WO2013144601A1

WO2013144601A1 - Rov deployable clamp

Info

Publication number: WO2013144601A1
Application number: PCT/GB2013/050769
Authority: WO
Inventors: James Stuart FOWLER
Original assignee: Pulse Structural Monitoring Limited
Priority date: 2012-03-28
Filing date: 2013-03-25
Publication date: 2013-10-03
Also published as: GB2500656A; GB2500656B; GB201205485D0

Abstract

This invention relates to a clamp which may be manipulated by an underwater remotely operable vehicle (ROV) to attach monitoring equipment to subsea structures. An ROV-deployable clamp for attachment to an exterior surface of a subsea structure comprises a main body (36), a pivot joint (18), a pair of ROV-gripping features (58) and a biasing means (66). The main body is in two main body portions (30,31) pivotably connected together at the pivot joint (18) and each of the main body portions comprises a jaw portion (14,16) and a handle portion (22,24), the jaw portions (14,16) being opposite one another on a first side of the joint. The main body portions (30,31) are pivotable about the joint between an engaged position in which the jaw portions (14,16) are relatively closed for gripping the exterior surface of the subsea structure and a disengaged position in which the jaw portions (14,16) are relatively open for releasing the exterior surface of the subsea structure. The biasing means (66), in use, biases the jaw portions (14,16) into the engaged position. Each of the ROV-gripping features (58) is fixed to one of the handle portions (22,24), and the handle portions (22,24) are opposite one another on a second side of the joint opposite the first side of the joint so that the ROV-gripping features (58) may be squeezed together to hold the main body portions (30,31) in the disengaged position or released to enable the biasing means (66) to move the jaw portions (14,16) into the engaged position. Each of the main body portions (30,31) is made from a plastic material.

Description

ROV Deployable Clamp

BACKGROUND a. Field of the Invention

This invention relates to a clamp. In particular this invention relates to a clamp which may be manipulated by an underwater remotely operable vehicle (ROV) to attach monitoring equipment to subsea structures. b. Related Art

It is often desirable to attach monitoring equipment to subsea structures to measure inclination, vibrations and strain, as well as other forces and physical properties of the structures.

The monitoring equipment is typically mounted or housed in a capsule that is attached to the subsea structure by means of a clamp that can be deployed by a remotely operated vehicle (ROV). Usually the clamp is positioned and attached to the structure using an ROV and, as such, the clamping device must be able to be carried by the ROV-deployable clamp, easily manoeuvre the clamp into position and then secure the clamp to the structure. Known clamping devices typically comprise a metal clamp apparatus that weighs in excess of 200 kg, to which the monitoring module is attached. In the underwater environment it is difficult for ROVs to carry and manipulate non-neutrally buoyant objects, and ROVs generally have the capabilities to carry around 100 kg. As such, the clamp apparatus requires additional, buoyancy modules so that the ROV is able to carry and manipulate the clamp underwater. The buoyancy modules typically comprise closed cell foam blocks which must be selected depending on the depth at which the clamp is to be located, as foam with an incorrect depth rating will be liable to collapse due to the significant water pressures encountered. The clamp and the buoyancy modules make the complete apparatus both heavy and bulky, and difficult for the ROV to handle. The metal clamps are typically made primarily from steel, with specific parts, such as the hinge pins and the monitoring equipment capsule, made from stainless steel such as Super Duplex stainless steel. Steel clamps require a heavily controlled manufacturing process and additional protection from corrosion. In particular, the clamps must be painted to protect the clamp from corrosion to some degree. Clamps are often painted bright yellow which additionally aids visibility underwater. Cathodic protection, in the form of a sacrificial anode, is also used to further protect the clamp against corrosion. The inclusion of an anode, however, presents several problems. Firstly, the anodes by their nature have a limited life, and secondly, the sacrificial nature of the anode creates a chemical reaction that, as a by-product, produces hydrogen. This hydrogen is then prone to cause hydrogen embrittlement in the stainless steel, which degrades the structural integrity of the housing surrounding the monitoring equipment. There is, therefore, a need for careful consideration of material compatibilities in the design of the clamp, and the need for corrosion protection increases the cost and complexity of the device.

The clamping force is typically provided by lead screws which are driven, by the ROV, to open and close the clamp once the clamp is in the required position. The interface between the ROV and the driven lead screw has to be considered in the design, as each ROV has its own particular set of manipulators. The force generated from the ROV though a lead screw can be excessive and is difficult to design around. On an insulated pipe this could lead to the clamp crushing the insulation as the ROV has no feel for the load it is applying It is an object of the present invention to provide an improved clamping device that overcomes the above mentioned problems with prior art devices. SUMMARY OF THE INVENTION

According to the invention, there is provided an ROV-deployable clamp for attachment to an exterior surface of a subsea structure, the clamp comprising a main body, a pivot joint, a pair of ROV-gripping features and a biasing means, wherein:

the main body is in two main body portions pivotably connected together at the pivot joint;

- each of the main body portions comprises a jaw portion and a handle portion, said jaw portions being opposite one another on a first side of said joint; the main body portions are pivotable about said joint between an engaged position in which said jaw portions are relatively closed for gripping said exterior surface of the subsea structure and a disengaged position in which said jaw portions are relatively open for releasing said exterior surface of the subsea structure;

the biasing means, in use, biases the jaw portions into the engaged position;

each of the ROV-gripping features is fixed to one of the handle portions; - said handle portions are opposite one another on a second side of said joint opposite said first side of said joint so that said ROV-gripping features may be squeezed together to hold the main body portions in the disengaged position or released to enable the biasing means to move the jaw portions into the engaged position; and

- each of the main body portions is made from a plastics material.

Because plastics material have a density approximately the same as water, the clamp, even with the addition of some metallic components, will have a relatively light weight in water as compared with a clamp made substantially entirely from metal. Therefore, there is no need for any additional buoyancy means to be attached to the clamp for this to be usable by an ROV, and as a result the clamp according to the invention can also be rated for use at any depth. The jaw and handle portions of each main body portion are advantageously formed as a single-piece of plastics material, so that there are no joins or interfaces within each main body portion that could weaken the structure between the jaw and handle portions.

Because the main body portions are of a plastics material, the clamp need not comprise any buoyancy means, in order for the clamp to be gripped and controlled by a conventional ROV, which may have a lifting capacity somewhat in excess of 100 kg. Therefore, the clamp may have an underwater weight of between 10 kg and 1 00 kg. Most preferably, the clamp has an underwater weight of between 25 kg and 50 kg, which would permit other objects, for example a sensor module, weighing typically 10 kg to 50 kg, to be attached to the main body of the clamp. In a preferred embodiment of the invention, the main body portions are essentially identical in form, apart from any mounts fixed to the main body portion for holding underwater monitoring equipment, for example a sensor module. Therefore the jaw portions may be identical with each other, and/or the handle portions may be identical with each other.

The monitoring equipment to be secured to the clamp may be any type of underwater monitoring or sensing equipment for sensing and monitoring water conditions around the underwater structure or the performance of the underwater structure to which the clamp is to be removeably attached.

In a preferred embodiment of the invention, there is a pair of mounts, each one of which spans both the jaw portion and the handle portion of one of the main body portions. The jaw portions may have any suitable internal shape depending on the shape of the portion of the underwater structure to be gripped by the jaws of the clamp, but in a preferred embodiment of the invention are curved to define a substantially cylindrical opening of the clamp jaws.

At least a part of an inner surface of each jaw portion may comprise a relatively softer plastics material, as compared with the remainder of the jaw portion.

Because the main bulk of the clamp will be formed from a plastics material, specifically at least the two main body portions, it is possible to use metal for strength or durability in those portions of the clamp which require this, without adding unduly to the cost or weight of the clamp. Because of the cost savings afforded by the use of plastics material, as opposed to the use of corrosion resistant metal throughout the main body portions of the clamp, it becomes possible to use high quality corrosion resistant material in the metal components of the clamp. The use of a plastics material for the main body portions also means that different metal components will not be in physical and electrical contact with each other, thereby reducing or eliminating corrosion and the need for cathodic protection.

Therefore, the ROV-gripping feature preferably comprises a metal bar, which may be made from stainless steel. Most preferably a central portion of the metal bar provides the gripping feature. End portions of the metal bar may then be retained within the plastics material of the handle portions. To distribute mechanical loads within the maximum amount of the plastics material, the metal bar may also extend for substantially the full length of the clamp.

The pivot joint, which may also be made from metal, preferably comprises a pivot pin that extends through a part of each of the two main body portions.

Similarly, to distribute mechanical loads throughout the main body portions, the pivot pin may extend for substantially the full length of the clamp and is secured at each of its ends by fastening means. This fastening means at a first end of the pivot pin may comprise a deformable portion so that the pivot pin may, in use, be removed from the clamp by applying a force to a second end of the pivot pin to deform the deformable portion and withdraw the pivot pin from the main body portions. In a preferred embodiment of the invention, the biasing means is a spring biasing means, most preferably at least one spring extending from the handle portion of one of the main body portions to the handle portion of the other one of the main body portions. In a preferred embodiment, a first end portion of the at least one spring bears on an end portion of the metal bar retained within the handle portion of one of the main body portions.

An ROV will have a maximum gripping width. Therefore, the clamp preferably further comprises a linkage to limit the separation of the handle portions when the main body portions are in the engaged position. In a preferred embodiment of the invention, the linkage comprises a pair of straps on opposite sides of the handle portions, each of these straps spanning a gap between the handle portions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a clamp according to a preferred embodiment of the present invention;

Figure 2 is a front view of the clamp of Figure 1 , showing in particular the handle portion for use by an ROV and the location of a monitoring equipment module;

Figure 3 is a side view of the clamp of Figure 1 , showing in particular the shape of jaw portions of the clamp and a hinge portion; Figure 4 is a top view of the clamp of Figure 1 ;

Figure 5 is a detailed cross-sectional view of a part of the hinge portion of the clamp of Figure 1 , showing a hinge pin assembly extending through the full width of the clamp;

Figure 6 is a detailed cross-sectional view of a part of an adjuster for adjusting the clamping force of the clamp of Figure 1 ;

Figure 7 is a pair of perspective drawings showing a single jaw portion of the clamp of Figure 1 ;

Figure 8 shows the clamp of Figure 1 in an engaged, or clamped, position around a pipe structure;

Figure 9 shows the clamp of Figure 1 in a disengaged, or undamped, position around a pipe structure; and Figure 1 0 is a perspective view of the clamp of Figure 1 when clamped to a pipe structure.

DETAILED DESCRIPTION

Figures 1 to 10 show a clamp 10 for attachment to a subsea structure 1 2 according to a preferred embodiment of the present invention. The clamp 1 0 comprises a pair of jaw portions 14, 16 arranged, in use, to grip an exterior surface of a structure such as a riser pipe 12. The jaw portions 14, 16 are connected by a pivot joint or hinge portion 1 8 and biasing means 20 are configured to bias the jaw portions 14, 16 of the clamp 1 0 into a clamped or engaged position. The clamp 1 0 further includes handle portions 22, 24, on the opposite side of the pivot joint 18 to the jaw portions 14, 16, which may be moved to open and close the jaws 14, 1 6 between a disengaged position and an engaged position.

The clamp 10 is designed to be deployed and manipulated by a remotely operated vehicle (ROV) (not shown) and, in particular, gripping features 58 are fixed to each of the handle portions 22, 24. The gripping features 58 are ROV-gripping features which are held by the ROV in use. Gripping of these gripping features 58 by the ROV, such that the ROV-gripping features are squeezed together, overcomes the force of the biasing means 20 and allows the clamp 10 to be held in an open or disengaged position, to enable the clamp 1 0 to be installed around the structure 12.

The clamp 1 0 also includes mounts 26 for securing a capsule 28 containing monitoring equipment to the clamp 10. In this embodiment, the mounts 26 are in the form of a pair of U-shaped retaining clips 27 that are attached to one of the jaw portions 16. The capsule 28 is held between an exterior surface 36 of the jaw portion 16 and the clips 27, and the clips are secured tightly to the jaw portion 1 6 by means of screws (not shown) or other suitable fastening means. The clamp 10 may, therefore, be used to attach monitoring equipment to the subsea structure 12 to monitor properties such as the strain, inclination and vibration of the structure.

The clamp 10 is typically about 650 mm in length, and the distance between a longitudinal edge 15 of the jaw portions 14, 16 and a longitudinal edge 23 of the handle portions 22, 24 is typically about 800 mm.

The clamp 10 comprises two main body portions 30, 31 , one of which 30 is shown most clearly in Figure 7. The main body portion 30 includes the jaw portion 14, the handle portion 22 and a part of the pivot joint 1 8. The design of the main body portions 30, 31 is such that both of the main body portions 30, 31 are identical, reducing the number of different components that must be manufactured, and thereby reducing the complexity and cost of the clamp 1 0.

Importantly, the main body portions 30, 31 are made from a plastics material, which minimises the weight of the clamp 10. Preferably the main body portions 30, 31 are made substantially from moulded polyurethane which, advantageously, has a relatively lower weight both in air and in water compared with traditional steel clamp components. In particular the clamp 10 typically has an underwater weight of between 10 kg and 100 kg, and more preferably is designed to have an underwater weight of between 25 kg and 50 kg. As such, the clamp 1 0 does not require any additional buoyancy components, which are typically a necessity on prior art metal clamps.

The use of a plastics material, such as polyurethane, also provides a relatively long life component, and one that does not require substantial amounts of corrosion protection. The lack of a need to apply layers of paint, or cathodic protection, further reduces the complexity, time and cost of manufacture of these components compared with traditional steel clamp assemblies.

In preferred embodiments the plastics material is coloured bright yellow or another similar bright colour. This aids in locating the clamp 1 0 when retrieving the clamp 10 from a subsea structure where visibility may be poor.

The jaw portions 14, 16 are curved about a longitudinal axis 32 of the clamp 1 0 so that the jaws 14, 1 6 have a concave inner surface 34 and a convex outer surface 36. The curvature of the inner surface 34 is such that, when the clamp 10 is in an engaged position, the jaw portions 14, 16 form part of a substantially circular or cylindrical opening 38. This means that when the clamp 1 0 is clamped around a cylindrical structure, such as a riser pipe 12, a substantial proportion of the inner surface 34 of the jaw portions 14, 16 is in contact with the exterior surface of the structure d.

To further aid in the gripping of the structure 12 by the clamp 1 0, in some embodi merits it is desirable if at least a part of the inner surface 34 of each of the jaw portions 14, 16 is coated with, or formed from, a relatively softer plastics material to form a grip layer 40. Preferably if the jaw portions 14, 16 are made from a first type or grade of polyurethane material, a second, softer grade of polyurethane material is used to form the grip layers 40.

Typically, the plastics main body portions 30, 31 will be formed by a pour moulding process. In a preferred embodiment, in order to form the grip layers 40, the second grade of plastics material is added to the mould before the first plastics material has fully cured. In this way, a bond is formed between the grip layer 40 and the rest of the jaw portions 14, 16, during the final curing of the plastics material, without the need for an additional adhesive or other bonding layer.

The handle portions 22, 24 of the clamp 10 each comprise two tab sections 42, 44 of the plastics main body portions 30, 31 that extend generally away from the pivot joint 1 8 and jaw portions 14, 1 6, as shown most clearly in Figures 2 and 7. The tab sections 42, 44 are formed at each end of the main body portions 30, 31 with a space 46 between them. A hole 48 is formed through each of the tab sections 42, 44, and the holes 48 in each tab section 42, 44 are aligned with each other and parallel to the longitudinal axis 32.

A slot 50 is formed in the edge 23 of one of the tab sections 44, the function of which will be described further below. The slot 50 extends only part of the way through the tab portion 44 so as to form two ears 52 of the tab 44. As such, the longitudinal hole 48 extends through each of the ears 52, above a base of the slot 50.

A bar or rod 54 is received within and extends through the longitudinal holes 48 for the full length of the clamp 10, as shown most clearly in Figures 1 and 2. The bar 54 is preferably made from metal and is typically made from a suitable grade stainless steel material, such as super duplex stainless steel. The bar 54 is retained within the plastic tab sections 42, 44 by means of washers and nuts, or other suitable retaining means 56, at each end of the bar 54.

A central region of the bar 54 in the space 46 between the two tab sections 42, 44 forms a grip portion of the bar 54; this is the gripping feature 58 that is fixed to each of the handle portions 22, 24. When the clamp 10 is to be held and manipulated by a remotely operated vehicle (ROV), the ROV will grip or hold the clamp 10, typically by means of an ROV manipulator arm or gripper (not shown), using the ROV-gripping features 58 of the grab bars 54. Because the bar 54 extends through the handle portions 22, 24 the forces exerted by the ROV gripper on the ROV-gripping features 58 are transmitted along the length of the clamp 10 and to the handle portions 22, 24. This decreases the likelihood of deformation of the bar 54 during use. The pivot joint 18 comprises a series of cylindrical bearings 60 integrally formed in each of the main body portions 30, 31 between the jaw portions 14, 16 and the handle portions 22, 24. The cylindrical bearings 60 are spaced apart along the length of the clamp 10, and are arranged such that when the two main body portions 30, 31 are joined together the bearings 60 interleave.

A pivot pin or rod 62 extends through a longitudinal bore 61 through the interleaved cylindrical bearings 60 to join the two main body portions 30, 31 together and form the pivot joint 1 8, as shown in Figure 5. The pivot pin 62 extends through the full length of the clamp 1 0 and is preferably made from a suitable stainless steel material such as super duplex stainless steel.

With the two main body portions 30, 31 pivotally connected in this way, the handle portions 22, 24, or ROV-gripping features 58 when squeezed together cause the jaw portions 14, 1 6 to be opened to a disengaged position, as illustrated in Figure 9. Similarly, when the handle portions 22, 24, or ROV-gripping features 58, are released or pulled apart, the jaw portions 14, 1 6 close to an engaged position, as illustrated in Figure 8. The pivot pin 62 is secured at a first end 61 by mechanical fastening means 64, which in the example comprises a bolt that attaches to the end 61 of the pivot pin 62 such that a head of the bolt prevents the pin 62 being drawn out through the bearings 60 in a first direction. The second end 63 of the pivot pin 62 is secured by means of a deformable rubber washer 65 and a bolt 67 that extends through the washer 65 and into the second end 63 of the pivot pin 62. The washer 65 and bolt 67 generally prevent movement of the pivot pin 62 through the bearings 60 in a second direction during normal use.

However, if the pivot joint 18 seizes, the clamp 1 0 may be disassembled by applying a large force to the fastening means 64 to deform the washer 65 and pull the pin 62 out of the clamp 1 0 in the second direction. Removal of the pin 62 in this way separates the two main body portions 30, 31 so that the clamp 1 0 can be removed from the structure 12. Typically the pivot pin 62 will be removed in this way by an ROV if the clamp 1 0 has seized in position around a subsea structure 12 after prolonged use.

The clamp 10 further includes biasing means 20 that biases or urges the jaw portions 14, 16 into the clamped or engaged position. The biasing means 20 comprises springs 66 that extend between respective handle portions 22, 24 of the two main body portions 30, 31 , such that when the ROV-gripping features 58 are released the handle portions 22, 24 are urged apart. Each spring is preferably a coil spring 66 connected at a first end 68 to a part of the bar 54 that extends across the slot 50 between the two ears 52 of the tab 44 on a first one of the main body portions 30, 31 . A second end 70 of the spring 66 is received within a recess 72 in the tab 42 of the opposing handle portion 22, 24 of the other one of the main body portions 30, 31 , as shown most clearly in Figures 1 and 4. The configuration of the springs 66 is, therefore, such that the jaw portions 14, 1 6 are urged or biased into the engaged position, and the clamp 10 remains clamped around a structure 12. To disengage or open the jaws 1 2, 14 of the clamp 1 0, the ROV-gripping features 58 must be squeezed together by the ROV gripper with enough force to compress the springs 66 and then held in this position until the clamp 10 has been positioned around or removed from the structure 12. Because the biasing means 20 are configured to urge the handle portions 22, 24 apart, the extent of opening of the handle portions 22, 24 must be limited to ensure that the ROV gripper is able to grip both sides of the clamp 10 at the same time, to be able to squeeze the two ROV-gripping features 58 together. A limiting strap or plate 90 is, therefore, attached between the ends of the bars 54 at each end of the clamp 10.

The strap 90 comprises a strip of metal, preferably stainless steel, with a hole 91 proximate a first end 92 and an elongate slot 93 proximate a second end 94, as shown in Figure 8. The end of one of the bars 54 is secured through the hole 91 and the corresponding end of the other bar 54 is secured through the slot 93, so that the bar 54 is free to move along the length of the slot 93.

When the clamp 10 is in the disengaged position the end of the bar 54 is located at a first end 95 of the slot 93 nearest the first end 92 of the strap 90. When the clamp 10 is in the engaged position, the bar 54 moves to the other end 96 of the slot 93 nearest the second end 94 of the strap 90. The length of the strap 90 and the length of the slot 93, therefore, limit the extent of separation of the handle portions 22, 24. In this embodiment, the biasing means 20 further comprises spring adjusting means 74. The adjusting means 74 can be used to adjust the separation of the jaws 14, 16 in the engaged position, to fit different pipe sizes, by varying the distance between opposing handle portions 22, 24. As shown in Figure 6, the adjusting means 74 comprises a first member 76 attached proximate a first end 77 to the bar 54, and a second member 78 engaged with the end 68 of the spring 66. The second member 78 is movable along the length of the first member 76 so that the position of the end 68 of the spring 66 may be moved with respect to the first member 76 and the bar 54. Preferably the first and second members 76, 78 are threaded such that rotation of one of the first or second member 76, 78 with respect to the other member 76, 78 causes movement of the second member 78 along the length of the first member 76.

The adjusting means 74 may also be used to adjust the tension of the spring 66 by varying the length of the spring 66. This is achieved by varying the position of the end 68 of the spring 66 as described above, while keeping the other end of the spring 66 in a fixed position, i.e. maintaining a fixed separation of the handle portions 22, 24, such that the overall length of the spring 66 is changed. In this way, the clamping or gripping force required by the ROV may be altered. Typically the maximum clamping force that can be applied by an ROV is 450 kg.

The clamp 10 also includes alignment features 80 on the rear, or inwardly facing, surface 82 of the handle portions 22, 24. As shown most clearly in Figure 7, the alignment features 80 comprise a longitudinal groove 84 formed in one of the tab sections 44, and a corresponding longitudinal ridge 86 formed on the other tab section 42. When the clamp 10 is held in the disengaged position such that the two ROV- gripping features 58 and the two handle portions 22, 24 are squeezed fully together, each ridge 86 is seated in the opposing groove 84, as illustrated in Figure 9. These alignment features 80, therefore, assist in keeping the two body portions 30, 31 aligned when the clamp 10 is held and manipulated by an ROV gripper. In particular, the seating of the ridges 86 in the grooves 84 prevents relative twisting of the two body portions 30, 31 .

Additionally, the forces that are transmitted along the bar 54 when the two ROV- gripping features 58 are squeezed together are, in turn, transmitted to the plastics tab sections 42, 44. The seating of the alignment features 80 ensures that the rear surfaces 82 of the handle portions 22, 24 press against each other and the plastics material in these regions is in compression. Because the clamp 1 0 is made from a plastic material, but has no buoyancy means, the clamp can be handled and installed on or retrieved from an underwater structure by an ROV, regardless of the depth of operation. This invention, therefore, provides an improved ROV-deployable clamp that overcomes at least some of the known problems with prior art devices.

Claims

1 . An ROV-deployable clamp for attachment to an exterior surface of a subsea structure, the clamp comprising a main body, a pivot joint, a pair of ROV-gripping features and a biasing means, wherein:

each of the main body portions comprises a jaw portion and a handle portion, said jaw portions being opposite one another on a first side of said joint; - the main body portions are pivotable about said joint between an engaged position in which said jaw portions are relatively closed for gripping said exterior surface of the subsea structure and a disengaged position in which said jaw portions are relatively open for releasing said exterior surface of the subsea structure;

- the biasing means, in use, biases the jaw portions into the engaged position;

each of the ROV-gripping features is fixed to one of the handle portions; said handle portions are opposite one another on a second side of said joint opposite said first side of said joint so that said ROV-gripping features may be squeezed together to hold the main body portions in the disengaged position or released to enable the biasing means to move the jaw portions into the engaged position; and

each of the main body portions is made from a plastics material.

2. An ROV-deployable clamp as claimed in Claim 1 , in which the jaw and handle portions of each main body portion are formed from a single-piece of plastics material.

3. An ROV-deployable clamp as claimed in Claim 1 or Claim 2, in which the clamp comprises no buoyancy means.

4. An ROV-deployable clamp as claimed in any preceding claim, in which the clamp has an underwater weight of between 10 kg and 1 00 kg.

5. An ROV-deployable clamp as claimed in any one of Claims 1 to 3, in which the clamp has an underwater weight of between 25 kg and 50 kg.

6. An ROV-deployable clamp as claimed in any preceding claim, in which the jaw portions are identical.

7. An ROV-deployable clamp as claimed in any preceding claim, in which the handle portions are identical.

8. An ROV-deployable clamp as claimed in any preceding claim, in which the clamp further comprises at least one mount for securing monitoring equipment to the clamp.

9. An ROV-deployable clamp as claimed in Claim 8, in which said at least one mount spans both the jaw portion and the handle portion of one of said main body portions.

10. An ROV-deployable clamp as claimed in any preceding claim, in which the jaw portions are curved to define a substantially cylindrical opening of the clamp.

1 1 . An ROV-deployable clamp as claimed in any preceding claim, in which at least a part of an inner surface of each jaw portion comprises a relatively softer plastics material.

12. An ROV-deployable clamp as claimed in any preceding claim, in which the ROV-gripping feature comprises a metal bar.

13. An ROV-deployable clamp as claimed in Claim 1 2, in which the ROV- gripping feature comprises a central portion of the metal bar, end portions of the metal bar are retained within the handle portions, and wherein the metal bar extends for substantially the full length of the clamp.

14. An ROV-deployable clamp as claimed in Claim 1 2 or Claim 13, in which the metal bar is made from stainless steel.

15. An ROV-deployable clamp as claimed in any preceding claim, in which the pivot joint comprises a pivot pin that extends through a part of each of the two main body portions.

16. An ROV-deployable clamp as claimed in Claim 15, in which the pivot pin extends for substantially the full length of the clamp and is secured at each of its ends by fastening means, the fastening means at a first end of the pivot pin comprising a deformable portion, and wherein, in use, the pivot pin may be removed from the clamp by applying a force to a second end of the pivot pin to deform said deformable portion and withdraw the pivot pin from the main body portions.

17. An ROV-deployable clamp as claimed in any preceding claim, in which the biasing means comprises a spring extending from the handle portion of one of the main body portions to the handle portion of the other one of the main body portions.

18. An ROV-deployable clamp as claimed in Claim 1 7, when dependent on Claim 13, in which a first end portion of the spring bears on an end portion of the metal bar retained within the handle portion.

19. An ROV-deployable clamp as claimed in any preceding claim, in which the clamp further comprises a linkage between the handle portions to limit the separation of the handle portions when the main body portions are in said engaged position.

20. An ROV-deployable clamp as claimed in Claim 1 9, in which said linkage comprises a pair of straps on opposite sides of the handle portions, each of said straps spanning a gap between said handle portions.