GB2397363A

GB2397363A - Rotary gate valve actuator override system

Info

Publication number: GB2397363A
Application number: GB0400759A
Authority: GB
Inventors: Richard James Pond
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-01-17
Filing date: 2004-01-14
Publication date: 2004-07-21
Anticipated expiration: 2024-01-14
Also published as: GB0400759D0; GB0301068D0; GB2397363B

Abstract

In order to manually disconnect a hydraulic piston device for actuating a rotary gate valve, an operation push rod 9 is arranged through the centre of a helix tube 4. The operation rod 9 is in direct contact with the valve stem of the rotary valve and under normal hydraulic operation is slotted into the end of the helix tube 4 to transfer rotational torque from the helix tube to the valve stem. To disconnect the hydraulic system, the operation rod 9 is simply pushed inwards, which disengages a cross key 11 from an end slot 13 in the helix tube 4, allowing free rotation of the manual operation rod 9. The rod 9 can then be rotated in order to operate the valve fully. To manually close the valve the reverse procedure is carried out.

Description

"Rotary Gate Valve Actuator System" A rotary gate valve is an open/closed

valve which is operated by rotating a valve stem which moves flat sealing buttons through an arc to close or open flow portways. The sealing buttons and stem are enclosed in an all metal sealed housing. Patent No GB 9916144 describes a valve of this type where the stem is rotated manually to operate the valve.

It is an objective of this invention to provide a rotary gate valve using a hydraulic actuator, but provided also with a manual override system. This device needs to allow disconnection of the hydraulic system so that the valve can be operated manually.

In accordance with the invention there is provided an override system for a rotary actuator for a rotary gate valve, wherein the actuator incorporates a push rod slidably received within a tube, the push rod being arranged at a drive end to be linked to a valve-operation stem, the push rod being connected, at the drive end thereof, to the tube by a slot and keyway structure enabling the rod to be disengaged from the tube by sliding away from the end of the tube, the drive end of the rod incorporating a pressure-loaded connection enabling the rod end to move away from the tube when subjected to longitudinal loading.

Normally the loading on the pressure-loaded connection will cause the slot and keyway structure to be engaged so that, when the actuator is operated it will cause rotation of the valve through the valve-operation stem. When the actuator is in the non-operated state the push rod can be disengaged from the tube by putting longitudinal physical force or load on the other end of the rod to compress the pressure-loaded connection against the pressure loading so that the slot and keyway structure becomes disengaged. The rod can then be rotated to operate the valve in an override manner.

Preferably the non-drive end of the rod will be linked to an operating paddle. Ideally the paddle and rod linkage will comprise a further slot and keyway structure, normally held apart longitudinally by a second pressure loaded connection of a power loading greater than that of the first pressure loaded connection. When load is applied to the paddle for the purpose of disengaging the first slot and keyway structure, that action will occur before the further slot and keyway structure becomes engaged due to the difference in the power loading on the two pressureloaded connections. This protects the normal actuating mechanism from application of a high torque from an external 1 0 source.

The pressure loadings are ideally provided by springs.

The invention may be performed in various ways and a preferred example thereof will now be described, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a longitudinal section through a rotary gate valve actuator structure of this invention; Figure 2 is a further longitudinal section, but at 90 to that of Figure 1; Figure 3 shows parts of an override system for the actuator system of Figures 1 and 2; Figures 4 to 6 show stages of operation of the override system of Figure 3; and Figures 7 to 9 show stages of operation of parts attached to an operation end of the override system of Figure 3.

A hydraulic actuator for a rotary gate valve is shown in detail in Figures 1 and 2. To rotate the valve-operation stem 1 of a valve 10, a hydraulic piston device 2 is arranged to give straight-line movement. This is converted to rotational movement through a helix groove 3 in a tube 4 into which run rollers 5 l connected to the piston 2. The hydraulic piston is restrained from rotating using a keyway and the helix tube 4 is restrained from longitudinal movement by a roller thrust bearing 6. To reverse the operation of the hydraulic piston, a return spring 7 is positioned around the cylinder for the piston, which extrudes the working fluid from the cylinder when pressure is released, to provide a fail safe return or valve closure. The helix profile has a varying helix angle to gain maximum torque output at valve closure with minimum torque output over the lightly loaded remainder of stroke.

This valve actuator is particularly suited for subsea use. All areas are pressure balanced making it water depth insensitive. The hydraulic piston will however displace volume when stroking. To prevent a hydraulic lock, a diaphragm is arranged in the end cover of the actuator allowing the volume to expand/contract against ambient sea water pressure.

In order to manually disconnect the hydraulic piston device 2, an operation push rod 9 is arranged through the centre of the helix tube 4. These two parts are shown in Figure 3. The operation rod 9 is in direct contact with the valve stem 1 and under normal hydraulic operation is slotted into the end of the helix tube 4 to transfer rotational torque from the helix tube to the valve stem.

The normal position of the rod 9 within the tube 4 is shown in Figure 4. To disconnect the hydraulic system, the operation rod 9 is simply pushed inwards towards the valve 10, which disengages a cross key 11 to an end slot 13 in the helix tube 4, as shown in Figure 5, allowing free rotation of the manual operation rod 9. The rod 9 can then be rotated to the position shown in Figure 6 in order to operate the valve 10 fully. To manually close the valve the reverse procedure should be carried out. Again, this operation rod 9 is pressure balanced so that is not affected by ambient sea water pressure. To reinstate hydraulic operation, a return spring 12 (Figure 1) is provided between the valve stem 1 and override

F

operation rod 9. When inward manual load is released, this spring 12 moves the operation rod 9 outwards for re-engagement of the cross key 11 to the helix tube slot 13.

The actuator override could be operated manually with a suitable key wrench, but for the most part it is intended that the actuator will be operated by an underwater Remotely Operated Vehicle (ROV). All following actions could, however, be duplicated manually at the surface or underwater by a diver. To ensure that excess torque does not occur from the ROV, a further spring 14 (Figures 1 and 2) is arranged at the outer operating end of the actuator. This spring 14 is typically twice the strength of the inner stem interface spring 12. An operation paddle 15 from where the manual override rod 9 is rotated, has a slot 16 and cross 17 keyway similar to that at the end of the helix tube 4 (see Figure 7). Therefore to disconnect the hydraulic cylinder, the operation paddle 15 is pushed inwards by the ROV. This immediately disconnects the helix tube 4 from the manual operating rod 9, but because the outer spring 14 is significantly stronger than the inner spring 12, further load and rotation (see Figures 8 and 9) has to be applied by the ROV to locate the outside cross key 17 into its drive slot 16. Once located, the ROV can then be used to rotate the valve stem 1 to open or close the valve. The purpose of the double spring arrangement is to ensure that operating torque cannot be applied to the valve 10 until the inner helix tube 14 to cross key 11 is disconnected, thereby protecting the hydraulic actuator mechanism from high torque applied from an external source.

One further advantage of the override system is that, after initial operation by an ROV to rotate to an open valve position, the valve 1 will stay in that position until subsequently operated to close the valve 10. However if the valve is opened by rotation from the ROV, the hydraulic actuator can then be pressurised to the open position which will then pick up the cross key 11 to the helix tube slot 13. With release of cylinder pressure, the valve will return to its closed position using the actuator fail-safe return spring 7.

Claims

1. An override system for a rotary actuator for a rotary gate valve, wherein the actuator incorporates a push rod slidably received within a tube, the push rod being arranged at a drive end to be linked to a valveoperation stem, the push rod being connected, at the drive end thereof, to the tube by a slot and keyway structure enabling the rod to be disengaged from the tube by sliding away from the end of the tube, the drive end of the rod incorporating a pressure loaded connection enabling the rod end to move away from the tube when subjected to longitudinal loading.

2. An override system according to claim 1, wherein said pressure loading is provided by a spring.

3. An override system according to claim 1 or claim 2, wherein the nondrive end of the rod is linked to an operating paddle.

4. An override system according to claim 4, wherein the paddle and rod linkage comprises a further slot and keyway structure, normally held apart longitudinally by a second pressure-loaded connection of a power loading greater than that of the first pressure-loaded connection.

5. An override system according to claim 4, wherein the pressure loading of the second pressure-loaded connection is provided by a spring.

6. An override system for a rotary actuator for a rotary gate valve substantially as herein described with reference to the accompanying drawings.

7. Any novel combination of features of an override system for a rotary actuator for a rotary gate valve as herein described and/or as illustrated in the accompanying drawings.