GB2617618A

GB2617618A - Underwater pipeline anchoring apparatus

Info

Publication number: GB2617618A
Application number: GB2205607.1A
Authority: GB
Inventors: Gerard Allan Peter
Original assignee: Pace Geotechnics Ltd
Current assignee: Pace Geotechnics Ltd
Priority date: 2022-04-14
Filing date: 2022-04-14
Publication date: 2023-10-18
Also published as: WO2023198933A1; GB202205607D0

Abstract

Underwater pipeline anchoring apparatus 10, the apparatus comprising a fixing device 12 for fixing the apparatus in an installed condition to an underwater pipeline 14, and an anchor member 16 which, in in the installed condition, extends outwardly downwardly from the pipeline into seabed material to resist movement of the pipeline relative to the seabed material, and wherein, in the installed condition, the anchor member is not fixed to the seabed material. The apparatus can be installed to an existing pipeline in situ without requiring any break in the pipeline. Aspects include: the fixing device is movable between an open condition and a closed condition and comprises a clamp device; the apparatus includes a pair of the anchor members, each of which, in the installed condition, may extend laterally and downwardly outwardly from the pipeline, one member extending outwardly on each side of the longitudinal axis of the pipeline (into seabed material to resist movement of the pipeline relative to the seabed material); the anchoring apparatus includes a water supply arrangement to provide a water supply to a lowermost part of the or each anchor member at an elevated pressure relative to the sea pressure local to the lowermost part.

Description

Underwater Pipeline Anchoring Apparatus

Technical Field

The present invention relates to underwater pipeline anchoring apparatus.

Background

Traditionally, pipelines are not fixed when laid on the surface of the seabed as the cost of fixing is high, particularly in deep water locations, which maybe typically 500 to 2000m in depth. Also, fixing can itself lead to problems due to the power of currents in the water. Pipelines carrying hydrocarbons are often operated at high temperatures due to the temperature of the oil or gas coming out of the well. This results in thermal expansion of the pipeline, most significantly, in an axial direction. When the flow is shut down for any reason, the pipeline cools and contracts.

As a number of shut downs may occur over the operational life of a pipeline, the axial expansion and contraction can result in the pipeline 'walking' over the seabed. The consequence of this is that pipelines can break connections at their ends, or buckle laterally along their length. Both are undesirable and the usual solution to place a large single anchor at one end of the pipeline to prevent it walking. A more efficient solution is a number of small anchors which can be strategically placed along the pipeline.

In this specification, the relative positional terms above, below, etc are used in relation to a normal pipeline installation in which "below" means into or towards the seabed floor. "Axially directed" means in or along a direction which is aligned or parallel to the longitudinal axis of the pipeline. "Transversely directed" means in or along a direction which is transverse to the longitudinal axis of the pipeline.

Statements of Invention

According to a first aspect of the present invention, there is provided underwater pipeline anchoring apparatus, the apparatus comprising: a fixing device for fixing the apparatus in an installed condition to an underwater pipeline, and an anchor member which, in the installed condition, extends outwardly downwardly from the pipeline into seabed material to resist movement of the pipeline relative to the seabed material, and wherein, in the installed condition, 10 the anchor member is not fixed to the seabed material.

Possibly, the pipeline extends along a longitudinal axis. Possibly, the anchor member is arranged to resist movement of the pipeline along the longitudinal axis.

Possibly, the anchor member is substantially planar. Possibly, the anchor member plane extends substantially orthogonally to the longitudinal axis.

Possibly, the apparatus includes a pair of the anchor members, each of which, in the installed condition, may extend laterally and downwardly outwardly from the pipeline, one member extending outwardly on each side of the longitudinal axis of the pipeline.

Possibly, the anchor members are substantially coplanar.

Possibly, the pipeline has a cross-sectional area. Possibly, the or each anchor member has a cross-sectional area, which may be greater than the cross-sectional area of the pipeline and may be greater by a factor of at least 30 four.

Possibly, the pipeline has a diameter. Possibly, each anchor member has a transverse dimension and a depth dimension.

Possibly, the transverse dimension is greater than the pipeline diameter, and may be greater by a factor of at least 1.5.

Possibly, the depth dimension is greater than the pipeline diameter, and may be greater by a factor of at least two.

Possibly, in some embodiments, the depth dimension is greater than the transverse dimension. Possibly, in some embodiments, the transverse dimension is substantially the same as the depth dimension.

Possibly, the anchor members 16 are substantially the same shape and size.

Possibly, the anchoring apparatus defines an aperture, which may extend axially. Possibly, the aperture includes a pipeline receiving part, which in the installed condition receives the pipeline. Possibly, the aperture includes a slot part. The slot part may be defined between the anchor members. Possibly, the slot part has a width which is greater than the diameter of the pipeline, possibly to permit the pipeline to pass therealong.

Possibly, the apparatus includes a bracing/stability arrangement.

Possibly, the bracing/stability arrangement includes a yoke part, which 25 extends between the anchor members.

Possibly, the bracing/stability arrangement includes a bracing member.

Possibly, the apparatus includes a support member, which supports the 30 fixing device and the or each anchor member.

Possibly, in some embodiments, the bracing member is in the form of a strut which extends from the anchor member to the support member.

Possibly, in some embodiments, the bracing member is substantially planar Possibly, one bracing member is fixed to the or each anchor member and, in the installed condition, may extend downwardly, possibly substantially vertically downwardly. Possibly, the or each bracing member tapers downwardly.

Possibly, in some embodiments, the bracing/stability arrangement includes a lateral stability member, which may be substantially planar, one of which may be fixed to the or each respective anchor member and may extend axially outwardly from the respective anchor member. Possibly, in the installed condition, the or each lateral stability member extends downwardly, possibly substantially vertically downwardly, and may taper downwardly.

Possibly, the or each bracing member comprises the or one lateral stability member.

Possibly, in some embodiments, the bracing/stability arrangement includes a vertical stability member, which may be substantially planar, one of which may be fixed to the or each respective anchor member and, in the installed condition, may extend axially outwardly from the anchor member, possibly substantially horizontally and may extend transversely across the respective anchor member.

Possibly, the fixing device is moveable between an open condition and a closed condition. Possibly, the fixing device comprises a clamp device, which may comprise a pair of clamp arms.

Possibly, the clamp device includes one or more pivot members around which the or each clamp arm pivots.

Possibly, the clamp device includes an actuator for moving the clamp arms between the open and the closed conditions. The actuator may comprise a screw mechanism.

Possibly, the fixing device includes a resilient arrangement to permit misalignment and/or movement. The resilient arrangement may comprise a spring which comprises a part of the actuator.

Possibly, the fixing device includes one or more upper contact members, which in the installed condition contact an upper surface of the pipeline.

Possibly, in some embodiments, the fixing device includes a pair of spaced upper contact members, and the clamp device may be located between the contact members.

Possibly, the clamp device contacts an under surface of the pipeline and in the installed condition may exert a clamping force to draw and hold the upper contact members, the pipeline and the clamp device together.

Possibly, the or each anchor member is located axially between the contact members, and may be located adjacent the clamp device.

Possibly, the support member extends axially and may support the contact members and/or the or each anchor member, and/or the clamp device.

Possibly, the support member is circular in cross-section and may, in some embodiments, comprise the pivot member.

Possibly, the apparatus includes two pairs of anchor members, which 30 are spaced apart along the support member.

Possibly, the apparatus includes two fixing devices, each of which may be associated with one of the pairs of anchor members.

Possibly, the support member is hollow and may define an interior in which ballast is receivable.

Possibly, the or each anchor member includes a pair of axially directed surfaces.

Possibly, the anchoring apparatus includes a release member which may locate against one of the axially directed surfaces of the/each anchor 10 member.

Possibly, the release member is permeable and may comprise a membrane.

Possibly, the anchoring apparatus includes a plurality of release members. Possibly, one release member is located against each of the axially directed surfaces of the/each anchor member.

Possibly, the anchoring apparatus includes a hole formation device which may extend along an edge, possibly a lowermost edge in the installed condition, of the or each anchor member. Possibly, the hole formation device is relatively enlarged in width relative to the width of the anchor member. Possibly, the hole formation device includes a hole forming surface, which in an installed condition, may be a lowermost surface and may be a rounded surface. Possibly, the hole formation device is substantially rounded in cross-sectional shape and may be circular in cross-sectional shape.

Possibly, the anchoring apparatus includes a water supply arrangement to provide a water supply to a lowermost part of the or each anchor member.

Possibly, the water supply arrangement provides the water supply at an elevated pressure relative to the sea pressure local to the lowermost part.

Possibly, the hole formation device is hollow and defines an interior, and the water supply arrangement provides water to the interior. Possibly, the hole formation device defines water supply holes, which may be directed upwardly and through which, in use, water flows therethrough from the interior.

According to a second aspect of the present invention, there is provided a method of anchoring an underwater pipeline, the method including providing underwater pipeline anchoring apparatus, the apparatus comprising: a fixing device for fixing the apparatus in an installed condition to an underwater pipeline, and an anchor member which, in the installed condition, extends outwardly downwardly from the pipeline into seabed material to resist movement of the pipeline relative to the seabed material, and wherein, in the installed condition, the anchor member is not fixed to the seabed material.

Possibly, the apparatus includes any of the features shown or described in any of the preceding statements, following description or accompanying drawings. Possibly, the method includes any of the steps shown or described in any of the preceding statements, following description or accompanying drawings.

Figures Embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:-Fig. 1 is a view on a first axially directed side of an underwater pipeline anchoring apparatus; Fig. 2 is a view on a first transversely directed side of the anchoring 30 apparatus; Fig. 3 is a perspective view of the apparatus from below, on the first axially directed side and on the first transversely directed side; Fig. 4 is a view on a second axially directed side of the anchoring apparatus; Fig. 5 is a perspective view from above, on the first axially directed side and on a second transversely directed side, with the anchoring apparatus in the installed condition fitted to the pipeline; Fig. 6 is a view on the second transversely directed side of the anchoring apparatus; Fig. 7 is a cross-sectional view of a lowermost part of another anchoring apparatus; Fig. 8 is a perspective view of a third anchoring apparatus; Fig. 9 is an end view of the third anchoring apparatus; and Figs. 10A and 10B are end views of the third anchoring apparatus located on a pipeline in, respectively, an unclamped condition and a clamped condition.

Description -First Embodiment

Figs. 1 to 6 show underwater pipeline anchoring apparatus 10, the apparatus 10 comprising a fixing device 12 for fixing the apparatus 10 in an installed condition to an underwater pipeline 14, and an anchor member 16 which, in the installed condition, extends outwardly downwardly from the pipeline 14 into seabed material S to resist movement of the pipeline 14 relative to the seabed material S and wherein, in the installed condition, the anchor member 16 is not fixed to the seabed material S. The pipeline 14 extends along a longitudinal axis 20.

In one example, as shown in the Figures, the apparatus 10 includes a pair of the anchor members 16, each of which, in the installed condition, may extend laterally and downwardly outwardly from the pipeline 14, one anchor member 16 extending outwardly on each side of the longitudinal axis 20 of the pipeline 14.

The anchor members 16 are arranged to resist movement of the pipeline 14 along the longitudinal axis 20.

Each anchor member 16 is substantially planar. The anchor members 16 extend substantially orthogonally to the longitudinal axis 20 and are substantially coplanar.

The pipeline 14 has a cross-sectional area. Each anchor member 16 has a cross-sectional area, which is greater than the cross-sectional area of the pipeline 14 and could be greater by a factor of at least ten, possibly twenty and desirably forty.

Each anchor member 16 has a transverse dimension 22 and a depth dimension 24.

The transverse dimension 22 is greater than the pipeline diameter 26, and could be greater by a factor of at least three, possibly five and desirably six.

The depth dimension 24 is greater than the pipeline diameter 26, and could be greater by a factor of at least three, possibly five and desirably six.

The transverse dimension 22 is substantially the same as the depth dimension 24.

The anchor members 16 are substantially the same shape and size. In the installed condition, each anchor member 16 includes a pair of axially directed surfaces 78.

The anchoring apparatus 10 defines an aperture 28, which extends axially. The aperture 28 includes a pipeline receiving part 30, which in the installed condition receives the pipeline 14, and a slot part 32, which is defined between the anchor members 16. The slot part 32 has a width 34 which is greater than the diameter 26 of the pipeline 14, to permit the pipeline 14 to pass therealong.

The apparatus 10 includes a bracing/stability arrangement 36.

The bracing/stability arrangement 36 includes a yoke part 38, which extends between the anchor members 16.

The bracing/stability arrangement 36 includes bracing members 40, each of which is substantially planar. In the example shown, two bracing members 40 are fixed to each anchor member 16 and, in the installed condition, extend substantially vertically downwardly. Each bracing member 40 tapers (narrows) in axial dimension downwardly.

The bracing/stability arrangement 36 includes lateral stability members 42, which are substantially planar. In the example shown, two lateral stability members 42 are fixed to each respective anchor member 16. Each lateral stability member 42 extends axially outwardly from the respective anchor member 16. In the installed condition, each lateral stability member 42 extends substantially vertically downwardly, and tapers (narrows) in axial dimension downwardly.

In the example shown, each bracing member 40 comprises one of the lateral stability members 42.

The bracing/stability arrangement 36 includes vertical stability members 44, each of which are substantially planar. One vertical stability member 44 is fixed to each anchor member 16, and, in the installed condition, extends substantially horizontally axially outwardly from the anchor member 16 and transversely across the anchor member 16.

In the example shown, one vertical stability member 44 extends between upper parts of each of the bracing members 40/lateral stability members 42 of each respective anchor member 16, and an intermediate vertical stability member 44A extends between the neighbouring upper parts of the adjacent bracing members 40/lateral stability members 42 of the two anchor members 16, just above the aperture 28.

The fixing device 12 is moveable between an open condition and a closed condition. The fixing device 12 comprises a clamp device 46, which comprises a pair of clamp arms 48 and includes a pivot member 50 around which the clamp arms 48 pivot. The clamp device 46 includes an actuator 72 for moving the clamp arms 48 between the open and the closed conditions. In the example shown, the actuator 72 comprises a screw mechanism 52.

The fixing device 12 includes a pair of spaced upper contact members 54, which in the installed condition contact an upper surface of the pipeline 14. 15 The clamp device 46 is located between the upper contact members 54.

The anchor members are located axially between the upper contact members 54, adjacent the clamp device 46.

The apparatus 10 includes a support member 56, which extends axially and supports the upper contact members 54, the anchor member 16, and the clamp device 46.

In the example shown, the support member 56 is circular in cross-section 25 and comprises the pivot member 50. The support member 56 has a longitudinal axis 76 which in the installed condition is aligned substantially in parallel with the pipeline longitudinal axis 20.

First Embodiment -In Use Advantageously, the apparatus 10 can be installed to an existing pipeline in situ without requiring any break in the pipeline 14 as follows: The apparatus 10 is lowered from above onto the pipeline 14 with the clamp arms 48 in the open condition. As the apparatus 10 is lowered, the pipeline 14 passes along the slot part 32 and is received in the pipeline receiving part 30.

As the apparatus 10 is lowered, the anchor members 16 sink into the seabed S by the self weight of the apparatus 10. The seabed S usually comprises loose material which becomes denser or stiffer with depth. The anchor members 16 will sink until sufficient resistance is reached to balance the self weight of the apparatus 10.

Additional temporary weight can be provided to aid the installation process.

The bracing/stability arrangement 36 and in particular the vertical stability members 44, 44A increase the resistance of the seabed S to the sinking of the anchor members 16. The anchor members 16 will sink until the seabed S reaches the vertical stability members 44, 44A. The vertical stability members 44, 44A thus provide a stop or a limit to the sinking of the apparatus 10.

When the pipeline 14 is mostly within the aperture pipeline receiving part 30, the screw mechanism 52 can operated to move the clamp arms 48 from the open to the closed condition. As the clamp arms 48 move to the closed condition, the clamp arms 48 contact an under surface of the pipeline 14 and exert a clamping force to draw and hold the upper contact members 54, the pipeline 14 and the clamp arms 48 together. This can also aid in embedding the anchor members 16 in the seabed S as the action of embedding is now as a result of both the self weight of the apparatus 10 and the inertia of the pipeline 14 which can act as a static point or base for pushing the anchor members 16 downwardly into the seabed S. In the installed condition, with the clamp arms 48 in the closed condition, the anchoring apparatus 10 resists movement of the pipeline as follows.

The Applicant has realised that the primary source of movement of the pipeline 14 is as a result of thermal change causing expansion and contraction along the longitudinal axis 20. The relatively large cross sectional area of the anchor members 16 is arranged orthogonally to the longitudinal axis 20 to resist this movement.

The Applicant has further realised that it is not necessary to fix the pipeline to the seabed and completely immobilise the pipeline and that in fact this might be a disadvantage as the pipeline can be more prone to damage if fully immobilised. It is advantageous, simpler and more economic to resist the longitudinal movement which is the major cause of damage to pipelines. The present invention thus provides an optimum in cost benefit since it is relatively simple to install and can be installed while the pipeline is in operation.

The lateral stability members 42 (which are of a relatively smaller area) resist lateral movement. This movement can be caused by ocean currents but 20 is secondary as a cause of pipeline movement to the expansion and contraction movement and hence these members are of a relatively smaller area.

Removal of the anchoring apparatus 10 is a reversal of the process described above.

The anchoring apparatus 10 provides an anchoring solution which is scalable both in numbers and physical size to suit different situations.

The anchoring apparatus 10 facilitates installation as part of the pipelay and commissioning process, or at a suitable time during it's operational life.

This enables the system to be deployed in either a pre-emptive or reactive capacity.

The anchoring apparatus 10 provides the ability to be recovered at the end of the operational life of the pipeline. This will ease recovery of the pipeline, should that be a requirement.

Other Embodiments Figs. 7 to 10 show other embodiments of the invention, many features of which are similar to those already described in relation to the embodiment of Figs 1 to 6. Therefore, for the sake of brevity, the following embodiments will only be described in so far as they differ from the embodiment already described. Where features are the same or similar, the same reference numerals have been used and the features will not be described again.

Second Embodiment Fig. 7 shows a detail of a lowermost part of an anchor member 216 of an anchoring apparatus 210. In the example shown, the apparatus 210 includes a plurality of release members 58, with one release member 58 located against each of the axially directed surfaces 78 of the anchor member 216.

Each release member 58 is permeable and comprises a membrane.

The release members 58 advantageously reduce soil resistance during installation and permit release of the seabed material from the sides of the 25 anchor members 216 during movement. This has benefits to the axial response of the pipeline 14.

The Applicant has surprisingly found that while it is advantageous to resist movement of the pipeline 14, some movement should be permitted to prevent stress build up. In certain situations, the seabed material S on a rear face of the anchor members 16 relative to a forward movement can have a suction effect, substantially preventing or hindering the forward movement. The release members 58 permit separation of the rear face from the seabed material to permit an amount of movement.

The release members 58 could be provided to one or both of the axially 5 directed surfaces 78 of the anchor member 216.

The anchoring apparatus 210 includes a hole formation device 60 which extends along a lowermost edge in the installed condition of the or each anchor member 216. The hole formation device 60 is relatively enlarged in width relative to the width of the anchor member 216. The hole formation device 60 includes a hole forming surface 64, which in an installed condition, is a lowermost surface and is a rounded surface. In the example shown, the hole formation device 60 is substantially circular in cross-sectional shape.

In one example, the width of the hole formation device 60 is larger than the width of the anchor member 216 by a factor of at least two and approximately three, but no more than four.

The relatively enlarged hole formation device 60 acts to push the seabed material outwards during installation and friction on the sides of the anchor member 216 during installation.

The anchoring apparatus 210 includes a water supply arrangement 66 to provide a water supply to a lowermost part of the or each anchor member 25 216. The water supply arrangement 66 provides the water supply at an elevated pressure relative to the sea pressure local to the lowermost part.

In the example shown, the hole formation device 60 is hollow and defines an interior 68. The water supply arrangement 66 provides water to the interior 68. In one example the water supply arrangement 66 includes one or more bores 74 defined within the anchor member 216. In another example, the water supply arrangement 66 could include one or more pipes (not shown) external to the anchor member 216 to provide water to the lowermost part of the anchor member 216.

The hole formation device 60 defines water ejection holes 70, which in the example shown are directed upwardly and through which, in the installed condition, water flows therethrough from the interior 68.

The water supply at the lowermost part of the anchor member 216 aids installation by reducing friction by the seabed material on the sides of the 10 anchor members 216.

The water supply could be provided on one or both sides of the anchor member 216.

Third Embodiment Figs. 8 to 10 show a third embodiment, apparatus 310. In this embodiment, the apparatus 310 comprises a support member 56 which supports two spaced pairs of anchor members 16. The apparatus 310 comprises two fixing devices 12, with one fixing device 12 associated with each pair of anchor members 16.

The pipeline 14 has a diameter 26. Each anchor member 16 has a transverse dimension 22 and a depth dimension 24.

The transverse dimension 22 is greater than the pipeline diameter 26, and in this example is greater by a factor of approximately 1.5.

The depth dimension 24 is greater than the pipeline diameter 26, and in this example is greater by a factor of approximately 2.4.

In this example, the depth dimension 24 is greater than the transverse dimension 22 by a factor of approximately 1.6.

The shape of the anchor members 16 in terms of the ratio of the depth dimension to the transverse dimension could be varied to suit the seabed material, with a higher ratio being used for softer and/or deeper seabed materials.

In this example, each anchor member 16 has a cross-sectional area, which is greater than the cross-sectional area of the pipeline 14 and could be greater by a factor of approximately 4.5.

The size of the anchor members 16 in terms of the ratio of the cross-sectional area of each anchor member 16 to the cross-sectional area of the pipeline 14 could be varied to suit the seabed material, with a higher ratio being used for softer and/or deeper seabed materials.

The apparatus 310 includes a bracing/stability arrangement 36. The bracing/stability arrangement 36 includes a yoke part 38, which extends between the anchor members 16. The bracing/stability arrangement 36 includes bracing members 40, each of which is in the form of a strut which extends from an inward facing surface of the respective anchor member 16 to the support member 56.

Each fixing device 12 is moveable between an open condition and a closed condition. Each fixing device 12 comprises a clamp device 46, which comprises a pair of clamp arms 48. Each clamp arm 48 is associated with one of the anchor members 16 and comprises a pair of clamp arm members 48A which are located one on either side of the respective anchor member 16. Each clamp arm 48 is pivotally connected to the respective anchor member 16 by a pivot member 50. Each clamp arm member 48A includes an arm contact member 90 at one end. The arm contact members 90 of the clamp arm 48 are connected together by an arm pin 92 which extends through a guide slot 94 defined by the respective anchor member 16.

Each fixing device 12 includes an upper contact member 54 which extends downwardly from the support member 56.

Each clamp device 46 includes an actuator 72 for moving the clamp 5 arms 48 between the open and the closed conditions. In the example shown, the actuator 72 comprises a screw mechanism 52.

The actuator 72 includes a threaded connector 84 for connecting one of the clamp arms 48 to the screw mechanism 52 and a sliding connector 86 for connecting the other of the clamp arms 48 to the screw mechanism 52. The actuator 72 includes a pair of stops 88 which limit the sliding movement of the sliding connector 86 and a spring 96 which biases the sliding connector 86 to one of the stops 88 but permits a degree of resiliently biased movement of the sliding connector 86 between the stops 88.

The spring 96 provides a resilient arrangement 100 to permit misalignment and/or movement.

The actuator 72 includes a handle 80 for manually turning the screw 20 mechanism 52.

The anchor members 16 are rounded or chamfered on their lower inner corners to provide guide surfaces 98 to help the location of the anchor members 16 on the pipeline 14.

Third Embodiment -In Use The apparatus 310 is installed in a similar way to the previous embodiments. The apparatus 310 is lowered from above onto the pipeline 14 with the clamp arms 48 in the open condition. In this condition, the arm pins 92 are located at or towards an outer end of the guide slots 94 and the arm contact members 90 are clear of the slot part 32 of the aperture 28.

As the apparatus 310 is lowered, the anchor members 16 sink into the seabed S by the self weight of the apparatus 310. In one example, the support member 56 could be hollow, defining an interior 82, in which ballast (not shown) could be located, to increase/vary the self weight.

The apparatus 310 is lowered until the upper contact member 54 contacts the pipeline 14, as shown in Fig. 10A. Fig. 10A shows the anchoring apparatus 310 located on the pipeline 14 in an unclamped condition, in which the fixing devices 12 are in the open condition.

The actuator 72 is then operated to move the fixing devices 12 to the closed condition as shown in Fig. 10B. The handle 80 is turned to move the threaded connector 84 away from the sliding connector 86, which moves the arm contact members 90 towards each other and inwardly and upwardly, to clamp the pipeline 14 against the upper contact member 54, with the arm pins 92 moving along the guide slots 94 to or towards an inner end of the guide slots 94 In the closed condition, the spring 96 permits the clamp device 46 to apply a clamping force to the pipeline 14 while allowing a degree of movement.

It also permits a degree of misalignment if, for example, the pipeline 14 is not straight.

Fig. 10B shows the anchoring apparatus 310 located on the pipeline 14 in a clamped condition, in which the fixing devices 12 are in the closed condition.

Advantageously, the Applicant has found that the arrangement of two pairs of anchor members 16 improves orientation and stability, in particular 30 helping to ensure that the anchor members 16 penetrate the seabed material S perpendicularly.

In one example, the leverage exerted by the clamp arms 48 could achieve a force of several tonnes at each arm contact member 90. Such forces are typically available through the use of remotely operated vehicle (ROV) manipulators which are commonly used in subsea environments.

The arm contact members 90 could be shaped. For example, in clay soils, the arm contact members 90 could define grooves to allow any clay soils to be displaced. In sandy soils, a zip pump from an ROV may be required to clear a small amount of material where the arm contact members 90 will sit.

The compression in the spring 96 provides visual confirmation of the clamping force being exerted. This both ensures that the clamping load is well defined, and negates any problems with creep movement of the clamping system and pipeline coating or similar over time.

Other Modifications Various other modifications could be made without departing from the scope of the invention. The apparatus and its various components could be of any suitable size and shape, and could be formed of any suitable material (within the scope of the specific definitions herein).

In particular, the anchor members could be of different size and shape to that shown.

The anchor members 16 could include a rubbing strip (not shown) on their internal sides/edges to reduce friction/abrasion against the pipeline.

The self weight of the apparatus could be altered by, for example, 30 changing the thickness of the anchor members.

Any of the features or steps of any of the embodiments shown or described could be combined in any suitable way, within the scope of the overall disclosure of this document.

Final Remarks There is thus provided anchoring apparatus with a number of advantages over conventional arrangements. The apparatus is relatively easy to fit and requires no maintenance to continue satisfactory operation. The apparatus resists in particular the movement caused by thermal expansion and contraction which causes pipeline walking and is an economical and effective solution to this problem.

Claims

Claims 1. Underwater pipeline anchoring apparatus, the apparatus comprising: a fixing device for fixing the apparatus in an installed condition to an underwater pipeline, and an anchor member which, in the installed condition, extends outwardly downwardly from the pipeline into seabed material to resist movement of the pipeline relative to the seabed material, and wherein, in the installed condition, the anchor member is not fixed to the seabed material.
2. Apparatus according to claim 1, in which the pipeline extends along a longitudinal axis and in which the anchor member is arranged to resist movement of the pipeline along the longitudinal axis.
3. Apparatus according to claim 2, in which the anchor member is substantially planar, and in which the anchor member plane extends substantially orthogonally to the longitudinal axis.
4. Apparatus according to claims 2 or 3, in which the apparatus includes a pair of the anchor members, each of which, in the installed condition, may extend laterally and downwardly outwardly from the pipeline, one member extending outwardly on each side of the longitudinal axis of the pipeline.
5. Apparatus according to claim 4 when dependent on claim 3, in which the anchor members are substantially coplanar.
6. Apparatus according to any of the preceding claims, in which the pipeline has a cross-sectional area, and the or each anchor member has a cross-sectional area, which is greater than the cross-sectional area of the pipeline and may be greater by a factor of at least four.
7. Apparatus according to any of the preceding claims, in which the pipeline has a diameter, and the or each anchor member has a transverse dimension and a depth dimension; the transverse dimension is greater than the pipeline diameter, and may be greater by a factor of at least 1.5, and the depth dimension is greater than the pipeline diameter, and may be greater by a factor of at least two.
8. Apparatus according to any of the preceding claims, in which the anchoring apparatus defines an aperture, which extends axially; the aperture includes a pipeline receiving part, which in the installed condition receives the pipeline; the aperture includes a slot part, which is defined between the anchor members, and the slot part has a width which is greater than the diameter of the pipeline, to permit the pipeline to pass therealong.
9. Apparatus according to any of the preceding claims, in which the fixing device is moveable between an open condition and a closed condition and the fixing device comprises a clamp device.
10. Apparatus according to claim 9, in which, the clamp device comprises a pair of clamp arms; a pivot member around which the clamp arms pivot; and an actuator for moving the clamp arms between the open and the closed conditions.
11. Apparatus according to any of the preceding claims, in which the fixing device includes one or more upper contact members, which in the installed condition contact an upper surface of the pipeline.
12. Apparatus according to claim 11 when dependent on claims 9 or 10, in which the clamp device contacts an under surface of the pipeline and in the installed condition exerts a clamping force to draw and hold the upper contact members, the pipeline and the clamp device together.
13. Apparatus according to any of the preceding claims, in which the fixing device includes a resilient arrangement to permit misalignment and/or movement.
14. Apparatus according to any of the preceding claims, in which the apparatus includes a support member, which supports the fixing device and the or each anchor member.
15. Apparatus according to claim 14, in which the apparatus includes two pairs of anchor members, which are spaced apart along the support member.
16. Apparatus according to claim 15, in which the apparatus includes two fixing devices, each of which is associated with one of the pairs of anchor members.
17. Apparatus according to any of claims 14 to 16, in which the support member is hollow and defines an interior in which ballast is receivable. 15
18. Apparatus according to any of the preceding claims, in which the or each anchor member includes a pair of axially directed surfaces; and the anchoring apparatus includes one or more release members which locate against one or both of the axially directed surfaces of the/each anchor member; the or each release member may be permeable and may comprise a membrane.
19. Apparatus according to any of the preceding claims, in which the anchoring apparatus includes a hole formation device which extends along a lowermost edge in the installed condition of the or each anchor member; the hole formation device is relatively enlarged in width relative to the width of the respective anchor member; the hole formation device includes a hole forming surface, which in an installed condition, is a lowermost surface and may be a rounded surface; the hole formation device may be substantially rounded in cross-sectional shape and may be circular in cross-sectional shape.
20. Apparatus according to any of the preceding claims, in which the anchoring apparatus includes a water supply arrangement to provide a water supply to a lowermost part of the or each anchor member at an elevated pressure relative to the sea pressure local to the lowermost part.
21. Apparatus according to claim 20 when dependent on claim 19, in which the hole formation device is hollow and defines an interior, and the water supply arrangement provides water to the interior; the hole formation device defines water supply holes, which may be directed upwardly and through which, in the installed condition, water flows therethrough from the interior.
22.A method of anchoring an underwater pipeline, the method including providing underwater pipeline anchoring apparatus, the apparatus comprising: a fixing device for fixing the apparatus in an installed condition to an underwater pipeline, and an anchor member which, in the installed condition, extends outwardly downwardly from the pipeline into seabed material to resist movement of the pipeline relative to the seabed material, and wherein, in the installed condition, the anchor member is not fixed to the seabed material.
23.A method according to claim 22, in which the apparatus is according to any of claims 1 to 21.