GB2511546A

GB2511546A - Subsea securing device

Info

Publication number: GB2511546A
Application number: GB1304087.8A
Authority: GB
Inventors: Patrick Joseph Cosgrove; Terence Burgon
Original assignee: MSCM Ltd
Current assignee: MSCM Ltd
Priority date: 2013-03-07
Filing date: 2013-03-07
Publication date: 2014-09-10
Anticipated expiration: 2033-03-07
Also published as: GB201304087D0; GB2511546B

Abstract

A securing device, which may be used on a subsea wellhead, comprising a drive shaft 20 longitudinally reciprocable forwards and backwards along its axis and having at one end a head 19 adapted to pass through a key aperture 17 in a wall when the drive shaft is in a first angular position. The head is adapted to engage the wall when the drive shaft is in a second angular position and is moved backwards. A guide 38 is defined in one of a drive housing 22 and the drive shaft and is engageable by a guide follower 37 carried on the other of the drive shaft and the drive housing. The guide defines a base track (44, figure 6) which extends parallel to the axis of the drive shaft, and two transverse tracks (45, 46, figure 6), which extend from the base track at separate locations. An operating member (40, figure 1), which may be a sleeve to which is connected a paddle (43, figure 1) can rotate the drive shaft independently of a captive nut (25, 28, figure 1) which can be rotated by an ROV.

Description

SUBSEA SECURING DEVICE

Field of the invention

This invention relates to securing devices and particularly fly to place' units which may be used to bring subsea devices, such as stab-plates, together and to secure them.

Background to the invention

Subsea stab plates contain an array of equipment, typically self-sealing hydraulic couplings and/or electrical connections. There is typically a fixed stab plate which is attached to a sub-sea structure to which hydraulic or electrical lines are run to an array of fixed half-couplings on this stab plate. The free stab plate has a corresponding array of the free halves of the electrical and hydraulic couplings to which hydraulic tubes or electric cables connected to surface equipment are attached. A so-called umbilica'l connection, often many kilornetres long, takes the supply lines from the surface equipment to the free stab plate. Initially the free stab plate would be at the surface awaiting deployment. The free stab plate would then be transported, preferably by means of a remote operated subsea vehicle (Roy), to the subsea structure. The invention relates particularly but not exclusively to the means whereby two members, and particularly a free' plate and a fixed' plate, are oriented to accept each other, captured, brought together and clamped and eventually unclamped.

One example of such a device is fully described in our GB patent No. 2453910, to which reference may be made for general background. In that device a longitudinally reciprocable shaft carries a lobed head which for a particular angular position of the shaft may pass through a corresponding shaped key aperture. The shaft, which may be driven by a captive nut, carries two cam followers which move within shaped slots in a fixed sleeve. The device requires both angular movement and lengthwise movement of the shaft and for these purposes the specific device in the aforementioned patent has in the sleeve cam slots which have an oblique portion, causing rotation of the shaft, and axially directed portions, which allow only lengthwise movement of the shaft. The slots in the example have the form of a 7.

Summary of the invention

One object of the invention is to provide a securing device in which rotation of the shaft between positions that allow and prevent passage of the head through the key aperture can normally be caused by an operating member rather than by a cam action converting axial movement of the shaft into rotary motion. In its preferred form the securing device includes specially shaped guide slots and an operating member which is external to the drive housing in which the cam slots are located. Further objects of the invention include providing improved recovery from seizure. I0

According to a preferred embodiment of the invention, a securing device comprises a drive shaft longitudinally reciprocable forwards and backwards along its axis and having at one end a head adapted to pass forwards through a key aperture in a wall member when the drive shaft is in at least a first angular position, the head being adapted to engage the wall member when the drive shaft is in a second angular position and is moved backwards; at least one guide defined in one of a drive housing and the drive shaft and engageable by a guide follower carried on the other of the drive shaft and the drive housing, the guide defining a base track, which extends parallel to the axis of the drive shaft so as to constrain the drive shaft to axial movement, and two transverse tracks, which extend from the base track at separate locations and which allow rotation of the drive shaft; and an operating member for rotating the drive shaft.

Preferably the ends of the transverse tracks remote from the base track define the said first angular position and accommodate axial movement of the shaft.

In a preferred form of the guide one of the two transverse tracks tapers from a narrow width adjacent the base track to a wider width at its end remote from the base portion and a second) of the two tracks tapers from a relative wide width adjacent the base track to a narrower width at its end remote from the base track. The transverse tracks may be separated by a bar which has oblique sides engageable by the guide follower.

The operating member may comprise a rotatable member disposed outside the drive housing and may be coupled to a manually operable paddle.

In preferred embodiments the guide follower is carried on the drive shaft and the guide is disposed in the drive housing. Preferably there are two guide followers, disposed diametrically opposite each other and each engageable with a respective guide.

The invention extends to a subsea assembly comprising a securing device, a fixed stab plate including said wall member, and a free stab plate to which the drive housing is fixed. The plates may carry a multiplicity of electrical and/or hydraulic couplings which are mated as the securing device pulls the plates together by rearward movement of the head against the wall member.

Description of the drawings

Figure 1 is a section view of one embodiment in one phase of operation Figure 2 is a part-sectional view of the embodiment in a different phase of operation Figures 3 to 6 illustrate several details of the embodiment shown in Figures 1 and 2 Figure 7 is a sectional view, corresponding to Figure 2, of a modified embodiment

Detailed description

Figure 1 of the drawings shows in side view, partly sectioned, a device I according to one embodiment of the invention in conjunction with a fixed, subsea stab plate 10 and a free subsea stab plate 11 after the plates have been brought into close proximity but are not yet closed together. Figure 2 is another side view (at right angles to the first) and shows the same plates 10 and 11 after they have been closed together.

The fixed and free plates each carry a plurality of respective halves of mateable couplings, either hydraulic or electric or both. One such half coupler is exemplified by a coupler 12 on the fixed plate; it can be mated with a complementary coupler 13 carried on the free plate.

For ease of illustration other couplers have been omitted. The fixed plate II carries a plurality of alignment pins such as the alignment pin 14 which extends in a direction normal to the fixed plate and can engage a corresponding aperture in the free plate 11.

One of the plates 10 and 11, in this example the free plate ii, carries stand-off pins 15 which set the maximum amount of make-up which can occur; that is to say, they set the minimum distance separating the plates 10 and 11. Lines A show the separation of the couplers in Figure land line B the minimum (zero) separation of the couplers in Figure 2.

Fixed to the plate 10 and extending normally to it is a central locking collar 16, which extends into a central aperture in the free plate. This collar 16 has an end wall 16a which contains a lobed keying aperture 17 which allows the passage, into a cavity 18, of a triple-lobed spigot head 19 of a drive shaft 20, which extends axially through the securing device 1 to a drive nut to be described.

The collar 16 contains an internal integral stop 21 which can be engaged by a lobe of the spigot head 19 to limit the permissible rotation of the lobed spigot head 19 while the spigot head is within in the collar 16. The cavity 18 including the lobed spigot head 19 and the stop 21 is shown in end view in Figure 3 and the spigot head 19 is shown in end view in Figure 4. As will be explained in more detail later, the head 19 can be, if correctly presented, passed though the key aperture 17, rotated and then pulled back against the end wall iGa in which the key aperture 17 is formed. Typically the clearance between the lugs or lobes of the spigot head 19 and the key aperture 17 would be about 0.3 mm and the required turn of the spigot head 19 would be about 60°.

Rebated in and secured to the free plate 11 (by bolts such as bolt 22a) is a generally cylindrical drive housing 22 which contains most of the working parts of the device. The drive housing 22 has at its end secured to the free plate an open cylindrical chamber 23 into which fits the end of thicollar 16.

The drive housing 22 is axially aligned with and secured to an operating guide 24. In this example the guide is in the ordinary form of an Roy bucket'. This has a conventional shape which allows an Ray to locate and engage an external operating member 25 for the device 1. The shape of the bucket is determined by the need to have in practice a common agreed shape for location and engagement by ROVs.

The operating member 25 for the device 1 is in this example an engageable rotary member constituted by a nut. The nut had a square head 26 within the bucket 24so that the nut can be rotated by the Roy. The body of the nut passes through an end plate 27 of the drive housing, the bucket being welded to this end plate 27. The nut has a flange 28 which is held captive within a collar 29 secured within the drive housing 22 and abutting the endplate 27.

Accordingly the nut 25 can rotate but is restrained against axial movement. Extending within the nut is a threaded part 30 of the drive shaft 20, which will move axially relative to the housing as the nut 25 is rotated.

In this example the drive housing 22 provides two end stops which, as will be explained, limit the axial movement of the drive shaft 20. These end stops are constituted by the inner end 31 of the collar 29 and an inwardly directed annular flange 32 at the inner end of the chamber 23 which receives the collar 16 within the drive housing 22. These end stops can be abutted by a hub 33 at the middle part of the drive shaft 20.

Fixed to the plate 10 and extending normally to it is a central locking collar 16, which extends into a central aperture in the free plate. This collar 16 has an end wall 16a which contains a lobed keying aperture 17 which allows the passage, into a cavity 18, of a triple-lobed spigot head 19 of a drive shaft 20. The collar 16 contains an internal integral stop 21 which can be engaged by a lobe of the spigot head 19 to limit the permissible rotation of the lobed spigot head 19 while the spigot head is within in the collar 16. The cavity 18 including the aperture 17 and the stop 21 is shown in end view in Figure 3 and the spigot head 19 is shown in end view in Figure 4. As will be explained in more detail later, the head 19 can be, if correctly presented, pass though the key aperture 17, rotated and then pulled back against the collar wall 16a in which the key aperture 17 is formed. Typically the clearance between the lugs or lobes of the spigot head 19 and the key aperture 17 would be about 0.3 mm and the required turn of the spigot head 19 would be about 60°.

Accordingly the nut 25 can rotate but is restrained against axial movement. Extending within the nut isa threaded part 3001 the drive shaft 20, which will move axially relative to the housing as the nut 25 is rotated.

The hub 33 has a radial slot 34 in which are disposed two pins 35 and 35a. These extend outwardly through a collar 36 to heads 37 and 37a which constitute guide followers and which cooperate as described below with guides constituted by specially shaped slots 38 and 38a in the drive housing. These slots are partly shown in Figure 5 and one of the guides 38 and the respective follower 37 will be fully described with reference to FigureS.

The heads 37 have a respective collar 39 and 39a fitting within respective apertures in a sleeve 40 which can rotate with respect to the drive housing. The sleeve carries an arm 41 which extends through an arcuate aperture 42a in a plate 42 to a paddle 43 disposed adjacent the bucket 24. In this manner the followers 37 and 37a are connected to an operating member which can rotate the drive shaft independently of the drive applied by way of the drive nut 25.

As is shown particularly in Figure 6, each guide slot has the general form of a U of which the base, extending between end locations V and Z in Figure 6, is an axially extending flat 44 which provides a track which is parallel to the axis of the shaft 20 and which can constrain movement of a guide follower (pin 37) and accordingly the shaft 20 to the axial direction.

The slot has two arms 45 and 46 which provide transverse tracks which extend peripherally and which allow rotation of the shaft 20, The arm 45 tapers from a width, at location V in the base, just greater than the follower 37 to a top 47, defining location W, where the arm is substantially greater in width than the follower 37. The other arm 46 tapers from a wide width at the base location Z inwardly to a top 48, defining location X, where this arm is just greater in width than the follower 37.

The central bar 49 which divides the arms has a substantially constant width between its sides 50 and Si (which partly define the taper in the arms 45 and 46) and is obliquely disposed. The angle of inclination of the bar 49 and its sides 50 and 51 relative to a normal to the axis of the shaft 20 is in this example about 21°. Each guide constituted by the U S shaped slots 38 and 38a does not tightly constrain the followers and the drive shaft 20 but allows substantial freedom thereof.

The operation of the device will be described in relation to one of the guidance systems (the follower 37 and the guide slot 38) for convenience but it will be understood that the diametrically disposed follower 37a and the guide slot 38a cooperate correspondingly and simultaneously. It may be feasible to provide only one guide but the use of two is preferred for avoiding unbalancing of the shaft 22.

Movement of the follower 37 from the bottom of the 44 of the cam slot to a top 47 or 48 thereof will provide a rotation of the drive shaft through approximately 60g. The main constraints governed by the U-shaped slot are the base track 44 (from Y to 7), which sets the clamping or locking position of the head 19 and the tops 47 and 48 (positions W and X) which set the install (or unclamp) position of the head 19 on the shaft 20.

By means of the paddle 43 the sleeve 40 can move the follower 37 freely along an arm of the U. It can turn the shaft 20 from an angular position permitting installation (unlocked) to the clamp position (locked) or vice versa. When the Roy drive shaft is rotated it can turn until the follower 37 strikes a face of the U slot. The reason for the angled centre bar is to aid the positioning of the shaft 20 so that it can, when the ROy drive shaft rotates in the appropriate direction, automatically guide the shaft 20 to the correct position for either clamping or de-clamping by movement of the head 19 through the key aperture 17.

The paddle 43 permits a manual operator or ROV to select the desired position but will not cause motion if the pin 37 is not in an appropriate position. When the units are clamped up (locked on) the paddle, which is preferably designed with restricted strength, cannot move the shaft 20 (i.e. cannot unlock the units). An indication of the angular position of the shaft 20 may be given by an indicator with coloured position markers independently attached to the sleeve 40. If (for example) the head 19 has not been fully installed, the lobes being still within the key plate, the paddle will be unable to turn the clamp shaft to the locked on position. The ROV will not be permitted to turn the ROy drive shaft and damage the mechanism In a typical method of installation subsea, a ROV is given the free stab plate with the securing device in its Install' state, i.e. when the shaft 20 has been has been rotated anticlockwise until the pin 37 is at position X at the top of the arm 46 of the slot 38 The ROV grips the torque bucket and enters the free stab plate into the fixed stab plate, pushing the unit till the top of the head 19 reaches the end (in the drawing the right-hand end) of the cavity 18 in the collar 16. The paddle may then be moved to shift the follower 37 (with consequent rotation of the shaft 20) to the location 7 at the bottom of the arm 46 of the guide slot 38. In this state the head 19 is in an angular position suitable for clamping.

A major advantage of this invention is that should the ROy have not fully inserted the securing device, i.e. the head 19 still being within the aperture 17, the paddle could not be moved, the location of the head within the key aperture preventing movement of the paddle. This is a major advantage, because clamping action by means of rotation of the drive nut and consequent axial movement of the shaft 20 before the device is in the correct state is quite liable to cause damage to the equipment.

On the assumption that the head 19 has been fully inserted into the cavity 18 clear of the key aperture 17, the ROy can proceed with driving the nut 25, typically nine or so turns clockwise, to pull the 19 head lobes into contact with the inner end wall of the collar 16.

The follower 37 will be driven along the base track 44 of the slot 38 to theY position when the clamping action is complete, as shown in Figure 2. The stab plates will have been fully drawn together and the couplings such as the couplings 12 and 13 will have been fully made up. The ROV may now be removed. The couplings may be either electrical or hydraulic but in any case may now be operated. The desired clamped state of the device may be indicated by the paddle and the indicator aforementioned.

It is possible that the action of the paddle 43 does not move the follower pin 37 fully to the position 7 but provided that the head 19 is clear of the key aperture the axial movement of the drive shaft by means of the nut 25 driven by the ROV can by virtue of the oblique face 51 rotate the drive shaft to bring the follower pin 37 to the base 44 of the slot 38 so that the follower is on its correct track to move towards location V. In order to perform an unclamping operation, a ROV may be reinstalled to grip the torque bucket. The follower 37 pin will still be in the V position shown in Figure 6. The ROy can now proceed to turn the nut 25 (anticlockwise in this example) to drive the head 19 away from the end wall of the cavity 18. The follower 37 will travel from position V to position Z along the base 44 of the slot 38. The paddle may now be operated so that the shaft 20 rotation to move follower pin 37 from position Z to the top of the arm 45 (position X). The angular position of the shaft will now allow withdrawal of the head through the key aperture 17 and the drive shaft may be axially driven by way of the nut 25 to complete the withdrawal.

Unclamping in the manner just described may be prevented by marine growths or corrosion which may prevent relative rotation of the nut 25 and the threaded part of the drive shaft 20. In the clamped state normally large forces (25000 newtons from the ROy clamping torque of l300Nm) are clamping the lobes of the head 19 to the key plate of the collar 16.

The shape of the slot 38 allows the seizure of the threaded connection to be overcome by rotation of the drive shaft. For this purpose the ROV may be reinstalled to grip the torque bucket. The follower 37 will still be in the V position shown in Figure 6 when the ROV turns the nut 25 anticlockwise then owing to the seizure of the threaded connection the shaft 20 will turn, with it forcing the lobes of the clamp head across the key plate until the follower 37 reaches the position W. Since this position defines the same angular position as does position X, the shaft will have been pu in the correct angular position to allow withdrawal of the head 19 from the cavity 18 through the key aperture 17.

Marine growths or corrosion may occur also between the head 19 and the key plate defining aperture 17. Again this may be overcome by means of rotation of the hut 25 by the ROy.

The paddle and followers will still be in the y position (on diagram 2 view). When the ROV turns the nut 25 anticlockwise and because of the seizure of the threaded connection the shaft to force the lobes of the 19 head across the key plate, follower 37 moving to position W. A reason for the angle on the side 50 of the central bar 49 to give clearance for the follower 37 to move as the ROV stops anticlockwise turning of the nut 25, , then turns the nut clockwise to regain the initial position at 1, then resumes the standard unclamping procedure.

-10 -The normal final position of the uninstalled device is with the follower 37 at the W position of the slot 38. From here the follower 37 can be moved by the paddle 43 directly to the V position. Anticlockwise rotation of the nut 25 by the ROV will now extend the shaft 20 to a position wherein follower 37 is at position 4 whence the paddle can cause movement of the shaft 20 to move follower 37 to the position X If the follower 37 is only partially moved by the paddle towards the V position the follower may strike the central angled bar 49 of the slot 38 and be automatically directed to its correct path if the continued rotation of the ROy drive shaft is in the appropriate direction.

Figure 7 illustrates a modification of the device previously described. Figure 7 resembles Figure 2 and the operation of the illustrated device is exactly as previously described above.

In the modification, the collar 16a differs from the collar 16 in Figures 1 and 2 in that it is entirely hollow, the cavity 18 being a through bore extending to an open end 18a. This modification permits the extraction of a severed lobed-head through the collar 16.

In the foregoing the followers 37 and 37a are carried by the drive shaft and the cam slots are defined in the drive housing. A converse arrangement in which the or each guide slot is defined in or by the drive shaft and each respective follower is disposed in the drive housing may be feasible but is not a preferred option.

Claims

-11 -Claims 1. A securing device comprising a drive shaft (20) longitudinally reciprocable forwards and backwards along its axis and having at one end a head (19) adapted to pass forwards through a key aperture (17) in a wall member when the drive shaft is in at least a first angular position, the head being adapted to engage the wall member when the drive shaft is in a second angular position and is moved backwards; at least one guide (38) defined in one of a drive housing (22) and the drive shaft (20) and engageable by a guide follower (37) carried on the other of the drive shaft and the drive housing, the guide defining a base track (44), which extends parallel to the axis of the drive shaft so as to constrain the drive shaft to axial movement, and two transverse tracks (45, 46), which extend from the base track at separate locations and which allow rotation of the drive shaft; and an operating member (40) for rotating the drive shaft.
2-A device according to claim 1 in which the ends of the tracks (45, 46) remote from the base portion define the said first angular position.
3. A device according to claim 1 or 2 in which the tracks (45, 46) accommodate axial movement of the shaft.
4. A device according to claim 3 in which one of the two transverse tracks (45) tapers from a narrow width adjacent the base track to a wider width at its end (47) remote from the base portion and a second (46) of the two tracks tapers from a relative wide width adjacent the base track to a narrower width at its end (48) remote from the base track
5. A device according to claim 4 in which the said transverse tracks (45. 46) are separated by a bar (49) which has oblique sides engageable by the guide follower.
6. A device according to any of claims 1 to 5 in which the said operating member (40) comprises a rotatable member disposed outside the drive housing (22).
7. A device according to claim 6 in which a manually operable paddle (43) is coupled to the rotatable member (40) -12 -
8. A device according to any foregoing claim, in which the guide follower (37) comprises a radially directed pin.9. A device according to any of claims 1 to 8 in which the drive housing (22) is a generally cylindrical housing through which the drive shaft (20) extends.10. A device according to any of claims 1 to9 in which the guide follower (37) is carried on the drive shaft and the guide (38) is disposed in the drive housing.11. A device according to any of claims ito 10 in which there are two guide followers (37, 37a), disposed diametrically opposite each other and each engageable with a respective guide (38, 38a).12. A device according to any of claims 1 to 11 in which the drive housing (22) is secured to a bucket guide (24) which is locatable by a subsea ROV and within which an engageable member (25) for the drive shaft is located.13. A device according to any of claims ito 12 in which the drive shaft (20) engages threadingly a drive nut (25) which is restrained against axial movement.15. A subsea assembly comprising a securing device according to any of claims ito 13, a fixed stab plate (10) including said wall member (16a),and a free stab plate (ii) to which the drive housing is fixed.15. An assembly according to claim 15 in which the plates (10, 11) carry a multiplicity of electrical and/or hydraulic couplings which are mated as the securing device pulls the plates together by rearward movement of the head against the wall member.AMENDMENT TO CLAIMS HAVE BEEN FILED AS FOLLOWSClaims 1. A securing device comprising a drive shaft (20) longitudinally reciprocable forwards and backwards along its axis and having at one end a head (19) adapted to pass forwards through a key aperture (17) in a wall member when the drive shaft is in at least a first angular position, the head being adapted to engage the wall member when the drive shaft is in a second angular position and is moved backwards; at least one guide (38) defined in one of a drive housing (22) and the drive shaft (20) and engageable by a guide follower (37) carried on the other of the drive shaft and the drive housing, the guide defining a base track (44), which extends parallel to the axis of the drive shaft so as to constrain the drive shaft to axial movement, two transverse tracks (45, 46), which extend from the base track at separate locations and which allow rotation of the drive shaft; and an operating member (40) for rotating the drive shaft; wherein the transverse tracks accommodate axial movement of the shaft, one of the two transverse tracks (45) tapering from a narrow width adjacent the base track to a wider width remote from the base portion and a second (46) of the two tracks tapering from a relatively wide width adjacent the base track to a narrower width remote from the base track.2. A device according to claim 1 in which the ends of the tracks (45. 46) remote from the base portion define the said first angular position.3. A device according to claim 1 in which the said transverse tracks (45, 46) are separated by a bar (49) which has oblique sides engageable by the guide follower.* * 25 4. A device according to any of claims ito 3 in which the said operating member (40) comprises a rotatable member disposed outside the drive housing (22).S*.55 5* * 5. A device according to claim 4 in which a manually operable paddle (43) is coupled * S *5*5 * to the rotatable member (40).6. A device according to any foregoing claim, in which the guide follciwer (37) comprises a radially directed pin.7. A device according to any of claims 1 to 6 in which the drive housing (22) is a generally cylindrical housing through which the drive shaft (20) extends.

S. A device according to any of claims ito 7 in which the guide follower (37) is carried on the drive shaft and the guide (38) is disposed in the drive housing.
9. A device according to any of claims 1 to 8 in which there are two guide followers (37, 37a), disposed diametrically opposite each other and each engageable with a respective guide (38, 38a).
10. A device according to any of claims ito 9 in which the drive housing (22) is secured to a bucket guide (24) which is locatable by a subsea ROV and within which an engageable member (25) for the drive shaft is located.
ii. A device according to any of claims ito lOin which the drive shaft (20) engages threadingly a drive nut (25) which is restrained against axial movement.
12. A subsea assembly comprising a securing device according to any of claims ito 11, a fixed stab plate (10) including said wall member (16a), and a free stab plate (11) to which the drive housing is fixed.

i3. An assembly according to claim 12 in which the plates (10, 11) carry a multiplicity of electrical and/or hydraulic couplings which are mated as the securing device pulls the plates together by rearward movement of the head against the wall member. * . ** *ee* * * S.... * . *SSeS S...SS..... S *