WO1993023692A1

WO1993023692A1 - Valve member and ball valve

Info

Publication number: WO1993023692A1
Application number: PCT/NO1993/000075
Authority: WO
Inventors: Knut V. Horvei
Original assignee: Den Norske Stats Oljeselskap AS
Current assignee: Equinor ASA
Priority date: 1992-05-13
Filing date: 1993-05-11
Publication date: 1993-11-25
Anticipated expiration: 1994-11-13
Also published as: NO921881L; NO175398C; AU4092493A; NO921881D0; NO175398B

Abstract

Valve member for a ball valve, in particular a large ball valve for use in oil and gas installations for offshore production, of the kind comprising a rotatable valve member (2) having a through passage (6), two moveable seat or seal holders (8, 9) and means (11, 12) for moving the holders (8, 9) in a direction towards and from cooperating portions of the valve member. Three main parts (6, 21, 22) of the valve member are made of a tubular material being in principle of the same diameter, and one main part being in the form of a tube section (6) which forms said through passage. The other two main parts (21, 22) are joined to said one main part (6) at diametrically opposite sides thereof so that the axes of the three main parts intersect at the rotational axis (20) of the valve member and extend at right angles thereto. The free ends of the three main parts (6, 21, 22) are designed with said cooperating portions (6A, 21A, 22A), lie in planes forming a right angle to their respective axes and have approximately the same distance from the rotational axis (20).

Description

VALVE MEMBER AND BALL VALVE

This invention relates to a valve member for a modified ball valve, in particular a large ball valve for use in oil and gas installations for offshore production. Valves of actual interest here are valves of the kind comprising a rotatable valve member with a through flow passage, two moveable seat or seal holders and means for moving the hol¬ ders in directions towards and/or from cooperating parts of the valve member. The invention can be regarded as a further development or modification of a valve structure being proposed in Norwe¬ gian Patent Application No. 91.2763 of 12.07.91, and is directed in particular to a composition of valve members which does not involve casting and machining of large work pieces, as is required in the case of such conventional valve balls.

Previously known are corresponding valves having valve members or balls composed of individual parts which can be welded together into a unitary structure. Examples may be found in Norwegian Patent 134.670, GB 1.214.404, GB 1.315.- 942, GB 1.344.606 as well as DE 1.814.881 and DE 2.628.645. However, none of these known designs comprises means for providing an active movement of seat or seal holders, which is an essential condition in connection with the present invention. Moreover, it is evident that the valve member designs shown make these in principle equivalent to conven¬ tional valve balls for ball valves.

Compared to the known designs mentioned above, the present invention represents a substantial modification and improvement, whereby in addition to the novel and specific valve member, the invention also comprises a modified form of ball valve based upon the employment of this valve member.

The novel and specific features of the valve member and the modified ball valve respectively, according to the inven- tion, taking as a starting point what is stated in the above introduction, is defined more closely in the appended claims. The invention results in a substantially simplified and more lightweight, but at the same time mechanically strong, structure of the valve member, the manufacture of which will also be comparatively inexpensive. In combination with a valve structure being otherwise mainly as described in the above Norwegian Patent Application No. 91. 2763, this new valve member implies a modified ball valve which, because of the actively moveable seat or seal holders, has deviated considerably from the pure ball valve principle. In the following description the invention shall be explained more closely with reference to the drawings, illus¬ trating by way of example various valve embodiments according to the invention. In the drawings: fig. 1 shows axial sections through a valve in three dif- ferent operative positions (fig.lA/fig.IB/fig.1C) , fig. 2 schematically and in partial cross-section (II fig.3) shows a valve member according to the inven¬ tion, which can be incorporated into the valve of fig. 1, and fig 3 shows a cross-section along the line III-III in fig. 2. In fig. 1 there is shown a valve housing 1 with a valve member 2 having a central, tubular through flow passage 6 with an axis 10. Fig. 1A shows the valve member 2 in closed position, i.e. with the axis of the flow passage running vertically in the figure. Figs. IB and 1C show the valve in an open posi¬ tion, i.e. with the axis 10 horizontal. Fig. IB shows a seat or seal holder 8 in retracted position, whereas the holder 9 in fig. 1A and holder 8 in fig. 1C are moved forward into cooperating and sealing positions against valve member 2.

Thus, as in Norwegian Patent Application 91.2763 holders 8 and 9 are adapted to be moved in a direction towards valve member 2, which can for example take place by means of hyd- raulic pressure against piston areas 11 and 12 respectively on the two holders. Corresponding opposite piston areas can serve for an oppositely directed movement or displacement. Conduits for supplying hydraulic pressure have been omitted in the drawing. As in previously known designs there may also be provided springs for exerting a permanent biassing force on the seat or seal holders.

Fig. 1 further shows details with respect to the mount¬ ing of holders 8 and 9 in valve housing 1, namely by means of a retainer ring 8A and 9A respectively and a locking ring 8B and 9B respectively.

The term seat or seal holders is used here because these holders as the case may be can be designed without any seal¬ ing or gasket elements, since according to the circumstances such elements can be mounted on cooperating surfaces or portions of the actual valve member.

In the open position as illustrated in particular in fig. 1C, there is formed a continuous passage through the valve, i.e. between end fittings 3 and 4 at opposite ends of valve housing 1, incorporating the flow passage 6 through valve member 2, and holders 8 and 9 which have internal confining surfaces generally flush with the remaining inter¬ nal passage cross-section, so that through-flow of media in question through the valve in open position, can take place with a minimum of hindrance.

The specific structure of valve member 2 is seen in particular from figs. 2 and 3. These show in the first place one main part in the form of a tube section 6 serving to form the flow-through passage in the open position of the valve, as illustrated in particular in fig. 1C. In this connection it is pointed out that figs. 2 and 3 show the main structural features, whereby for example the particular design of seal¬ ing surfaces at the free ends of the valve member main parts, are not shown in these figures. Two further main parts 21 and 22 are also made of tubu¬ lar material having in principle the same diameter as tube section 6 and are joined thereto at diametrically opposite sides, as will appear from figs. 2 and 3. In fig. 3, how¬ ever, the main part 22 has been shown somewhat separated from tube section 6 i.e. before being joined thereto.

The common axis 30 of the two smaller main parts 21 and 22 extends at a right angle to axis 10 of tube section 6, and the two axes intersect at the rotational axis 20 of valve member 2, as also indicated in fig. 1. The free ends of the three main parts, which in fig. 1 are denoted 6A, 21A and 22A respectively, lie in planes being normal to their respective axes 10 and 30. Moveover, it will be realized that these end planes advantageously are located at approximately the same distance from the rotational axis 20.

For the journaling and turning of valve member 2 the same is provided with trunnions 25 and 26, at the bottom and on top respectively (fig. 3), and an associated spindle 27. The above fundamental geometry of valve member 2 as illustrated in particular in figs. 2 and 3, involves the cutting of both tubular main parts 21 and 22 with contours which preferably will tightly engage with the cylindrical surface of tube section or main part 6. In view of the wall thickness of the tubular main parts 21 and 22 the surfaces of engagement facing tube section 6 will be relatively wide at the portions being at the largest distance from the free ends of these main parts. For main part 22 these contours are shown at 22B and 22C respectively in fig. 2. Circular por¬ tions must also be cut out for the two trunnions 25 and 26. For main part 21 corresponding weld seams are shown at 2IB and 21C respectively.

With such a structure the exterior cylindrical surface of tube section 6 will form a tightly closed bottom in either of the additional two main parts 21 and 22. In the closed position of the valve (fig. 1A) this results in a sealed closing of the valve against through-flow.

When all parts forming valve member 2 are welded to¬ gether, they are machined in order to be mated to correspond¬ ing parts and portions of valve housing 1, including the gasket system employed and the design of cooperating sealing parts on holders 8 and 9 as shown in fig. 1.

From the above and from the illustrations in the draw¬ ings it is further noted that the distances between the pairs of opposite free ends of valve member 2 preferably are some-^* what larger, but only a little larger, than the outer dia¬ meter of the tubular main parts 6, 21 and 22. This will be favourable inter alia with respect to the total dimensions of the valve and valve housing 1. The seat or seal holders 8 and 9 each have a forward portion provided with a seal element adapted to cooperate with suitably shaped sealing surfaces on valve member 2, in the closed and open positions respectively of the valve. As to holder 8 there is shown a forward portion 17 having an exterior conical and annular seal element 18 for the purpose of establishing a sealing effect. The free end of one main part in the form of tube section 6 as shown at 6A in fig. l has a corresponding annular and at least partially conical sealing surface 6AC, which in fig. 1C has been shown in engagement with seal element 18 on holder 8. This estab¬ lishes the open position of the valve.

Main parts 21 and 22 of valve member 2 have annular sealing surfaces 21AC and 22AC respectively, shaped in prin- ciple in a corresponding way as the above sealing surface

6AC, so as to be active in the closed position of the valve (fig. 1A) .

As also seen in fig. 1 in closed position and open position respectively of the valve, the inactive sealing surfaces in the valve position concerned, will be isolated from the media in the pipelines being connected to the valve, so that the sealing portions or surfaces being at any time inactive, will not be contaminated or subjected to any other detrimental effect from the media. It will be realized that when for example holder 8 is urged (to the left in fig. 1) against valve member 2, there may be generated a quite significant sealing pressure between the cooperating conical surfaces 18 and 6AC (fig. IB) , so that the desired sealing effect is obtained also under diffi- cult conditions and at high pressures of the flowing media.

In this connection it may be very advantageous to arrange for the holder to be self-locking in relation to the valve member in this position, subsequent to being placed against the valve member with a given force, for example generated by the hydraulic system mentioned above. For the purpose of such a self-locking effect it is practical to adjust the conicity of the sealing surfaces, the surface finish and the choice of material in the cooperating parts, so that sufficient fric¬ tion is obtained between surfaces 18 and 6AC. This means that an oppositely directed, for example hydraulic, force must be employed for removing the sealing effect, i.e. by re¬ tracting holder 8 (to the right in fig. 1C) from valve member 2 for example in order to turn it to the closed position. As illustrated in fig. 1A in the embodiment shown, there is a certain difference between the dimensions of the more or less axially facing end surfaces of holder 9 (and correspond¬ ingly at holder 8) . The difference can be regarded as repre¬ sented by a radius difference indicated at 9F in the fig. of drawings. A medium pressure PI, for example of oil or gas, accordingly will exert a nett axial force component on holder 9 directed towards valve member 2, provided that the pressure P2 in valve housing 1 is lower than the medium pressure P2. In the embodiment shown the conical seal element 18 on holders 8 and 9 is facing outwardly, with corresponding inwardly facing sealing surfaces 6AC, 21A and 22AC on valve member 2. It is obvious that the relationships could be reversed with respect to this mutual orientation of the cooperating sealing surfaces and parts. Moreover, these can be provided with separate gasket elements, either on the holders or on the valve member. Besides, other variants and modifications of the cooperating sealing means in such a valve can be contemplated.

Claims

C l a i m s

1. Valve member for a ball valve, in particular a large ball valve for use in oil and gas installations for offshore production, of the kind comprising a rotatable valve member (2) with a through flow passage (6) , two moveable seat or seal holders (8,9) and means (11,12) for moving the holders (8,9) in directions towards and/or from cooperating parts of the valve member, c h a r a c t e r i z e d in - that three main parts (6,21,22) of the valve member are made of tubular material having in principle the same dia¬ meter, whereby one main part is in the form of a tube section (6) which forms said passage, and that the two other main parts (21,22) are joined to said one main part (6) at diametrically opposite sides thereof so that the axes (10,30) of the three main parts intersect at the rotational axis (20) of the valve member and extend at a right angle thereto, and that the free ends of the three main parts (6,21,22) are provided with said cooperating parts (6A,21A,22A) , lie in planes being normal to their respective axes (10,30) and have approximately the same distance from the rotational axis (20).

2. Valve member according to claim 1, c h a r a c t e r i z e d in that adjacent cylindrical and external surface portions of said one main part (6) form a closed bottom for each of the other main parts (21,22).

3. Valve member according to claim 1 or 2, c h a r a c t e r i z e d in that the distance between the free ends (21A,22A) of the two other main parts, is app¬ roximately equal to the length of said one main part (6) between the free ends thereof.

4. Valve member according to claim 3, c h a r a c t e r i z e d in that said distance is somewhat larger than the outer diameter of the main parts (6,21,22).

5. Valve member according to claims 1-4, c h a r a c t e r i z e d in that the three main parts (6,21- ,22) are joined by welding.

6. Ball valve provided with a valve member according to any one of claims 1-5, c h a r a c t e r i z e d in that the free ends of one main part (6) has an annular and at least partially conical sealing surface (6AC) that a forward portion (17) of each seat or seal holder (8) has an annular seal element (18) adapted to cooperate with the sealing surface (6AC) of said one main part (6) in the open position of the valve, and that an annular sealing surface (21AC,22AC) shaped in principle corresponding to said sealing surface (6AC) , is formed at the free ends (21A,22A) of the two other main parts (21,22) for cooperation with the seal element (18) on each holder (8) in the closed position of the valve.

7. Ball valve according to claim 6, c h a r a c t e r i z e d in that said sealing surfaces (6AC,21AC,22AC) and the seal element (18) of the holders have such mutually adapted shape and/or material composition and/or surface finish that the holder (8) will be self-lock¬ ing in relation to the valve member subsequent to being pressed against the valve member with a certain minimum force.

8. Ball valve according to claim 6 or 7, c h a r a c t e r i z e d in that the seal element (18) of the holders is so designed that adjacent end surfaces adapted to be influenced in axial direction by medium pressure, for example oil or gas, in or on the valve, are smaller than oppositely facing end surfaces in particular at the other end of each holder (8,9), whereby said medium pressure contri¬ butes to an enhanced sealing effect.