GB2344152A

GB2344152A - Cylindrical plug valve seat

Info

Publication number: GB2344152A
Application number: GB9923806A
Authority: GB
Inventors: Keith Crawford
Original assignee: Pacson Ltd
Current assignee: Pacson Ltd
Priority date: 1998-11-28
Filing date: 1999-10-11
Publication date: 2000-05-31
Anticipated expiration: 2019-10-11
Also published as: GB9923806D0; GB9826027D0; GB2344152B

Abstract

A valve comprises a cylindrical valve member 11 having a hole 12 extending through it and which can be turned, preferably by a rotating mechanism (13 figure 1). Valve seats 14 engage the valve member at respective ends of the hole in a fluid sealing manner. The seats preferably comprise a boss having a through hole (19) and a profiled seating surface (17), which is preferably resilient, and is free to move along an axis perpendicular to the axis of the valve member. The flexibility of the valve seat is preferably influenced by slots or cut outs formed internally or externally of the valve seat. The slots or cut outs may be tapered to give the seats more stiffness at the lateral edges. The seats may be held against the valve member by springs 20 and seals 21.

Description

"Valve Apparats" The present invention relates to a valve apparatus, and in particular to a valve apparatus for use in high pressure and arduous environments.

Conventional valve apparatus includes a metal sealing ball valve which comprises a ball adapted to have a hole through it. When the hole in the ball is in the correct orientation (ie. lined up with the pipes), fluid can pass through the valve. In the same respect, when the ball is turned in such a way that the hole through the ball is not lined up with the pipes, no fluid will pass through the valve. The valve is sealed by having a high surface finish on both the ball and two seats, which are attached to the ends of each of the pipes. The disadvantage of this type of valve is that the seats are flat and only a small amount of the seats are finished in such a way as to create a seal between the ball and the seats. Also, the rotary action of the valve tends to cause small particles to be dragged across the seat, thus reducing the life of the valve.

Another conventional type of valve assembly is a conduit gate valve which consists of a solid rectangular slab of metal located between two seats.

Valve operation is achieved by producing linear travel of the rectangular solid slab. The slab has a hole located towards one end of the slab and this can be lined up with the seats to allow fluid to flow. When the slab is moved in the opposite direction, the solid surface of the slab is lined up with the seats thus closing the valve. The valve is sealed by achieving a high surface finish on both the slab and the seats and because both the slab and the seats are flat, sealing is achieved over the whole seat width. Also, because the slab and seats are flat, during operation, solid particles tend to be wiped off the slab as it travels between the seats, thus increasing the operational life of the valve. However, the linear movement is not always desirable due to increased space requirements and premature valve failure caused by the gate cavity filling with solids thus preventing the slab from travelling to the fully open or fully closed positions.

According to the present invention, there is provided a valve assembly comprising: a cylindrical valve member having a cylindrical hole extending through the valve member; a valve member rotating means adapted to turn the valve member about the axis of said cylindrical valve member from a valve open position to a valve closed position; first and second valve seats adapted to engage the cylindrical valve member such as to create a seal between the valve member and the first and second seats whilst still allowing the cylindrical valve member to rotate.

Preferably, said valve seats are in the form of a seat boss having a through hole and being provided with profiled seating surfaces adapted to co-operate with the external cylindrical surface of the cylindrical valve member.

Preferably, the valve seat is provided with a degree of freedom along an axis perpendicular to the axis of the cylindrical valve member.

Preferably, said profiled seating surfaces are resilient to permit flexing of the valve seats to closely engage the external surface of the valve member.

Preferably, the valve seats are provided with means for influencing the flexibility of the valve seat.

Preferably, said means for influencing the flexibility of the valve seat includes slots and/or cut outs formed internally or externally on the valve seat.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic exploded perspective view of the present invention; Fig. 2 is a cross-sectional plan view of one embodiment of the present invention, the valve being in the closed position; Fig. 3 is an end view of the embodiment of Fig. 2, the valve being in the open position; and Figs. 4,5,6,7 and 8 are cross-sectional plan views of the present invention, the valve being in the closed position and illustrating alternative means for influencing the flexibility of valve seats.

Referring to the drawings, there is illustrated a valve assembly 10 comprising a cylindrical valve member 11 made from extruded metal having a high surface finish.

A hole 12 is machined diametrically through the width of the valve member 11.

The valve member 11 is attached to a rotating means 13 in the form of a drive shaft connected to the valve member to turn the valve member 11 about its longitudinal axis. The rotating mechanism 13 can be rotated either by hand via a lever 23 or by other drive means (not shown).

The valve assembly 10 also includes first and second valve seats 14 and 15 respectively. In this embodiment, the two valve seats 14 and 15 are substantially the same as one another. The valve seats 14 and 15 have valve member seating surfaces 16 and 17 respectively which have high surface finishes and a contour which matches that of the cylindrical valve member 11. The valve seats 14 and 15 also have through flow holes 18 and 19 respectively.

The flow holes 18 and 19 have diameters of similar dimension as the diameter of the hole 12.

The high surface finishes on both the valve member 11 and the contact surfaces 16 and 17 of the valve seats 14 and 15 provide a seal between the valve member 11 and the valve seats 14 and 15 when the valve seats are held against the valve member 11. The valve seats 14 and 15 are held against the valve member 11 by means of springs 20 and seals, in the form of energised lip seals 21 or variable area seals 24 (as shown in Fig.

4). The springs 20 being held by a valve body 22 which encases the valve assembly 10.

The contoured shape of the valve seats 14 and 15 allows the seats 14 and 15 to flex slightly around their respective vertical axes, being parallel to the axis of the cylindrical valve member thus compensating for any tolerance introduced during the manufacture of the surface finish of either the valve member 11 or the valve seats 14 and 15.

Referring to Fig. 5, in order to influence this flexibility, the valve seats 14 and 15 are provided with radial slots 25 on the top and bottom rear edges of the valve seats 14 and 15.

Referring to Figs. 6 and 7, internal and external circumferential grooves 26 and 27 respectively may be provided on the valve seats 14 and 15, also to increase the flexibility of the valve seats 14 and 15. Said internal and external circumferential grooves 26 and 27 may be tapered (as shown in Fig. 8) in such a way as to provide variable stiffness to the valve seats 14 and 15 so that the valve seats 14 and 15 have more stiffness at the lateral edges.

Modifications and improvements may be made to the foregoing within the scope of the present invention.

Claims

CLAIMS 1 A valve assembly comprising: a cylindrical valve member; a through hole extending through the valve member; valve member rotating means adapted to turn the valve member about the axis of said cylindrical valve member from a valve open position to a valve closed position; first and second valve seats adapted to engage the cylindrical valve member at respective ends of said through hole; seal means arranged to create a seal between the valve member and the first and second seats whilst still allowing the cylindrical valve member to rotate.
2 A valve assembly as claimed in Claim 1, wherein each of said valve seats is in the form of a seat boss having a through hole and being provided with profiled seating surface adapted to co-operate with the external cylindrical surface of the cylindrical valve member.
3 A valve assembly as claimed in either Claim 1 or Claim 2, wherein each valve seat is provided with a degree of freedom along an axis perpendicular to the axis of the cylindrical valve member.
4 A valve assembly as claimed in Claim 2, wherein said profiled seating surface is resilient to permit flexing of the valve seat to closely engage the external surface of the valve member.
5 A valve assembly as claimed in any preceding Claim, wherein the valve seat is provided with means for influencing the flexibility of the valve seat.
6 A valve assembly as claimed in Claim 5, wherein said means for influencing the flexibility of the valve seat includes slots and/or cut outs formed internally or externally on the valve seat.
7 A valve assembly substantially as hereinbefore described, with reference to the accompanying drawings