GB1563333A

GB1563333A - Fluid flow control valves

Info

Publication number: GB1563333A
Application number: GB2389176A
Authority: GB
Original assignee: Saunders Valve Co Ltd
Current assignee: Crane Process Flow Technologies Ltd
Priority date: 1977-06-01
Filing date: 1977-06-01
Publication date: 1980-03-26

Description

(54) IMPROVEMENTS IN AND RELATING TO FLUID FLOW CONTROL VALVES (71) We, SAUNDERS VALVE COMPANY LIMITED, a British Company of Cwmbran, Gwent, Wales, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to fluid flow control valves, and more particularly to ball valves.

A ball valve comprises a valve body defining flow passages extending from the outside of the body to a central cavity.

A generally spherical plug or ball is rotatably mounted in the central cavity and is provided with a through passage which may be aigned with flow passages in the valve body to open the valve to fluid flow.

A seat which is in sealing engagement with the body and the ball is provided at the inner end of at least one of flow passage in the valve body in order to prevent the controlled fluid from passing through the gap defined between the ball and the valve body at that inner end.

The valve seat must be capable of slidingly engaging the ball without undue wear, and must be chemically resistant to the controlled fluid up to the maximum operating temperature and pressure to which the valve will be subjected. For this reason, seating rings are commonly manufactured of PTFE. However, problems have arisen with PTFE seating rings due to the fact that the coefficient of expansion of PTFE is considerably higher than that of the metals used for the valve body and ball. Thus, as the valve is heated in use, the seating rings expand and are compressed between the valve body and the ball. The pressure on the seating rings tends to cause them to extrude inelastically with the result that when the valve cools down, they no longer effectively sealingly engage the ball.Further, the seating rings may extrude in such a manner that they jam the ball, and resist or prevent its rotation to close the valve.

According to the present invention there is provided a ball valve comprising: a valve body defining a central cavity and flow passages extending to the central cavity; a closure ball rotatably mounted in the central cavity; and a seating ring in sealing engagement with the valve body and the ball at the inner end of one of the flow passages for preventing the flow of fluid between the valve body and the ball, the seating ring having an annular surface in sliding and sealing contact with the ball, a first surface which spans the gap between the inner end of the associated flow passage and the annular surface and which includes a first recessed portion, and a second surface which spans the gap between the wall of the central cavity and the annular surface and which includes a second recessed portion, the arrangement being such that the first recessed portion extends radially outwardly from the axis of the associated flow passage beyond the radially innermost extremity of the annular surface and the second recessed portion extends axially outwardly along the direction of the axis of the associated flow passage beyond the axially innermost extremity of the annular surface whereby the recessed portions can accommodate elastic deformation of the material defining the seating ring.

The provision of the recessed portions enables the material defining the annular surface to expand elastically when the seating ring is heated, and thus no extrusion of this material takes place.

Further, the recessed portions increase the flexibility of the part of the ring on which the annular surface is defined, and thereby allow the annular surface to ac accommodate slight variations in the ball.

The invention will be better understood from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawing, wherein the single Figure is a cross-sectional view of part of a ball valve, taken in a plane perpendicular to the axis of rotation of the plug.

The ball valve 1 shown in the drawing comprises a valve body 2 and a generally spherical plug or ball 3 rotatably mounted in a central cavity 4 defined by the valve body. The body 2 comprises a central portion 5 and end members 6, only one of which is shown. The end members each define a flow passage 7 in the valve body, and the ball is provided with a through passage 8 which may, by rotation of the ball, be brought into register with the flow passages 7 at opposite ends of the body to open the valve to fluid flow. A seat 9 is provided at the inner end of each flow passage 7 in sealing engagement with the body 2 and the ball 3 to prevent the controlled fluid from passing through the gap between the ball and the body at this point.

The seat 9 comprises a body portion 10 and an external seal portion 11 integral with the body portion and positioned in sealing contact with the central portion 5 and the end member 6 of the valve body. The external seal portion 11 provides a fluid tight seal between the seat 9 and the body 2, and also seals the joint between the central portion 5 and end member 6 of the body.

The body portion 10 of the seat 9 includes annular surface portion 12 of part spherical shape which slidingly engages the ball 3 to provide a fluid tight seal between the seat and the ball. First and second surfaces 13, 14 extend respectively from opposite sides of the annular surface to the adjacent surfaces 15, 16 of the valve body, the surface 15 being the wall of the flow passage 7 and the surface 16 being the wall of the central cavity 4.

The first surface 13 spans the gap between the inner end of the associated flow passage 7 and the annular surface 12 and is formed by a generally cylindrical surface portion and a recessed surface portion 17. The radial extent of the recessed portion 17, relative to the axis of the flow passage 7, is such that the recessed portion 17 extends radially outwardly beyond the radially innermost extremity of the annular surface 12.

The second surface 14 is formed by a generally planar surface portion and a second recessed portion 18. The axial extent of the recessed portion 18, relative to the axis of the flow passage 7, is such that the recessed portion 18 extends axially outwardly beyond the axially innermost extremeity of the annular surface 12.

The first and second recessed portions 17, 18, are formed as continuous annular grooves.

The grooves 17, 18 allow the material defined between the grooves and the first surface portion 12 to deform elastically when the valve is heated, and therefore avoid the extrusion of the seat which would result if the material of the seat could not expand elastically.

The face of the seat adjacent the end member 6 is provided with a large groove 19 which, with the grooves 18, defines a narrow bridge 20 of material which flexibly connects the radially inner part of the seat body to the remainer of the seat. The seat is sized such that when the seat is in use on the upstream side of the ball fluid from the flow passage 7 can enter the groove 19 by passing between the radially inner part of the seat body and the adjacent end member. Because of the pressure differential which, in use, exists between the flow passage 7 and the central cavity 4, the fluid in groove 19- will tend to force the first surface portion 12 firmly into contact with the ball. This pressure loading effect is particularly marked on the upstream side of the ball when the valve is closed.

When the seat is located on the downstream side of the ball of a valve, the load applied to the seat by the ball is transmitted to the adjacent end member 6 by an annulus of solid material of thickness "A". The seat is thus suitable for use at both upstream and downstream ends of a valve, and a valve may be provided with identical seats at both ends.

The above described seat construction is particularly intended for seats made of PTFE but may, of course, be used for seats made of other materials.

WHAT WE CLAIM IS:- 1. A ball valve comprising: a valve body defining a central cavity and flow passages extending to the central cavity; a closure ball rotatably mounted in the central cavity; and a seating ring in sealing engagement with the valve body and the ball at the inner end of one of the flow passages for preventing the flow of fluid between the valve body and the ball, the seating ring having an annular surface in sliding and sealing contact with the ball, a first surface which spans the gap between the inner end of the associated flow passage and the annular surface and which includes a first recessed portion, and a second surface which spans the gap between the wall of the central

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. accommodate slight variations in the ball. The invention will be better understood from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawing, wherein the single Figure is a cross-sectional view of part of a ball valve, taken in a plane perpendicular to the axis of rotation of the plug. The ball valve 1 shown in the drawing comprises a valve body 2 and a generally spherical plug or ball 3 rotatably mounted in a central cavity 4 defined by the valve body. The body 2 comprises a central portion 5 and end members 6, only one of which is shown. The end members each define a flow passage 7 in the valve body, and the ball is provided with a through passage 8 which may, by rotation of the ball, be brought into register with the flow passages 7 at opposite ends of the body to open the valve to fluid flow. A seat 9 is provided at the inner end of each flow passage 7 in sealing engagement with the body 2 and the ball 3 to prevent the controlled fluid from passing through the gap between the ball and the body at this point. The seat 9 comprises a body portion 10 and an external seal portion 11 integral with the body portion and positioned in sealing contact with the central portion 5 and the end member 6 of the valve body. The external seal portion 11 provides a fluid tight seal between the seat 9 and the body 2, and also seals the joint between the central portion 5 and end member 6 of the body. The body portion 10 of the seat 9 includes annular surface portion 12 of part spherical shape which slidingly engages the ball 3 to provide a fluid tight seal between the seat and the ball. First and second surfaces 13, 14 extend respectively from opposite sides of the annular surface to the adjacent surfaces 15, 16 of the valve body, the surface 15 being the wall of the flow passage 7 and the surface 16 being the wall of the central cavity 4. The first surface 13 spans the gap between the inner end of the associated flow passage 7 and the annular surface 12 and is formed by a generally cylindrical surface portion and a recessed surface portion 17. The radial extent of the recessed portion 17, relative to the axis of the flow passage 7, is such that the recessed portion 17 extends radially outwardly beyond the radially innermost extremity of the annular surface 12. The second surface 14 is formed by a generally planar surface portion and a second recessed portion 18. The axial extent of the recessed portion 18, relative to the axis of the flow passage 7, is such that the recessed portion 18 extends axially outwardly beyond the axially innermost extremeity of the annular surface 12. The first and second recessed portions 17, 18, are formed as continuous annular grooves. The grooves 17, 18 allow the material defined between the grooves and the first surface portion 12 to deform elastically when the valve is heated, and therefore avoid the extrusion of the seat which would result if the material of the seat could not expand elastically. The face of the seat adjacent the end member 6 is provided with a large groove 19 which, with the grooves 18, defines a narrow bridge 20 of material which flexibly connects the radially inner part of the seat body to the remainer of the seat. The seat is sized such that when the seat is in use on the upstream side of the ball fluid from the flow passage 7 can enter the groove 19 by passing between the radially inner part of the seat body and the adjacent end member. Because of the pressure differential which, in use, exists between the flow passage 7 and the central cavity 4, the fluid in groove 19- will tend to force the first surface portion 12 firmly into contact with the ball. This pressure loading effect is particularly marked on the upstream side of the ball when the valve is closed. When the seat is located on the downstream side of the ball of a valve, the load applied to the seat by the ball is transmitted to the adjacent end member 6 by an annulus of solid material of thickness "A". The seat is thus suitable for use at both upstream and downstream ends of a valve, and a valve may be provided with identical seats at both ends. The above described seat construction is particularly intended for seats made of PTFE but may, of course, be used for seats made of other materials. WHAT WE CLAIM IS:-

1. A ball valve comprising: a valve body defining a central cavity and flow passages extending to the central cavity; a closure ball rotatably mounted in the central cavity; and a seating ring in sealing engagement with the valve body and the ball at the inner end of one of the flow passages for preventing the flow of fluid between the valve body and the ball, the seating ring having an annular surface in sliding and sealing contact with the ball, a first surface which spans the gap between the inner end of the associated flow passage and the annular surface and which includes a first recessed portion, and a second surface which spans the gap between the wall of the central

cavity and the annular surface and which includes a second recessed portion, the arrangement being such that the first recesed portion extends radially outwardly from the axis of the associated flow passage beyond the radially innermost extremity of the annular surface and the second recessed portion extends axially outwardly along the diretcion of the axis of the associated flow passage beyond the axially innermost extremity of the annular surface whereby the recessed portions can accommodate elastic deformation of the material defining the seating ring.

2. A ball valve according to claim 1 wherein the first surface includes a generally cylindrical surface, the first recessed portion being formed as an annular groove in the cylindrical surface.

3. A ball valve according to claim 1 or claim 2 wherein the second surface includes a generally planar portion at one end of the seating ring, the second recessed portion being provided as an annuar groove formed in the planar surface.

4. A ball valve according to claim wherein a further annular groove is formed in the opposite end of the seating ring to form with the groove in the planar surface a bridge of material which flexibly connects relatively rigid radially inner and outer portions d the body, the radially inner portion including the annular surface.

5. A ball valve according to claim 4 wherein the radially inner portion includes an annular region of solid material extending through the entire thickness of the ring for supporting axial thrust loads which, in use, are applied to the ring.

6. A ball valve according to any preceding claim wherein the seating ring includes an annular seal flange which is clamped between body members of the valve to seal the joint between the body members and to seal between the seating ring and the valve body.

7. A ball valve according to any preceding claim wherein the seating ring is an integral moulding.

8. A ball valve, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.