Technical Field of the Invention

The present invention relates to an apparatus and to a method for forming a bolted connection between flanges of adjacent conduits of a subsea installation. Background to the Invention

Bolted flanges are the most commonly used method of connecting sub-sea pipelines. This is due to their long term performance which ensures that adjacent pipes remain connected for at least the working lifetime of the pipe. Although a remotely operated vehicle (ROV) may be used, it is more typical for a team of divers to make the bolted connection manually. However, the manual installation of the bolts presents a problem to diver safety because the bolts are cumbersome to lift and manoeuvre and typically weigh in excess of 60 kg. In certain installations the bolts may weigh in excess of 100 kg. The size and weight of the bolts also increases diver fatigue, meaning that that there is an increased risk of decompression sickness for divers. In order to transport the nuts and bolts to the subsea pipeline it is conventional to load them into a deployment basket on a work platform. The deployment basket is then lowered into water to a location close to the subsea pipeline. However, this method of transporting the nuts and bolts has the disadvantage that there is an increased risk of thread damage prior to or during deployment of the basket. Moreover, if the damage goes unnoticed then then this could lead to a failure of the bolted flange and the pipeline itself which would be expensive to repair.

Accordingly, it is an object of the present invention to provide an apparatus and method for forming a bolted flange subsea which improves diver safety, It is another object of the present invention to provide an apparatus and method for forming a bolted flange subsea which reduces diver fatigue.

It is a further object of the invention to provide an apparatus and method for forming a bolted flange subsea which reduces the risk of the nuts and bolts becoming damaged prior to their use in forming the bolted flange.

Summary of the Invention

According to a first aspect of the invention there is provided an apparatus for use in forming a bolted connection between flanges of adjacent conduits of a subsea installation, the apparatus comprising first and second frame members adapted for fitting around the body of a pipe and at least one hinged connection for connecting the first and second frame members, wherein the first and second frame members comprise at least one sleeve adapted for housing a stud bolt prior to its use in forming the bolted connection.

The apparatus according to the first aspect of the invention has the advantage that diver fatigue may be reduced because it is no longer necessary for the diver to hand lift the bolts when aligning and inserting the bolts through flange holes provided in each of the flanges. Instead the sleeve supports the bolts as they are aligned and inserted through the flange holes, meaning that the diver only needs to push the bolts and not lift and push them through the flange holes. This is significant because stud bolts which are typically used in such subsea installations can weigh in excess of 100 kg. A further advantage is that the sleeve protects the bolt while it is in transit and also significantly reduces the risk of thread damage caused by other equipment on the platform, i.e. prior to lowering the apparatus into the water. The sleeve also reduces the bolt's exposure to sea bed grit, silt or plant life which could adversely affect the installation. Additionally, since the stud bolts are supported by the sleeves, the divers have the possibility to either load each bolt individually or load more than one bolt at the same time depending on the number of divers present.

The sleeve may comprise a push rod system for pushing the stud bolts out of the sleeve. The push rod system preferably comprises a push rod that is adapted for insertion into a sleeve aperture located at a substantially closed end of the sleeve. The push rod may be T-shaped and may be made from metal or a metal alloy such as steel. In order to reduce the detrimental effects of corrosion the push rod may be coated with a suitable corrosion protective coating.

Preferably the push rod system is a manual push rod system. By manual push rod system it is meant that the divers themselves push the bolts out of the sleeve using rods or the like. The use of a push rod system to push the bolts into the flange holes allows for a greater degree of accuracy when aligning the flanges. Accordingly, the apparatus of the invention does not require a hydraulic system to load the bolts into the flange holes. This means that the apparatus is less expensive to manufacture and also less expensive to transport due to its reduced weight. A further benefit of using a manual push rod system is that the risk of mechanical failure is reduced and the apparatus can be left underwater for extended periods of time relative to comparable hydraulic devices.

The sleeve may comprise a mouth adapted for receiving a stud bolt and in a preferred embodiment the apparatus comprises a retaining element for retaining the stud bolt within the sleeve. This ensures that the stud bolt does not accidently slide out of the sleeve as the apparatus is lifted from the platform or when being transported to the subsea installation. This has the further benefit that worker and diver safety is improved.

The retaining element may comprise a wire, a chain, a bar or a combination thereof. A retaining element in the form of a wire is particularly preferred since it can be removed quickly and easily by the diver when under water. Multiple retaining elements may also be used to retain the stud bolt within the sleeve. For instance, this may be necessary when transporting larger stud bolts, e.g., when the stud bolt weighs in excess of 100 kg. The retaining element may be made from a metal or metal alloy such as steel.

Preferably the sleeve is formed from a metal or metal alloy such as steel. The sleeve may be formed from stainless steel since stainless steel is inherently resistant against corrosion. Alternatively, the metal or metal alloy sleeve may be provided with a corrosion protective coating to extend the longevity of the sleeve before it has to be replaced.

The first and/or second frame members may comprise a plate section that comprises at least one spigot, preferably the plate section comprises a plurality of spigots.

Preferably the spigot is formed on or attached to the plate section. The spigot may be adapted for receiving at least one nut such that the nut may be stored/held on the apparatus prior to its use in forming the bolted connection. This has the benefit that the nuts are easily accessible which is important when divers are working in poor or nil- visibility surroundings. By transporting the nuts and bolts in their unassembled state, i.e. by storing the bolts in sleeves and the nuts on spigots, a significant amount of time is saved during installation because the nuts do not need to be removed from the bolts prior to forming the bolted connection.

The plate section may be a flange alignment plate section. The flange alignment plate section differs from the plate section in that it comprises a shoulder that can aid alignment of the stud bolts with the flange holes. This can make loading of the bolts into the flange holes easier and quicker. This means that the divers spend less time in the water which is advantageous both in terms of cost and diver's health.

The apparatus may comprise a second retaining element for retaining the at least one nut on the spigot. This ensures that the nuts are secured on the spigot as the apparatus is transported to the subsea installation. The second retaining element is preferably in the form of a split pin which may be attached to the plate section, flange alignment plate section or another part of the apparatus using a chain or the like. This enables the split pins to be removed easily and quickly and prevents the split pins from being dropped and lost.

Each frame member may comprise an attachment member. The attachment member may be in the form of a projecting loop which defines an aperture adapted for receiving a connector of a lifting bridle for connecting the lifting bridle to the apparatus. Alternatively, the attachment member may be in the form of a plate having an aperture formed therethrough. Preferably, the first frame member and the second frame member each comprise at two attachment members, more preferably at least four attachment members and most preferred at least eight attachment members. Each attachment member may be bolted or welded to the first and second frame members. In use the attachment members allow the first and second frame members to be manipulated during installation, opening, closing and when removing the apparatus from around the Pipe- Each frame member may comprise a clamping plate and in a preferred embodiment each frame member comprises two clamping plates. Once the apparatus has been arranged around the pipe it may be secured to the pipe by passing clamping nuts and bolts through apertures in abutting claiming plates. In addition to securing the apparatus to the body of the pipe the clamping plates also provide increased stability to the apparatus as it is being transported, e.g. in its open configuration on the flatbed of a truck. Alternatively, the frame members may be secured together using a load binder. In particular, the load binder may be ratchet type load binder. In use, chains which are used in conjunction with the load binder are threaded through the apertures in the abutting clamping plates. The user can then use the ratchet mechanism to incrementally tighten the chains securely and safely until the frame members are secured together. The load binder (and chains) can be adapted as appropriate or as needed to secure frame members of varying sizes together. It will however be appreciated that any suitable fastening means can be used for fastening the frame members together.

The apparatus may comprise an anode for providing catholic protection to the apparatus. Preferably the apparatus comprises a sacrificial anode. Since the nuts and bolts will be protected from corrosion the apparatus may be wet stored subsea for extended periods of time.

According to a second aspect of the invention there is provided a method for forming a bolted connection between flanges of adjacent conduits of a subsea installation, said method comprising the steps of: (i) providing an apparatus for forming a bolted connection between flanges of adjacent conduits of a subsea installation, said apparatus comprising at least one sleeve adapted for receiving a bolt;

(ii) preloading the sleeve with bolts above water;

(iii) aligning the bolts with flange holes located in the flanges subsea, and

(iv) pushing the bolts out of the sleeve and into the flange holes.

The method according to the second aspect of the invention may, as appropriate, incorporate any or all of the features described in relation to the apparatus according to the first aspect of the invention.

Detailed Description of the Invention

In order that the invention may be more clearly understood embodiments will now be described, by way of example only, with reference to the accompanying drawings, of which:

Figures 1-9 show perspective views of the apparatus of the invention being used to form a bolted connection between flanges of adjacent pipes of a subsea installation.

Figure 10 shows a perspective view of the apparatus of the invention with plate sections.

Figure 1A shows a perspective view of the apparatus 1 according to the first aspect of the invention on a flatbed 2 of a delivery truck. The apparatus 1 comprises a first frame member 3 and a second frame member 4 that are joined together by three hinge connections. The first and second frame members 3, 4 comprise a plurality of curved plates 5 and a plurality of flange alignment plates 6 with shoulders 7. The curved plates 5 are aligned in parallel and the flange alignment plates 6 extend perpendicularly through slots in each of the curved plates 5. Each curved plate 5 comprises apertures that are arranged and adapted for receiving a plurality of sleeves 8. The sleeve 8 has a cylindrical body 9, a substantially closed end 10, a mouth 11 and apertures 12 located in the walls of the sleeve 8 proximal to the mouth 11. The substantially closed end 10 comprises a central hole 13 that is adapted for receiving a pushing rod 14 while the mouth 11 and the cylindrical body 9 are adapted to receive and house a stud bolt 15 respectively. In this embodiment a retaining element in the form of a single piece of wire 16 is threaded through the apertures 12 in order to retain the stud bolts 15 within the sleeve 8.

The flange alignment plates 6 additionally comprise spigots 17. The spigots project radially outwards from either side of the flange alignment plate 6. Each spigot 17 is adapted for receiving a nut 18, which together with the stud bolt 15 will be used to form the bolted connection. The nut 18 is held on the spigot 17 using a second retaining element 19 in the form of a split pin. The split pin 19 itself is secured to the spigot or another part of the apparatus by a fixing member (not shown), e.g. a chain, for fixedly connecting the second retaining element 19 to the apparatus 1.

In this embodiment the first and second frame members 3, 4 each comprise two projecting loops 20 that are adapted to receive a lifting bridle 21. A first loop 20a is provided on a curved plate 5 proximal to the shoulder 7 while the second loop 20b is provided on a curved plate 5 away from the first loop. This ensures that the apparatus 1 remains stable when being lifted from the flatbed 2 of the truck or when being deployed underwater. As best shown in Figure 1 each end of each curved plate 5 abuts and is joined to a clamp plate 22 with openings 23 that are adapted for receiving clamping bolts 24. The clamping bolts 24 and clamping nuts 25 secure the apparatus 1 around the pipe 26 once the apparatus 1 has been suitably positioned around the pipe 26 adjacent to the pipe flange.

Figure 1 shows a perspective view of the apparatus 1 on a flatbed 2 on a delivery truck. In this embodiment the apparatus 1 comprises twenty sleeves 8 and each sleeve 8 holds a stud bolt 15 within its cylindrical body 9. Due to the apparatus 1 comprising sleeves 8, stud bolts 15 weighing in excess of 100 kg can be deployed with relative ease by the dive team. As best shown in Figure 2 the apparatus 1 is manoeuvred towards the pipe 25 and its associated flange 26 using a lifting bridle 21 which attaches to the looped projections 20. In this embodiment the bridle 21 is connected to four looped projections 20. The apparatus 1 will naturally close as it is lifted from the flatbed 2 leaving an opening that is large enough to allow the apparatus 1 to fit around the body of a pipe 27. Figure 2 also shows that the pipe 27 is provided with a concrete coating 28 for protecting the pipe 27 from corrosion. The apparatus 1 is oriented such that the flange alignment plate shoulders 7 face the flange 26 and thereafter the apparatus 1 is lowered over the pipe 27ensuring that the clamping area aligns with the uncoated section of the pipe 27 immediately behind the flange 26. Advantageously, the apparatus 1 is designed such that it will close around the pipe 27 naturally thereby avoiding the need for the apparatus 1 to comprise hydraulic equipment. Once the apparatus 1 has been positioned around the pipe 27 clamping bolts 24 are inserted through the openings 23 in the clamping plates 22 and are loosely secured to the clamping plates by clamping nuts 25. At this stage the bolts 26 should not be fully tightened. As best shown in Figure 4, the apparatus 1 is then manipulated to ensure that the sleeves 8 are aligned with the flange bolt holes 29 provided in the flange 26. The shoulders 7 aid alignment of the apparatus 1 and ensure that the mouth 11 of the sleeve 8 is at least 225 mm away from the back face of the flange 26. Once alignment is complete the clamping bolts 24 are fully tightened to secure the apparatus 1 around the pipe 27 and to maintain alignment of the sleeves 8 with the flange holes 29. Then, the stud bolt retaining wire 16 is removed from the mouth 11 of the sleeve 8 simply by pulling at one end of the retaining wire 16. The stud bolt retaining wire 16 may be removed from all of the sleeves 8 in a single step or the retaining wire 16 may be removed sequentially, i.e. one sleeve 8 at a time, whichever is most appropriate.

As best shown in Figure 5, a T-shaped pushing rod 14 is used to load the stud bolts 15 into the flange holes 29. The pushing rod 14 is first aligned with the central hole 13 at the substantially closed end 10 of the sleeve 8. The pushing rod 14 is then inserted through the hole 13 and pushed along the cylindrical body 9 until it abuts one end of the stud bolt 15. As the pushing rod 14 is pushed further into the sleeve 8 this causes the stud bolt 15 to move along the cylindrical body 9, out of the mouth 11 and into the flange hole 29. For clarity, mating flange or equipment has been omitted from Figure 5. However, it will be appreciated that the stud bolts 15 will extend through flange holes 29 of a first flange 26 a second flange (not shown) abutting the first flange (not shown).

Figure 6 shows a flange 26 where all of the stud bolts 15 have been inserted into the flange holes 29. Next, and as best shown in Figure 7, the second retaining elements (split pins) 19 are removed so that the nuts 18 are removed from the spigots 17. The nuts 18 are then fitted to the stud bolts 15 and tightened to secure the bolts 15 to the flange 26. Now that a bolted connection has been made between flanges 26 of adjacent pipes 27, the clamping bolts 24 can be removed so that the apparatus 1 may be opened (Figure 8). The apparatus 1 is then lifted away from the installation (Figure 9) and returned to the platform. Figure 10 shows an embodiment where the first and section frame members 2,

3 comprise plate sections. Unlike the flange alignment plates 6, the plate sections do not comprise shoulders 7 for aligning the sleeves 8 with the flange holes 29.

The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention.