GB2404696A

GB2404696A - Actuator with integral lock

Info

Publication number: GB2404696A
Application number: GB0318370A
Authority: GB
Inventors: Craig Hendrie; Bilderbeek Ben Van
Original assignee: Plexus Ocean Systems Ltd
Current assignee: Plexus Ocean Systems Ltd
Priority date: 2003-08-05
Filing date: 2003-08-05
Publication date: 2005-02-09
Also published as: GB0318370D0

Abstract

A hydraulic actuator for a gate valve comprising a piston (20) within a housing 40 and connected to a piston rod 22 and valve gate 24 valve can be controlled by application of a first hydraulic pressure to extension inlet 46 causing the valve to open. The valve is mechanically locked open by the first pressure acting axially in the closing direction on shouldered piston ring 27 to expand radially inwardly biassed locking ring 28 to engage annular groove 48 such that the valve will remain open even if the first hydraulic pressure is removed. When a second, retracting hydraulic pressure is applied through inlet 50, the piston ring is moved in the retracting direction against stop 29, the lock is disengaged and valve closes. A return spring may be provided to return the valve to its closed position even if the second hydraulic pressure is removed.

Description

ACTUATOR WITH INTEGRAL LOCK The invention relates to actuators, and in particular actuators that are used to open and close valves. Several types of actuators are used to open and close valves, for example, manually-operated wheel actuators, pneumatic actuators, hydraulic failsafe actuators, etc.. For some applications, such as large-bore, high-pressure oilfield applications, the valves used in Xmas trees or manifolds can become very large. In some cases it is not appropriate to use pneumatic technology actuators and thus it is necessary to use either manual hand wheel or hydraulic failsafe valves (or a combination of such technologies, as is appropriate. Generally surface Xmas trees or well control manifolds have a combination of manually operated wheel type valves and hydraulic failsafe valves. As the bore size and pressure rating of these trees or manifolds increases, the size of each component gets larger and the power required to drive the valve gate into the valve bore increases. In general these problems can be overcome by increasing the diameter of the operating wheels and by constructing platforms so as to give the operator proper access to each valve location. These platforms impose additional costs that have little associated benefit, whilst the weight and inconvenience of the structures and the torque requirement of the manual wheels pose additional problems that need to be addressed. According to a first aspect of the invention there is provided an actuator comprising a piston body received within a piston housing, the piston body comprising first engagement means and the piston housing comprising second engagement means, the piston body, in use, moving from a first position to a second position relative to the piston housing, such that the first engagement means interengage with the second engagement means to secure the piston body in the second position. The first engagement means may be disengaged from the second engagement means. Preferably, the actuator further comprises resilient means biased, in use, to return the piston body towards the first position when the first engagement means are disengaged from the second engagement means.In a preferred embodiment, the piston body is moved from the first position to the second position by the application of a first hydraulic force and the first engagement means are disengaged from the second engagement means by the application of a second hydraulic force. The actuator of the present invention can be manually controlled, with the actuators being controlled from a conveniently located control panel. This removes the requirement for personnel to be able to access the actuators, eliminating the need to provide any access structures. The actuator also comprises a mechanical locking system that prevents the actuator from being released when hydraulic pressure is removed. The mechanical lock may be overridden by applying a release pressure, such that the valve can be opened and closed using only two hydraulic functions. The mechanical lock additionally mitigates the effects of creep on the valve gate caused by bore pressure. The application of the second hydraulic force may also return the piston body towards the first position. Preferably the first engagement means comprise an annular ring and the second engagement means comprise an annular groove. The invention will now be described, by way of example only, with reference to the following Figures in which: Figure 1 shows a schematic depiction of an actuator according to the present invention; Figure 2 shows a schematic depiction of the actuator shown in Figure 1 when the piston has moved part of the distance between the first position and the second position; Figure 3 shows a schematic depiction of the actuator shown in Figure 1 when the piston has been secured in the second position; and Figure 4 shows a schematic depiction of the actuator shown in Figure 1 when the piston has been released from the second position in order to return to the first position. Figure 1 shows a schematic depiction of an actuator 10 and a valve assembly 11 according to the present invention. The actuator 10 comprises a piston 20 which is received within a piston housing 40.The piston 20 comprises a piston stem 22, which is attached to a valve gate 24 located at one end of the piston stem. The valve gate has a closed region 24b that can prevent the flow of fluid through a bore 60 in the valve assembly 11 and an open region 25a, that allows fluid to flow through the bore 60. A valve seat 54 is arranged between the bore and the valve gate. The other end of the piston stem 22 comprises a piston body 26, around which is provided an annular piston ring 27 and annular locking means 28. The annular locking means 28 is inwardly biased against the piston body. An annular retaining means 29 is received on the piston body 26. An helical spring 30 is arranged around the piston stem 22, with one end of the helical spring being secured within an annular recess formed within the piston body and the other end of the spring being restrained within a narrowed end portion 42 of the piston housing 40. An end cap 44 is secured to one end of the piston housing to limit the movement of the piston body 26. The end cap 44 comprises a first hydraulic port 46, that allows a hydraulic force to act upon the piston body 26 to urge the piston body away from the end cap. The piston housing further comprises an annular groove 48 and a second hydraulic port 50. Figure 1 shows the actuator when no hydraulic force is applied to either the first hydraulic port 46 or the second hydraulic port 50. The helical spring 30 is arranged so as to be under compression, and thus the helical spring urges the piston body against the end cap such that the closed region of the valve gate prevents the passage of fluid through the bore 60. Figure 2 shows the actuator of Figure 1 when a hydraulic force is first applied to the piston body via the first hydraulic port 46. When this hydraulic force is sufficient to overcome any potential pressure, the pressure in the valve cavity 52 and to further compress the helical spring 30, the piston body will be urged away from the end cap, moving the open region of the valve gate into the bore.Figure 3 shows the actuator shown in Figures 1 and 2 once the application of hydraulic force via the first hydraulic port has urged the piston body into engagement with the piston housing and such that the open region of the valve gate is aligned with the bore and the valve seat, allowing fluid to flow through the bore. Although the piston body is at the limit of its travel, the hydraulic force can further urge the piston ring 27 away from the end cap. The piston ring 27 is provided with a tapered shoulder and the locking means 28 is provided with a complementary recess such that when the piston ring 27 is urged to the full extent of its travel, the locking means 28 is forced outwards, against its inward bias, such that it caused into engagement with the annular groove 48. The locking means also engages against the shoulders of the piston body.These actions cause the piston body to be mechanically locked against the piston housing with the valve in the open position to allow fluid flow through the bore. The piston body will remain locked in position even if the hydraulic fluid is vented from the first hydraulic port. Figure 4 shows the actuator described above with reference to Figures 1 to 3 when the mechanical locking of the piston body is deactivated. A hydraulic force is applied via the second hydraulic port 50. The hydraulic force acts to urge the piston ring 27 upwards until the piston ring engages with the annular retaining means 29. As is shown in Figure 4, this moves the piston ring out of contact from the annular locking means 28.The annular locking means will revert to its original position with respect to the piston body and the piston ring (as shown in Figures 1 and 2), causing the locking means to disengage from the annular groove 48. This disengagement releases the piston body, which will return towards the end cap and revert to the position shown in Figure 1, causing the valve gate to move to a first position and prevent fluid flow along the bore. Even if the hydraulic pressure is bled from the second hydraulic port the extension of the helical spring and any potential pressure in the valve body will be sufficient to return the piston body to its original position. The motion of the actuator can be controlled by varying the opening of the hydraulic port, with an increased aperture size resulting in faster movement of the actuator. It will be understood that in an alternative arrangement, the annular ring may be outwardly biased and a complementary annular groove be provided to engage with the outwardly biased annular ring.

Claims

1. An actuator comprising a piston body received within a piston housing, the piston body comprising first engagement means and the piston housing comprising second engagement means, the piston body, in use, moving from a first position to a second position relative to the piston housing, such that the first engagement means interengage with the second engagement means to secure the piston body in the second position.

2. An actuator according to claim 1, wherein, in use, the first engagement means may be disengaged from the second engagement means.

3. An actuator according to claim 2, the actuator further comprising resilient means biased, in use, to return the piston body towards the first position when the first engagement means are disengaged from the second engagement means.

4. An actuator according to any preceding claim, wherein the piston body is moved from the first position to the second position by the application of a first hydraulic force.

5. An actuator according to any of claims 2 to 4, wherein the first engagement means are disengaged from the second engagement means by the application of a second hydraulic force.

6. An actuator according to claim 5, wherein the application of the second hydraulic force returns the piston body towards the first position.

7. An actuator according to any preceding claim, wherein the first engagement means comprise an annular ring and the second engagement means comprise an annular groove

8. An actuator according to any preceding claim, wherein the first engagement means comprise an inwardly or outwardly biased annular ring and the second engagement means comprise an annular groove.

9. An actuator according to any preceding claim, wherein, in use, moving the actuator from the first position to the second position and locking the actuator in place in the second position are controlled by a single hydraulic port.

10. An actuator according to any preceding claim, wherein, in use, unlocking the actuator and moving the actuator from the second position to the first position are controlled by a single hydraulic port.

11. An actuator according to any preceding claim, which is capable of interfacing with a standard valve assembly.

12. An actuator according to claim 9 or claim 10, wherein the speed of the actuator can be controlled by changing the size of the opening of the hydraulic port.

13. An actuator substantially as described hereinbefore and with reference to the Figures.