlarged portion of each of the passages is a hollow cylindrical insert 22, 23, each insert having an annular groove 24 in an outer wall 28 and with an annular sealing member 29 mounted in the groove 24 to provide a fluid-tight seal between the insert and the enlarged portion of the passage.Each of the inserts 22, 23 extends into the gate chamber 1 6 where it makes sliding contact with a flat valve gate 30 having a port 34 therethrough.

When the valve gate 30 is moved into the closed position shown in Fig. 1 the valve gate 30 blocks the flow of fluid between the right and left portions of the passage 1 2. When the valve gate 30 is moved into the open position shown in Fig. 2 the gate port 34 interconnects the right and left portions of the fluid flow passage to allow fluid to flow between an inlet end 35 and an outlet end 36, although it should be realised that fluid can also flow in the opposite direction with the port 36 being the inlet and the port 35 being the outlet.

A bonnet 40 (Figs. 1, 2) is attached to the upper portion of the body 11 by a plurality of capscrews 41 each of which projects through a hole 42 in the bonnet and is turned into a threaded bore 46 in the body 11. The bonnet 40 includes a bore 47 extending vertically through the centre of the bonnet, and the bonnet includes a cylindrical threaded upper end 48.

Extending through the bore 47 of the bonnet 40 is a generally cylindrical valve stem 52 having a lower portion 52a with a lower end 53 secured to the valve gate 30 and with an upper end 54 threaded to a lower end 58 of an upper stem portion 52b. A setscrew 59 mounted in a threaded hole 60 in the upper stem portion 52 or other suitable locking device prevents the upper and lower portions 52a, 52b from inadvertently becoming separated during normal operation of the valve gate, but allows the upper and lower portions of the stem to unscrew for separation during service operations. An enlarged upper portion 47a of the bore 47 contains a cylindrical sleeve 64 and resilient packing 65 mounted between the sleeve 64 and a shoulder 66 at the lower end of the bore 47a.The packing 65 and an O-ring 67, mounted in an annular groove 70 in the sleeve provide a fluid-tight seal between the valve stem 52 and a wall 71 of the bore 47a of the bonnet.

An annular metal sealing member 72 mounted between a lower end 40a (Fig. 2) of the bonnet and a wedge-shaped surface 76 at the upper end of the body 11 provides a fluid tight seal between the body 11 and the bonnet 40. The metal sealing member 72 includes an annular bore 77 (Fig. 2) having a wedge-shaped cam surface 78 which mates with a wedge-shaped cam surface or seat portion 82 on the valve stem 52b to provide a fluid-tight seal between the gate chamber 1 6 and the bonnet bore 47 when the valve stem 52 is in the lower or retracted position shown in Fig. 2.Another wedge-shaped cam surface or seat portion 83 (Figs. 1, 2) on the metal sealing member 72 mates with a wedge-shaped cam surface 84 on the valve stem 52a to provide a fluid-tight seal between the gate chamber 1 6 and the bonnet bore 47 when the valve stem 52 is in the upper or extended position shown in Fig. 1. Thus, the valve stem 52 and a single sealing member 72 provide a fluid-tight seal at the upper end of the gate chamber 1 6 when the valve is in the open position and also when the valve is in the closed position.

An annular cap 88, having a bore 89 (Fig.

1) with an enlarged portion 90 extending vertically through the cap, is threaded to the upper end 48 of the bonnet 40. An annular spacer 94 having a central bore 95 therein is mounted in the enlarged portion of the cap bore between a shoulder 96 and the upper end 48 of the bonnet 40. When the cap is tightened against the spacer 94, the spacer 94 forces the sleeve 64 against the packing 65 and compresses the packing between the stem 52 and the wall 71 of the bonnet 40 to ensure a fluid-tight seal between the stem and the bonnet.

A cylindrical drive nut 99 (Fig. 1) having a threaded axial bore 100 and a radially outward flange 101 is rotatably mounted in the bore 89 of the valve cap 88 with the flange 101 in the bore 90. The flange 101 is mounted between a pair of sets of roller bearings or other bearing means 102,103 each having a plurality of rollers 107 mounted in a bearing race 108. An annular sealing member 109 mounted in an annular groove 114 in the valve cap 88 provides sealing between the drive nut 99 and the bore 89 of the valve cap.A threaded upper end 11 5 of the valve stem 52 is mounted inside the threaded bore 100 of the drive nut 99, so that rotation of the drive nut 99 moves the valve stem 52 up or down inside the nut 99 and inside the bonnet 40 and moves the valve gate 30 up or down inside the gate chamber 1 6. The drive nut 99 is rotated by a handwheel 11 6 having a central portion 1 20 with an axial bore 121 extending through the portion 1 20 and having an upper portion of the drive nut 99 mounted in the bore 121.

The handwheel 11 6 is secured to the drive nut 99 by a setscrew 122 mounted in a threaded bore 1 26 in the central portion 1 20 and extending into a bore 1 27 in the drive nut 99.

When it is desired to replace either the resilient packing 65 or the O-ring 67 in the bonnet 40, the handwheel 11 6 (Fig. 1) and the drive nut 99 are rotated until the cam surface 84 of the gate stem is pressed securely against the cam surface 83 of the sealing member 72 to prevent fluid from leaking out of the gate chamber 16. The set screw 1 22 is moved radially out of the threaded bore 1 26 and the bore 127, and the handwheel lifted off the drive nut 99. The valve cap 88 is unscrewed from the bonnet 40 and the valve cap 88 and handwheel 11 6 are removed from the valve 1 0. The drive nut 99 is then unscrewed from the threaded end 11 5 of the gate stem 52 and lifted off the upper end of the gate stem along with the spacer 94.The tip of a screw driver (not shown) can be inserted into an annular groove 1 28 in the upper portion of the cylindrical sleeve 64 and the sleeve lifted out of the bore 47a. The packing 65 and/or the O-ring 67 can be replaced by sliding them down over the stem 52 into position, and the sleeve 64, spacer 94, drive nut 99 and handwheel 11 6 replaced on the valve 10 in reverse order of the removal. Any pressurized fluid in the gate chamber 1 6 presses upward against the lower end 52a of the valve stem during the packing replacement to aid in providing firm contact between the surfaces 83, 84 and reducing leakage from the gate chamber.

Another embodiment of the gate valve 1 Oa incorporating the features of the present invention is disclosed in Fig. 3. The gate valve 1 Oa of Fig. 3 differs from the gate valve 10 of Figs. 1 and 2 by the inclusion of a lower cylindrical valve stem 152a, the associated cylindrical sleeve 164, packing and an annular cap 88a. All of the details of the gate valve 1 Oa (Fig. 3) positioned above the fluid flow passage 1 2 are identical to the details of the valve 10 shown in Figs. 1 and 2, therefore many of these details have been omitted from Fig. 3 in order to enlarge the drawing of the lower portion of the valve. Elements of the valve 1 Oa of Fig. 3 which are similar or identical to the elements of the valve 10 of Figs. 1, 2 have been labelled with similar numbers.

The body 1 la of the gate valve 10a includes a gate chamber 131 extending through a portion of the body 11 a at right angles to and intersecting the fluid flow passage 1 2.

The gate chamber 1 3 extends approximately equidistant above and below the fluid flow passage 1 2. A bonnet 140 is attached to the lower portion of the body 11 a by a plurality of capscrews 41 each of which projects through a hole 42a in the bonnet and is turned into a threaded bore 46a in the body 11 a. The bonnet 140 includes a bore 147 extending vertically through the centre of the bonnet, and the bonnet includes a cylindrical threaded lower end 48a.

Extending through the bore 147 of the lower bonnet 140 is a generally cylindrical lower valve stem 1 52 having an upper portion 1 52a with an upper end 1 53 secured to the valve gate 1 30 and with a lower end 1 54 threaded to an upper end 1 58 of a lower stem portion 152b. An enlarged lower portion 1 47a of the bore 147 contains a cylindrical sleeve 1 64 and a resilient packing 1 65 mounted between the 147a.The packing 165 and an O-ring 167, mounted in an annular groove 1 70 in the sleeve provide a fluid-tight seal between the valve stem 1 52 and a wall 1 71 of the bore 1 47 of the bonnet.

An annular metal sealing member 1 72 mounted between an upper end 1 40a of the bonnet 1 40 and a wedge-shaped surface 1 76 at the lower end of the body 11 a provides a fluid-tight seal between the body 1 1a and the bonnet 1 40. The metal sealing member 1 72 includes an annular bore 1 77 having a wedge-shaped cam surface 1 78 which mates with a cam surface 1 84 on the valve stem 1 52a to provide a fluid-tight seal between the gate chamber 1 31 and the bonnet bore 147 when the valve stem 1 52 is in the retracted position shown in Fig. 3.Another wedgeshaped cam surface 1 82 presses against the metal sealing member 1 72 to provide a fluidtight seal between the gate chamber 131 and the bonnet bore 1 47 when the valve stem 1 52 is in the upper or extended position as shown in Fig. 1. Thus, the valve stem 1 52 and a single metal sealing member 1 72 provide a fluid-tight seal at the lower end of the gate chamber 131 when the valve is in the open position and also when the valve is in the closed position.

An annular cap 88a having a bore 89a extending vertically through the cap, is threaded to the lower end 48a of the bonnet 1 40. An annular spacer 94a having a central bore 95a therein is mounted in the enlarged portion of the cap bore between a shoulder 96a and the lower end of the bonnet 140.

When the cap 88a is tightened against the spacer 94a, the spacer 94a forces the sleeve 1 64 against the packing 1 65 and compresses the packing between the stem 1 52 and the wall 1 71 of the bonnet 140 to insure a fluidtight seal between the stem and the bonnet.

The packing 1 65 and the O-ring 167( Fig.

3) provide a primary seal about the lower valve stem 152, and the packing 65 and the O-ring 67 (Fig. 1) provide a primary seal about the upper valve stem 52. The metal sealing members 72, 1 72 provide secondary seals about the valve stems 52, 1 52 during normal operation and provide sealing in case of damage to the primary seals.

The present invention provides a single metal sealing member which combines with cam surfaces on a valve stem to develop a metal-to-metal seal which prevents fluid leakage from the gate chamber of the valve when the valve is either open or closed. If the usual resilient packing around the valve stem should be damaged the packing can be replaced while the valve remains in either the open or closed position without interfering with the operation of the valve.

Claims (8)

1. A gate valve comprising a valve body, a bonnet mounted on the valve body, a valve member mounted within the body, a valve stem connected to the valve member and slidable longitudinally within the bonnet, an annular metallic sealing member surrounding the stem and fixed relative to the bonnet, the stem having seat portions at spaced apart positions thereon on opposite sides of the sealing member, the stem being movable in one direction to bring one seat portion into sealing engagement with the sealing member and in the opposite direction to bring the other seat portion into sealing engagement with the sealing member.

2. A gate valve comprising a valve body having a fluid flow passage therethrough, a gate chamber extending through a portion of said body at right angles to and intersecting said fluid flow passage, a valve gate having a port therethrough and slidably mounted in said valve body to open the flow passage when said valve gate is in a first position, said valve gate blocking the flow of fluid through said passage when said valve gate is in a second position, a bonnet mounted on said valve body to close one end of said gate chamber, said bonnet having a bore therethrough,- an annular metallic sealing member mounted between said body and said bonnet, a gate stem mounted within said bore in said bonnet and connected to the valve gate, said gate stem extending through the annular sealing member and having first and second seat portions, said first seat portion forming a fluidtight seal with said sealing member when said stem is in a fully extended position and said second seat portion forming a fluid-tight seal with said sealing member when said stem is in a fully retracted position.

3. A gate valve according to claim 1 or claim 2 wherein said first and said second seat portions of said gate stem each include a wedge-shaped cam surface which makes sealing contact with a wedge-shaped cam surface on said sealing member.

4. A gate valve according to any preceding claim wherein said gate stem comprises a first part containing one of said seat portions, and a second part containing the other of said seat portions, said parts of the stem being separable to facilitate replacement of said metallic sealing member.

5. A gate valve according to any preced ing claim including resilient packing mounted between said gate stem and the bonnet to provide a fluid-tight seal between said gate stem and said bonnet.

6. A gate valve according to any preceding claim wherein said sealing member comprises a disc having first and second surfaces disposed at an inclination to each other, for engagement with the seat portions on the stem.

7. A gate valve according to claim 2 including a second bonnet mounted on the valve body and having a bore therethrough, said second bonnet being mounted at a second end of said gate chamber, a second annular metallic sealing member mounted between said body and said second bonnet, a second gate stem connect to the valve gate being slidable within the second bonnet and extending through the second sealing member, the second gate stem having first and second seat portions for forming a fluid-tight seal with the second sealing member when the second and first seat portions respectively of the first stem are in sealing engagement with the first sealing member.

8. A gate valve substantially as herein described with reference to the accompanying drawings.