GB2472200A

GB2472200A - Ball valve

Info

Publication number: GB2472200A
Application number: GB0913037A
Authority: GB
Inventors: Alexander Stuart Jamieson
Original assignee: BiFold Fluidpower Ltd
Current assignee: BiFold Fluidpower Ltd
Priority date: 2009-07-27
Filing date: 2009-07-27
Publication date: 2011-02-02
Anticipated expiration: 2029-07-27
Also published as: GB2472200B; GB0913037D0

Abstract

A ball valve has a single valve seat that can be disposed upstream or downstream of the ball. On one side of the ball 7 there is a valve seat assembly 20 comprising a valve seat seal 22 defining a sealing surface 25 that seals against the valve ball 7 at an effective first diameter (D1, Fig. 4). On the other side of the ball there is a valve support 30 that has a beating 34 that defines a non-sealing beating surface 35, the valve support 30 being fixed, in use, against axial movement relative to the valve body 1. A second seal 27 is provided between the valve seat assembly 20 and the valve body 1 for sealing at an effective second diameter (D2, Fig. 4) that is outboard of the first diameter D1. The difference in diameters determines the force applied to the valve seat assembly 20 to seal against the ball 7 when the valve is closed.

Description

BALL VALVE

The present invention relates to a ball valve.

A ball valve typically comprises a valve body defining a fluid flow path that is interrupted by a valve chamber in which a valve ball is rotatably disposed. The valve body defines ports for the fluid flow path and is connectable into a pipeline or the like. The flow may be bi-directional such that each port can serve either as an inlet or outlet port. The valve ball has a bore therethrOugh that is selectively brought into register with the flow path by rotation of the ball. In an open position the ball is oriented such that the bore is in register with the inlet and outlet ports so that fluid may flow from inlet to outlet through the bore. In a closed position the valve is rotated through 90 degrees so as to block the flow. Upstream and downstream annular seats of resilient sealing material are provided in the valve chamber immediately adjacent to the valve ball on each side. The seats provide a fluid-tight seal against opposite surfaces of the valve ball.

The valve ball may be arranged in the valve chamber such that it can move slightly in the axial direction along the fluid flow path relative to the seats. A ball valve of this kind is often referred to in the art as a floating ball" valve. In operation, when the valve is closed, fluid tends to leak around the upstream valve seat and pressure forces the valve ball in the downstream direction and against the downstream valve seat (adjacent to the outlet port) to provide a seal. It will be appreciated that either of the seats may serve as the downstream seal, depending Ofl the direction of flow. In order for the downstream seat to seal positively and effectively against the valve ball, even after seat wear, fine tolerances are required in the manufacture of the components that make up the ball valve, including the valve body, the ball and the valve seats that each support a sealing ring. The friction provided by the contact between the seats and the ball results in a resistance to rotation of the valve ball and * therefore a relatively high torque may have to be applied to operate the valve between the open and closed positions It is an object of the present invention to obviate or mitigate the aforesaid disadvantages. It is also an object of the present invention to provide for a ball valve that is relatively inexpensive to manufacture and assemble and yet which is reliable : in operation.

According to the present invention there is provided a ball valve comprising a valve body defining a fluid flow path extending between an inlet and an outlet and a valve chamber, the valve chamber being disposed intermediate the inlet and outlet; a rotary valve ball in the valve chamber and having a bore therethroUgh, the valve ball being rotatable between an open position in which the bore is in flow register with the inlet and outlet and a closed position in which it is out of register and prevents fluid flow between the inlet and outlet; a valve seat assembly comprising a valve seat seal defining a sealing surface that seals against the valve ball at an effective first diameter; a second seal between the valve seat assembly and the valve body for sealing at an effective second diameter that is outboard of the first diameter; a valve support disposed Ofl an opposite side of the valve ball to the valve seat assembly, the valve support comprising a bearing that defines a non-sealing bearing surface, the valve support being fixed, in use, against axial movement relative to the valve body.

When the ball valve is closed and fluid flows in a direction such that the valve seat assembly is upstream of the valve support, the fluid pressure acts on an annuluS of the valve seat assembly defined between the first and second effective diameters. This has the effect of applying a force to the area of the annulus so as to move the valve seat assembly against the ball such that the seat seal seals against an external surface of the ball. The area of the annulus and therefore the force applied by a given fluid pressure is determined by the difference between the first and second effective diameters i.e. the sealing positions of the seat seals and the second seal. When fluid flows in the opposite direction such that the valve seat assembly is downstream of the valve support fluid pressure acts on the ball so as to move it against the downstream valve seat seal as in a conventional floating ball valve. S..'

In this arrangement there is only one functioning valve seat seal that may be upstream or downstream of the ball depending on the flow direction, The valve support only provides a bearing surface for guiding rotation of the ball relative to the valve body and does not serve to provide any significant sealing against the ball.

When the valve support is upstream fluid can flow past the bearing to force the ball :,,. against the downstream valve seat seal as in a conventional ball valve.

The ball valve structure is such that allows a reduction in component complexity and a reduced number of components to be used. This makes it relatively simple to manufacture and assemble. The design also allows for a reduced torque required for operating the valve as the bearing of the support does not provide any significant resistance to rotation of the ball.

The valve seat seal and the bearing may be substantially annular. The valve seat assembly may be substantially annular and the valve support may be substantially annular. The valve seat seal is preferably made from a resilient sealing material.

The valve seat assembly may comprise a valve seat carrier having a first recess facing the valve ball in which the valve seat seal is received. The valve seat carrier may have a second recess facing the valve body, the second recess receiving the second seal. The valve seat seal and the second seal are preferably axially spaced apart. The second recess may face towards an inlet or outlet of the valve body. The first and second recesses may be provided in opposing end faces of the valve seat carrier.

The valve seat assembly may be slidable within and relative to the valve body.

The valve seat assembly may be supported in an axial direction against a substantially radially extending wall of the valve body in the flow path. This prevents the valve seat assembly from moving relative to the valve body beyond a certain axial location. The wall may be integrally formed with the valve body and may be substantially annular. As an alternative to the wall a fixing may be provided for retaining the valve seat assembly in an axial direction.

The second seal may disposed between a side face of the valve seat assembly and the wall or may be disposed between an outer circumferential surface of the valve seat assembly and an internal surface of the valve body.

The flow path may be further defined by a first bore in the wall and a second bore in the valve seat assembly, the first and second bore being of substantially the Sell same diameter. This may be substantially the same diameter as the bore in the valve ball.

The valve support may comprise a support member that supports the bearing. The bearing may be supported in a recess in the support member.

The valve support may be fixed in the valve body by any suitable connection such as a threaded connection between the valve support and the valve body.

However, it is desirable that the support is releasable such that it can be removed from the housing. The valve support may be disposed wholly within the valve body and is preferably axially spaced from the nearest inlet or outlet.

A valve stem may extend from the valve body and may be connected to the valve ball such that rotation of the valve ball is achieved by rotation of the valve stem. The valve stem may have a flange disposed in the valve body. A sealing and bearing assembly may be disposed between the flange and the valve body.

The ball valve is preferably configured to allow bi-directioflal flow of fluid. The valve body may be a unitary structure and may be assembled by insertion of the components into one of the inlet and outlet.

A specific embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective exploded view of an embodiment of a ball valve in accordance with the present invention; Figure 2 is a longitudinal sectioned view of the ball valve of figure 1, shown in the open position; Figure 3 is a longitudinal sectioned view of the ball valve of figure 1, shown in the closed position; and Figure 4 is an enlarged view of part of figure 3, illustrating differential sealing diameters of the valve seat.

Referring now to the drawings, the exemplary ball valve comprises a unitary valve body I which defines a fluid flow path 2 for bi-directioflal fluid flow therethrough along a longitudinal axis. The path 2 extends from an inlet opening to an outlet opening and has first and second ports 3, 4; one at each end which, in use, are connectable to another conduit such as a pipeline. Threads 5 are provided internally in the ports to facilitate connection to the conduit or to interface fittings. In use, the first and second ports 3, 4 define an inlet (upstream) and an outlet (downstream), depending on the direction of flow along the flow path.

The fluid flow path 2 is interrupted by a valve chamber 6 in which a valve ball 7 is rotatably disposed between open and closed positions. The valve ball 7 is *.S.SS * S substantially spherical and is penetrated by a central bore 8 that is selectively brought into register with the flow path 2. In the open position the bore 8 is in coaxial alignment with the ports 3, 4 so that fluid may flow from the inlet to the outlet via the valve chamber 6. In the closed position the ball 7 is rotated through 90 degrees such that the bore extends perpendicular to the inlet and outlet and the flow is blocked.

The balI 7 is connected to a rotatable, elongate valve stem 9 that projects through an opening 10 in the top of the valve body 1 above the valve chamber 6. On the outside of the body 1 the stem 9 is connected to a handle 11 that is operable manually or automatically so as to rotate the stem 9 about its longitudinal axis and thereby rotate the ball 7. The connection between the valve stem 9 and the ball 7 is provided by a keyway 12 machined in an upper surface of the ball 7 that receives a corresponding key 13 integrally formed at a bottom end of the valve stem 9.

The valve stem 9 is generally cylindrical with an annular flange 14 towards its lower end and adjacent to the key 13. This flange 14 is larger than the opening 10 in the body I so as to prevent the stem 9 being blown out of the body 1 when there is high pressure in the valve chamber 6. An internal sealing arrangement comprising an annular seal 15 and stem bearing 15a is supported between an upper surface of the flange 14 and an internal surface of the body I around the opening 10.

An annular wall 16 is defined inside the body 1 between the second port 4 and the valve chamber 6. This provides a supporting annulus for a valve seat assembly 20 that comprises a seal carrier 21 slidably received within the body 1 on one side of the ball 7 and a seat seal 22. The carrier 21, which is typically manufactured from metal e.g. stainless steel, is penetrated by a central bore 23 having a diameter is substantially equal to that of the ball 7 and an inner surface defined by the annular wall 16. The carrier 21 of the valve seat assembly 20 supports the annular valve seat seal 22 for sealing against the outer surface of the valve ball 7 at a nominal or effective diameter D1. The valve seat seal 22 may be made of any suitable resilient sealing material such as, for example, PEEK (polyetherether ketone), PTFE, nylon or other suitable elastomeric sealing material and is received in a corresponding annular groove 24 defined in a first end face 21a of the carrier 21 that faces the ball 7. The seat seal 22 defines a profiled sealing surface 25 that bears against the external surface of the ball 7. An opposite end face 21b of the carrier 21 has an annular groove 26 in which an 0-ring seal 27 is disposed for sealing against the annular wall 16 at a nominal or effective diameter D2. S...

An annular ball support member 30 is disposed diametrically opposite the valve seat assembly 20 on the other side of the balI 7 and valve chamber 6 and has an external thread 31 for engagement with the internal thread 5 defined in the first *5* port 3. In the same manner as the carrier 21 of the valve seat 20, the support member 30 is penetrated by a bore 32 that is of the substantially same diameter as the bore 8 through balI 7 and the inner surface of the annular wall 16. A ball-facing 5. end face 30a of the support member 30 has an annular groove 33 that receives an annular guide bearing 34 designed to provide a bearing surface 35 for supporting the rotational movement of the ball 7. The guide bearing 34 may be manufactured from any suitable bearing material such as, for example, bronze or aluminium bronze. The guide bearing may also be coated, at least on the guide surface 35, with an appropriate material for increase wear resistance and/or reduced friction. The bearing surface 35 of the guide bearing 34 has a profile suitable for bearing against the external surface of the ball 7 so as to guide its rotational movement without providing any significant sealing against the passage of fluid.

The ball valve is relatively easy to assemble. First, the valve seat assembly (comprising the carrier 21, the seat seal 22 and the 0-ring seal 27) is inserted through the first port 3 and pushed towards the second port 4 until it abuts against the annular wall 16 as shown in figures 2, 3 and 4. The valve stem 9 with seal 15 and bearing 15a is then inserted through the same port 3 with its elongate axis generally parallel to the longitudinal axis of the flow path into the valve chamber 6, whereupon it is rotated through 90 degrees until its axis is substantially vertical and aligned with the opening 10. The stem 9 is then passed through the opening 2, a stem plate 36 is placed over the stem 9 and fixed to the body 1 by fixing screw 37, the handle 11 placed over the stem 9 and the stem 9 fixed in place by a threaded nut 38 with washer 39. The stem 9 is rotated about its axis by the handle until the length of the key 13 is aligned with the longitudinal axis of the flow path 2 and the ball 7 is then inserted through the first port 3 with its keyway 12 aligned with the key 13. The ball 7 is moved into the valve chamber 6 until it abuts the valve seat 20 at which point the key 13 and keyway 12 are fully inter-engaged along their lengths. The support member 30 (complete with guide bearing 34) is then passed into the first port 3 and screw-threaded into position until the bearing surface 35 of the guide bearing 34 is in close proximity to the external surface of the ball 7. A torque wrench (not shown) may be used for this purpose, with formations on the wrench inter-engaging with complementary formations (not shown) defined on the end surface 30b of the support member 30 that faces the open end of the first port 3. In this manner the

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support member 30 can be screwed in to the correct axial position relative to the ball 7 and the valve chamber 6.

In operation, if the fluid is flowing from the first port 3 to the second port 4 (right to left in figures 2 to 4) and the valve ball 7 is then rotated to the closed * position, the fluid passes between the bearing surface 35 of the guide bearing 34 * * and the valve ball 7 and applies pressure on the valve ball 7 so as to force it against the valve seat seal 22 such that downstream sealing is provided.

If the fluid is flowing in the direction from the second port 4 to the first port 3 (left to right in figures 2 to 4) and the valve ball 7 is then rotated to the closed position, the fluid passes between the second end face 21b of the valve seat carrier 21 and the annular wall 16 to the point (at diameter D2) where the 0-ring seal 27 seals against the annular wall 16. The pressure of the fluid thus acts on the end face 21 b over an annulus that extends from the outer edge of the bore 23 to diameter D2.

The difference between diameters D2 and D1 determines the resultant force that acts on the valve seat 20 arid urges it to the left in figures 2 to 4 such that the seat surface 25 of the seat seal 22 is urged against the surface of the valve ball 7. The resultant force imparted by the valve seat 20 against the ball 7 determines the torque required to turn the valve stem 8 and ball 7 between the open and closed positions.

It will be appreciated that the design of the valve seat 20 can be varied to alter the positions of the sealing diameters D2 and D1 so that the loading force on the ball can be varied. In effect the sealing diameters D2 and D1 can be tuned" to govern the torque required to operate the valve.

The arrangement provides for a simple two-way ball valve structure that is relatively low cost to manufacture and assemble and is relatively easy to operate.

The single valve seat seals in both directions of flow and is loaded according to its sealing diameters against the ball and the body.

In a modified embodiment, the support member 30 may have a longer length and the internal surface that defines the bore 32 may be threaded for connection to a conduit (e.g. a pipe) or to an interface fitting (e.g. a pipe fitting). This would replace the threads 5 defined in that particular port 3. This would allow the overall length of the body I to be reduced in length. The support member in such an embodiment would be fixed in place by means other than threads e.g. a sealed locking pin fitted through a wall of the valve body.

It is to be understood that the invention has application to ball valves of any size or application.

In the particular embodiments described above the valve seat and valve seat seals are not otherwise biased (by compression springs or the like) towards the ball.

It will be appreciated that numerous modifications to the above described design may be made without departing from the scope of the invention as defined in * * the appended claims. For example, the 0-ring seal 27 may be disposed between the * * outer periphery of the valve seat carrier (e.g. in a groove) and a facing surface of the valve body 1. Furthermore, the exact form of connection between the valve stem and

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the ball may be varied as this is not critical to the inventive concept. The same arrangement may be provided in two-piece or a multi-piece body. Moreover the fixing method by which the support member 30 is fixed to the body can be of any suitable form including, for example, one or more bolts, screws, circlips, retaining rings or locking pins or a combination thereof.

The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the scope of the inventions as defined in the claims are desired to be protected. It should be understood that white the use of words such as "preferable", "preferably", "preferred" or "more preferred" in the description suggest that a feature so described may be desirable, it may nevertheless not be necessary and embodiments lacking such a feature may be contemplated as within the scope of the invention as defined in the appended claims. In relation to the claims, it is intended that when words such as "a," "an," "at least one," or "at least one portion" are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim. When the language "at least a portion" and/or "a portion" is used the item can include a portion and/or the entire item unless specifically stated to the contrary. S...

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Claims

CLAIMSA ball valve corn prising: a valve body defining an inlet and an outlet, a fluid flow path extending between the inlet and outlet, the valve chamber being disposed in the fluid flow path intermediate the inlet and outlet; a rotary valve ball in the valve chamber and having a bore therethroUgh, the valve ball being rotatable between an open position in which the bore is in flow register with the inlet and outlet and a closed position in which it is out of register and prevents fluid flow between the inlet and outlet; a valve seat assembly comprising a valve seat seal defining a sealing surface that seals against the valve ball at an effective first diameter; a second seal between the valve seat assembly and the valve body for sealing at an effective second diameter that is outboard of the first diameter; a valve support disposed on an opposite side of the valve ball to the valve seat assembly, the valve support comprising a bearing that defines a non-sealing bearing surface, the valve support being fixed, in use, against axial movement relative to the valve body.
2. A ball valve according to claim 1, wherein valve ball is movable relative to the valve support in an axial direction.
3. A ball valve according to claim 1 or 2, wherein the valve seat assembly comprises a valve seat carrier having a first recess facing the valve ball, the valve seat seal being received in the first recess.
4. A ball valve according to claim 1, 2 or 3, wherein the valve seat carrier *S..has a second recess facing the valve body the second recess receiving the second seal. S. *

*
5. A ball valve according to any preceding claim, wherein the valve seat assembly is supported in an axial direction against a radially extending wall of the valve body in the fluid flow path.
6. A ball valve according to claim 5, wherein the radially extending wall is substantially annular.
7. A ball valve according to claim 5 or 6, wherein the second seal is disposed between a side face of the valve seat assembly and the radially extending wafl.
8. A ball valve according to any one of claims 5 to 7, wherein the flow path is further defined by a first bore in the radially extending wall and a second bore in the valve seat assembly, the first and second bore being of substantially the same diameter.
9. A ball valve according to any preceding claim, wherein the valve support comprises a support member that supports the bearing.
10. A ball valve according to claim 9, wherein the bearing is supported in a third recess defined in the support member.
11 A ball valve according to any preceding claim, wherein the valve support is fixed relative to the valve body by a threaded connection between the valve support and the valve body.
12. A ball valve according to any preceding claim, wherein the valve support is disposed wholly within the valve body.
13. A ball valve according to any preceding claim, further comprising a valve stem that extends from the valve body and is connected to the valve ball such that rotation of the valve ball is achieved by rotation of the valve stem, the valve stem having a flange disposed in the valve body, a sealing and bearing assembly being disposed between the flange and the valve body. *
14. A ball valve according to any preceding claim, the valve being designed to *S * *. .: allow bi-directional flow.
15. A ball valve according to any preceding claim, wherein the valve body is a unitary structure. e..S S... S.S * *5* S.. * * S * *5'* IS * S * * S **