This invention relates to high-pressure valves. Valves for the control of fluid flow are among the most common of engineering components. All are based on the physical placement of an obstruction, the obturator, into the line of fluid flow. Controlled rotation or linear sliding of this device out of the flow path allows flow resumption.

Fluid pressures acting on the closed valve force the obturator onto its sealing faces and its bearings. The resulting friction forces must be overcome before the valve can be opened. At extremely high-pressures of the order of 1000 atmospheres, these forces can become so large that the obturator is not readily moved. When obturator motion is achieved, serious damage to the fluid closure seals can result. These problems are encountered in remotely operated high integrity pipeline fluid isolating valves such as are used in marine petrochemical pipelines, for example. Such valves may be in a range of sizes, (e.g. 0.15m, 0.25m, 0.5m) and may be designed to operate under a wide range of temperatures, (e.g. 0°C, 200°C), and pressures (e.g. 100 bar, 1000 bar).

US-A-2034216 discloses a ball valve for controlling flow of fluid under pressure which is provided with means whereby the pressure of fluid will move the valve off its seat when manually operated means are actuated so that the valve can be turned to the closed position with the minimum amount of effort and without wear upon the valve seat. The disclosed ball valve has a diametrically opposed pair of trunnions and the means operable to unseat it comprise a separate annular piston which is coupled to the ball valve by a diametrically opposed pair of axially extending arms or ears in each of which a respective one of the trunnions is journalled. This is

difficult to assemble. Also, since the ball valve is designed to be closed by the action on the valve itself of the pressure of the flow of fluid it is controlling, a substantial force must be generated by the separate piston to lift the valve off its seat against that pressure. Hence the loading on the trunnions will be substantial as they will have to take that substantial force that is generated by the separate annular piston and applied to them by the arms or ears. Moreover the annular piston is used to provide the area necessary to generate the required lift off force, the area of the piston being substantially larger than the area of the trunnions on which that generated lift off force will be exerted. The difficulties in assembly and the problems of the loading on the trunnions increase as the pressure of the flow of fluid to be controlled increases to an extent that the valve design disclosed in US-A-2034216 will not be practical for use for controlling the extremely high pressures referred to above.

An object of the present invention is to provide a valve which can be used at high-pressures whilst avoiding serious damage to the valve closure seals.

Basically the present invention, in one aspect, avoids the use of a separate piston for generating the required obturator lift off force. Rather it uses the trunnions of the obturator as piston means whereby the problem of overloading the trunnions is avoided.

According to one aspect of this invention there is provided a high pressure valve comprising a valve body which acts as a pressure body and defines a path for fluid flow, an obturator which has an opposed pair of trunnions by which it is pivotally mounted in the valve body on opposite sides of the fluid flow path for

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movement into and out of the fluid flow path, a seat for the obturator, the seat being formed on or carried by the valve body so that the obturator is normally urged to seat thereon by upstream pressure, wherein control means are provided which are operable to effect a controlled application of the upstream fluid pressure whereby to create a pressure differential which causes the obturator to be lifted off the seat prior to being moved into or out of the fluid flow path, the trunnions comprising an opposed pair of pistons to each of which upstream fluid pressure is applied by operation of said control means to cause the obturator to be lifted off the seat.

Preferred features of a high pressure valve according to this aspect of the invention are defined by claims 2 to 8.

By another aspect, this invention simplifies the problems of construction and assembly by mounting the obturator in a cartridge, which is in the form of a split sleeve, which is inserted into the valve body that is the pressure body.

According to this other aspect of the invention there is provided a high pressure valve comprising a valve body which acts as a pressure body and defines a path for fluid flow, an obturator which is moveable into and out of the fluid flow path, and a seat for the obturator, the seat being formed on or carried by the valve body so that the obturator is normally urged to seat thereon by upstream pressure, wherein the obturator is pivotally mounted within a cavity formed by a split sleeve mounted within the valve body.

Preferred features of this other aspect of the present invention are defined by claims 10 to 16.

A third aspect of the present invention is the provision of a secondary sacrificial seal upstream of the

obturator which secondary seal interacts with the obturator to throttle fluid flow passed it when it is lifted off the seat whereby to reduce the pressure of fluid flow passed the primary seal and thus to reduce the risk of erosion of the primary seal.

According to this third aspect of the present invention there is provided a high pressure valve comprising a valve body which acts as a pressure body and defines a path for fluid flow, an obturator which is moveable into and out of the fluid flow path, a seat for the obturator, the seat being formed on or carried by the valve body so that the obturator is normally urged to seat thereon by upstream pressure, there being primary sealing means incorporated in the seat, wherein control means are provided which are operable to effect a controlled application of the upstream fluid pressure whereby to create a pressure differential which causes the obturator to be lifted off the seat prior to being moved into or out of the fluid flow path, and secondary sealing means are provided upstream of the primary sealing means and are adapted to interact with the obturator during obturator motion off the seat whereby to reduce the pressure of flow passed the obturator and erosion of the primary sealing means. Preferred features of a high pressure valve according to this third aspect of the invention are defined by claims 19 to 22 inclusive.

Several forms of valve for the control of high pressure fluid flow in which this invention is embodied will now be described by way of example with reference to the accompanying drawings, of which:-

Figure 1 is an end elevation of one form of valve for the control of high pressure fluid;

Figure 2 is a sectional view of the valve shown in

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Figure 1 in its normal operating mode with an actuator and a fluid pressure control system shown diagrammatically thereon, the valve being sectioned on the line II-II in Figure 1; Figure 3 is a sectioned fragment of the valve shown in Figures 1 and 2, the section being on the line III-III in Figure 2;

Figure 4 is a view similar to Figure 2 showing the obturator lifted off its seat and turned to its closed setting;

Figure 5 is a view similar to Figure 2 of another form of valve for the control of high pressure fluid flow; and

Figure 6 is a partly sectioned fragmentary view, similar to the corresponding part of Figure 2 and illustrating a modified form of valve for the control of fluid flow.

Figure 2 shows a pipe 9 with a bore 10, and an enlarged end portion 11 which forms a mouth at its end. The pipe 9 is rebated from the mouth of the enlarged end portion 11 for a substantial part of the length of the enlarged end portion 11. The rebated bore portion is radiused at its end remote from the mouth and an annular step is formed at the junction of the rebated bore portion with the remainder of the pipe 9. Towards the end of the enlarged end 11, its outer diameter is reduced so that a ring 12 is formed around the mouth. The outer face of the ring 12 is threaded. A second pipe 13 with a bore 14, has an enlarged end 15 with an annular recess 16 in its generally radially extending end face. The radially outer wall of the annular recess 16 is threaded. The annular recess 16 is sized to snugly receive the ring

12 when the latter is screwed into it. The pipes 9 and

13 are shown screwed together. Seals are provided to

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prevent fluid leakage. The bores 10 and 14 of the two pipes 9 and 13 are substantially coaxial, and of the same inner diameter. The outer diameter of the enlarged end 11, away from the region where the ring 12 is formed, and that of the enlarged end 15 are substantially the same, so that when the pipes 9 and 13 are fitted together the outer faces of the two parts 11 and 15 are flush.

An annular recess 17 is defined by the rebated bore portion of the enlarged end portion 11 and by the end face of the enlarged end 15. Two diametrically opposing channels 18 are formed through the enlarged end 11. One end of each channel 18 opens into the annular recess 17. The other end of each channel 18 is connected at the exterior of the enlarged end 11 to a respective conduit by which it is connected to a respective valve 18A, 18B whereby that end of the channel 18 is selectively vented or closed.

A split sleeve 20 is fitted into the annular recess 17. The split sleeve 20 is formed of two substantially identical interengaging half shells 20A and 20B. The split line E is shown dotted in Figure 2. Each half shell, 20A and 20B respectively has a radially inwardly extending semi-annular lip 19, formed at its inner end adjacent the annular step in the rebated bore portion of the enlarged end portion 11. The radially inner ends of the lips 19 are substantially flush with the unrebated portion of the bore 10, the inner diameter of the remainder of the split sleeve 20 being greater than that of the bores 10 and 14. Two opposing recesses 21 are formed in the inner faces of the half shells 20A and 20B of the split sleeve 20. The recess 21 in the half shell 20A has a hole 20C which communicates with a larger radial hole 11A in the enlarged end portion 11. Each recess 21 is almost

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cylindrical in that, as can be seen from Figure 3, it comprises two opposed semi-cylindrical wall portions which extend radially outwardly from the axis of the bores 10 and 14 and which are joined by short wall portions which each extend generally parallel to that axis. A groove 24 is formed in the downstream one of the semi-cylindrical wall portions of each recess 21. A conduit 28 which opens into the upstream one of the semi- cylindrical wall portions of each recess 21, communicates with a respective one of the channels 18 in the enlarged end 11, so that a vent line is provided for each recess 21. The vent lines are operable to be opened or closed by the action of the valves 18A and 18B in the channels 18. Each half shell 20A, 20B has a groove 29 formed in its outer surface. Only the groove 29 in the half shell 20B can be seen in Figure 2. Each groove 29 communicates at one end with the respective groove 24 and extends towards the end of the lip 19 of that half shell 20A, 20B where it opens into an annular cavity 31 formed between the annular step of the enlarged end portion 11 and the respective lip 19. That annular cavity 31 opens into the bore 10. Hence, the grooves 24 are each in direct communication with the bore 10. An annular sacrificial secondary seal 34 is fitted into the annular corner formed on the split sleeve 20 between the lips 19 and the inner faces of the half shells 20A and 20B.

A pair of diametrically opposed trunnions 35, formed on an obturator 36, project one into each recess 21. The trunnions 35 are substantially circular in section (see Fig. 3). Each trunnion 35 projects from a respective flat surface 37 which is formed on the obturator 36 and has an outer end 38 in sliding engagement with a cooperating

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guide surface of the recess 21 into which it projects. The two flat surfaces 37 are substantially normal to the axis of the trunnions 35, substantially parallel to the axis of the pipes and are slidably in contact with the inner face of the split sleeve 20.

When each trunnion 35 is in its 'at rest' position, it abuts the downstream semi-cylindrical wall portion of the respective recess 21 adjacent the respective groove 24 as is shown in Figures 2 and 3, and is spaced from the upstream semi-cylindrical wall portion so that a chamber 39 is formed. The spacing of the parallel wall portions of the recesses 21 is substantially the same as the diameter of each trunnion 35, so that each trunnion 35 is in sliding engagement with the respective pair of those parallel wall portions. Hence, the trunnions 35 are free to move in the direction of the axis of the pipes 9 and 13 and to be rotated in the recesses 21, but are prevented from moving in a transverse direction.

The portion of the obturator 36 between the two flat surfaces 37 is a part sphere penetrated by a circular hole 41 which has a diameter substantially equal to that of the bores 10 and 14 of the pipes 9 and 13. When the circular hole 41 through the obturator 36 is aligned with the axis of the pipes 9 and 13 (as shown in Figure 3), the flow through the pipes 9 and 13 is unimpeded but when the obturator 36 is rotated through 90° about the axis of the trunnions 35 (as shown in Figure 4) the flow is obstructed. The obturator 36 abuts a seal face 32 on the enlarged end 15 when it is in its "at rest" position. This is the primary seal of the valve.

A rotary actuator 42 is connected to the trunnions 35 through the hole 20C in the split sleeve 20 and is provided to rotate the obturator 36 about the axis of the trunnions 35. The rotary output of the rotary actuator

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42 is coupled to one of the trunnions 35 by a suitable universal coupling 43, such as a 'dog-bone coupling', which allows for lateral displacement of the trunnions 35 within the recesses 21. The design of the valve is such that the split sleeve 20 is subject to uniform pressures and not to high load bearing forces. Hence, the material of the split sleeve 20 can be selected for its bearing and wear characteristics rather than its mechanical strength. When in use the valve should be positioned so that the direction of fluid flow is from pipe 9 to pipe 13.

When the obturator 36 is in its 'open' position, the vent lines 18 and 28 are closed, the obturator 36 abuts the seal face 32, to form a seal, which may be a metal to metal seal, and is aligned so that the axis of the hole 41 is coincident with the axis of the pipes 9 and 13 (as shown in Fig. 3), thereby allowing fluid to pass therethrough. In this position the trunnions 35 abut the downstream semi-cylindrical wall portions of the recesses 21 into which they project, and both the chambers on either side of each trunnion 36, which comprise the respective groove 24 and chamber 39, contain fluid at the same pressure as the fluid in the pipes 9 and 13. In the 'closed' position shown in Figure 4, the position of the trunnions 35 in the recesses 21 is the same, and the obturator 36 abuts the seal face 32, but is rotated by 90O so that the axis of the hole 41 is perpendicular to the axis of the pipes 9 and 13.

The pressure exerted on the seal face 32 by the obturator 36 in the open or closed position tends to resist any attempt to rotate the obturator 36, and so at high pressures the seal face 32 may be damaged by such an attempt. In order to move the obturator 36 from one position through 90O to the other position, without so

damaging the seal face 32, a pressure difference across the trunnions 35 is created, thereby allowing the obturator 36 to be lifted off the seal face 32 and facilitating the rotation. To create this pressure difference, the vent lines are opened and the pressure in the chambers 39 upstream of the trunnions is released, so that the pressure in each groove 24 is greater than that in each chamber 39, and the trunnions 35 are forced upstream to enlarge the chambers 44 on the downstream sides of the trunnions 36, with which the grooves 24 communicate. Hence, the obturator 36 is lifted from the seal face 32.

Once lifted from the seal face 32, the obturator 36 moves towards the secondary sacrificial seal 34 which is provided to restrict the flow of fluid over the seal face 32, reducing its pressure to a level which is tolerable as far as the seal face 32 is concerned and thereby to reduce the likelihood of erosion of the seal face 32. The clearances at the secondary sacrificial seal 34 are set to ensure that the obturator 36 can be rotated with ease via the rotary actuator 42. When the obturator 36 is rotated into the required position, the vents are closed by operation of the valves 18A and 18B and the pressures in the chambers 39 and 44 respectively, are allowed to equalise, as a result of the leakage of fluid past the sliding faces 37 of the obturator 36, the faces 38 of the trunnions 35, and the walls of the recesses 21.

When the obturator 36 is in its closed position, the equalisation of the pressure in the chambers 39 and 44 and the fluid flow from pipe 9 to pipe 13, forces the obturator 36 against the seal face 32, thereby establishing an effective blockage of the upstream fluid, and providing a seal. In the embodiment described, the seal formed is a metal to metal seal. However, it may be

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another type of seal such as an 'O'-ring of elastomeric material.

The high pressure valve described above is simple to use and involves only one moving part. This simplifies the construction and assembly of the valve, as does the split design of the sleeve 20. The latter is advantageous also because it incorporates virtually all the stress inducing features so that the outer pressure body can be optimally designed for that purpose. Mounting the rotary obturator within a split sleeve casing and arranging for it to be lifted off its seat by the action of high pressure fluid within the split sleeve casing, that split sleeve casing in turn being housed within the valve body, is advantageous in that virtually all awkwardly shaped parts of the valve which will induce stress will be in the cartridge that comprises the split sleeve and its contents, and thus will be in the fluid flow contained within the valve body. That is advantageous because, in addition to the use of the split sleeve facilitating assembly, the shape of the valve body will be simple and thus will be simple to machine, will have minimal stress inducing features and thus will be well suited for its functions as the pressure body of the valve. The design is tolerant to the presence of debris in the pipeline fluid. The valve is designed so that the combined cross- sectional area of the trunnions, that is to say the area of the trunnions to which the upstream fluid pressure is applied to lift the obturator off its seat, whereby the trunnions function as pistons, exceeds the cross- sectional area contained by the primary seal by a small amount. Hence the obturator is lifted off its seat and moved towards the secondary seal by a small force which is a differential fluid pressure loading on it itself so that the risk of damaging the secondary seal is reduced.

It is sufficient for the obturator to be moved close to the secondary seal so that flow between them is throttled and its pressure reduced. It is not vital for the obturator to seat on the secondary seal. The secondary seal is liable to be damaged by erosion by flow past it. It is designed to be replaceable and it is sacrificial in that, by allowing it to be damaged in the process of reducing the pressure of the flow to a level which can be tolerated by the primary seal, it will protect the primary seal from similar damage. Wear caused by abrasive particles drawn between the sliding faces increases the leakage of fluid into the cavities formed between the trunnions 35 and the walls of the recesses 21, during obturator 36 turning. However, this is compensated by the sizing of the vents which ensure reliable operation of the trunnions 35 as actuator pistons.

The geometry of the obturator sliding faces 37 is selected so that jamming cannot occur. The high pressure valve in which the present invention is embodied is suitable for use at high temperatures .

Figure 5 illustrates a modification of the obturator 36 shown in Figures 2 and 4 whereby, instead of the grooves 24 and 29 which provide communication between the chambers 44 on the downstream sides of the trunnion pistons 35 and the fluid flow path through the pipes 9 and 13 and the hole 41 in the obturator 36, the modified obturator 36A has oblique drillings 45 through it for providing that communication.

Figure 6 illustrates another modification of the valve shown in Figures 1 to 4. By this modification each trunnion is journalled within a collar 47 which has a rectangular periphery. The end faces of the rectangular

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periphery of each collar 47 serve as the piston faces to which the fluid pressure in the chambers on either side of the respective trunnion is applied by operation of the valve. The side faces of the collars serve as sliding guide surfaces which slidably engage mating sliding surfaces formed by the side of the respective recess of the respective half shell. This arrangement has the advantage that the erosion effect of the fluid passing the trunnions is reduced because the collars 47 present a larger surface area to it.

Each collar 47 is advantageously journalled on the respective trunnion by a squeeze film bearing arrangement 48 as the collars, bearings and trunnions are immersed in the fluid.