Field of the invention

The invention concerns a connecting pin assembly for a pipe joint of a pipe structure, particularly a pile jacket connection. Furthermore, the invention relates to a method for securing a connection between axially overlapping pipes, such as a pile and jacket, for example a tubular tower leg and a pile.

Prior art

When securing a joint of axially overlapping pipes, like connecting a tower leg of an offshore platform to a pile extending from a seabed, some sort of grout filling the annulus is often used as a medium to lock the pile /jacket connection. The lifetime of such connector means is limited, the limited lifetime often limiting the lifetime of structure to which the joint belongs.

To extend the lifetime of grouted pipe joints, the use of various kinds of bolts provided in the joint is well known, one or more bolts extending through bores provided in the joint section. For joint diameters allowing tools and possibly operator(s) to enter the inner pipe, short bolts extending one joint wall maybe used, while bolts extending diametrically through the joint is normally used for smaller diameter joints. A well- known drawback of reinforcing joints of this kind using bolts is the risk of buckling of the pipe wall material surrounding the bolt holes, thus causing the bolt holes to be extended. Extended bolt holes may result in severely weakening of expected effect of the bolts, which may cause failure of the joints. This is particularly relevant for onshore and offshore platforms for hydrocarbon production that are subjected to fluctuating wind and/or sea loads that are born by tower legs of the platforms that are often pile and jacket constructions.

US 2020173133 discloses an offshore structure provided with a foundation structure in the form of piles extending through sleeves. The interspace formed between the pile and the sleeve is filled with a casting compound. Shear elements are provided on the piles and/or the sleeves, wherein the shear elements extend into the interspace, effecting an axial load dissipation into the casting compound filling.

It is an object of the present invention to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

Summary of the invention

The object is achieved by a pile jacket connection pin according to claim i and by a method for securing a connection between a pile and a jacket according to claim 16.

Preferably, a pile jacket connecting pin comprising a pin body having a first end portion, a second end portion, a central portion, and two wedge portions, one at each of the first and second end portions, wherein a cross-sectional area of the pin body at the two wedge portions increases from each of the first end portion and the second end portion in direction to the central portion; two sets of slidable wedges abutting against inclined wedge sliding bases of the two wedge portions, and two wedge actuating members configured for sliding the wedges along the respective wedge portions to radially expand the connection pin at the first and second end portions.

The expandable pile jacket connecting pin can be used for securing a pipe joint of a pipe structure like a joint connecting tubular piles extending from a seabed or the like to tubular legs of a platform, a tower or the like, wherein an annulus in the pipe joint is grouted. The connecting pin is extending substantially diametrical through a through bore with a set of wedges abutting against inclined wedge sliding bases at the end portions of the pile jacket connecting pin. By sliding the wedges along the respective wedge portions by means of two wedge actuating members the connection pin at the first and second end portions radially expands. This expansion provides a secure connection of the pile and jacket, i.e. the two overlapping tubes. Due to the expansion play of the pile jacket connecting pin and the periphery of the bores of the inner and outer pipes is securely eliminated. The expanding wedges securely contact the inner wall of the through bore, even if the through bore is not exact dimensioned or not exact cylindrically. Due to the lack of play the risk of deformation of the through bores during the lifetime of the offshore platform is minimized or prevented. Further, the pile jacket connection pin can accommodate a high pile to jacket eccentricity. For example, in one embodiment a pile to jacket eccentricity of +/- 30mm for the 20” pile can be accommodated.

Preferably, the wedge actuation member is operated by means of a first set of actuating means. The actuating means generate an operation force that applies to the wedge actuation member for shifting or sliding the wedges.

Preferably, the first set of actuating means is a tension bolt extending from each end portion of the pin body, the tension bolt being arranged to extend through a bolt hole arranged in the wedge actuating member; and a first tensioning nut arranged to engage with the tension bolt and apply pressure on the respective wedge actuating member. By means of a tension bolt and a tensioning nut veiy high actuating pressures to the respective wedge actuating member can be generated and held during lifetime of the connection. The tension bolt preferably comprises elastic properties such that the expansion force acting on the wedges and the contact of the wedged to the through hole is maintained during load reversals acting on the connection by fluctuating wind and/or sea loads. In this case the tension bolt preferably maintains its pre-tension during load reversals occurring in use. Further, the first set of actuating means is reliable and simple in use and construction.

Preferably, the connecting pin further comprises two end caps arranged axially outside each wedge actuating member. The end caps can be filled with a corrosion inhibitor material and provide corrosion resistance to the pile jacket connecting pin and the overall pile jacket connection.

Preferably, the end caps can be a structural element that reinforces the jacket hole edge. The force introduced by the end caps in the area around the jacket hole prevents buckling of the jacket hole and thus significantly reduces through hole deformation in total. FEM simulations showed that through hole deformation can be reduced by a factor of 5 to 10 when end caps are used to reinforce the jacket hole edge.

Preferably, each end cap comprising a cap flange for, in a position of use, abutting against an outer surface portion of a jacket wall surrounding a through bore housing a portion of the connection pin, wherein the end caps being operatively connected to a second set of actuating means arranged to axially move the end caps with respect to the pin body, so that a pressure is applied by the end caps towards the outer surface portion of the jacket wall. Thus, the end caps are additionally preventing or minimizing the risk of deformation of the portion of the outer pipe material surrounding the bore.

Preferably, the second set of actuating means is a tension bolt extending from each end portion of the pin body, the tension bolt being arranged to extend through a bolt hole arranged in the end cap, and a second tensioning nut arranged to engage with the tension bolt and apply pressure on the respective end cap. By means of a tension bolt and a tensioning nut very high actuating pressures to the respective end cap can be generated and held during lifetime of the connection. Further, the second set of actuating means is reliable and simple in use and construction. The tension bolt of the end cap and the tension bolt of the wedge actuating member are preferably the same element.

Preferably, the tension bolt is extending through a through axial bore of the pin body. Thus, the tension bolt is the same element for the two actuating members arranged at the first and second end portions of the pin body. Since the tension bolt extends through axial bore of the pin body, it has defined elastic properties for maintaining the actuation pressure in an elastic manner. Further, the tension bolt better equalizes the actuation pressure to both wedge actuation members on both sides of the pile jacket connection pin. A further effect of this feature is that the end caps can be tensioned from one end of the connecting pin only, and furthermore that material quality of the tension bolt may be selected independently of the material quality of the pin body.

Preferably, the tension bolt is provided with a through axial bore accommodating a second tension bolt arranged to engage with the second tensioning nuts. The wedge actuation members and the end caps can preferably have individual tension bolts. Thus, the actuation pressures for the end caps and for the wedge actuation members can be set individually, preferably, in terms of the elastic properties of the tension bolts. The operation of the second set of actuating means is not influencing on the tensioning of the wedge actuating member applied by the first set of actuating means. Preferably, a first spring package is arranged on the tension bolt between at least one of the wedge actuating members and the respective first tensioning nut. The first spring package further increases the elasticity of the tension bolt for improving the elastic characteristic of the pressure application to the wedge actuating members. The first spring package move the wedges collectively if the through bore is deformed during the lifetime of the platform. The energy stored in the first spring package maintains proper tension on the wedge actuating member(s) thereby collectively displacing the respective wedges if any kind of deformation occurs in a joint secured by the connecting pin.

Preferably, the wedge actuating members are provided with a plurality of wedge adjusting bolts, wherein at least one wedge adjusting bolt facing an end portion of each of the wedges. The wedge adjusting bolts allow an individual actuation of the respective wedge. This allows an individual non-centric expansion of the wedges that improves the contact of the wedges to the periphery of the bores of the inner and outer pipes even if the bores are non-centric. An individual displacement of the wedges may be performed, thereby adapting the connecting pin to any kind of out-of-roundness shape of the through bore of a joint to be secured by the connecting pin

Preferably, a second spring package is arranged between at least some of the wedge adjusting bolts and the corresponding end portion of the respective wedge. This allows an individual elastic actuation of each of the wedges that further improves the contact of the wedges to the periphery of the bores of the inner and outer pipes. Thereby maintaining the wedge tension is maintained despite a deformation of the through bore during the lifetime of the platform. Energy stored in the second spring packages maintains proper tension on the wedges thereby individually displacing the respective wedges if any kind of deformation occurs in a joint secured by the connecting pin.

Preferably, the cap flange of the end cap comprises a cap flange seal arranged to sealingly close an end cap interior from an environment. The cap flange seal helps to maintain the corrosion inhibitor material within the interior of the end cap. Further, the end cap interior is not exposed by corrosive compounds in the environment surrounding the connecting pin end portions. Preferably, a sacrificial anode is arranged within the end cap interior. The sacrificial anode further improves the corrosion resistance of the pile jacket connection, preferably for sub-sea pile jacket joints.

Preferably, the end cap is provided with at least one closable port arranged for filling of corrosion inhibitor material into the end cap interior. The closable port facilitates filling of corrosion inhibitor material into the end cap interior.

Preferably, the closable port is arranged for applying and monitoring a fluid pressure in the end cap interior. Thus, it can be determined if the end cap is tight or if additional corrosion inhibitor material is needed.

Preferably the above-mentioned object is also achieved by a method for securing a connection between a pile and a jacket, wherein the method comprises the steps of: a) drilling a through bore diametrically through the connection; b) inserting a pile jacket connecting pin, preferably a pile jacket connecting pin as described above, into the through bore; and c) radially expanding the pile jacket connecting pin within the through bore so that the connecting pin abuts against a perimeter of the through bore of walls of pipe and jacket to transfer an axial load between the overlapping walls of pipe and jacket, the radially expansion is obtained by applying pressure on respective wedges in an axial direction of a pin body by means of a first set of actuating means acting on a wedge actuating member arranged axially outside respective wedge portions of said pin body.

The expansion provides a secure connection of the pile and jacket, i.e. the two overlapping tubes. Due to the expansion play of the pile jacket connecting pin and the periphery of the bores of the inner and outer pipes is securely eliminated. Thereby, the risk of deformation of the through bores during the lifetime of the offshore platform is minimized or prevented.

Preferably, the method further comprises the steps of: d) arranging one end cap axially outside each wedge actuating member; wherein a cap flange of each end cap abuttingly contacts an outer surface portion of a pipe wall surrounding the through bore; and e) applying pressure on the end caps in the axial direction of the pin body by means of a second set of actuating means.

The end caps apply a pressure towards the outer surface portion of the jacket wall. Thus, the end caps are additionally preventing or minimizing the risk of deformation of the portion of the outer pipe material surrounding the bore.

Preferably, the method comprises the further step of: ci) prior to step d) torquing wedge adjusting bolts provided in the wedge actuating member, to individually adjust each of the wedges.

By this step the pile jacket connecting pin can be non-centrically extended in radial direction to improve the connection between pile and jacket with eccentric through bores. The individual displacement of the wedges allows the connecting pin to be adapted to any kind of out-of- roundness shape of the through bore of a joint to be secured by the connecting pin

Preferably, the method comprises the further step of: f) filling corrosion inhibitor in an end cap interior through a closable port provided in the end cap.

The end caps can be filled with a corrosion inhibitor material and provide corrosion resistance to the pile jacket connecting pin and the overall pile jacket connection. The end cap interior is not exposed by corrosive compounds in the environment surrounding the connecting pin end portions.

Preferably, the method comprises the further step of: g) pressurizing an end cap interior by applying a fluid through a closable port provided in the end cap, to monitor the state of the connection.

Thus, it can be determined if the end cap is tight or if additional corrosion inhibitor material is needed. Further, the monitoring may be performed without dismantling any critical components of the pipe joint.

Short description of the figures

In the following preferred embodiments of the invention are illustrated by the accompanying drawings, wherein: Fig. 1 shows an axial section through a joint of a pipe structure, wherein an upper end portion of a pile is accommodated inside a tower leg;

Fig. 2 shows a perspective and partial axial section view of a first embodiment of a pile jacket connecting pin, wherein end caps are not shown;

Fig. 3 shows a side view of a pipe joint secured with a pile jacket connecting pin;

Fig. 4 shows a perspective and partial axial section view of a grouted pipe joint secured with a pile jacket connecting pin;

Fig. 5 shows in perspective a first alternative embodiment of a wedge actuating member provided with several wedge adjusting bolts;

Fig. 6a shows in larger scale a view of the end portion shown in fig. 5;

Fig. 6b shows an axial section through A-A of fig. 6a showing a portion of the wedge actuating member provided with wedge adjusting bolts;

Fig. 7 shows an axial section of the end portion of the pile jacket connecting pin abutting against a portion of the pipe joint, wherein the connecting pin has an alternative embodiment of a tension bolt;

Fig. 8 shows an axial section of an end portion of the pile jacket connecting pin, where the end cap for clarity reasons has been removed, showing a second alternative embodiment of the wedge actuating member comprising a first spring package on the tension bolt between the wedge actuating member and a first tensioning nut, and also a third alternative embodiment of the wedge actuating member comprising a second spring package arranged between the wedge adjusting bolts and the corresponding end portion of the respective wedges; and

Fig. 9 shows an exploded view of a wedge and a portion of the pin body with two wedge sliding bases each provided with guiding means to engage with a guide slot in the corresponding wedge. Preferred embodiments

In the following preferred embodiments of the invention are described with respect to the figures.

Any positional indications refer to the position shown in the figures. In the figures, same or corresponding elements are indicated by same reference numerals. For clarity reasons, some elements may in some of the figures be without reference numerals. A person skilled in the art will understand that the figures are just principle drawings. The relative proportions of individual elements may also be distorted.

In figure 1 an axial section of a portion of a pipe structure 1 is shown. The pipe structure 1 is typically an offshore platform where first pipes 11 (one shown), here shown as an outer pipe, in the form of tower legs or sleeves are mating corresponding second pipes 12, here shown as the inner pipes, in the form of piles extending from a seabed or the like (not shown). A pipe joint 14, also called pile/jacket connection is secured by some type of grout 131, typically cement, filling at least an axial portion an annulus 13 formed by the mating portions of said pipes 11, 12. To overcome the challenges of the lifetime of the pipe structure 1 exceeding the designed lifetime of the grout 131, one or more connecting pins 2 according to the disclosed invention, is inserted in the pipe joints 14 of this kind.

It is now referred to figure 2, wherein a basic embodiment of a pile jacket connecting pin 2 is depicted. A pin body 21 is provided with a first end portion 211, a second end portion 212, a central portion 210 and opposing wedge portions 213. A cross-sectional area of the pin body 21 increases from each of the first end portion 211 and the second end portion 212. Each wedge portion 213 is provided with slanted wedge sliding bases 214 arranged to carry respective wedges 22. A tension bolt 23 is projecting from each end of the pin body 21 and is here shown as a separate item extending through a center bore 215 of the pin body 21. However, the tension bolt 23 may also be integrated portions of the pin body 21, projecting from the first and second end portions 211, 212 of the pin body 21. The end portions of the tension bolt 23 are threaded, each end portion receiving a wedge actuating member 24 and a first tensioning nut 25. The first tensioning nuts 25 and the tension bolt 2023 are forming part of a first set of adjusting IO means capable of applying a pressure on the respective wedge actuating members 24, said wedge actuating members 24 facing ends 221 of respective sets of wedges 27, thus forcing the wedges 22 to be displaced along the slanted wedge sliding bases 214 to radially expand the connecting pin 2.

It is now referred to figures 3 and 4. The pile jacket connecting pin 2 is positioned in a through bore 141 extending approximately diametrical through the first and second pipes 11, 12, the intermediate annulus 13 filled with grout 131 and possibly any grout or other filling material inside the inner pipe, here shown as the second pipe 12 (see figure 4), and then being locked by the displacement of the wedges 22 by torquing the first tensioning nuts 25, forcing the wedges 22 towards the peripheiy of the bore through the pipe walls 111, 121. End caps 27 are arranged to cover the pin end portions 211, 212 projecting from an outer pipe wall 111 of the pipe joint 14. When the end caps 27 are forced against the outer pipe wall 111 by second tensioning nuts 26 engaging with the tension bolt 23, the portion of the outer pipe wall 111 surrounding the bore 141 through the outer pipe 11 is prevented from buckling, thus reducing the risk of the through bore 141 being deformed by the expansion of the connecting pin 2.

For protection purposes the second tensioning nuts 26 are protected by nut covers 275 sealingly attached to the end caps 27, the second tensioning nuts 26 being accommodated inside said nut covers 275.

In order to sealingly close an interior 277 of the end cap 27, the cap flange 271 may be provided with a cap flange seal 272 as depicted in figure 4, the cap flange seal 272 being located in a groove 279 provided in the cap flange 271.

The sealing of the end cap interior 277 is useful for the corrosion protection of the connecting pin 2 by preventing water intruding into the end cap 27 and by allowing the end cap interior 277 to be filled with corrosion inhibitor. For this purpose, the end cap 27 may be provided with one or more closable ports 276. Said port(s) 276 may even be used for test purposes, e.g., by applying pressure thereby monitoring the state of the grout 131 of the pipe joint 14. For corrosion protection purposes the end cap interior 277 may even house a sacrificial anode 278.

It is now referred to figures 5 and 6b. To provide individual adjustment of the wedges 22, an alternative embodiment of the wedge actuating member 24 includes several threaded bores 246 wherein wedge adjusting bolts 245, here shown as inhex set screws, are inserted, each facing the end 221 of a wedge 22. By applying torque to said wedge adjusting bolts 245, the wedges 22 may be individually adjusted for any out-of- roundness of the through bore 141 of the pipe joint 14.

It is now referred to figure 7, showing an alternative embodiment of the tension bolt 23. To avoid the tensioning of the end caps 27 influencing on the tensioning of the wedge actuating member 24 by applying additional tension force on the tension bolt 23, thus stretching said tension bolt 23, a second tension bolt 23a is arranged in a through axial bore 231 in the (first) tension bolt 23, projecting from the ends of the first tension bolt 23 and engaging with the second tensioning nuts 26, the first tensioning nuts 25 only engaging with the first tension bolt 23.

It is then referred to figure 8 depicting alternative embodiments of the wedge actuating member 24. Firstly, to compensate for deformation of the through bore 141 over time, a tension bolt spring 242 may be provided between the wedge actuating member 24 and the first tensioning nut 25 to collectively maintain the proper tension on the wedges 22. Secondly, an adjusting bolt spring 247 may be provided between the wedge adjusting bolts 245 and the respective wedge ends 221, individually maintaining the proper tension on the wedges 22. The springs 242, 247 maybe packages of disc springs.

Finally, it is referred to figure 9. In a preferred embodiment of the wedge portions 213 of the connecting pin 2, the wedge sliding bases 214 are flat. The flat sliding bases 214 provide a perfect contact between pin body 21 and wedge 22 in any wedge position or set location. In order to provide proper guiding of the wedges 22, the wedge sliding bases 214 are provided with one or more wedge guides 216 engaging with a counteracting guide portion 222 of the wedges 22, here in the form of T-head bolts projecting from the wedge sliding bases 214 engaging with a slot 222 provided in a sliding face 223 of the wedge, the slot 222 having a T-shaped cross section. A preferred method for securing a connection (14) between a pile (12) and a jacket (11), wherein the method comprises some or all the following steps preferably in the following sequence: a) Drilling a through bore (141) diametrically through the connection (14). b) Inserting the pile jacket connecting pin (2) into the through bore (141). c) Radially expanding the pile jacket connecting pin (2) within the through bore (141) so that the connecting pin (2) abuts against a perimeter of the through bore of walls of pipe (12) and jacket (11) to transfer an axial load between the overlapping walls of pipe (12) and jacket (12).

The radially expansion is obtained by applying pressure on the respective wedges (22) in an axial direction of the pin body (21) by means of the first set of actuating means (23, 25) acting on the wedge actuating member (24) arranged axially outside respective wedge portions (213) of said pin body (21). ci) Torquing the wedge adjusting bolts (245) provided in the wedge actuating member (24), to individually adjust each of the wedges (22). d) Arranging one end cap (27) axially outside each wedge actuating member (24), wherein the cap flange (271) of each end cap (27) abuttingly contacts an outer surface portion of a pipe wall (111) surrounding the through bore (141). e) Applying pressure on the end caps (27) in the axial direction of the pin body (21) by means of the second set of actuating means (23, 26; 23a, 26). f) Filling corrosion inhibitor into the end cap interior (277) through the closable port (276) provided in the end cap (27). Grease can be used to act as corrosion inhibitor. g) Pressurizing an end cap interior (277) by applying a fluid, preferably the corrosion inhibitor, through a closable port (276) provided in the end cap (27), to monitor the state of the connection (14). It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.