GB2205629A

GB2205629A - Valve override mechanism

Info

Publication number: GB2205629A
Application number: GB08712062A
Authority: GB
Inventors: Murray Mcintosh
Original assignee: NAT SUPPLY CO
Current assignee: NAT SUPPLY CO
Priority date: 1987-05-21
Filing date: 1987-05-21
Publication date: 1988-12-14
Anticipated expiration: 2007-05-21
Also published as: GB8712062D0; GB2205629B

Abstract

The present invention provides a remotely operably mechanical override system for a hydraulically operated valve (10) having an obturator (16). The override system comprises a plunger (44) which acts on the valve obturator (16), a rotatable drive member (62) and a driving mechanism (54, 58, 60, 70). The driving mechanism (54, 58, 60, 70) translates rotary motion of the drive member (62) into reciprocating motion of the plunger (44). The valve (10) is preferably of the normally closed type and the manual override system beneficially enables the valve (10) to be locked in the open position. <IMAGE>

Description

Title: Valve Override Mechanism The present invention relates to a valve override mechanism and finds particular but non-limiting application to sub-sea valves as used in association with fluid production systems such as an oil or gas well.

There has been an increasing trend towards the use of hydraulically operated valves in sub-sea fluid production systems. In the event of failure of hydraulic operation of the valve it is often necessary to send a diver to effect manual override. This involves the diver in significant risk, is expensive and is not feasible for some existing and many proposed deep water wells.

With a view to alleviating this problem, the present invention provides a remotely operable mechanical override system for a hydraulically operated valve having an obturator, comprising a plunger which acts on the valve obturator. a rotatable drive member and a driving mechanism for translating rotary motion of the drive member into reciprocating motion of the plunger.

Preferably, the driving mechanism comprises a nut threadedly engaged with the plunger and constrained to rotate with the drive member. Advantageously, the nut is capable of reciprocating motion with respect to the drive member.

An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawing. Figure 1, which illustrates a hydraulically operated valve and a mechanical override system which embodies the invention.

Figure 1 shows a valve 10 having a valve housing 12 including a control chamber 14 in which an obturator 16 is reciprocated. The obturator includes an aperture 18 which, in the position shown in Figure 1, permits fluid to flow through the control chamber 14 without restriction. As obturator 16 reciprocates the flow of fluid through the control chamber 14 is regulated and may be completely cut off. However, the valve 10 is primarily intended to operate in a fully open or fully closed position.

On one side of valve housing 12 is a hydraulic actuator 20 and on the opposite side of the valve housing 12 is a remotely operable mechanical override. Both the hydraulic actuator 20 and the mechanical override 22 are generally cylindrical shaped devices bolted to the valve housing 12 with their respective longitudinal axis being aligned with the reciprocating path of obturator 16.

The valve 10 is normally operated by the hydraulic actuator 20 but can alternatively be operated1 for example in the event of failure of the hydraulic system, by the mechanical override unit 22.

The hydraulic actuator 20 comprises a body 24 bolted to valve housing 12 and supporting a cylindrical housing 26. Cylindrical housing 26 is closed by an end plate 28 having a central aperture which connects with a hydraulic fluid supply line 30. Enclosed within the housing 26 is a piston 32 which is urged away from the body 24 by two compression spring 34 positioned between the piston 32 and the body 24. A plunger 36 passes through a central aperture in body 24 and is connected to piston 32. A fluid seal 38 is provided between plunger 36 and body 24. Plunger 36 is connected to one end of obturator 16 and the hydraulic actuator operates in the following manner.

Valve 10 is initially closed and in this position piston 32 rests against end plate 28. When it is desired ta open the valve hydraulic pressure is supplied via supply line 30 and this causes piston 32 to move against the action of springs 34 which are thus compressed. As piston 32 moves in this manner the plunger 36 forces obturator 16 to move through the control chamber 14 thus enabling fluid flow through the chamber 14 via aperture 18. Movement of the plunger and obturator continues until valve 10 is fully open. When it is desired to close the valve, the hydraulic pressure is released and piston 32 is propelled back to its original position under the action of springs 34. This causes plunger 36 to be withdrawn into the actuator unit 20. Consequently obturator 16 is moved through control chamber 14 until valve 10 is fully closed.It will be seen that as obturator 16 moves between the fully open and fully closed positions, fluid in control chamber 14 flows through aperture 18 and into the space in valve housing 12 in which plunger 36 reciprocates. Seal 38 prevents the fluid from entering the actuator 20 and a fluid tight seal is maintainedwbetween the actuator 20 and the valve housing 12.

Mechanical override unit 22 includes a body 40 which is bolted to valve housing 12 and which supports a hollow cylindrical cover 42. Cylindrical cover 42 has an integral end plate. A plunger 44 passes through a central aperture in body 40 and a seal 46 is provided to prevent fluid entering unit 22 in the event of leakage from control chamber 14. However, it should be noted that fluid would not automatically come into contact with this seal. That is, there is no by-pass effect provided by aperture 18. Aperture 18 only passes out of control chamber 14 on the side of the hydraulic actuator 20.

Plunger 44 has three sections each of different external diameter. The section of smallest diameter, section 48 is that which passes through body 40 and which is connected to one end of obturator 16. Section 50 of the plunger has the largest diameter and this section reciprocates within a chamber 52 formed by an enlarged section of the bore through body 40. The enlarged bore 52 opens to the inside of mechanical override unit 22 and the cylindrical surface defining chamber 52 is provided with longitudinal splines 54. The outer cylindrical surface of section 50 is provided with a complementary spline configuration which prevents rotation of the plunger 44, while maintaining the ability for reciprocating motion thereof.

Section 56 of plunger 44 is of intermediate diameter and is provided with a threaded external surface 58.

Threadedly engaged with section 58 is a nut 60 which is radially more extensive than section 50 of plunger 44'.

A drive cylinder 62 is rotatably mounted inside cover 42 by means of bearings 64. Additional bearings 66 are provided where the drive cylinder 62 contacts body 40.

Drive cylinder 62 has a central bore which receives section 56 of plunger 44 such that the plunger can freely reciprocate within the bore. The bore is enlarged at the end of cylinder 62 which contacts body 40 thus providing a chamber 68 which encloses nut 60.

The cylindrical surface defining chamber 50 is provided with splines 70 and the external cylindrical surface of nut 60 is provided with a complementary spline configuration. Thus, nut 60 is constrained to rotate with cylinder 62 but is free to move longitudinally within chamber 68.

A bevel gear 72 is attached to a boss at the end of drive cylinder 62 furthest from valve 10. A shaft 74 is held by a bearing 76 journalled into the cylindrical surface of cover 42. Shaft 74 is terminated inside hollow cover 42 by a bevel gear 78 which meshes with bevel gear 72. Shaft 74 is rigidly connected to a drive shaft 80 which extends to a remote location where rotary motion is imparted to it by suitable means.

Normally, nut 60 is positioned on thread 58 so that plunger 44 reciprocates freely, together with obturator 16 under control of the hydraulic actuator 20. The mechanical override unit 22 can however be used to lock valve 10 in the open position and Figure 1 illustrates the valve when so locked in the open position. It will be appreciated that with the mechanical lock thus provided by override system 22, it is not necessary to maintain hydraulic pressure via supply line 30 and this provides a singificant advantage. Assuming nut 60 is initially located at some point within chamber 68 spaced from each end thereof with the valve in the open position, locking is obtained in the following manner.

Rotary motion is imparted to drive shaft 80 which in turn drives shaft 74 and its associated bevel gear 78.

This in turn drives bevel gear 72 which causes drive cylinder 62 to rotate. Rotation of drive cylinder 62 causes rotation of nut 60 which therefore progresses along thread 58. A predetermined sense of rotation and number of revolutions is imparted to drive shaft 80 in order to drive nut 60 into contact with body 40, at the end of chamber 68 adjacent valve 10. Consequently, if the hydraulic pressure supplied via supply line 30 is released, the action of springs 34 to drive piston 32 away from valve 10 is resisted by tension which is established in the link between piston 32, plunger 36, obturator 16 and plunger 44. Plunger 44 is prevented from moving towards valve 10 by abutment of nut 60 with body 40.

With the valve fully open, section 50 of plunger 44 is at the extreme end of chamber 52 furthest from valve 10 and thus section 50 abuts against nut 60.

The main purpose of mechanical override unit 22 is to provide mechanical operation of valve 10 in the event of failure of hydraulic actuator 20. Assuming the hydraulic actuator 20 to be inoperative due to a failure in the hydraulic system, valve 10 can be opened and closed by mechanical override unit 22 in the following manner. If the arrangement is in the condition as shown in Figure 1, valve 10 can be closed by rotation of drive shaft 80 in a sense which causes rotation of nut 60 to propel the nut along thread 58 towards the valve.

However, since nut 60 is already at the limit of its travel in that direction, thread 58 acts to drive plunger 44 towards valve 10 under continued rotation of nut 60 - splines 54 preventing rotation of the plunger.

This has the effect of gradually releasing the mechanical lock so that obturator 16 moves to close off valve 10. As valve 10 closes, section 50 of plunger 44 travels along chamber 52.

If valve 10 is closed, mechanical override unit 22 can be used to open the valve in the following manner. With the valve closed. section 50 of plunger 44 is adjacent the valve end of chamber 52 and nut 60 is at the valve end of chamber 68. If for any reason nut 60 is not at the valve end of chamber 68, rotation of drive shaft 80 in the appropriate sense will cause nut 60 to progress along thread 58 until this position is obtained.

Further rotation of drive shaft 80 in this sense, or initiation of such rotation, causes thread 58 to retract plunger 44 away from valve 10 since nut 60 is prevented from further progress towards the valve by abutment with body 40. Retraction of plunger 44 causes corresponding movement of obturator 16 with the effect of bringing aperture 18 into control chamber 14 thus opening the valve. This movement of plunger 44 acts against the force of springs 34 which are compressed by movement of piston 32 towards the valve.

Drive shaft 80 is hollow and encloses a non-rotating shaft 82. Shaft 82 is connected to a chain linkage 84 encased in a flexible cover 86. Flexible cover 86 passes through a central bore in shaft 74 and into a cylindrical recess provided in the free face of plunger 44, that is the end of plunger 44 furthest from valve 10. Chain linkage 84 is connected to a stud 88 which is attached to plunger 44 inside the said recess. Since stud 88 is secured to plunger 44 reciprocation of the plunger results in reciprocating movement of shaft 82 within drive shaft 80. Thus, shaft 82 provides a remote indication of reciprocation of plunger 44 which thus enables opening and closing of valve 10 to be monitored.

One embodiment of the invention has been described with reference to the accompanying drawing. It will be readily apparent to those skilled in the art that various modifications can be made without departing from the scope of the present invention. For example, drive cylinder 62 may be directly driven by a shaft entering through the end face of cover 42, as compared with the described and illustrated use of bevel gears.

Claims

Claims:

1. A remotely operable mechanical override system for a hydraulically operated valve having an obturator, comprising a plunger which acts on the valve obturator, a rotatable drive member and a driving mechanism for translating rotary motion of the drive member into reciprocating motion of the plunger.

2. A mechanical override system as claimed in claim 1, wherein the driving mechanism comprises a nut threadedly engaged with the plunger and constrained to rotate with the drive member.

3. A mechanical override system as claimed in claim 2, wherein the nut is capable of reciprocating motion with respect to the drive member.

4. A mechanical override system as claimed in any preceeding claim, wherein the plunger, drive member and driving mechanism are contained within a housing which is secured to the valve, the plunger being restrained against rotary motion relative to the housing.

5. A mechanical override system as claimed in claim 2 or claim 3, wherein the drive member is rotated via a bevel gear.

6. A mechanical override system as claimed in any preceeding claim, comprising an elongate element connected to the plunger so as to provide a remote indication of the relative position of the plunger.

7. A mechanical override system as claimed in any preceeding claim, wherein the plunger is connected to the obturator.

8. A mechanical override system as claimed in any preceeding claim, further comprising an abutment against which the nut of the driving mechanism may be brought to bear so as to lock the obturator with the valve open.

9. A remotely operable mechanical override system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

10. A valve including a mechanical override system as claimed in any preceeding claim.

11. A valve as claimed in claim 10, wherein the valve obturator reciprocates transversely to the flow of fluid through the valve with the mechanical override system being located on one side of the obturator and a hydraulic operating system being located on the opposite side of the obturator.

12. A valve substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

12. A valve as claimed in claim 10, wherein the hydraulic operating system comprises a piston which is resiliently biased so as to normally close the valve.

13. A valve substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows Claims:1. A remotely operable mechanical override system for a hydraulically operated valve having a hydraulic operating mechanism and an obturator which reciprocates transversely to the flow of fluid through the valve, comprising a plunger which acts on the valve obturator, a rotatable drive member and a driving mechanism for translating rotary motion of the drive member into reciprocating motion of the plunger, the override system being adapted to act on the obturator at the opposite side thereof to the hydraulic operating mechanism.

10. A valve including a mechanical override systems claimed in any preceeding claim.

11. A valve as claimed in claim 10, wherein the hydraulic operating system comprises a piston which is resiliently biased so as to normally close the valve.