GB2496647A

GB2496647A - Clamping device for subsea tubular member

Info

Publication number: GB2496647A
Application number: GB1119878.5A
Authority: GB
Inventors: Peter James Curry
Original assignee: Britannia Engineering Consultancy Ltd
Current assignee: Britannia Engineering Consultancy Ltd
Priority date: 2011-11-17
Filing date: 2011-11-17
Publication date: 2013-05-22
Also published as: WO2013072688A2; WO2013072688A3; GB201119878D0

Abstract

The device clamps the tubular member 2 by an outer tubular piece 1 and a collar, a compressive clamping force being applied to the collar by a force applying member, e.g. a hydraulic cylinder 12, via a thrust rod 5 and a pressure pad 4 to the piece and collar, the applied force defining a load path; a reaction member 6 is coupled to the tubular piece 1 such that the reaction member is located in the load path to provide a reaction force in a second opposite direction. The reaction member 6 is an annular plate coupled to the piece via stiffeners 7, 8 and is coupled to the cylinder 12 via screw threads, a slip ring or a bayonet connection. A load retaining nut 9 is threaded on the thrust rod 5 and, after the required clamping force has been applied by the cylinder 12, the nut is screwed up to the reaction member 6 to prevent release of the force. A load gauge 10 is located between the nut 9 and the reaction member 6.

Description

Improved Clamping Device The present invention relates to the clamping together of two tubular members.

In particular, but not exclusively, the invention relates to the clamping together of two rigid and concentric tubular members of a subsea structure.

Devices currently exist in the subsea oil and gas industry for connecting tubular members. For instance, WO 2009/027694 and WO 2010/100473, both in the name of the applicant, describe such clamping devices.

However, it is still desirable to make further improvements relating to safe, simple and speedy attachment and detachment.

Load gauges exist for indicating at least the general magnitude of an applied load. In clamping arrangements, apparatus for verification of an initial load currently exists in the form of load indicating washers. Typically, the washers have projecting features that set the otherwise flat laying surfaces of the nut and washer apart by a known distance. During the application of loads, such as using a bolt tensioning tool, these projections progressively reduce or flatten. This allows the use of a gap measurement tool, commonly a feeler gauge, to measure the gap to establish that a level of load between washer and nut is present at the end of the tensioning operation.

However, the use of feeler gauges to measure this gap is problematic in difficult or harmful environments such as subsea, outer space or areas subject to harsh temperatures or potentially harmful conditions e.g. radioactivity. In such environments, the use of such feeler gauges is often impractical as the operator or remote robotic tool may have limited dexterity due to the use of diver gloves or an F1OV manipulator tool. This may also be under conditions of poor or restricted visibility or access.

I

It is desirable to provide means to confirm or indicate that a specified or predetermined clamping load is present within the connection, preferably both at the time of making the connection and during the lifetime of the clamping connection.

It is desirable to provide such means that requires minimal dexterity, visibility and/or acess.

According to a first aspect of the present invention there is provided a clamping device for clamping together two subsea tubular members, the device comprising: a force applying member which is operable to apply a force in a first direction to bring the two subsea tubular members into contact with each other and subsequently generate a compressive clamping force, the applied force defining a load path; a reaction member which is couplable to at least one of the tubular members such that the reaction member is located in the load path to provide a reaction force in a second opposite direction.

The reaction member may include a body portion and one or more support members. The support member may interpose the body portion and the tubular member.

The reaction member may be adapted to receive the force applying member.

The force applying member may include a piston arrangement. The force applying member may comprise a jack device, such as a hydraulic, pneumatic or electric jack.

The two tubular members may be arranged concentrically. The two tubular members may be rigid.

The force applying member may be attachable to the reaction member. The force applying member may be releasably attachable to the reaction member.

The clamping device may include a pressure pad device adapted to contact one of the tubular members and apply the force. The pressure pad device may be operable to contact the inner tubular member and apply the force.

A collar member may be provided, interposing the inner and outer tubular members. The collar member may be fixed within the outer tubular member.

The pressure pad device may be movable towards the inner tubular by applying a load to a thrust rod member using the force applying member.

The reaction member may include an aperture through which the thrust rod may extend. The reaction member may comprise a plate and the aperture may be located centrally at the plate. The force applying member may be attachable to the reaction member such that the piston of the force applying member is in contact with the thrust rod and the cylinder body is in contact with the plate of the reaction member The clamping device may be operable to deform one or both of the tubular members. The clamping device may be operable to elastically deform one or both of the tubular members.

The clamping device may include a locking device which is operable to capture and maintain the deformation of the tubular member. The locking device may comprise a locking nut.

The locking nut may be threadably connected to a section of the thrust rod. The locking nut may be rotatable to move axially along the threaded section of the thrust rod. Axial movement of the locking nut may be adapted to make contact with the reaction member.

The clamping device may include a retaining pin for securing the thrust rod and pad member in position prior to activation of the force applying member. The retaining pin may be insertable within an aperture provided at an aperture provided at the reaction member to engage the thrust rod.

The force applying member and the reaction member may include complementary threads for attachment.

Alternatively, the reaction member may include a rotatable slip collar. The force applying member may include a lip portion that is engagable with a corresponding lip provided at the slip collar. The slip collar may have a threaded connection and lever members to allow the slip collar to be rotated thereby engaging the slip collar thread to the thread of the body of the reaction member.

Alternatively, the body of the force applying member may be provided with one or more protrusions that are engagable with corresponding recesses at the reaction member. The protrusions may be integral with the cylinder body.

The protrusions may include one or more teeth. Each tooth may include horizontal and vertical faces that mate with a corresponding recess in the reaction member. The teeth may be symmetrical about a centre line of the protrusion to minimise bending stress. Each protrusion may be tapered to assist engagement. The depth of each tooth may be predetermined such that the teeth will engage only with the correct recess.

Alternatively, the body of the force applying member may be provided with one or more recesses that are engagable with corresponding protrusions at the reaction member.

The thrust rod may include biasing means to encourage the thrust rod and the cylinder piston to separate once the applied pressure has been released. The biasing means may comprise a spring loaded piston provided within a recess at the end of the thrust rod.

The clamping device may include an enclosure for at least partially enclosing the thrust rod. The enclosure may be flexible to accommodate movement of the thrust rod. The enclosure may comprise a flexible bellows device.

The reaction member may include a removable cover plate. The reaction member may include one or more injection ports for injecting preservatives and/or lubricants. The cover plate may have lifting means for manoeuvring, rotating or securing it to the reaction member.

The clamping device may include a load gauge device. The load gauge device may comprise at least one ring member provided in the load path. The ring member may be arranged around the thrust rod. The ring member may be adapted to indicate the applied load by axial deformation or shortening of the gauge ring lengths.

The ring member may be configured to be freely rotatable prior to applying a first predetermined load and non-rotatable once the first predetermined load has been reached. One or more gaps may be provided in the load path to allow free rotation. The clamping device may be configured such that reaching the first predetermined load causes the gap to close.

The ring member may be threadably attached to the thrust rod. The clamping device may include measuring means to indicate the amount of rotation of the ring member that is possible under the applied load.

The ring member may have a stepped profile in cross section. An outer ring may be provided around a small step of the ring member and may define the gap.

The large step may include a head portion for effecting rotation. The outer ring may be configured to be freely rotatable prior to applying a first predetermined load and non-rotatable once the first predetermined load has been reached.

The ring member may comprise a split ring having two or more segments.

A plurality of ring members may be provided. Each of the plurality of ring members may be configured to be freely rotatable prior to applying a different predetermined load and non-rotatable once the respective predetermined load has been reached.

According to a second aspect of the present invention there is provided a load gauge device adapted to indicate a clamping force provided by a clamping device which is operable to apply a compressive clamping force to two members, the applied force defining a load path, the load gauge device comprising: at least one compressible member provided in the load path, the compressible member being configured to be freely rotatable prior to applying a first predetermined load and non-rotatable once the first predetermined load has been reached.

One or more gaps may be provided in the load path to allow free rotation. The clamping device may be configured such that reaching the first predetermined load causes the gap to close.

The load gauge device may comprise at least one ring member arranged around a shaft member.

The ring member may be threadably attached to the shaft member. The load gauge device may include measuring means to indicate the amount of rotation of the ring member that is possible under the applied load.

The compressible member may have a stepped profile in cross section. An outer ring may be provided around a small step of the compressible member and may define the gap. The large step may include a head portion for effecting rotation.

The outer ring may be configured to be freely rotatable prior to applying a first predetermined load and non-rotatable once the first predetermined load has been reached.

The ring member may comprise a split ring having two or more segments.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective view of inner and outer tubular members and a clamping device according to a first embodiment of the invention using a threaded connection; Figure 2 is a perspective view of the inteinal load transmitting elements of the clamping device of Figure 1; Figure 3 is a perspective view of the clamping device of Figure 1 with the outer tubular member removed;

S

Figure 4 is a perspective view of a hydraulic cylinder with an external thread, viewed from the ram end; Figure 5 is a perspective view of the hydiaulic cylinder of Figure 4, viewed from the cylinder end; Figure 6 is a perspective view of clamping device according to a second embodiment of the invention with a hydraulic cylinder with a rotatable slip collar; Figure 7 is a perspective view of the clamping device of Figure 6 with the rotatable threaded slip collar removed; Figure 8 is a sectional side view of the clamping device of Figure 6 with the hydraulic cylinder shown offset and aligned with the reaction plate recess; Figure 9 is a perspective view of a clamping device according to a third embodiment of the invention with a hydraulic cylinder with integral lugs, shown with the hydraulic cylinder offset and aligned with the reaction plate recess; Figure 10 is another perspective view of the hydraulic cylinder shown in Figure 9; Figure 11 a is a cross sectional side view through the integral lugs of the hydraulic cylinder shown in Figure 9 and the female receptacle within the reaction plate, shown in the disengaged position with teeth not interlocking; Figure 11 b is a cross sectional side view through the integral lugs and the female receptacle within the reaction plate, shown in the engaged position with teeth interlocking; Figure 12 is another perspective view of the hydraulic cylinder with integral lugs, shown with the hydraulic cylinder offset and aligned with the reaction plate recess; Figure 13 is a perspective view of a clamping device according to a fourth embodiment of the invention with a hydraulic cylinder with an alternative example of integral lugs, shown with the hydraulic cylinder offset and aligned with reaction plate recess; Figure 14 is a perspective view of the clamping device of Figure 13, shown with the hydraulic cylinder offset and aligned with the reaction plate recess; Figure 1 5a is a cross sectional side view through an alternative example of integral lugs and the female receptacle within the reaction plate, shown in the disengaged position with teeth not interlocking; Figure 15b is a cross sectional side view through an alternative example of integral lugs and the female receptacle within the reaction plate, shown in the engaged position with teeth interlocking; Figure 16 is another perspective view of the clamping device of Figure 13, shown with the hydraulic cylinder offset and aligned with the reaction plate recess; Figure 17 is a perspective view of a two ring load gauge for use with conventional bolt tensioning equipment; Figure 18 is an exploded perspective view of the two ring load gauge of Figure 17; Figure 19 is a perspective view of the two ring load gauge of Figure 17; Figure 20 is a perspective view of a three ring load gauge for use with conventional bolt tensioning equipment; Figure 21 is a cross sectional side view of the three ring load gauge of Figure 20; Figure 22 is an exploded perspective view of the three ring load gauge of Figure 20; Figure 23 is a perspective view of the three ring load gauge of Figure 20; Figure 24 is a side view of a measurable load gauge; Figure 25a is a cross section of the measurable load gauge of Figure 24 prior to axial compression loading; Figure 25b is a cross section of the measurable load gauge of Figure 24 after axial compression loading; Figure 26 is a perspective view of the measurable load gauge of Figuie 24; Figure 27 is a side view of a thrust rod; Figure 28 is a cross section through the thrust rod of Figure 27 showing an integrated spring return device with the spring return set within the recess; Figure 28a is a part cross section through the thrust rod of Figure 27 showing the spring return piston projecting from the recess; Figure 29 is an exploded perspective view of the spring return device elements; Figure 30 is a side view of a clamping device according to an eighth embodiment of the invention using a load gauge integrated within a hexagonal nut; Figure 31 is a cross sectional side view of the clamping device of Figure 30; Figure 32 is a side view of a clamping device according to a ninth embodiment of the invention using a split ring load gauge with the outer ring halves removed and offset and aligned with the receptacle in the inner ring halves; Figure 33 is a side view showing the split ring load gauge of Figure 32 assembled; Figure 34 is a part sectional view showing the split ring load gauge of Figure 32 with the outer ring halves removed and offset and aligned with the receptacle in the inner ring halves; Figure 35 is a perspective view of a clamping device and showing a cover plate for the reaction plate; Figure 36 is another perspective view of the clamping device of Figure 35; and Figure 37 is a perspective view of a stepped split ring arrangement.

Embodiment 1 (Figs 1, 2, 3, 4 and 5) The figures show a clamping device for clamping together two subsea tubular members. The tubular members are circular in cross section and concentric, thus defining an outer (1) and an inner (2) tubular member.

The device comprises a force applying member in the form of a hydraulic jack or cylinder (12) which is operable to apply a force in a first direction to bring the two tubular members into contact with each other. Further applied force generates a compressive clamping force in a load path and the friction force generated prevents movement of the two tubular members relative to each other, particularly in the longitudinal direction of the tubular members.

The friction is developed as a result of a pressure inducing pad (4) that forces the inner tubular against a heavy collar (3) fixed within the outer tubular (1). The pad is urged towards the inner tubular (2) by applying a load to the end (11) of a threaded thrust rod (5) using the hydraulic cylinder (12).

The clamping device also includes a reaction member or plate (6) and the device can be coupled to the outer tubular member (1) so that the reaction plate (6) is located in the load path to provide a reaction force in a second opposite direction.

The cylinder (12) can be temporarily attached to the clamping device at the reaction plate (6). The reaction plate (6) is a heavy plate with a central opening through which projects the end of the thrust rod (5). The cylinder (12) is attachable to the reaction plate (6) such that the cylinder piston is in contact with the thrust rod (5) and the cylinder body is in contact with the plate of the reaction member. Operation of the cylinder (12) applies a pressure to the thrust rod (5) via the piston to move the thrust rod (5) and therefore the pad (4). The pressure is delivered via a hose (15) at a hydraulic connection point (16).

The clamping device includes a number of support members or radial stiffeners (7) and ring stiffeners (8) provided in the load path and interposing the reaction plate (6) and the outer tubular (1). The stiffeners, supported by the outer tubular (1), in turn support the reaction plate (6) when a force is applied.

In the first embodiment, the hydraulic cylinder (12) is attached directly to the reaction plate (6) by means of an external threaded surface (14) on the hydraulic cylinder. The external threaded surface (14) mates with a corresponding internal threaded surface (13) on the reaction plate (6). The engagement is made by first aligning then rotating the hydraulic cylinder body.

Operating the cylinder (12) to move the pad (4) causes the inner tube (2) to deform and to ovalise' within the limits of the heavy collar (3). This displacement can be captured by rotation of the locking nut (9) or alternatively a threaded collar along the threaded section of the thrust rod (5) so that a load gauge (10) makes positive contact with both the locking nut (9) and the inside face of the reaction plate (6). The load gauge is in the load path but could be omitted. When the locking nut (9) has been engaged, the deformation of the inner tube is retained, even after the hydraulic pressure supply is removed from the hydraulic cylinder, along with the corresponding compressive load with the thrust rod and therefore the frictional resistance of the clamp connection is maintained.

The connection resists load by developing friction between the outer and inner tube. It is desirable to be able to confirm that the thrust rod axial load is retained not only at load application but also during the lifetime of the connection. To do this, the load gauge (10) is introduced between the load retaining nut or wedge and the inside face of the reaction plate (6). The load gauge is described in more detail below.

In order to preserve the condition of the thread a flexible bellows (17) is employed that will contain preservatives and lubricants and accommodate movement of the thrust rod without exposing the thread to the corrosive seawater environment.

Embodiment 2 (Figs 6, 7 and 8') A second embodiment utilises a rotatable slip collar. An advantage over the first embodiment is that the hydraulic cylinder (20) may in this embodiment remain stationary during attachment to the reaction plate. The hydraulic cylinder (20) in this embodiment has a lip (21) that engages with a corresponding lip (23) on the slip collar (22). The slip collar has an external threaded surface (25) and removable external spokes (24) or paddles that allow the slip collar to be rotated thereby engaging the slip collar thread to the internal threaded surface (13) of the reaction plate (6).

A retaining pin (26) is used to secure the thrust rod (5) and pad (4) in position prior to activation of the hydraulic cylinder (20). The retaining pin (26) passes through a hole in the reaction plate (6) and penetrates the recess (27) in the thrust rod. On withdrawal of the retaining pin the thrust rod is able to be moved by the ram (27) being urged against the end of the projecting end of the thrust rod (11).

Embodiment 3 (Figs 9,10.11 and 12) In a third embodiment, the body of the hydraulic cylinder (30) has projecting features or lugs (31) that engage with corresponding recesses (32) at the reaction plate (6). The lugs may form an integral part of the hydraulic cylinder body. Attachment of the hydraulic cylinder (30) to the permanent clamp structure is via a two step operation: stabbing the lugs into the receptacle, then rotation of the hydraulic cylinder to the engaged position.

The lug system has multiple teeth (34 and 35). Figure 10 shows an arrangement in which the lugs are formed in two opposing arcs of approximately 90 degrees.

Figures 11 a and 11 b show that a cross section through the lugs is symmetrical about the centreline along line R-R and consists of a series of teeth with essentially horizontal and vertical faces that mate with corresponding recess in the reaction plate (6). The symmetry ensures that bending stress in the core of the lug (33) is negligible as the loading from both sides is balanced. The plurality of teeth (34 and 35) ensures that a multiple number of contact bearing faces (36) are available and active under the applied tension from the hydraulic cylinder (30)

IS

thereby increasing the load transfer capacity. The basic profile of the lug and recess is tapered (28) to assist engagement. Simple stop features may be introduced to avoid over rotation of the lugs during engagement. A radial pin may be inserted through aligned holes to ensure that the correct orientation of the lugs is assured prior to activation of the hydraulic cylinder and application of loading.

In order to ensure the teeth have maximum engagement, the teeth depth is set so that the teeth will engage only with the correct grooves. For example the depth of at least one tooth (34) will be larger than the others (35), thereby preventing engagement with an unintended groove. It should be noted that if full engagement were not to occur this would lead to reduced interface contact area, which could lead to reduced load transfer capacity and could result in harm to the device and/or risk to the operator should the device fail under load. The profile is also tapered to assist in stabbing of the hydraulic cylinder lugs into the female receptacle.

External markings on the reaction plate (38 and 39) and on the hydraulic cylinder (39) are used to assist alignment and indicate externally if the lugs are fully engaged and in position for locking -LOCK' or free to release R'.

Fourth Embodiment (Figs 13. 14. 15 and 16) A fourth embodiment utilises a multiplicity of short lugs set in an arc. In this instance, the male lugs are in the form of multiple single stepped blocks with contact bearing features on both sides requiring only a part rotation to align and engage with the corresponding female recesses set within the reaction plate. An alternative arrangement could employ multiple stepped blocks to increase the available contact bearing area. Figures 1 5a and 1 Sb show that a cross section through the lugs is symmetrical about the centreline along line S-S and consists of lugs that mate with corresponding recesses in the reaction plate (6) and transferring load via bearing surfaces (47).

The hydraulic cylinder (48) has external projecting lugs (40) and internal projecting lugs (41) set around the circumference that pass through corresponding external recesses (42) and internal recesses (43) set within the reaction plate (6). Load will then be transferred between multiple bearing surfaces (47). The diameter of the reaction plate (6) will be sized to allow the remaining internal area (45) of the reaction plate (6) to be adequate to safely transfer the lug loads to the clamp structure whilst sufficient space is available to accommodate the recess (46) for the thrust rod (5). Should the load required for transfer be modest, a single set of external lugs (40) may be sufficient.

External markings on the reaction plate (38 and 39) and on the hydraulic cylinder (39) are used to assist alignment and indicate externally if the lugs are fully engaged and in position for locking -L' or free to release R'.

Fifth Embodiment (Figs 17, 18 and 19) Each of the above embodiments includes a load gauge which will now be described in more detail.

The load gauge device is intended to indicate that a certain level of load has been achieved and or retained within the connection device. This is achieved by means of an indicator that will allow the operator of the device to witness if an indicator movement is possible or not and also, where the movement is measurable, the amount of movement and then, by using a known movement/load relationship, to determine the level of load.

Often the load within a bolt or thrust rod is considered critical to the integrity of the connection. Verification that sufficient load is present would effectively confirm that the load transfer capacity of the connection is available. This is of particular interest in subsea applications where the ability to confirm axial load at a required value is present within the connection not only at the initiation of the connection but also at intervals during the design life of the connection. This activity may be carried out directly by a diver or indirectly via use of a Remote Operated Vehicle (ROV) or Remote Operated Tool (ROT).

An advantage of the present invention is that no modification is made to the bolt as the device relies on only compression (rather than tension). Importantly, the extent of compression to a given value may be monitored by the available movement of a ring. Thus the present invention could, if required, incorporate a large number of nested rings and therefore provided indication of a wide range of loading within the connection by identifying which rings are able to be moved and which are not able to be moved and thereby be able to determine a more accurate assessment of the load within the connection bolt or thrust rod.

Similarly the gauge could be incorporated into the nut as a combined item for convenience and economy. This is addressed in a separate embodiment.

A further embodiment employs a micrometer type device to take a direct reading of the load.

The load gauge device employs the axial deformation or shortening of the gauge ring lengths to register load. Initially before load application differences in lengths or gaps are introduced that permit rotational movement of the rings. Under certain predetermined values of load the longitudinal or axial gaps close and once gaps are closed rotational movement is no longer possible. The proposed system will then have significant benefits in that the device can easily be shown to allow rotational movement or not of the rings. Where the device allows movement then a predetermined load can be confirmed as not being present whereas if the element allows no movement then the load (at the predetermined value) can be confirmed as present. is

Figs 17, 18 and 19 show a basic form of the load indicating device in which two rings (101) and (102) are used to indicate the level of loading in a threaded bar (103) between two nuts (104) and (105). In this example the hydraulic tool (118) is used to clamp two plates (113 and 114) together. The conventional tensioning equipment (118) applies tension load to the tension bar (120) or bolt by pushing load nut (121) whilst reacting against the near plate (114) via a bridging piece (115). As the tension rod extends so the reaction nut (105) may be turned using a bar (not shown) inserted into the radial recesses (122) and rotated to capture the strain in the tension bar (120). On release of the hydraulic pressure delivered to hydraulic connectors (123) the bar is unable to return to its original position and therefore maintains load in the system thereby transferring load into the load gauge (101 and 102).

The load gauge (101 and 102) consists of a stepped inner ring (101) concentric within an outer ring (102). The dimensions of the rings are such that there is a small radial gap (112) to allow free rotation of the outer ring with respect to the inner ring. Whilst stacked together as in Fig 19 there is a small projection of surface (106) of the inner ring with respect to (110) of the outer ring. The small projection is a known value that has been carefully machined to a high level of accuracy.

Under this initial condition load may safely transfer from nuts (105) and (104) via bearing faces (106 and 107). As the load increases so the material in the inner ring wall (108) will be compressed axially. At a certain load point (the value of which may be predetermined as the material properties are known) the projection of surface (106) will reduce to zero. At this point any further load increment will be resisted not only by the inner ring wall (108) but also the outer ring (102) due to the outer ring face (110) coming into contact with nut (105) and by the outer ring contact face (115) coming into contact with the inner ring contact face (109).

Further load increments will then be shared by both inner and outer rings but importantly the free rotation between the ring and inner ring is now prevented by friction.

The ability of the outer ring (102) to rotate can be checked by applying pressure (for example manually by a diver or an ROV manipulator to spokes (113) set within a recess (112) of the outer ring. Fig 19 shows an alternative to spokes in the form of paddles or propeller blades (114) that would allow movement to be visible by the passage of water or air flow jet to the blade surface.

Sixth Embodiment (Figs 20, 21. 22 and 23) In a sixth embodiment the load gauge as described in the fifth embodiment has additional rings added.

Further rings may be introduced into the device. These additional intermediate rings (115) may be placed between the outer and inner rings. This will allow the load within the device to be monitored with greater accuracy by allowing a further load increment to be identified as having been reached or not. In this case it would be possible to detect a load has reached an intermediate level by noting if the intermediate ring (15) rotates whereas the outer ring (102) may not. This would show that sufficient load is present within the device to close the first gap (111) but not the second gap (116) and as a result the load is known to lie within known load limits that can be predetermined.

The material for the rings may be of steel but may also be of any material that is suitable for the intended environment such that its performance is reliable and predictable deformations would occur under given load values. For example the use of a corrosion resistant alloy may be preferable and this may have an anti marine growth property.

Seventh Embodiment (Figs 24, 25 and 26) A seventh embodiment utilises a fine threaded external ring (132) mounted on to an internal ring (130) such that the change in length of a compressed section of the internal ring (130) may be readily measured by rotating the threaded ring until a known initial gap (133) is closed. The reduced amount of rotation required to close the gap (133) as compared with the unloaded condition correlates with the axial deformation experienced by the internal ring. A graduated scale (131) on the surface of the internal ring (131) is used to allow load readings to be taken directly. A similar principle is used in micrometer measuring devices but with the proposed invention the rotatable measuring device may be incorporated permanently into the gauge and allows measurement of the change in length of the ring under load (and therefore the load) directly. The measurement would be made by noting the initial marker position (138) with respect to the graduated scale (131) and setting an initial unloaded gap then rotating the ring. The novelty of this invention being that this type of micrometer type system allows direct measurement of length change (and by correlation the corresponding load) within the thrust rod (5) at any stage during the life of the connection.

Eighth Embodiment (Figs 30 and 31) An eighth embodiment has the earlier load gauge but in the form of an integrated gauge nut (145 and 146).

As shown in Figure 31, the inner ring (145) is a hex head threaded nut but with a section raised clear of the threads on the threaded bar (105) so there is a clear gap (148). The nut has a recess to receive an outer ring (146). The length of the outer ring is slightly shorter than the recess such that a longitudinal or axial gap (a19) exists. As a result, when load is applied between nuts (105) and the gauge nut (145 and 145), the gap (149) reduces. At some point the load will be sufficient to close the gap and at that time the outer ring (146) will be unable to be rotated.

This will indicated a known level of load exists within the load gauge and therefore the threaded bar (5).

As with earlier embodiments the number of rings may be increased providing more accuracy in load assessment.

Ninth Embodiment (Figs 32. 33 and 34) A ninth embodiment has the earlier load gauge but in the form of split rings rather than complete rings. Here the rings are cut into two or more segments. The segments would be held together to form a complete ring using screws or similar.

A benefit of this is the ease by which the gauge could be assembled and disassembled without removal of the bolt or thrust rod.

Each half of each ring is attached to the other using a suitable method of fastening. It should be appreciated that the fastening is only required to carry light loading so in the case of screws (153) the size of screws will not need to be substantial.

As shown in Figure 34, the inner split ring (150) is stepped to receive the outer ring (151). The stepped recess is of a known length that is slightly longer than the width of the outer ring (151) such that a gap (152) is present once the gauge is assembled. As a result, when load is applied between the nuts (105) and (106), the gap (152) reduces. At some point the load will be sufficient to close the gap and at that time the outer ring (151) will be unable to be rotated. This will indicate a known level of load exists within the load gauge and therefore the threaded bar (5).

As with previous embodiments the number of rings may be increased providing more accuracy in load assessment.

Tenth Embodiment (Figs 27, 28 and 29) A tenth embodiment relates to a thrust rod that incorporates a spring return element that encourages the contacting surfaces between the thrust rod and the hydraulic cylinder ram to part once the hydraulic pressure has been released.

This is in the form of a spring loaded piston set within the end of the thrust rod.

The piston (142) is set within a recess (140) in the end of a thrust rod (5). The recess (140) accommodates both the piston (142) and the compressed spring (141). The piston is held within the thrust rod via a retaining plate (143) set into the surface of the thrust rod and held there by a threaded arrangement or screws (144) or alternatively by threading on the edge of the retaining plate (145) and the inside face of the recess (146). In the initial unloaded status the spring is extended and the piston projects forward of the front face of the thrust rod as shown in Figure 28a. When the hydraulic cylinder is first mounted onto the reaction plate the movable ram within the hydraulic cylinder is in the fully retracted position as shown in figure 28. When the hydraulic cylinder is pressurized the ram moves forward and contacts the projecting piston. As the piston is moved into the recess within the thrust rod the spring is depressed and stores energy. Once the hydraulic pressure is released the depressed spring energy pushes the ram back to its original position. This effectively reduces the contact pressure between the thrust rod and the ram, allowing the lugs to be rotated more easily in order to disengage the hydraulic cylinder from the permanent reaction plate.

Eleventh Embodiment (Figs 35 and 36) This embodiment relates to a cover plate (172) to be mounted on the reaction plate (6). The cover plate provides protection for the reaction plate threads or recesses shown in Fig 1(13), Fig 9 (32), and Fig 14(42 and 43) and also provides a means to retain injected preservatives such as grease or heavy oil.

The preservatives may be injected through an injection point or nipple (171) or through multiple injection points. The inside of the cover plate can have suitable features such as a thread or lugs to suit the various recess profiles in the reaction plate (6).

The cover plate can have suitable lifting means to manoeuvre, rotate and secure it to the reaction plate (6). The plate may be secured to the reaction plate by shoot bolts or similar. The plate lug profiles may be of a simpler form than the multi faceted lugs for the hydraulic cylinder but will essentially mimic the same and a stabbing or twisting operation can be used to engage. The plate material may be formed from steel or alternatively a non ferrous material e.g. plastic. The plate engagement may make use of a spring return element, such as shown in Fig 29, as the spring load will also assist to retain the cover plate in the engaged position. A lip around the plate may be introduced and mated with a matching recess in the reaction plate to further help provide a good seal to retain the preservatives.

Twelfth Embodiment (Figs 36 and 37) A twelfth embodiment relates to a split ring (160 and 161) that is set between the reaction nut (9) and the reaction plate (6). This may be used with or without a load gauge (101 and 102) in position.

The split ring has a length greater than the imposed radial deformation of the inner tubular (2). This allows the clamp to be released even if the thread of the thrust bolt (5) or nut (9) is not serviceable due to corrosion or marine growth.

The release operation requires the hydraulic cylinder to be reattached to the reaction plate and reapplying a load slightly in excess of the original clamping load. This effectively squeezes the inner tubular further thereby relieving load in the nut (9) and thereby the load in the split ring (160 and 161). As the split ring may be held together by tie-wraps (162) or similar, the operation could simply require cutting the tie-wraps and splitting the two halves of the ring. The splitting of the ring may be assisted by use of chamfers (164) along the length of the ring split line.

There are many forms of split ring that could be used. One shown has a slot set in the wall of the split ring allowing a key plate (163) to be set inside. The key plate will help to stabilise the ring under compression loads that may tend to open out the ring halves under compression. Alternatively the ends of the split rings could be retained within collars set on the adjacent nut (9) or reaction plate (6) or load gauge (101). On application of the hydraulic pressure, the compression in the split ring will be removed allowing the two halves of the split ring to be separated. Once separated and removed from the thrust rod (5), the hydraulic pressure may be released. This will allow the deformed inner tubular member (2) to return to its original shape and thereby allow the inner (2) and outer tube (1) to be separated.

Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention.

Claims

<claim-text>Claims 1. A clamping device for clamping together two subsea tubular members, the device comprising: a force applying member which is operable to apply a force in a first direction to bring the two subsea tubular members into contact with each other and subsequently generate a compressive clamping force, the applied force defining a load path; and a reaction member which is couplable to at least one of the tubular members such that the reaction member is located in the load path to provide a reaction torce in a second opposite direction.</claim-text> <claim-text>2. A clamping device as claimed in claim 1, wherein the reaction member includes a body portion and one or more support members.</claim-text> <claim-text>3. A clamping device as claimed in claim 2, wherein the support member interposes the body portion and the tubular member.</claim-text> <claim-text>4. A clamping device as claimed in any preceding claim, wherein the reaction member is adapted to receive the force applying member.</claim-text> <claim-text>5. A clamping device as claimed in any preceding claim, wherein the force applying member is releasably attachable to the reaction member.</claim-text> <claim-text>6. A clamping device as claimed in any preceding claim, including a pressure pad device adapted to contact one of the tubular members and apply the force.</claim-text> <claim-text>7. A clamping device as claimed in claim 6, including a thrust rod member, and wherein the pressure pad device is movable towards the tubular member by applying a load to a thrust rod member using the force applying member.</claim-text> <claim-text>8. A clamping device as claimed in claim 7, wherein the reaction member includes an aperture through which the thrust rod may extend.</claim-text> <claim-text>9. A clamping device as claimed in claim 1, wherein the force applying member comprises a cylinder and piston, and wherein the force applying member is attachable to the reaction member such that the piston is in contact with the thrust rod and the cylinder body is in contact with a reaction plate of the reaction member.</claim-text> <claim-text>10. A clamping device as claimed in any preceding claim, including a locking device which is operable to capture and maintain the deformation of the tubular member.</claim-text> <claim-text>11. A clamping device as claimed in claim 10, wherein the locking nut is threadably connected to a section of the thrust rod and rotatable to move axially along the threaded section of the thrust rod.</claim-text> <claim-text>12. A clamping device as claimed in any preceding claim, wherein the force applying member and the reaction member include complementary threads for attachment.</claim-text> <claim-text>13. A clamping device as claimed in any of claims 1 to 11, wherein the reaction member includes a rotatable slip collar.</claim-text> <claim-text>14. A clamping device as claimed in claim 13, wherein the force applying member includes a lip portion that is engagable with a corresponding lip provided at the slip collar.</claim-text> <claim-text>15. A clamping device as claimed in claim 13 or 14, wherein the slip collar has a threaded connection and lever members to allow the slip collar to be rotated thereby engaging the slip collar thread to the thread of the body of the reaction member.</claim-text> <claim-text>16. A clamping device as claimed in any of claims 1 to 11, wherein the body of the force applying member is provided with one or more protrusions that are engagable with corresponding recesses at the reaction member.</claim-text> <claim-text>17. A clamping device as claimed in claim 16, wherein the protrusions include one or more teeth.</claim-text> <claim-text>18. A clamping device as claimed in claim 17, wherein each tooth includes horizontal and vertical faces that mate with a corresponding recess in the reaction member.</claim-text> <claim-text>19. A clamping device as claimed in claim 17 or 18, wherein the teeth are symmetrical about a centre line of the protrusion to minimise bending stress.</claim-text> <claim-text>20. A clamping device as claimed in any of claims 17 to 19, wherein each protrusion is tapered to assist engagement.</claim-text> <claim-text>21. A clamping device as claimed in any of claims 17 to 20, wherein the depth of each tooth is predetermined such that the teeth will engage only with the correct recess.</claim-text> <claim-text>22. A clamping device as claimed in claim 9, wherein the thrust rod includes biasing means to encourage the thrust rod and the cylinder piston to separate once the applied pressure has been released.</claim-text> <claim-text>23. A clamping device as claimed in claim 22, wherein the biasing means comprises a spring loaded piston provided within a recess at the end of the thrust rod. 2S</claim-text> <claim-text>24. A clamping device as claimed in claim 9, including an enclosure for at least partially enclosing the thrust rod.</claim-text> <claim-text>25. A clamping device as claimed in claim 24, wherein the enclosure is flexible to accommodate movement of the thrust rod.</claim-text> <claim-text>26. A clamping device as claimed in any preceding claim, wherein the reaction member includes a removable cover plate with sealing means for retaining a preservative or lubricant.</claim-text> <claim-text>27. A clamping device as claimed in any preceding claim, wherein the reaction member includes one or more injection ports for injecting preservatives and/or lubricants.</claim-text> <claim-text>28. A clamping device as claimed in any preceding claim, including a load gauge device.</claim-text> <claim-text>29. A clamping device as claimed in claim 28, wherein the load gauge device comprises at least one ring member provided in the load path, the ring member being configured to be freely rotatable prior to applying a first predeteimined load and non-rotatable once the first predetermined load has been reached.</claim-text> <claim-text>30. A clamping device as claimed in claim 29, wherein the ring member is threadably attached to the thrust rod.</claim-text> <claim-text>31. A clamping device as claimed in claim 30, wherein the clamping device includes measuring means to indicate the amount of rotation of the ring member that is possible under the applied load.</claim-text> <claim-text>32. A clamping device as claimed in any of claims 29 to 31, wherein the ring member has a stepped profile in cross section and an outer ring is provided around a small step of the ring member to define a gap, the outer ring being configured to be freely rotatable prior to applying a first predetermined load and non-rotatable once the first predetermined load has been reached.</claim-text> <claim-text>33. A clamping device as claimed in any of claims 29 to 32, wherein the ring member comprises a split ring having two or more segments.</claim-text> <claim-text>34. A clamping device as claimed in any of claims 29 to 33, wherein a plurality of ring members are provided, each of the plurality of ring members being configured to be freely rotatable prior to applying a different predetermined load and non-rotatable once the respective predetermined load has been reached.</claim-text> <claim-text>35. A load gauge device adapted to indicate a clamping force provided by a clamping device which is operable to apply a compressive clamping force to two members, the applied force defining a load path, the load gauge device comprising: at least one compressible member provided in the load path, the compressible member being configured to be freely rotatable prior to applying a first predetermined load and non-rotatable once the first predetermined load has been reached.</claim-text> <claim-text>36. A load gauge device as claimed in claim 35, wherein one or more gaps are provided in the load path to allow free rotation.</claim-text> <claim-text>37. A load gauge device as claimed in claim 36, wherein the clamping device is configured such that reaching the first predetermined load causes the gap to close.</claim-text> <claim-text>38. A load gauge device as claimed in any of claims 35 to 37, wherein the load gauge device comprise at least one ring member arranged around a shaft member.</claim-text> <claim-text>39. A load gauge device as claimed in claim 38, wherein the ring member is threadably attached to the shaft member.</claim-text> <claim-text>40. A load gauge device as claimed in claim 39, wherein the load gauge device includes measuring means to indicate the amount of rotation of the ring member that is possible under the applied load.</claim-text> <claim-text>41. A load gauge device as claimed in any of claims 35 to 41, wherein the compressible member has a stepped profile in cross section.</claim-text> <claim-text>42. A load gauge device as claimed in claim 41, wherein an outer ring is provided around a small step of the compressible member and the outer ring defines the gap.</claim-text> <claim-text>43. A load gauge device as claimed in claim 42, wherein the outer ring is configured to be freely rotatable prior to applying a first predetermined load and non-rotatable once the first predetermined load has been reached.</claim-text> <claim-text>44. A load gauge device as claimed in any of claims 38 to 43, wherein the ring member comprise a split ring having two or more segments.</claim-text> <claim-text>45. A load gauge device as claimed in any of claims 35 to 44, wherein a plurality of ring members may be provided, each of the plurality of ring members being configured to be freely rotatable prior to applying a different predetermined load and non-rotatable once the respective predetermined load has been reached.</claim-text> <claim-text>46. A clamping device as claimed in Claim 9, including annular member formed from two or more segments which are removably attachable to each other to allow the annular member to be located around the thrust rod in the load path and sized to define an annular gap between the annular member and the thrust rod.</claim-text>