WO1991019921A1

WO1991019921A1 - Valve arrangement, in particular a large ball valve

Info

Publication number: WO1991019921A1
Application number: PCT/NO1991/000087
Authority: WO
Inventors: Knut Horvei
Original assignee: Den Norske Stats Oljeselskap A/S
Priority date: 1990-06-20
Filing date: 1991-06-17
Publication date: 1991-12-26
Also published as: AU7999791A

Abstract

Valve arrangement, in particular a large ball valve for use in oil and gas installations for offshore production, of the kind comprising a valve member (3) the active sealing faces (3A) of which are preferably adapted to undergo relative sliding against cooperating valve seat parts (11). The valve comprises a movable seat or seal holder (10). A front portion of the seat or seal holder (10) in association with a comparatively soft main gasket (11) is designed with a protruding edge or ridge (19) extending along the whole contour of the main gasket (11) and being directed towards the valve member (3), but having a certain, small spacing therefrom under normal sealing function provided by the main gasket (11). The protruding edge or ridge (19) upon an increase in sealing force and a movement of the seal holder (10) as a result thereof, is adapted to engage in direct and sealing contact with a cooperating surface (3A) on the valve member (3) for attaining an improved and secured sealing in the valve.

Description

VALVE ARRANGEMENT, IN PARTICULAR A LARGE BALL VALVE.

This invention relates to a valve arrangement, in particular large ball valves for use in oil and gas installations for offshore production. Such ball valves and various other common valve types, for example gate 5 valves, comprise a valve member, the active sealing faces of which may be adapted to undergo relative sliding against ^{• •} cooperating valve seat parts during valve operation, these valve seat parts being usually provided with a gasket element. Known valve designs of this kind may comprise a 0 seat or seal holder which is movable in relation to the valve member, for example under the influence of spring force.

Examples of prior art in this connection are to be found in GB patent publications Nos. 2.050.572 and 5 2.135.431, as well as application No. 34.09226.

With a movable seat or seal holder, which in addition to a spring force has a hydraulic or pneumatic system for being urged in a direction towards the valve member, it is possible to provide for a reserve or security with respect to the sealing effect. Thus,- it occurs that the seal or the main gasket in valves can fail for some reason or other. In such seals or gaskets there is often employed a comparatively soft material, such as PVC or the like, which under certain strain and in particular after exτended time may imply the possibility of leakage. One aspect of the invention is directed to a solution to safeguard against such leakage.

Accordingly, in a valve of the kind referred to above, the novel and specific features in the arrangement accor- ding to the invention consist therein that a front portion of the seat or seal holder in association with a compara¬ tively soft main gasket is designed with a protruding edge or ridge extending along the whole contour of the main gasket and being directed towards the valve member, but having a certain, small spacing therefrom under normal sealing function provided by the main gasket, and that the protruding edge or ridge upon an increase in sealing force and a movement of the seal holder as a result thereof, is adapted to engage in direct and sealing contact with a cooperating surface on the valve member for attaining an improved and secured sealing in the valve. It is particularly advantageous according to the invention to locate the protruding edge or ridge outwardly of the main gasket as seen in relation to the flow passage through the valve.

This arrangement will have the intended function irrespective of whether the main gasket is mounted'on the seat or seal holder or possibly on the movable .valve member. In both cases there is provided an auxiliary sealing element which can establish a purely metallic seal independent of or as an addition to the sealing effect of the main gasket. This comparatively soft main gasket will be pressed more or less flat when the movable seat or seal holder is urged under relatively large force against the valve member so that the protruding edge or ridge will enter into sealing engagement therewith.

In other words, the solution offered here will provide two separate sealing systems in the same valve, based on a comparatively soft sealing element respectively sealing between metal parts having a suitable hardness. This will secure tightness in all situations.

In addition to the above mentioned reserve or security effect under more or less normal conditions, the arrange- ment according to the invention will also be of specific advantage during a fire or other overheating, which can involve melting or deformation of the soft main gasket or seal.

A second aspect of the arrangement according to the invention consists therein that the seat or seal holder is provided with a piston member incorporated in a hydraulic or pneumatic system being at least adapted to move the seat or seal holder in a direction away from the valve member in order to facilitate movement thereof when a valve operation is initiated. This aspect of course is closely related to the preceding one.

A problem with valves of this kind, which have mechani¬ cally movable components and parts, is the. occurrence of collections or deposits of small particles from flowing media, in joints, cavities and chambers which communicate more or less directly with the flow passage through the valve. Especially in large valves which stand in the same position for extended times, .this can lead to significant difficulties, in the first place when the valves shall be moved or reset. Small particles and materials which gather.^:--irι joints, slits and openings or the like, after a time may harden to solid deposits which can cause damage of the valve parts concerned and perhaps in particular on gaskets in regions of relative movements during valve operation. What is novel and specific in a third aspect of the arrangement according to the invention mainly consists therein that cavities and chambers in the interior of the valve housing, in particular for a spring or springs involved in the structure, are adapted to be filled with a liquid filler mass through at least one injection, channel. Prior art being of a certain interest in this connection may be found in GB patent publications Nos. 2.073.855 and 2.130.345 as well as US patent No. 4.911.408. The filler mass referred to must be of such character and arranged in such a manner that it can easily be removed by means of an applied pressure or movement as the case may be. Nor should the mass be able to damage any parts of the valve if it enters into regions where an unfavourable effect could be possible, for example between valve ball and valve seat in a ball valve.

On the other hand it will be normal that expelling of the filler mass or material from the cavities, chambers, joints or openings to be protected, does not involve undesired contamination or damage of the medium to be transported through the valve, since according to the circumstances the filler mass may be pressed out into this flow passage.

Thus, according to a particularly preferred embodiment of this third aspect ^"of the invention, the cavities or chambers mentioned here are adapted to communicate with a flow passage through the valve, by means of at least one comparatively small orifice which is preferably adapted to lie at a high point in the filler mass system when the valve has been installed.

An additional and more advantageous embodiment consists therein that the above cavities or chambers are^' adapted to be put into communication with a flow passage through the valve, by means of a number of comparatively large openings which are normally closed with a blocking member adapted to be pressed out into the flow passage at a given increase of the pressure in the filler mass.

Other sides and advantages of the novel valve design will also be apparent from the following description.

In the following description the invention shall be explained more closely with reference to the drawings, which show an example of a ball valve intended for use in offshore oil or gas installations, where there is often a need for valves of very large dimensions.

Fig. 1 shows a simplified axial section through-^'the ball valve, Fig. 2 in partial section and enlarged shows a seat or seal ring which is incorporated in the valve of Fig. 1, and Fig. 3 in still more enlargement and in axial section shows details of the sealing between the valve ball and the housing in the valve of Fig. 1. In a common manner the ball valve of Fig. 1 comprises main parts in the form of a housing 1, a cover 2 and valve ball 3 which during valve operation is rotated by means of • 5 stem 5 which penetrates through the cover 2. As usual the valve is provided with seals, for example between housing and cover, and flanges or the like for connection to pipelines or other components in the installation concerned. With the arrow P the flow passage through the 10 valve is indicated, and Fig. 1 shows the valve in its open position.

A movable seat or seal holder 10 is provided for cooperation with active sealing ces on the ball 3, and is axially movable in relation to the ball. A seal ring 3 15 which is attached to the housing 1 by means .of bolts, serves to keep the seat or seal holder 10 in position. Details of this structure will appear better from Figs. 2 and 3.

Fig. 2 shows the holder 10 alone and without any 20 sealing elements inserted. Thus, there is only shown a groove 11A adapted to receive a main seal or gasket 11 as will be seen in Fig. 3. Radially outside the main part of the cylindrical holder 10 there is provided a piston having two oppositely facing piston areas 15A and 15B. Circu - 25 ferential grooves in the^* piston serve to receive gasket elements. Finally, in Fig. 2 there is shown an extended skirt 17 having details and functions to be explained more closely with reference to Fig. 3.

In Fig. 3 a main seal or gasket 11 is seen in sealing 30 engagement with an active sealing face 3A on the valve ball 3. ^" Thus, the holder 10 here comprises both the valve seat and the actual seal 11. A specific design of the front portion of the seal holder 10 towards the ball 3 makes it ^• possible to obtain an improved or secured sealing in the 35 valve, inter alia in the case of damage to the gasket 11, for example by fire or another accident. As appearing in particular from Fig. 3 this front portion has a protruding edge or ridge 19 which by normal valve function, i.e. wherein the main gasket 11 provides for the required sealing, has a certain small spacing from the cooperating sealing face 3A on the ball 3. The holder 10 can however by means of hydraulic pressure against piston area 15B be urged in a direction towards ball 3, so that edge or ridge 19 comes into contact with sealing face 3A and thereby provides a supplementary sealing effect which in a given situation can completely take over the sealing effect from the main gasket 11. According to usual practice the main gasket 11 will be made of a comparatively soft material, in particular when compared to the material in the holder 10 and thereby the edge 19, which normally will be of a metal, for example steel. As seen from Figs. 2 and 3 the edge or ridge 19 extends in a circle around the whole holder 10 in principle parallel to and quite near the groove for the main gasket 11. In modifications of this design the relationship between the edge or ridge 19 and the main gasket 11 can be changed, but it is preferred according to the invention that these elements have a mutual relation¬ ship substantially as illustrated in the drawing, so that both the main gasket 11 and the edge 19 can cooperate with substantially the same sealing surface 3A on the ball 3. The holder 10 is axially movable as already mentioned, and is for this purpose located in a cavity or chamber formed in the valve housing 1 itself, whereby a seal ring 8 by means of bolts 8A keeps the whole assembly in position. In order to maintain the required tightness there is shown a number of ring shaped seals or gaskets, of which for example gasket 9 seals between ring 8 and the radially outer cylindrical surface of holder 10, whereas gasket 16A in a corresponding way seals between holder 10 and the surrounding housing 1. A number of compression springs 13 provided each in a cavity 14 serve to urge holder 10 in a direction towards ball 3, so that all the time there is exerted a sealing force between main gasket 11 and sealing face 3A. Similar spring actuated seal holders are previously known per se.

An essential feature in the design consists in the double acting piston 15 having piston areas 15A and 15B respectively, of which the latter is subjected to a fluid pressure in a cylinder chamber 16 receiving hydraulic pressure through an oil channel 22. At a sufficient pressure through channel 22 holder 10 will be urged in a direction towards valve ball 3, i.e. in the same direction as compression springs 13 are acting. In order to obtain the above mentioned improvement or securing of the seal by means of edge 19, the pressure in channel 22 is thus raised in order to bring about a sufficiently large increase in the sealing force to bring edge 19 into sealing contact with surface 3A.

An opposite and perhaps much more important function provided for by the hydraulic system, consists in raising the pressure in the hydraulic oil channel 21 which gives an increased pressure on piston area 15A with a resulting movement of holder 10 away from ball 3. This is a highly- advantageous function for the purpose of avoiding problems with resetting a large ball valve for example, when this for an extended time has been standing in a certain position. Upon such movement of holder 10 main gasket 11 and possibly edge 19 will be lifted away from sealing face 3A of the ball, so that turning of valve ball 3 to another position, for example a closed position, can be initiated with a moderate or usual torque in stem 5 (Fig. 1) . It goes without saying that the pressure in channel 21 for this purpose must exceed the spring force of springs 13, possibly the hydraulic pressure in chamber 16 and besides a possible pressure difference in the main system when a medium is present in flow passage P. A still further channel 30 as shown in Fig. 3 pene¬ trates housing 1, and this channel has quite a different function from the above mentioned hydraulic oil channels 21 and 22. In valves of the kind concerned here, which for a long time may be left standing in one and the same posi¬ tion, it is often a problem that particles or substances in the flowing medium, for example crude oil, can deposit or penetrate into cavities and chambers which are found in the valve structure. In the structure described above, for example the cavity 14 for spring 13 with passages and slits particularly in association with skirt 17 on holder 10, will be subject to such deposits. Another point where a corresponding effect may occur is in the narrow gap between main gasket 11 and the actual flow passage P. At this latter point there is shown at 40 a specific filler material inserted, for example a foam material -which, depending on the circumstances, can be pressed out into the flow passage to be carried away by the medium therein.

It is more important however to prevent problems with intrusion or deposits in connection with the movable parts in the region of springs 13. In order to eliminate this problem an injection channel 30 as referred to, is provided for the purpose of injecting a filler mass, for example a particular type of oil or another liquid medium which can fill all cavities and chambers, in particular around springs 13 , so that the above problems of intrusion or deposits do not^" arise.

In order to carry out an effective filling with a filler mass in this manner, it is practical to have at least one venting orifice 31 which puts cavity 14 and other chambers or the like in communication with flow passage P. Provided that these orifices or openings 31 are relatively small there will be no problem with leakages between the filler mass system and the main flow passage P.

It will be realized that during the above mentioned pressing back of holder 10 in order to relieve the sealing pressure at main gasket 11, it is necessary to press out filler mass from the region behind holder 10, whereby among other things springs 13 are compressed. During this operation it may be found that the small orifice or orifices 31 are insufficient for letting filler mass escape from this region. This for example can be due to a certain solidification of the filler mass. In order to remedy this there is therefore provided a number of larger holes or openings 33, 34, 35 and so forth, each having a blocking member as shown at 33A for opening 33, so that there is normally a blocking against fluid connection between flow passage P in the region of cavities and chambers in association with holder 10. The number and the size of these openings 33, 34 and 35 and so forth eliminate any problem in urging holder 10 backwards, as the filler mass will press out any blocking member 33A into the flow* passage P itself where they are carried away -with the^' oil stream or the like. Blocking members 33A can be^{' "}suitably dimensioned metal discs which yield at a predetermined increased.pressure in the filler mass so that the desired fluid communication is obtained. The skirt 17 has a particular function in this connec¬ tion. As will be seen from Fig. 3 the end piece of the skirt is cut into an inclined edge which during return movement of seal holder 10 will have a cutting and/or cleaning effect on the adjacent interior cylindrical surface in housing 1.

Another possibility which can be utilized if required, is to inject a liquid solvent- in order to make it easier to press out a more or less solidified filler mass, either through the small orifices 31 or through the larger openings 33, 34, 35 and so forth. It is obvious that the location of this orifices and openings in skirt 17 must be so chosen in relation to the above mentioned adjacent cylindrical surface in housing 1, that fluid communication from the filled chambers, cavities etc. out to flow passage P will be maintained throughout a desired distance of the axial movement. In the example of an arrangement according to the invention as described above with reference to the drawings, there is described a hydraulic system for moving the seat or seal holder. It is obvious that a quite analogue function can be provided for with a pneumatic system. Moreover, a main gasket is shown mounted in the valve housing, i.e. on a movable seal holder. Also at this point a modification -is quite possible, namely in alterna¬ tive embodiments where the gasket is mounted on the valve ball or valve member in the case of other types of valves and a ball valve. In such case there will be a cooperating valve seat on a seat holder which may be moved quite in analogy to the seal holder in the embodiment of ^"the drawings. The situation in an alternative embodiment having a gasket element on the valve member, will be quite analogous and the solution according to the invention will have the same advantages as discussed above.

As to the type of filler mass or material, it will be possible to employ. various commercially available products which can for example be based on oil and are preferably water repellant, as well as having a more or less low viscosity, but preferably being mere fluid than common lubrication grease.

Claims

1. Valve arrangement, in particular a large ball valve for use in oil and gas installations for offshore production, of the kind comprising a valve member (3) the active sealing faces (3A) of which are preferably adapted to undergo relative sliding against cooperating valve seat parts (11) during valve operation, and the valve comprises a movable seat or seal holder (10) , characterized in that a front portion of the seat or seal holder (10) in association with a comparatively soft main gasket (11) is designed with a protruding edge or ridge (19) extending along the whole contour of the main gasket (11) and being directed towards the valve member (3) , but having a certain, small spacing therefrom under normal sealing function provided by the main gasket (11) , and that the protruding edge or ridge (19) upon an increase in sealing force and a movement of the seal holder (10) as a result thereof, is adapted to engage in direct and sealing contact with a cooperating surface (3A) on the valve member (3) for attaining an improved and secured sealing in the valve.

2. Arrangement according to claim 1, wherein the main gasket is mounted at the seat or seal holder, characterized in that the protruding edge or ridge (19) is located adjacent the main gasket (11) and said cooperating surface constitutes a portion of said sealing face (3A) on the valve member (3) .

3.. Arrangement according to claim 1 or 2 , characterized in that the protruding edge or ridge (19) is located outwardly of the main gasket (11) as seen in relation to the flow passage (P) through the valve.

4. Arrangement according to claim l, 2 or 3, characterized in that the seat or seal holder is provided with a piston member (15) which is incorporated in a hydraulic or pneumatic system (21, 22) adapted to move the seat or seal holder (10) at least in a direction away from the valve member (3) in order to facilitate movement thereof when a valve operation is initiated.

5. Arrangement according to claim 4, characterized in that the piston member (15) is double acting (15A, 15B.)- and the hydraulic or pneumatic system (21, 22) is also adapted to urge the seat or seal holder (10) in a direction towards the valve member (3) so as to provide for an increased sealing power.

6. Arrangement according to claim 5, wherein the seat or seal holder is shaped substantially as a cylindrical ring (10) the inside or which constitutes a length of the flow passage (P) through the valve, characterized in that the piston member (15) is formed at the outside of the cylindrical ring (10) and is received in an annular hydraulic or pneumatic cylinder (16) provided in the surrounding valve housing (1) .

7. Arrangement according to claim 4, 5 or 6, characterized in the provision of a spring (13) seaking to urge the seat or seal holder (10) in a direction towards the valve member (3) .

8. Arrangement according to any one of claims l to 7, characterized in that cavities and chambers (14) in the interior of the valve housing (10) , in particular for a spring or springs (14) incorporated in the structure, are adapted to be filled with a liquid filler mass through at least one injection channel (30) .

9. Arrangement according to claim 3, characterized in that said cavities or chambers (14) communicate with a flow passage (P) through the valve, by means of at least one comparatively small orifice (31) being preferably adapted to lie at a high point in the filler mass system when the valve is installed.

10. Arrangement according to claim 8 or 9, characterized in that said cavities or chambers (14) are adapted to be put in communication with a flow passage (P) through the valve, by means of a number of comparatively large openings (33, 34, 35) being normally closed with a^' blocking member (33A) adapted to be pressed out into the flow passage (P) at a given increase of the pressure in the filler mass.