WO2006006873A1

WO2006006873A1 - Directly operated control valve in a valve device

Info

Publication number: WO2006006873A1
Application number: PCT/NO2005/000265
Authority: WO
Inventors: Heyn Halfdan Magnus; Torstein Kasin; Vidar Braaten
Original assignee: Fmc Kongsberg Subsea As
Priority date: 2004-07-15
Filing date: 2005-07-15
Publication date: 2006-01-19
Also published as: NO320755B1; NO20043024D0

Abstract

The invention relates to a valve device comprising a housing (2) with a bore (7) and a slide (4) movably arranged in the bore and arranged to provide or cut a fluid connection, for example between a pressure fluid source and an actuator. According to the invention the slide comprises a valve element (50) arranged in a complementary through-going bore (48) in the slide (4), where the valve element (50) comprises a through-going fluid bore (52), and the housing comprises pressure elements (70, 74) on opposite sides of the valve element (50) and in abutment against it by means of at least one pressure device, which pressure device is mounted at a side of one of the pressure elements (70, 74) facing away from the valve element (50). The invention also relates to a directly operated control valve.

Description

Directly operated control valve in a valve device

The present invention relates to a valve device, more particularly a control valve for controlling a hydraulic actuator.

In subsea installations such as a wellhead Christmas tree, a so-called electrohydraulic system is normally used for operation of the hydraulically actuated well valves. The supply of hydraulic operating fluid to the well valves is controlled by a control valve that admits or shuts off the fluid flow to the actuator's pressure chamber in order to move the valve to its first position. When the control valve closes, the pressure is bled off and a return spring moves the valve to its second position, which is usually the closed position. The control valves are also usually hydraulically operated by the same pressure fluid, an electrically operated pilot valve being employed to guide pressure fluid to the control valve. The pilot valve therefore acts as an amplifier stage. The pilot valve comprises a piston which is moved by means of a solenoid. The disadvantage of this system is that the pilot valve is extremely small and therefore highly vulnerable to impurities that obstruct the valve's movement, resulting in interruption of operations. The hydraulic lines are therefore usually equipped with filters in order to filter out particles from the hydraulic fluid. The incorporation of pilot valves in the system also increases the complexity and thereby the possibility of error.

Control valves of the type that are the subject of the invention comprise a forward and backward moving slide that admits and shuts off the fluid flow respectively. The slide comprises a through-going bore which, with the valve in the open position, is in fluid connection with a bore in the valve housing. The slide has a sealing surface and can be pressed against a corresponding sealing surface or seat arranged in the valve housing. The sealing surfaces are made of metal and, in order for the valve to provide a satisfactory seal, it is necessary for the sealing surfaces to be pressed against each other with relatively great force. This force can be provided by means of springs or, more commonly, by means of the force from the pressure fluid.

Two examples of control valves are described in US 4,848,404 and US 6,474,362. In the first case the valve comprises a slide with two separate valve elements provided in a bore in the slide with an intermediate spring, which together with any existing fluid pressure presses the valve elements against abutment surfaces formed by the encircling housing. The valve elements are provided with relatively small sealing surfaces between the valve elements and the abutment surfaces. In US 6,474,362 there is also a slide with a valve element comprising two elements provided in the form of a piston device, in which case the abutment surfaces are different for the two sides of the valve element, since one abutment surface is composed of the element that forms the piston in the piston device and a second surface of the cylinder housing of the piston device.

In general it may be said that when the sealing surfaces are pressed against each other, a frictional force is created that has to be overcome in order to move the slide. The frictional force is a function of the pressure and the size of the surface. It is desirable to have the largest possible surface since it provides the best sealing effect and is least subject to problems due to particles in the fluid. However, this means that great force is required in order to move the slide. Conversely, small sealing surfaces offer less friction and therefore less force is required to move the slide, but on the other hand they are subject to problems due to particles in the fluid. In practice it has been shown that even the smallest optimal sealing surface has required such great forces that direct operation has been virtually impossible.

The control and pilot valve is normally mounted in an assembly which, together with others, is located in a control module. The control module also comprises equipment for control and monitoring of the well, i.e. it receives signals from various meters placed on the Christmas tree and it has equipment that can communicate with a remote station for receiving signals for activating the valves. In this kind of control module there is limited space and therefore a restriction on the size of motors that can be mounted therein. On account of the many disadvantages it has therefore long been desirable to remove the pilot step, but this has proved to be difficult, particularly on account of the aforementioned substantial power requirement with associated requirements for space and power supply, but also on account of the requirement for reliable operation, particularly the requirement for fail-safe operation since the valves must be brought to a closed position in the event of error in the system, such as loss of hydraulic or electric power. Due to this requirement the control valve must be equipped with a return spring and the drive motor, which is normally a solenoid, must therefore be under tension at all times in order to keep the control valve in the operating position. The object of the present invention is to provide a control valve that eliminates the pilot step, thereby permitting direct operation of the hydraulic actuators while at the same time safeguarding the safety aspects, i.e. fail-safe operation.

It is also an object to provide a valve device with larger sealing surfaces compared to previous control valves. It is a further object to provide a compact valve device with the capability of easily adjusting the prestressing of the elements.

This is achieved by a valve device and control valve according to the attached claims. The invention relates to a valve device comprising a housing with a bore and a slide movably mounted in the bore and arranged to provide or cut a fluid connection, for . example between a pressure fluid source and an actuator.

According to a first aspect of the invention the slide comprises a valve element mounted in a complementary through-going bore in the slide. This through-going bore in the slide will often be arranged across the bore for the slide in the housing, but this is not an absolute necessity. The valve element comprises a through-going fluid bore, and the housing comprises pressure elements on opposite sides of the valve element and in abutment against it by means of at least one pressure device, which pressure device is mounted at a side of one of the pressure elements facing away from the valve element.

Abutment surfaces between the valve element and the pressure elements are complementary surfaces, forming sealing surfaces between the elements. There are many different possible shapes for these surfaces, such as curved, angled etc., but in a preferred embodiment the surfaces are flat. The pressure element abuts against the valve element at least in a portion of the valve element's surface, but the abutment surfaces have larger dimensions than abutment surfaces in existing control valves. The valve element is detachably located in the bore in the slide and is preferably a uniform element. In an embodiment the pressure device that presses the pressure elements against the - valve element comprises a spring and/or a hydraulic piston device, and in a preferred embodiment both a spring and a hydraulic piston device, where the hydraulic fluid is the supply fluid in the valve device. This means that when fluid is supplied to the valve device, the pressure elements will be pressed against the valve element by the supply fluid in addition to the spring, but failure of the supply fluid will also affect the pressure device for the pressure elements against the valve element. This will lead to these being pressed with less force against each other and the slide will therefore be easier to move.

According to a preferred embodiment of the invention the pressure elements have a through-going fluid bore which in a position of the slide is located in line with the through-going fluid bore in the valve element. The through-going fluid bores in the valve element and the pressure elements form a fluid channel with a substantially uniform cross section. This provides a fluid passage that is as straight as possible without unnecessary deflections of the flow, that would result in greater flow loss than a straight flow. This is therefore an advantageous solution compared to known solutions where the channel for the supply fluid is deflected, changing the flow cross section several times in the course of the passage of the valve element.

In order to achieve a simple return path for the fluid in the outer actuator where the valve device is in a closed or shut-down position, the valve element comprises a recess with a longitudinal direction substantially across the longitudinal direction for the through-going fluid bore, whose recess extends at least over a part of the valve element. In one position of the slide, this recess in the valve element will form a fluid connection between the through-going fluid bore in one of the pressure elements and a return fluid bore in the housing and/or the slide.

For safety reasons the slide will normally also be connected to a hydraulically operated prestressing device. In the preferred embodiment of the invention the prestressing device comprises a hydraulic piston device mounted at least partly inside the housing, where a pressure chamber of the hydraulic piston device is located directly in the fluid supply flow in the housing, before the valve element. The prestressing device is prestressed with the result that in the event of a loss of hydraulic fluid supply it will ensure that the slide with the valve element is placed in a position where the fluid bore in the valve element is disposed at the side of the fluid bores in the pressure elements. This arrangement of the pressure chamber in the hydraulic piston device provides a more reliable prestressing device. Where the prestressing device has a separate fluid supply, it will be possible to obtain a blockage in the fluid supply by the prestressing device even though fluid is still being supplied to the valve device. Loss of fluid to the prestressing device may cause the valve device to be forced into a closed position, even though this is undesirable. In this respect the present invention is more reliable, with the hydraulic piston device of the prestressing device being directly located in the supply fluid flow.

In a preferred embodiment the slide is connected to an actuator for positioning the slide where the actuator comprises a solenoid. The solenoid comprises an inner coil arranged axially movably in a cylinder, where the coil contains a number of permanent magnets separated from one another by rings, which rings are made of a material with a high degree of saturation magnetisation and high permeability combined with low magnetic remanence, and where the cylinder contains a number of electromagnets. According to a second aspect of the invention it comprises a new solenoid that provides greater force relative to size. This is achieved with a solenoid of the above-described type. This type of solenoid will be directly capable of moving a slide in a valve device where the abutment surfaces have larger dimensions that previously known solutions. By this means the need is obviated for a pilot valve and the problems associated therewith.

The valve device preferably has the prestressing device mounted at one end of the slide and a drive actuator for the slide is mounted at the other end of the slide. The invention will now be described in greater detail by an embodiment with reference to the attached drawings, in which:

Fig. 1 illustrates a control valve, partly in section, Fig. 2 illustrates a section through the control valve in operating mode, Fig. 3 illustrates a partial section of the slide separately,

Fig. 4 illustrates a portion of the section corresponding to fig. 2 with the valve in a closed position,

Fig. 5 illustrates a portion of the section corresponding to fig. 2 with the valve in a fail-safe closed position, Fig. 6 is a section through the solenoid,

Fig. 7 is a detail view of a portion of fig. 2, and Fig. 8 is a partial section along line A-A in fig. 5.

Fig. 1 illustrates a control valve consisting of a valve part 1 and a drive part 100. The valve part comprises a housing 2. The housing 2 may, for example, be in two parts held together by bolts 3. In the housing is mounted a slide 4, which is movable between the two positions exemplified in fig. 2 and fig. 4 by means of a motor provided in the drive part 100. The drive part will be described in more detail later with reference to fig. 6. In a second end of the valve part 1 is mounted a spring housing 5, which is fastened to the housing 2 by means of bolts 6 or the like. In fig. 2 the control valve is illustrated in its operating position where hydraulic pressure fluid is supplied to the associated external actuator (not shown). The flow path for the pressure fluid will be explained further below. In the housing 2 is arranged a first, longitudinal through-going bore 7 in which the slide 4 is located. A second through-going bore 8 is arranged perpendicularly to the first bore 7 and in the same plane, with the result that the two bores intersect. In the housing 2 bores 12, 14 are further provided, forming a first flow channel for hydraulic fluid. The bore 12 extends at the side of the bore 7, and at its end is a coupling (not shown) for a line connected to a source for supply of hydraulic pressurised fluid. In the extension of the bore 14 is an additional bore 16 in which is mounted a piston 18. An additional bore 20 extends in the housing between the outside of the housing 2 and the first longitudinal bore 7 for the slide 4. At the end of the bore 20 is a coupling (not shown) for a line connected to a return line for hydraulic fluid. In the embodiment the starting point for the bore 12 and the bore 20 is shown to be on the same side of the housing, although this is not absolutely necessary and alternatives to this solution may be envisaged. The slide 4 comprises a main part 30 with a substantially cylindrical cross section. At each end of the main part 30 is a disc 32, 34 with a larger diameter than the main part 30, attached by, for example, bolts 36, 38 in order to restrict the movement of the slide in the bore 7. The bolt 36 is connected to a driving rod 37 for the drive motor as will be described later with reference to fig. 6. Seals 40, 42 are arranged to seal against the bore 7. A ring groove 44 is milled out in the main part 30 between the seals 40, 42 and from this ring groove 44 there extends a longitudinal milled-out groove 46. The main part 30 further comprises a bore 48 in which is mounted an element 50, the valve element. The element 50 has a through-going fluid bore 52 and a milled-out groove 54. The groove 54 is connected with the groove 46.

The element 50, the valve element, has a shape corresponding to the bore 48 in the slide 4. On each side the element 50 comprises flat surfaces 78, 79 respectively, sealing surfaces, which are indicated in fig. 8 and which in the embodiment are machined to form smooth surfaces. The seals 40 and 42 respectively make the slide 4 pressure-balanced with regard to both external pressure and return pressure.

The bore 8 in the housing has a first portion 55 wherein is inserted a first plug part 56, which is sealed against the bore 8 by an o-ring seal 58 and has a through-going bore 61. At one end of the bore 61 is a coupling (not shown) for a line connected to a line for hydraulic fluid that is connected to the pressure side in the external hydraulic actuator (which is not shown). At the opposite end of the bore 8 is a second portion 60 wherein it is inserted a second plug part 64. The plug part 64 has a front portion 68 with reduced diameter, thereby forming an annulus between the said portion and the bore 60. An o-ring seal 65 forms a seal between the plug part 64 and the bore 60.

The bore 8 has a central portion 62 with reduced diameter. It is in this central portion that the bore 8 intersects the bore 7. In this portion are inserted third 70 and fourth 74 plug parts, forming pressure elements on each side of the bore 8 and each extending slightly into the bore 7 to abut against the slide's element 50, as illustrated in figs. 2, 7 and 8, since the abutment surfaces 78, 77, 79, 80 between the plug parts 70, 74 (the pressure elements) and the element 50 (the valve element) in the embodiment are flat surfaces. The plug part 70 has a through-going bore 71 and an o-ring 72 for sealing against the bore's 8 portion 62. The plug part 74 has a through-going bore 73 and an o-ring 75 for sealing against the bore's 8 portion .62. Between the plugs 64 and 70 a spring 76 is provided that presses the plug part 70 into abutment against the element 50. In addition the pressure of fluid acting on the top of the plug part 70 will also press it against the element 50. The plug parts are held together and attached to the housing by, for example, a bolt 66 as illustrated in fig. 2. Each plug part 70 and 74 has sealing surfaces that act as valve seats and seal against the corresponding surfaces in the element 50,. illustrated in greater detail in fig. 7.

Since the element 50 is detachably mounted in the slide housing 30, the sealing force will act between the surfaces 77 of the plug part 70 (pressure element) and the surface 78 of element 50 (valve element) and the surface 79 of element 50 and the surface 80 of plug part 74 (pressure element).

The slide is pressure-balanced, with the fluid pressure in the valve having the same and opposite effect on the surfaces on both sides of the element 50. This in turn means that the force required to move the slide is independent of the pressure in the fluid, apart from the sealing surface pressed against element 50, which is dependent on the fluid pressure. The fluid pressure can be substantial, generally in the area of 20 MPa in a low pressure system of this type.

When the control valve is in normal operating condition, as illustrated in figs. 1 and 2, hydraulic fluid with sufficient driving pressure is supplied to the valve and flows through the channels 12 and 14 into the bore 8 and through the bores 71, 73 and 61, and thereafter through the line to the external actuator (not shown). In order to close the control valve, current is supplied to the motor in the drive part. This moves the slide 4, causing it to be moved to the position illustrated in fig. 4. A fluid connection will then be provided through the bore 61, the grooves 54 and 46, the ring groove 44 and the channel 20. The pressure in the fluid in the external actuator will thereby be relieved and the prestressing device's return spring will bring the valve to the closed position.

The control valve comprises a spring housing 5 which is attached to the valve housing 2 by means of, for example, bolts 6. The spring housing comprises a main body 81 round which is arranged a spring 82. A rear spring shoulder 84 is attached to the main body 81 and a front spring shoulder 86 is attached to the piston 18. The spring shoulder 86 comprises an abutment portion 88 which is arranged to rest against the rear end of the valve housing 2 and have a small clearance against the end disc 34 and/or the nut and/or the bolt 38 when the spring 82 is unloaded. In the normal operating position as illustrated in figs. 2 and 4, fluid under pressure is located in the bore space 16 and it will influence the piston 18 in such a manner that the spring 82 is pushed backwards. The slide 4 is therefore free to move in the bore 7.

In fig. 5 the control valve is shown in fail-safe position. If the pressure in the supply line drops below a set limit or disappears completely, the spring 82 will cause the spring shoulder 86 and the piston 18 to be pushed backwards, i.e. to the left in the drawing. The abutment portion 88 will thereby contact the disc 34, pushing the slide 4 to the left. In the same way as with normal closure, this movement will result in fluid connection between the bores 61 and 20 thus relieving the pressure in the external actuator's chamber (not shown). The operating valve is thereby closed.

Fig. 6 gives a more detailed illustration of a preferred example of a drive motor for the slide 4 which is a solenoid that provides a high torque relative to the size. The solenoid consists of an inner coil 102 which is axially movable in a cylinder 108 and, as mentioned previously, is attached to the valve element's drive shaft 37. The coil consists of a number of permanent magnets 104 separated from one another by rings 106 made of a material with high saturation magnetisation and high permeability combined with low magnetic remanence. A suitable material may be an iron-cobalt alloy. Attached to the cylinder 108 and mounted round the circumference thereof are provided a corresponding number of electromagnets 110 embedded in a matrix 112 of the same material as the rings 106.

The solenoid is activated by supply of direct current. By supplying the solenoid with current of different polarity, the coil will move to the right and the left respectively, thereby moving the slide 4 in a corresponding manner.

The invention provides a directly operated control valve where the pilot valve has been eliminated. The control valve has a fail-safe mode in the event of failure of both hydraulic pressure and electric power. Another advantage of the invention is that the solenoid is mounted outside the hydraulic system, thereby avoiding corrosion problems.

The invention has now been described by an embodiment, but many modifications and variants thereof may be envisaged within the scope of the invention as defined in the following patent claims. Instead of being flat, the sealing surfaces may, for example, be rounded or angled, the fluid bores in the housing and the elements may have different directions and shapes, the slide may have a different cross sectional shape, the valve device may be driven by a different type of actuator. The prestressing device and the actuator may be mounted on the same side of the slide, there may be pressure devices on both the pressure elements, one of the pressure elements may be composed of the housing and not protrude into the bore in the housing, several fluid bores may be envisaged in the valve element and pressure elements and more modifications and variants will be within the sphere of competence of a person skilled in the art.

Claims

1. A valve device comprising a housing (2) with a bore (7) and a slide (4) movably arranged in the bore (7) and arranged to provide or cut a fluid connection, for example between a pressure fluid source and an actuator, characterised in that the slide (4) comprises a valve element (50) provided in a complementary through-going bore (48) in the slide (4), which valve element (50) comprises a through-going fluid bore (52), and the housing (2) comprises pressure elements (70, 74) on opposite sides of the valve element (50) and in abutment against it by means of at least one pressure device, which pressure device is arranged at a side of one of the pressure elements (70, 74) facing away from the valve element (50).

2. A valve device according to claim 1, characterised in that abutment surfaces (70, 78, 79, 80) between the valve element (50) and the pressure elements (70, 74) are complementary surfaces, forming sealing surfaces between the elements.

3. A valve device according to one of the above-mentioned claims, characterised in that the pressure element (70, 74) abuts against the valve element (50) in at least a portion of the valve element's surface.

4. A valve device according to one of the above-mentioned claims, characterised in that at least one of the complementary sealing surfaces

(77, 78, 79, 80) between the valve element (50) and the pressure elements (70, 74) is a flat surface.

5. A valve device according to one of the above-mentioned claims, characterised in that the valve element (50) is detachably located in the bore (7) in the slide (4).

6. A valve device according to one of the above-mentioned claims, characterised in that the pressure device comprises a spring (76) and or a hydraulic piston device.

7. A valve device according to one of the above-mentioned claims, characterised in that the pressure elements (70, 74) have a through-going fluid bore (71, 73) which in one position of the slide (4) is in line with the through-going fluid bore (52) in the valve element (50).

8. A valve device according to claim 7, characterised in that the through-going fluid bores (71, 52, 73) in the valve element (50) and the pressure elements (70, 74) form a fluid channel with a substantially uniform cross section.

9. A valve device according to one of the above-mentioned claims, characterised in that the valve element (50) comprises a recess (54) with a longitudinal direction substantially across the longitudinal direction of the through-going fluid bore (52), whose recess (54) extends at least over a part of the valve element (50).

10. A valve device according to claim 9, characterised in that the recess (54) in the valve element (50) in one position of the slide (4) forms a fluid connection between the through- going fluid bore (73) in one of the pressure elements (74) and a return fluid bore (44, 46, 20) in the housing (2) and or the slide (4).

11. A valve device according to one of the above-mentioned claims, characterised in that the slide (4) is connected to a hydraulically operated prestressing device comprising a hydraulic piston device (16, 18) arranged at least partly inside the housing (2), and where a pressure chamber (16) of the hydraulic piston device is located directly in the fluid supply flow in the housing (2), before the valve element (50).

12. A valve device according to claim 1, characterised in that the prestressing device is prestressed with the result that in the event of loss of hydraulic fluid supply it will ensure that the slide (4) with the valve element (50) are placed in a position where the fluid bore in the valve element (50) is arranged at the side of the fluid bores (71, 73) in the pressure elements (70, 74).

13. A valve device according to one of the above-mentioned claims, characterised in that the slide (4) is connected to an actuator (100) in order to position the slide (4).

14. A valve device according to one of the above-mentioned claims, characterised in that the actuator (100) comprises a solenoid containing an inner coil (102) arranged axially movably in a cylinder (108), where the coil contains a number of permanent magnets (104) separated from one another by rings (106), which rings are made of a material with a high degree of saturation magnetisation and high permeability combined with low magnetic remanence and where the cylinder comprises a number of electromagnets (110).

15. A valve device according to one of the above-mentioned claims, characterised in that the prestressing device is arranged at one end of the slide (4) and a drive actuator (100) for the slide (4) is arranged at the other end of the slide (4).

16. A directly operated control valve comprising a housing (2) with a bore (7) and a slide (4) movably arranged in the bore (7) and arranged to provide or cut a fluid connection, for example between a pressure fluid source and an actuator, characterised in that the slide (4) comprises a valve element (50) arranged in a complementary through-going bore (48) in the slide (4), which valve element .(50) comprises a rectilinear through- go ing fluid bore (52), where an extension of the slide is directly connected to an actuator (100) in the form of a solenoid.

17. A directly operated control valve according to claim 16, characterised in that the solenoid comprises an inner coil (102) arranged axially movably in a cylinder (108), where the coil contains a number of permanent magnets (104) separated from one another by rings (106), which rings are made of a material with a high degree of saturation magnetisation and high permeability combined with low magnetic remanence and where the cylinder contains a number of electromagnets (110).