GB2539268A

GB2539268A - Method of assembling a ball valve housing

Info

Publication number: GB2539268A
Application number: GB1510321.1A
Authority: GB
Inventors: Gough Mark
Original assignee: HEAP & PARTNERS Ltd
Current assignee: HEAP & PARTNERS Ltd
Priority date: 2015-06-12
Filing date: 2015-06-12
Publication date: 2016-12-14
Also published as: GB201510321D0

Abstract

A method of assembling a ball valve housing comprises providing a valve body member 35 having a recess for receiving a valve seat. The recess has a first portion 37 with a first radial depth and a second portion 39 with a second greater radial depth, and a shoulder 45 between the first and second portions. The method further comprises selecting either a hard valve seat (48, Fig. 2a) comprising a sleeve member arranged to correspond to the first portion 37 of the recess, or a soft valve seat 43 comprising a sleeve member arranged to correspond to both first and second portions 37, 39 of the recess and carrying an elastic sealing member (44, Fig. 3a). The appropriate valve seat is then fitted into the recess.

Description

Method of Assembling a Ball Valve Housing This invention relates to ball valves, and in particular to a method of assembling a ball valve housing.

Ball valves are commonly used as flow valves in industries such as the chemical and petrochemical industries. In such a valve, a valve ball is rotatably mounted in a housing comprising a valve body having a flow channel. The ball can be rotated between a position in which it provides a barrier to flow, and a position in which a bore through the ball is aligned with the flow channel. A valve seat provides a seal at the interface between the ball and the flow channel opening in order to prevent leakage of fluid past the ball. The seat can be provided by an insert located in a recess formed at the opening of the flow channel.

In some applications the valve seat may be a relatively thin hard sleeve, commonly of metal, depending upon the properties of the fluid with which the valve is to be used and upon the amount of leakage which is acceptable. However other applications require a tighter seal, such as can be achieved with a softer material such as a plastics material. In this case the valve seat may be a composite part comprising a metal sleeve mounting an annular soft seal. Such a 'soft' seat may be thicker than the 'hard' seat, at least at the sealing end of the part, and therefore a larger recess in the valve body is required to house the 'soft' seat.

Thus it has been the case that ball valves requiring different seals have required valve bodies having different configurations.

According to the present invention, there is provided a method of assembling a ball valve housing comprising: providing a valve body member having a flow channel and a recess at the opening of the flow channel for receiving a valve seat, the recess comprising a first distal portion having a first radial depth and a second proximal portion having a second greater radial depth, and a shoulder between the first and second portions; selecting either a hard valve seat comprising a sleeve member arranged to fit closely within the first portion of the recess, or a soft valve seat comprising a sleeve member arranged to fit closely within both the first and the second portions of the recess and mounting a resilient sealing member; and fitting the valve seat into the recess.

Since either type of valve seat may be fitted to the same valve body, either type of valve may be provided using the same valve body parts. The valve seat member may be either a hard seat or a soft seat, since the second wider portion of the recess is able to accommodate the necessary increased width of the sealing end of the soft seat.

The hard seat and the soft seat are preferably arranged to extend out of the opening of the flow channel, so as to form a seal against a valve ball in an assembled ball valve. The soft seat may have a mounting part having a radial thickness corresponding with the depth of the first portion of the recess, and a wider seal part having a radial thickness corresponding to the depth of the second portion of the recess. The wider part preferably mounts a relatively elastic seal member on an end face thereof The hard seat may also have a mounting part having a radial width substantially corresponding to the depth of the first portion of the recess, and the sealing end may be of substantially the same width, such that a gap is formed between the hard seat member and the second portion of the recess.

The valve seat member, and in particular the hard seat member, preferably comprises a seal groove in the outer surface of the mounting part, and a seal member in the groove for providing a seal between the seat and the first portion of the recess of the flow channel. The groove is arranged to be closely adjacent the shoulder of the recess when the seat is received therein, allowing for manufacturing tolerances. For example, the groove may be arranged to be between about 1 mm and 10 mm away from the shoulder, preferably between 5 mm and 8 mm, with an example being about 6 mm. The distance between the groove and the sealing end of the valve seat may thus be as small as possible; likely about 20-30 mm, but possibly 10-20 mm, a typical example being 27 mm.

A ball valve may be provided by assembling the valve body with a valve ball mounted adjacent the opening and rotatable between valve open and valve closed positions to control the flow, such that the valve seat extends between the opening and the valve ball. For example, the valve ball may be mounted between two opposed valve bodies, which may be attached together.

In order that the invention may be more readily understood, reference will now be made, by 5 way of example, to the accompanying drawings, in which: Figure 1 is a cross-sectional side view of a ball valve according to the prior art; Figure la is an enlarged view of part of the valve of Figure 1; Figure 2 is a cross-sectional side view of a ball valve according to one embodiment of the present invention including a hard valve seat; Figure 2a is an enlarged view of part of the valve of Figure 2; Figure 3 is a cross-sectional side view of a ball valve according to one embodiment of the present invention including a soft valve seat; and Figure 3a is an enlarged view of part of the valve of Figure 3.

Referring to Figures 1 and la, the ball valve 2 comprises a valve housing 4, which is formed in two valve body parts 6, 8 for ease of assembly. The body parts 6, 8 each included a flow channel 10, 12, which are aligned to form a flow passage through the housing. A valve ball 14 provides a valve member for opening and closing the valve. The ball 14 includes a bore 16 extending therethrough, and is mounted for rotation in the flow passage such that the bore 16 may be aligned with the channels 10, 12 in the open position of the valve, as shown in the figure, or may block the channels in a closed position of the valve, when the ball 14 is rotated through 90 degrees about an actuation axis 18. An actuating handle 20 is provided for operating the valve.

The valve is essentially symmetrical, so the structure on one side only will be referred to in the following description for ease of reference. The channel 10 has an opening 22 adjacent the ball 14, provided with a valve seat member 24. The seat 24 is sleeve shaped, and is mounted in a recess 26 of the body, which is formed as a widened portion of the channel 10, so that the seat extends out of the opening towards the ball 14. The recess 26 has a radial width substantially corresponding to the width of the seat 24, and may also contain a seat follower 28 and a spring 30 housed in a spring carrier 32 so as to bias the seat 24 into contact with the ball 14 along a sealing end surface 34 of the seat 24. The valve seat 24 also includes a groove 25 located in the axial outer surface thereof for receiving a sealing member such as an 'o' ring seal 27. The groove 25 is arranged to be located as close as possible to the opening 22 in the channel 10, allowing for manufacturing tolerances.

The valve seat 24 is suitably formed of a strong hard material such as a metal. However for certain applications a relatively more elastic or resilient sealing surface is required. Thus a softer material may be provided on the sealing end surface 34, for example by providing an annular groove in the end surface into which a resilient material such as PTFE is fitted. However in order to provided sufficient rigidity to the seat whilst also providing a sufficiently large sealing area, a greater width is required at the sealing surface of the 'soft' seat than for a hard' seat. The 'soft' seat has therefore required a larger recess in the valve body to accommodate it.

Figure 3 shows a ball valve formed according to the invention having a soft seat 36. The soft seat 36 has a mounting portion 38 similar to the hard seat. However, the sealing end portion of the soft seat is wider in the radial direction than the mounting portion. The end portion includes an annular depression 42 formed in the sealing surface of the seat and extending in an axial direction. The depression 42 houses a relatively soft sealing material 44 for sealing against the ball 46.

In order to accommodate the greater width of the soft seat required for mounting the soft seal, in the valve body 35 of the invention, the recess 37 has a second portion 39, proximal the opening 42 of the flow channel 44, which is wider in the radial direction than the first portion 41 of the recess, distal from the opening. The valve body 35 is otherwise substantially as shown in figure 1.

Figure 2 shows the same valve body 35 with a hard valve seat 48 according to the invention. The hard seat 48 is similar to the soft seat 36 of the invention, except that it does not have a wider end portion, as the end surface 49 of the hard seat forms a hard seal surface. The seal groove 50 is provided further away from the end surface 49 because of the widened portion 39 of the recess. The seal groove 50 is therefore arranged to be as close as possible to the shoulder 45 between the first portion 41 and the second portion 39 of the recess 37.

Surprisingly, it has been found that the valve body and the hard and soft seats can be configured such that both seats perform to an adequate standard when placed in the same valve body having a two part recess, even though this leads to the hard seat having a greater unsupported length, and a seal groove further away from the flow channel opening. With this arrangement, the valve may be provided with a hard or soft seat according to requirements without providing a different valve body structure. This has the advantage of simplifying manufacture and stock of the valve body.

Claims

Claims 1. A method of assembling a ball valve housing comprising: providing a valve body member having a flow channel and a recess at the opening of the flow channel for receiving a valve seat, the recess comprising a first portion having a first radial depth and a second portion having a second greater radial depth, and a shoulder between the first and second portions; selecting either a hard valve seat comprising a sleeve member arranged to correspond to the first portion of the recess, or a soft valve seat comprising a sleeve member arranged to correspond to both the first and the second portion of the recess and mounting an elastic sealing member; and fitting the valve seat into the recess.
2. A method as claimed in claim 1, in which the soft seat has a mounting part having a radial thickness corresponding with the depth of the first portion of the recess, and a wider seal part having a radial thickness corresponding to the depth of the second portion of the recess and being arranged to extend out of the opening, and mounting an elastic seal member.
3. A method as claimed in claim 1 or 2, in which the hard seat has a mounting part having a radial width substantially corresponding to the depth of the first portion of the recess, and a sealing end of substantially the same width, and arranged to form a gap between the hard seat member and the second portion of the recess.
4. A method as claimed in claim 1, 2 or 3, in which at least the hard valve seat member comprises a seal groove in the outer surface of the mounting part, and a seal member in the groove for providing a seal between the seat and the first portion of the recess of the flow channel, the groove arranged to be closely adjacent the shoulder of the recess when the seat s received therein.
5. A method as claimed in claim 4, in which the groove is between about 10 mm and mm from the sealing end of the seat.
6. A method of assembling a ball valve comprising assembling a valve housing according to the method as claimed in any preceding claim, and assembling the valve body with a valve ball mounted adjacent the opening and rotatable between valve open and valve closed positions to control the flow, such that the valve seat extends between the opening and the valve ball.
7. A valve seat for a ball valve comprising a sleeve member having a substantially constant cross section, and a seal groove provided in an outer surface thereof, the groove being between about 1 mm and 10 mm from the sealing end of the sleeve.
8. A valve seat as claimed in claim 7, in which the cross sectional width of the sleeve is between about 2 mm and 70 mm.
9. A ball valve made by the method as claimed in any one of claims 1 to 6.
10. A method of assembling a ball valve substantially as described herein, with reference to Figures 2, 2a, 3 and 3a of the accompanying drawings.
11 A ball valve substantially as described herein, with reference to Figures 2, 2a, 3 and 3a of the accompanying drawings.
12. A valve seat for a ball valve substantially as described herein, with reference to Figures 2, 2a, 3 and 3a of the accompanying drawings.