GB2597836A

GB2597836A - Apparatus and method for the protection of structures from corrosion

Info

Publication number: GB2597836A
Application number: GB2110196.9A
Authority: GB
Inventors: Patrick Thomson John; Robert Dunsterville Brian; Michael Crawley Stephen; Leader Darlow Ryan; Barry Tonks Adrian
Original assignee: Winn and Coales International Ltd
Current assignee: Winn and Coales International Ltd
Priority date: 2020-07-16
Filing date: 2021-07-15
Publication date: 2022-02-09
Anticipated expiration: 2041-07-15
Also published as: GB202010972D0; GB2597256A; GB2597836B; GB2597256B; GB202110196D0

Abstract

The apparatus comprises a jacket for cladding the structure, the jacket comprising: a jacket sheet 38; and one or more jacket flanges for the jacket sheet. Each jacket flange is elongate and has a slot 37 running lengthwise along the jacket flange and each jacket flange is joined to the jacket sheet by weld material 39 or an adhesive. The weld material or adhesive fills or substantially fills the slot in the jacket flange and extends from the slot to engage a surface of the jacket sheet. The apparatus may comprise a plurality of jacket sheets and one or more jacket flange(s) for each sheet. The slot may have a rectangular, trapezoid, circular or T-shaped cross-section taken perpendicular to the longitudinal axis of the jacket flange. The jacket flange may be connected to another jacket flange by a plurality of bolts. Also provided is a jacket sheet and a pair of jacket flanges with a plurality of keyway sections and sockets (140, fig. 14b).

Description

Apparatus and Method for the protection of structures from corrosion The present invention relates to apparatus and a method for the protection of structures, e.g. steel, wooden or concrete structures, from corrosion, particularly those exposed to aquatic environments including oceanic, marine, riverine, estuarine, paludal, and lake environments be they fresh water or saltwater.

In particular, the invention is concerned with the protection of piles of jetties and the protection of sheet pile walls from corrosion. Jetty piles are often tubular steel members, preferably of circular, hexagonal or square cross section, which are exposed to a marine environment, i.e. which are immersed partially, or completely, in sea water or are within the splash zone above sea level, or which are exposed to estuarine or fresh water, e.g. in rivers, lakes, harbours and docks. Sheet piling is used also for jetties and harbour walls.

As detailed in GB2161886A costal and offshore structures, such as jetties, oil-drilling platforms etc., are made from tubular steel members and the protection of these members from corrosion has constituted a major problem. Whilst petrolatum tape will provide long-term protection from corrosion to steel surfaces exposed to a marine environment, there has been a practical problem of maintaining the integrity of the tape.

In coastal areas, the scouring action of waves is very severe and shingle bombardment can damage the corrosion protection. Waves and floating debris can damage offshore structures. Impacts with boats can also damage the protection. This applies equally to sheet piling.

In the preamble of 0B2161886A there is described an anti-corrosion system having an outer protective jacket which consists of preformed semi-circular jacket sections of glass fibre reinforced polyester resin. These preformed semi-circular jacket sections are provided with longitudinal jacket flanges which are bolted together to form a circular cross-section cover. In the prior art document the space between the jacket and the protective tape is filled with a layer of foamed polyethylene sheet that is compressible and accommodates any irregularities of the space when the flanges are bolted together.

In GB2161886A there is described a method which comprises: 1. wrapping a petrolatum tape or sheet around the steel structure; 2. next applying a layer of a filler material to the petrolatum tape or sheet; and 3. thereafter encasing the filler material with a jacket formed of one or more jacket sections formed from jacket sheets of a flexible thermoplastic resin. Each jacket sheet is provided at one edge thereof with a plurality of openings and at the other edge thereof with a plurality of complementary openings and the jacket sheets are secured in position by fastening means that pass through the openings and the complementary openings.

The jacket of GB2161886A is made of any suitable thermoplastic resin, for example, polypropylene. The jacket is provided at one edge thereof with circular bolt holes and at the other edge thereof with complementary elongate holes. The jacket is secured in place by bolts which pass through these holes and the use of matching nuts and washers. The provision of elongate holes at one edge of the each cover sheet enables the sheets to be adapted to be wrapped around tubular steel structures of different circumferences and also to enable any variations in the circumference of the surface of a single structure to be readily accommodated. To assist during installation the jacket is clamped tightly around the tubular steel member by means of temporary bands or straps or the like. The straps are removed after the jacket edges have been secured together by the nuts and bolts.

A further prior art system is illustrated in figure 1. In the figure there can be seen a jetty pile 10 having a cylindrical external surface 11. A liquid primer is applied as a coating 12 to the surface 11. Next a petrolatum tape 13 is wound around the primed surface.

Then two HDPE (High-density Polyethylene) jacket parts 14, 15 are used to encase the jetty pile 10. These jacket parts 14, 15 comprise jacket sheets and jacket flanges 16, 17, each jacket flange 16, 17 provided with apertures which can be aligned by an installer to allow the parts 14, 15 to be fastened together by bolts 18 and nuts 19.

The formation of the flange 17 is shown in more detail in figure 2. The jacket part 17 is formed of a flexible jacket sheet 20 of HDPE of approximately 2 mm thickness. This sheet 20 is wrapped around two faces 21 and 22 of a jacket flange 23 also formed of HDPE. The jacket flange 23 is an elongate extrusion of a generally rectangular cross-section, as can be seen in the figure 2. The jacket sheet 20 is welded to the jacket flange 23 by a weld 24 between a surface 26 of the jacket flange 23 not overlain by the jacket sheet 20 and an extension part 25 of the jacket sheet 20 that extends beyond the jacket flange 23, the extension part 25 being an extension of that part of the sheet 20 that overlays the face 22. Bolt holes need to be formed, e.g. by drilling, through both the jacket flange 23 and the overlying jacket sheet 20.

As detailed in W090/09488, steel piling for quays and other waterside structures can have anti-corrosion cladding fitted comprising flexible water-impermeable sheets fastened to the steel piling by rigid bars, with the sheets stretched between the rigid bars to follow the contours of the steel piling.

The present invention provides apparatus for protecting a structure from corrosion as claimed in claim 1, preferred features of which are found in claims 2 to 15. The present invention also provides a method of protecting a structure from corrosion as claimed in claim 16 and preferred steps of the method are found in claims 17 to 24. The present invention further provides a method of manufacture of apparatus for protecting a structure from corrosion as claimed in claim 25, with preferred steps of the method of manufacture found in claims 26 and 27. Additionally the present invention provides apparatus for protecting a structure from corrosion as claimed in claim 28, preferred features of which are found in claims 29 to 32. Lastly the present invention provided a method of protecting a structure as claimed in claim 33, with preferred steps of the method found in claims 34 and 35.

The present invention will be further described with reference to specific embodiments thereof as shown in the accompanying drawings, in which: Figure 1 is a schematic cutaway view of corrosion protection apparatus of the prior art; Figure 2 is a cross-section view of a jacket flange which forms part of the jacket of the apparatus of figure 1; Figures 3a, 3b and 4 all show a first embodiment of a jacket flange according to the invention, with Figure 3a being a perspective view of the jacket flange. Figure 3b being a detailed perspective view of one end of the jacket flange illustrated in Figure 3a and 4 -Figure 4 being a cross-section through the jacket flange when welded to a sheet as part of a jacket; Figures 5a, 5b and 6 all show a second embodiment of a jacket flange according to the invention, with Figure 5a being a perspective view of the jacket flange. Figure 5b being a detailed view of one end of the jacket flange illustrated in Figure 5a and Figure 6 being a cross-section through the jacket flange when welded to a sheet as part of a jacket; Figures 7a, 7b and 8 all show a third embodiment of a jacket flange according to the invention, with Figure 7a being a perspective view of the jacket flange, Figure 7b being a detailed view of one end of the jacket flange illustrated in Figure 7a and Figure 8 being a cross-section through the jacket flange when welded to a sheet as part of a jacket; Figures 9a, 9b and 10 all show a fourth embodiment of a jacket flange according to the invention, with Figure 9a being a perspective view of the jacket flange, Figure 9b being a detailed view of one end of the jacket flange illustrated in Figure 9a and Figure 10 being a cross-section through the jacket flange when welded to a sheet as part of a jacket; Figures 11a, llb and 12 all show a fifth embodiment of a jacket flange according to the invention, with Figure lla being a perspective view of the jacket flange, Figure llb being a detailed view of one end of the jacket flange illustrated in Figure 11 a and Figure 12 being a cross-section through the jacket flange when welded to a sheet as part of a jacket; Figures 13a, 13b, 14a and 14b all show a sixth embodiment of a jacket flange according to the invention, with Figure 13a being a perspective view of the jacket flange, Figure 13b being a detailed view of one end of the jacket flange illustrated in Figure 13a and Figure 14a being a perspective view of a pair of the Figure 13a jacket flanges in mating engagement and Figure 14b being a detailed view of one end of the engaged jacket flanges of Figure 14a;

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Figures 15a, 15b, 16a and 16b all show a seventh embodiment of a jacket flange according to the invention, with Figure 15a being a perspective view of the jacket flange, Figure 15b being a detailed view of one end of the jacket flange illustrated in Figure 15a and Figure 16a being a perspective view of a pair of the Figure 15a flanges in mating engagement and Figure 16b being a detailed view of one end of the engaged flanges of Figure 16a; and Figure 17 is a schematic view of a sheet pile wall protected with corrosion protection apparatus according to an eighth embodiment of the invention.

Figures 18a, 18b and 19 all show a ninth embodiment of a jacket flange according to the invention, with Figure 18a being a perspective view of the jacket flange, Figure 18b being a detailed perspective view of one end of the jacket flange illustrated in Figure 18a and Figure 19 being a cross-section through the jacket flange when welded to a sheet as part of a jacket.

Figures 20a, 20b and 21 all show a tenth embodiment of a jacket flange according to the invention, with Figure 20a being a perspective view of the jacket flange, Figure 20b being a detailed view of one end of the jacket flange illustrated in Figure 20a and Figure 21 being a cross-section through the jacket flange when welded to a sheet as part of a jacket.

Figures 22a, 22b and 23 all show a eleventh embodiment of a jacket flange according to the invention, with Figure 22a being a perspective view of the jacket flange, Figure 22b being a detailed view of one end of the jacket flange illustrated in Figure 22a and Figure 23 being a cross-section through the jacket flange when welded to a sheet as part of a jacket.

Figures 24a, 24b and 25 all show an twelfth embodiment of a jacket flange according to the invention, with Figure 24a being a perspective view of the jacket flange, Figure 24b being a detailed view of one end of the jacket flange illustrated in Figure 24a and Figure 25 being a cross-section through the jacket flange when welded to a sheet as part of a jacket. 6 -

Figure 26 shows a thirteenth embodiment of a jacket flange according to the invention, and in particular shows a cross-section through the jacket flange when welded to a sheet as part of a jacket.

Looking at Figure 3a, there can be seen in the figure an elongate jacket flange 30 according to a first embodiment of the invention. The jacket flange 30 is formed as an HDPE extrusion with a cross-section formed generally as a truncated triangle, providing four faces. There are two parallel planar faces 31 and 32 (see figure 3b), with the face 31 having a width W1 less than half a width W2 of the face 32. There is a third planar abutment face 33 which lies in a plane perpendicular to the planes of the faces 31 and 32. There is an inclined face 34 which lies in a plane inclined at an acute angle to the plane of the abutment face 33.

A series of regularly spaced countersunk bolt holes 35 are provided in the jacket flange 30 spaced along the length of the jacket flange 30, each bolt hole 35 extending between the faces 33 and 34. Each countersunk bolt hole 35 is provided with a circular planar rim, e.g. the rim 36 in figure 3b, the rims lying together in plane parallel to and spaced from the plane of the face 33. Only the inclined face 24 of the jacket flange 30 is countersunk, the apertures in face 33 are flush with face 33. The rims, e.g. 36, each provide a flat surface for engagement by a bolt head or a nut. The countersunk bolt holes 35 are drilled through the jacket flange 30 after it has been formed by an extrusion process and machined to the desired form and cut to a desired length.

The jacket flange 30 is provided with a weld slot 37 in the inclined face 34. The weld slot 37 can be formed during the extrusion of the jacket flange or machined in the inclined face 34 after initial formation of the face 34 by extrusion and perhaps by an earlier machining process as well. The weld slot 37 extends perpendicular to the inclined face 34, as can be clearly seen in figure 4, and extends lengthwise along the jacket flange 30, along the whole or substantially the whole of the length of the jacket flange 30. It can also be seen in figure 4 that the weld slot 37 has a rectangular cross section, with two parallel side surfaces 37a and 37b extending perpendicular to a flat end surface 37c, which faces the opening of the weld slot 37. The opening typically has a 5mm minimum width. The weld slot 37 is provided to facilitate the welding of the jacket flange 30 to a flexible HDPE jacket sheet 38 which forms a jacket section of the 7 -anti-corrosion apparatus. This jacket sheet 38 will be similar to the jacket sheet of the jacket part 15 or 14 shown in figure 1.

In figure 4 is there can be seen weld material 39 used to fix the jacket flange 30 to the HDPE sheet 38. The weld material 39 extends into and fills the weld slot 37 and extends between the jacket flange 30 and the HDPE sheet 38 to join one to the other. HDPE is a thermoplastic well suited to welding. However, an acceptable alternative would be to use an adhesive to affix the jacket flange 30 to the sheet 38, with the slot 37 in this case not being a weld slot, but nevertheless providing an increased surface area for adhering the flange 30 to the sheet 38.

When comparing the weld of figure 4 with the weld of figure 2, it can be seen that the weld slot 37 provides an increased surface area for engagement by the weld material 39 and also an undercut to provide a physical interlock for the weld material 39 when solidified. Furthermore, due to the improved engagement, the HDPE sheet 38 may only contact a surface of a single face of the flange 30, and there is no need to wrap the HDPE sheet 38 around the jacket flange 30, unlike in figure 2, so there is avoided the stress placed on the HDPE in the corner region 29 of figure 2. Additionally, the HDPE sheet 38 can provide an overlap region 40 which can lie under the HDPE sheet of a mating jacket part engaged with the jacket flange 30. Typically each jacket part of this embodiment of the invention will have one end as shown in figure 4 provided with an overlap region and then a second end which is as shown in figure 4 except that no overlap region is provided and the jacket flange is provided coincident with the end of the HDPE sheet 38. As another alternative, both ends of the jacket part can be as shown in figure 4, but one overlap region 40 is sandwiched between opposing abutment faces 33 of a pair of jacket flanges 30 instead of underlying an adjacent jacket sheet. It is advantageous to provide for an overlap region in order to minimise ingress of water and other material into the region between the jacket and the jetty pile.

The weld slot 37 is a feature easily inspected for quality assurance purposes. For instance a light can be shone along the weld slot 37 to make sure there are no obstructions to block the passage of the light. After welding (described later) a light can be shone along to the weld slot to see if the weld slot has been completely filled at at least one point along its length. 8 -

In use the jacket flange 30 of a first jacket part will be brought into engagement with an identical jacket flange 30 of a second jacket part, with abutment faces 33 of the jacket flanges 30 engaging and abutting each other. The jacket flanges 30 and thereby the jacket parts are secured together by nuts and bolts, with the bolts passing through the bolt holes 35. The narrow width surfaces 31 of the jacket flanges 30 will be the surfaces facing the cylindrical outer surface of the jetty pile. This is advantageous in comparison with the figure 2 arrangement since it minimises the percentage of the flat surfaces that are not in engagement with the cylindrical surface of the tape wrapping immediately underneath the jacket. The use of the weld slot 37 means that there is sufficient surface area for engagement by the weld material despite the reduced width of the surfaces 31. The jacket part of figure 2 comprising the jacket flange 30 will be used in a system as illustrated in figure 1 with the jacket flanges 16 and 17 of figure 1 each replaced with a jacket flange 30 according to the invention.

The invention provides a method of protecting a structure such as a metal jetty pile from corrosion, in which the external cylindrical surface of the jetty pile 10 is first prepared by removing weld spatter, sharp points and edges as well as removing marine growth, loose rut, loose paint and foreign matter from the cylindrical outer surface 11 of the jetty pile 10. This will be done by hand or with power tools. For instance, a hydraulic whirl away or high pressure water blasting may be used to prepare the surface.

Next the prepared surface is coated with a primer 12. This will typically comprise saturated petroleum hydrocarbons (petrolatum), inert fillers and passivating agents.

The primer 12 is used to displace moisture, passivate the surface and fill surface imperfections on corroded areas. It is important to coat all areas of the cylindrical surface with corrosion pits greater than 2mm diameter. The primer 12 will fill such pits. The primer 12 is applied by hand. When the primer 12 is applied underwater then the worker applying the primer 12 will use a gloved hand to displace water and slowly rub the primer 12 on to the cylindrical surface and fill the pits.

The next (optional) step is to use a mastic (not shown) to smooth surface irregularities. For instance in the protection of complex surfaces with configurations such as brackets and flanges, the mastic is used to fill and pack to achieve a smooth contour to which tape can be applied without bridging or voids. The mastic is also used to fill in cavities at the interface between the jetty pile 10 and a pile cap (not shown). The mastic will typically comprise saturated petroleum hydrocarbons (petrolatum), inert fillers, reinforcing fibres and thermal extenders and may contain beads of cellular polymer and/or flow control additives. The mastic is cold applied by hand around irregular shaped fittings to provide a suitable profile for the subsequent use of a tape wrapping 13.

Next the primed surface (with mastic applied, if appropriate) is spirally wrapped with tape 13, with a 55% overlap, which will provide a double thickness of tape along the length of the pile. The tape 13 is applied starting at a vertically highest point and then wound downwards (the reverse is also possible, but less preferred, i.e. the tape 13 is applied starting at the vertically lowest point and then wound upwards). The end of the tape 13 is firmly pressed against the starting point and then the tape 13 unrolled while keeping the tape 13 close to the primed surface, applying sufficient tension to provide continuous adhesion without stretching of the tape. During application of the tape 13 all folds and air pockets should be pressed out. Typically the tape 13 is applied by hand, but a tape application machine can be used. The tape 13 is formed from a non-woven synthetic fibre carrier fully impregnated and coated with a neutral saturated petroleum hydrocarbon (petrolatum) based composition having inert siliceous fillers, water displacing agents and corrosion inhibitors. The tape 13 has an HDPE film backing. The tape 13 is stable in composition and plasticity over a wide temperature range and is non-hardening and non-cracking. The tape 13 can accommodate vibration and movement of the jetty pile. The tape 13 is resistant to mineral acids and alkalis.

The HDPE sheets used to make the jacket 15 are substantially seamless and substantially uniform and substantially free from cracks, bubbles and other defects. The jacket 15 prevents damage to the underlying tape 13. The jacket 15 will be custom engineered to provide the correct fit for the diameter of the jetty pile 10. The jacket flanges 30 of the jacket 15 (used in place of the jacket flanges 16 and 17 illustrated in figure 2) are secured together by the use of M12 x 90 mm hexagon bolts of 316 stainless steel and M12 hexagon nuts, also of stainless steel. Two flat washers will be -10 -used for each nut and bolt, the flat washers being M12 x 35 mm x 1.5mm washers of A4-70 stainless steel.

Typically a hydraulic clamp is used to during installation of the jacket 15. The clamp has jaws which engage adjacent jacket flanges 30 and then hydraulic pressure is used to force the jacket flanges 30 into engagement. Then the bolts are inserted through the aligned bolt holes in the jacket flanges 30 and washers applied and nuts tightened. The clamp jaws are adapted to leave the bolt holes 35 (or at least a plurality of them) uncovered. Typically a hydraulic hand pump is used to generate a pressure of around 1500 psi (10.34 MPa) while the jacket flanges 30 are brought together and then a clamping pressure of around 5000 psi (34.47 MPa) once the jacket flanges 30 are engaged. The hydraulic clamp is removed once the bolts have been installed (and then any remaining bolts are installed in any remaining empty bolt holes).

Figures 5 to 16 show variants of what has already been described above. For brevity for each of the figures 5 to 16 embodiments not all of the above description will be repeated, but it should be understood that the above description applies equally to each of the second to seventh embodiments. Each of the second to seventh illustrated embodiments is a different variant of jacket flange. Each of the different variants of jacket flange (30, 50, 70, 90, 110, 130, 150) will be used in a jacket arrangement as shown in figure 1 in place of the jacket flanges 16, 17 shown in that figure; otherwise all other aspects of the jacket arrangement will remain as illustrated in figure 1 and described above. The steps of the method of installation will remain as described above. The reference numerals selected show correspondence. They are based on the figure numbers. For instance the reference numeral 30 is used for the jacket flange of figure 3 and 35 for the bolt holes, while reference numeral 50 is used for the jacket flange of figure 5 and 55 for the bolt holes, reference numeral 70 is used for the jacket flange of figure 7 and 75 for the bolt holes, and so on.

Looking at Figure 5a, there can be seen in the figure an elongate jacket flange 50 according to a second embodiment of the invention. The jacket flange 50 is formed as an HDPE extrusion with a cross-section formed generally as a truncated triangle, providing four faces. There are two parallel planar faces 51 and 52, with the face 51 having a width less than half the width of the face 52. There is a third planar abutment face 53 which is lies in a plane perpendicular to the planes of the faces 51 and 52. There is an inclined face 54 which lies in plane inclined at an acute angle to the plane of the abutment face 53.

A series of regularly spaced countersunk bolt holes 55 are provided in the jacket flange 50, the bolt holes being spaced lengthwise along the elongate jacket flange 50, each bolt hole 55 extending between the faces 53 and 54. Each countersunk bolt hole 55 is provided with a circular planar rim, e.g. the rim 56 in figure 5b, the rims lying together in plane parallel to and spaced from the plane of the face 53. Only the inclined face 54 of the jacket flange 50 is countersunk, the apertures in face 53 are flush with face 53. The rims, e.g. 56, each provide a flat surface for engagement by a bolt head or a nut. The countersunk bolt holes 55 are drilled through the jacket flange 50 after it has been formed by an extrusion process and machined and cut to a desired length.

The jacket flange 50 is provided with a weld slot 57 in the inclined face 54. The weld slot 57 can be formed during the extrusion of the jacket flange or machined in inclined face 54 after initial formation of the face 54 by extrusion and perhaps by an earlier machining process as well. The weld slot 57 extends lengthwise along the elongate jacket flange 50, extending the whole or substantially the whole of the length of the jacket flange 50. It can be seen in figure 6 that the weld slot 57 has a cross section with a shape of a trapezoid (American English) or trapezium (English), with a flat end surface 57c lying in a plane parallel to and spaced apart from the inclined surface 54. The end surface 57c is wider than the opening of the weld slot 57 which it faces (these width measurements being taken in a plane perpendicular to the longitudinal axis of the jacket flange 50). Two side surfaces 57a and 57b extend from the edges of the end surface 57c to the opening of the weld slot, with the side surfaces 57a and 57b non-perpendicular and inclined relative to the end surface 57c so that the slot 57 narrows in width from the base 57c towards the opening. The opening typically has a 5mm minimum width. The weld slot 57 is provided to facilitate the welding of the jacket flange 50 to a flexible HDPE sheet 58 which forms a jacket part of the anti-corrosion apparatus. This jacket part will be similar to the jacket part 15 or 14 shown in figure 1.

In figure 6 there can be seen weld material 59 used to fix the jacket flange 50 to the HDPE sheet 58. The weld material 59 extends into and fills the weld slot 57 and -12 -extends between the jacket flange 50 and the HDPE sheet 58 to join one to the other. As mentioned above, HDPE is a thermoplastic well suited to welding. However, an acceptable alternative would be to use an adhesive to affix the jacket flange 50 to the sheet 58, with the slot 57 in this case not being a weld slot, but nevertheless providing an increased surface area for adhering the flange 50 to the sheet 58.

When comparing the weld of figure 6 with the weld of figure 2, is can be seen that the weld slot 57 provides an increased surface area for engagement by the weld material 59. The trapezoid/trapezium shape of the weld slot 57 provides a strong physical interlock for the weld material when solidified. Furthermore, due to the improved engagement, the HDPE sheet 58 may only contact a surface of a single face of the flange 50, and there is no need to wrap the HDPE sheet around the jacket flange 50, unlike in figure 2, so there is avoided the stress placed on the HDPE in the corner region 29 of figure 2. Additionally, the HDPE sheet 58 can provide an overlap region 60 which can lie under the HDPE sheet of a mating jacket part engaged with the jacket flange 50.

The weld slot 57 is a feature easily inspected for quality assurance purposes. For instance a light can be shone along to the weld slot 57 to make sure there are no obstructions to block the passage of the light. After welding (described later) a light can be shone along to the weld slot to see if the weld slot has been completely filled at at least one point along its length.

In use the jacket flange 50 of a first jacket part will be brought into engagement with an identical jacket flange 50 of a second jacket part, with abutment faces 53 of the jacket flanges 50 engaging and abutting each other. The jacket flanges 50 and thereby the jacket parts are secured together by nuts and bolts, with the bolts passing through the bolt holes 55. The narrow width surfaces 51 of the jacket flanges 50 will be the surfaces facing the cylindrical outer surface of the jetty pile. This is advantageous in comparison with the figure 2 arrangement since it minimises the percentage of the flat surfaces that are not in engagement with the cylindrical surface of the tape wrapping immediately underneath the jacket. Nevertheless it is important that the jacket flange has an overall size sufficient to bear the clamping loads. The use of the weld slot 57 means that there -13 -is sufficient surface area for engagement by the weld material despite the reduced width of the surfaces 51.

Turning now to Figure 7a, there can be seen in the figure an elongate jacket flange 70 according to a third embodiment of the invention. The jacket flange 70 is formed as an HDPE extrusion with a cross-section formed generally as a truncated triangle, providing four faces. There are two parallel planar faces 71 and 72, with the face 71 having a width less than half the width of the face 72. There is a third planar abutment face 73 which is lies in a plane perpendicular to the planes of the faces 71 and 72. There is an inclined face 74 which lies in plane inclined at an acute angle to the plane of the abutment face 73.

A series of regularly spaced countersunk bolt holes 75, spaced along the length of the elongate jacket flange 70, are provided in the jacket flange 70 extending between the faces 73 and 74. Each countersunk bolt hole is provided with a circular planar rim, e.g. the rim 76 in figure 7b, the rims lying together in plane parallel to and spaced from the plane of the face 73. Only the inclined face 74 of the jacket flange 70 is countersunk, the apertures in face 73 are flush with face 73. The rims, e.g. 76, each provide a flat surface for engagement by a bolt head or a nut. The countersunk bolt holes 75 are drilled through the jacket flange 70 after it has been formed by an extrusion process and machined and cut to a desired length.

The jacket flange 70 is provided with a weld slot 77 in the inclined face 74. The weld slot 77 can be formed during the extrusion of the jacket flange or machined in inclined face 74 after initial formation of the face 74 by extrusion and perhaps by an earlier machining process as well. The weld slot extends lengthwise along the jacket flange 70, for the whole or substantially the whole length of the jacket flange 70. The shape of the weld slot 77 makes it very suitable for machining. It can be seen in figure 8 that the weld slot 77 has a cross section with a circular section 77a (which can be formed by a drilling operation) and a straight-sided neck section 77b (which can be formed by a milling operation) extending from the circular section 77a to the slot opening. The circular section 77a has a diameter greater that the width of the neck section 77b, whose width is the same as that of the opening of the weld slot 77. The opening typically has a 5mm minimum width. The weld slot 77 is provided to facilitate the -14 -welding of the jacket flange 70 to a flexible HDPE sheet 58 which forms a jacket part of the anti-corrosion apparatus. This jacket part will be similar to the jacket part 15 or 14 shown in figure 1.

In figure 8 there can be seen weld material 79 used to fix the jacket flange 70 to the HDPE sheet 78. The weld material 78 extends into and fills the weld slot 77 and extends between the jacket flange 70 and the HDPE sheet 78 to join one to the other. As mentioned above, HDPE is a thermoplastic well suited to welding. However, an acceptable alternative would be to use an adhesive to affix the jacket flange 70 to the sheet 78, with the slot 77 in this case not being a weld slot, but nevertheless providing an increased surface area for adhering the flange 70 to the sheet 78.

When comparing the weld of figure 8 with the weld of figure 2, it can be seen that the weld slot 77 provides an increased surface area for engagement by the weld material 79. The circular section 77a of the slot 77, since it has a diameter greater than the width of the neck portion 77b, provides a strong physical interlock for the weld material 79 when solidified. Furthermore, due to the improved engagement, the HDPE sheet 78 may only contact a surface of a single face of the flange 70, and there is no need to wrap the HDPE sheet 78 around the jacket flange 70, unlike in figure 2, so there is avoided the stress placed on the HDPE in the corner region 29 of figure 2. Additionally, the HDPE sheet 78 can provide an overlap region 80 which can lie under the HDPE sheet of a mating jacket part engaged with the jacket flange 70.

The weld slot 77 is a feature easily inspected for quality assurance purposes. For instance a light can be shone along to the weld slot 77 to make sure there are no obstructions to block the passage of the light. After welding (described later) a light can be shone along to the weld slot to see if the weld slot has been completely filled at at least one point along its length.

In use, the jacket flange 70 of a first jacket part will be brought into engagement with an identical jacket flange 70 of a second jacket part, with abutment faces 73 of the jacket flanges 70 engaging and abutting each other. The jacket flanges 70 and thereby the jacket parts are secured together by nuts and bolts, with the bolts passing through the bolt holes 75. The narrow width surfaces 71 of the jacket flanges 70 will be the surfaces -15 -facing the cylindrical outer surface of the jetty pile. This is advantageous in comparison with the figure 2 arrangement since it minimises the percentage of the flat surfaces that are not in engagement with the cylindrical surface of the tape wrapping immediately underneath the jacket. Nevertheless it is important that the jacket flange 70 has an overall size sufficient to bear the clamping loads. The use of the weld slot 77 means that there is sufficient surface area for engagement by the weld material despite the reduced width of the surfaces 71.

Turning now to Figure 9a, there can be seen in the figure an elongate jacket flange 90 according to a fourth embodiment of the invention. The jacket flange 90 is formed as an HDPE extrusion with a cross-section formed generally as a truncated triangle, providing four faces. There are two parallel planar faces 91 and 92, with the face 91 having a width less than half the width of the face 92. There is a third planar abutment face 93 which is lies in a plane perpendicular to the planes of the faces 91 and 92. There is an inclined face 94 which lies in plane inclined at an acute angle to the plane of the abutment face 93.

A series of regularly spaced countersunk bolt holes 95, spaced lengthwise along the elongate jacket flange 90, are provided in the jacket flange 90 extending between the faces 93 and 94. Each countersunk bolt hole is provided with a circular planar rim, e.g. the rim 96 in figure 9b, the rims lying together in plane parallel to and spaced from the plane of the face 93. Only the inclined face 94 of the jacket flange 90 is countersunk, the apertures in abutment face 93 are flush with face 93. The rims, e.g. 96, each provide a flat surface for engagement by a bolt head or a nut. The countersunk bolt holes 95 are drilled through the jacket flange 90 after it has been formed by an extrusion process and machined and cut to a desired length.

The jacket flange 90 is provided with a weld slot 97 in the inclined face 94. The weld slot 97 can be formed during the extrusion of the jacket flange or machined in the inclined face 94 after initial formation of the face 94 by extrusion and perhaps by an earlier machining process as well. The weld slot 97 extends lengthwise along the elongate jacket flange 90, for the whole or substantially the whole of the length of the elongate jacket flange 90. It can be seen in figure 10 that the weld slot 97 has a T-shaped cross section with a head section 97a and a tail section 97b extending from the -16 -head section 97a to the slot opening. The head section 97a has a width greater that the width of the slot opening, the width of the slot opening being equal in width to the width of the tail section 97b (the widths measured in a plane perpendicular to the longitudinal axis of the jacket flange 90). The opening typically has a 5mm minimum width. The weld slot 97 is provided to facilitate the welding of the jacket flange 90 to a flexible HDPE sheet 98 which forms a jacket part of the anti-corrosion apparatus. This jacket part will be similar to the jacket part 15 or 14 shown in figure 1.

In figure 10 there can be seen weld material 99 used to fix the jacket flange 90 to the HDPE sheet 98. The weld material 99 extends into and fills the weld slot 97 and extends between the jacket flange 90 and the HDPE sheet 98 to join one to the other. As mentioned above, HDPE is a thermoplastic well suited to welding. However, an acceptable alternative would be to use an adhesive to affix the jacket flange 90 to the sheet 98, with the slot 97 in this case not being a weld slot, but nevertheless providing an increased surface area for adhering the flange 90 to the sheet 98.

When comparing the weld of figure 10 with the weld of figure 2, it can be seen that the weld slot 97 provides an increased surface area for engagement by the weld material 99. The head section 97a of the slot 97, since it has a width greater than the width of the tail portion 97b, provides a strong physical interlock for the weld material 99 when solidified. Furthermore, due to the improved engagement, the HDPE sheet 98 may only contact a surface of a single face of the flange 90, and there is no need to wrap the HDPE sheet 98 around the jacket flange 90, unlike in figure 2, so there is avoided the stress placed on the HDPE in the corner region 29 of figure 2. Additionally, the HDPE sheet 98 can provide an overlap region 100 which can lie under the HDPE sheet of a mating jacket part engaged with the jacket flange 90.

The weld slot 97 is a feature easily inspected for quality assurance purposes. For instance a light can be shone along to the weld slot 97 to make sure there are no obstructions to block the passage of the light. After welding (described later) a light can be shone along to the weld slot to see if the weld slot has been completely filled at at least one point along its length.

-17 -In use the jacket flange 90 of a first jacket part will be brought into engagement with an identical jacket flange 90 of a second jacket part, with abutment faces 93 of the jacket flanges 90 engaging and abutting each other. The jacket flanges 90 and thereby the jacket parts are secured together by nuts and bolts, with the bolts passing through the bolt holes 95. The narrow width surfaces 91 of the jacket flanges 90 will be the surfaces facing the cylindrical outer surface of the jetty pile. This is advantageous in comparison with the figure 2 arrangement since it minimises the percentage of the flat surfaces that are not in engagement with the cylindrical surface of the tape wrapping immediately underneath the jacket. Nevertheless it is important that the jacket flange 90 has an overall size sufficient to bear the clamping loads. The use of the weld slot 97 means that there is sufficient surface area for engagement by the weld material despite the reduced width of the surfaces 91.

Turning now to Figure 11a, there can be seen in the figure lla an elongate jacket flange 110 according to a fifth embodiment of the invention. The jacket flange 110 is formed as an HOPE extrusion with a cross-section formed generally as a truncated triangle, providing four faces. There are two parallel planar faces 111 and 112, with the face 111 having a width less than half the width of the face 112. There is a third planar abutment face 113 which is lies in a plane perpendicular to the planes of the faces 111 and 112. There is an inclined face 114 which lies in plane inclined at an acute angle to the plane of the abutment face 113.

A series of regularly spaced countersunk bolt holes 115, spaced lengthwise along the elongate jacket flange 110, are provided in the jacket flange 110 extending between the faces 113 and 114. Each countersunk bolt hole 115 is provided with a circular planar rim, e.g. the rim 116 in figure 11 b, the rims lying together in plane parallel to and spaced from the plane of the face 113. Only the inclined face 114 of the jacket flange 110 is countersunk, the apertures in face 113 are flush with face 113. The rims, e.g. 116, each provide a flat surface for engagement by a bolt head or a nut. The countersunk bolt holes 115 are drilled through the jacket flange 110 after it has been formed by an extrusion process and machined and cut to a desired length.

The jacket flange 110 is provided with a weld slot 117 in the inclined face 114. The weld slot 117 can be formed during the extrusion of the jacket flange or machined in -18 -inclined face 114 after initial formation of the face 114 by extrusion and perhaps by an earlier machining process as well. The weld slot 117 extends lengthwise along the elongate jacket flange 110, for the whole or substantially the whole length of the jacket flange 110. It can be seen in figure 12 that the weld slot 117 has a rectangular cross section, with two parallel side surfaces 117a and 117b extending perpendicular to a flat end surface 117c, which faces the opening of the weld slot 117. Unlike in figure 4 the slot 117 extends not perpendicularly to the surface 114, but at an acute angle to the surface, being inclined away from the surface 114 toward the end surface 111. The slot opening typically has a 5mm minimum width. The weld slot 117 is provided to facilitate the welding of the jacket flange 110 to a flexible HDPE sheet 118 which forms a jacket part of the anti-corrosion apparatus. This jacket part will be similar to the jacket part 15 or 14 shown in figure 1.

In figure 12 there can be seen weld material 119 used to fix the jacket flange 110 to the HDPE sheet 118. The weld material 119 extends into and fills the weld slot 117 and extends between the jacket flange 110 and the HDPE sheet 118 to join one to the other. As mentioned above, HDPE is a thermoplastic well suited to welding. However, an acceptable alternative would be to use an adhesive to affix the jacket flange 110 to the sheet 118, with the slot 117 in this case not being a weld slot, but nevertheless providing an increased surface area for adhering the flange 110 to the sheet 118.

When comparing the weld of figure 12 with the weld of figure 2, it can be seen that the weld slot 117 provides an increased surface area for engagement by the weld material 99. The slot 117, since it is inclined relative to the face 114, provides a strong physical interlock for the weld material 119 when solidified. Furthermore, due to the improved engagement, the HDPE sheet 118 may only contact a surface of a single face of the flange 110, and there is no need to wrap the HDPE sheet 118 around the jacket flange 110, unlike in figure 2, so there is avoided the stress placed on the HDPE in the corner region 29 of figure 2. Additionally, the HDPE sheet 118 can provide an overlap region 120 which can lie under the HDPE sheet of a mating jacket part engaged with the jacket flange 110.

The weld slot 117 is a feature easily inspected for quality assurance purposes. For instance a light can be shone along to the weld slot 117 to make sure there are no -19 -obstructions to block the passage of the light. After welding (described later) a light can be shone along to the weld slot to see if the weld slot has been completely filled at at least one point along its length.

In use the jacket flange 110 of a first jacket part will be brought into engagement with an identical jacket flange 110 of a second jacket part, with abutment faces 113 of the jacket flanges 110 engaging and abutting each other. The jacket flanges 110 and thereby the jacket parts are secured together by nuts and bolts, with the bolts passing through the bolt holes 115. The narrow width surfaces 111 of the jacket flanges 90 will be the surfaces facing the cylindrical outer surface of the jetty pile. This is advantageous in comparison with the figure 2 arrangement since it minimises the percentage of the flat surfaces that are not in engagement with the cylindrical surface of the tape wrapping immediately underneath the jacket. Nevertheless it is important that the jacket flange 110 has an overall size sufficient to bear the clamping loads. The use of the weld slot 117 means that there is sufficient surface area for engagement by the weld material despite the reduced width of the surfaces 111.

A sixth embodiment of the invention is shown in figures 13a, 13b, 14a and 14b. It can be seen in figures 13a and 13b that an elongate jacket flange 130 is not provided with bolt holes like the earlier embodiments. Instead the jacket flange 130 is configured so that when a pair of jacket flanges 130 are in mating engagement as seen in figures 14a and 14b then together they define a keyway into which an elongate locking key in the form of a circular (or oval or similar) cross-section rod can be inserted so as to secure the mating jacket flanges 130 to each other. This arrangement can provide a faster installation method, avoiding the need for the installation of multiple bolts.

Turning to figures 13a and 13b, the elongate jacket flange 130, which is formed from HDPE, has a continuous weld slot section 131 of a rectangular form and a first width W3, extending lengthwise along the jacket flange 130, the width W3 taken transverse to the length of the jacket flange. In this continuous lower section 131 there is provided a weld slot 137 of the same configuration as figures 11a, llb and 12, which will be used as described above in relation to the fifth embodiment. The weld slot 137 extends lengthwise along the elongate jacket flange 130, for the whole or substantially the -20 -whole length of the jacket flange 130. The weld slot 137 could be configured in the manner of any of the first to fourth embodiments and used as described above in relation to those embodiments.

The jacket flange 130 is also provided with a plurality of keyway sections 132 spaced apart on the length of the elongate jacket flange 130. They are integral with the lower weld slot section 131. Typically the jacket flange 130 will initially be formed as an extrusion and then the spaced apart keyway sections 132 formed by a machining operation.

Each keyway section 132 is generally U-shaped in a cross-section taken transverse to a longitudinal axis of the jacket flange 130, each keyway section 132 having: a first part 133 which extends from the weld slot section 131 perpendicular to the keyway section 131; a side part 134 which extends perpendicular to the first part 133 and in a plane parallel to and spaced apart from the plane of the face of lower weld slot section 131 in which the weld slot opening is present; and a third part 135 which extends perpendicular to the side part 134 in a plane parallel to and spaced apart from the plane of the first part 133. In other embodiments the keyway sections could be configured with a T-shaped or Triangular cross-section (or other shape) instead of a U-shape.

A channel, which is U-shaped in a cross-section transverse to the length of the jacket flange 130, is defined by the parts 133, 134, 135 with an opening on the same side face of the jacket flange 130 as the opening of the weld slot 137. The face of the U-shaped channel opposite to the opening of the channel is curved with a radius to match the radius of the circular key (or if the key is not circular, but another, e.g. oval, shape, then the face will be shaped differently to match the key shape). The U-shaped channels of the plurality of keyway sections 131 are aligned when the jacket flange 130 is viewed end on.

The keyway sections 131 have a width W4, taken transverse to the length of the jacket flange 130, greater than the width W3. The keyway sections provide castellations along the length of the jacket flange 130, i.e. the jacket flange 130 is castellated by the provision of the plurality of keyway sections 132 spaced along its length. Each pair of -21 -opposed faces of adjacent keyway sections 132 define therebetween a keyway socket for receiving a keyway section of another jacket flange. The opposed faces are flat and generally perpendicular to the longitudinal axis of the jacket flange 130.

The lengths the keyway sections 132 (taken lengthwise along the jacket flange) match the lengths of the keyway sockets (taken lengthwise along the jacket flange) defined between the keyway sections 132. Hence two jacket flanges 130 can be brought together in mating engagement with the keyway sections 132 of one inserted into the keyway sockets defined between the keyway sections 132 of the other (with one jacket flange 130 inverted with respect to the other). This is seen in figures 14a and 14b. The keyway sections 132 of the two jacket flanges 130 in mating engagement as illustrated in figures 14a and 14b define a keyway 140 into which can be inserted an elongate locking key (not shown) in the form of a rod of circular transverse cross-section (transverse to longitudinal axes of the engaged jacket flanges). Since the openings of the U-shaped keyway sections of one jacket flange 130 face in one direction and the openings of the other U-shaped keyway sections of the other jacket flange 130 face in the opposite direction, the inserted locking key engages with the keyway sections of both jacket flanges 130 to prevent them being disengaged from each other and to thereby lock them together. In embodiments in which the keyway sections are not U-shaped, but T-shaped or triangular shaped (or with another shape) then the keyway defined by the keyway sections will have a transverse cross-section other that circular and the locking key will have a matching transverse cross-section.

The jacket flanges 130 will be used with a jacket as illustrated in figure 1 in place of the flanges 16, 17 illustrated in the figure. The method of installation and method of protection of the pile 10 from corrosion will be the same as previously described with e.g. the application to the cylindrical surface 11 first of primer, then optionally mastic, then tape and then the assembly of the jacket. As described above, a hydraulic clamp is used to during installation of the jacket. The clamp has jaws which engage the adjacent jacket flanges 130 and then hydraulic pressure is used to force the jacket flanges 130 into engagement. Then the key is inserted through the keyway 140 provided by the keyway sections 132 of the engaged jacket flanges 130. The hydraulic clamp is removed once the key has been installed. Compared with earlier embodiments, the use of the locking key speeds assembly since there is no need to -22 -install bolts and tighten nuts. The use of bolts and nuts is obviated which has the further advantage of preventing theft of these high value items from the installed assembly. Also the locking key can be made of HOPE (or another plastic) to be less susceptible to corrosion than steel bolts. Likewise, the key can be made from composite materials including plastic sheathed metal. Typically the locking key will be inserted vertically downwards and will have an enlarged head to act as an end stop limiting insertion of the key and keeping the key from sliding further under gravity when installed.

A seventh embodiment of the invention is shown in figures 15a, 15b, 16a and 16b.

There can be seen in figures 15a and 15b an elongate jacket flange 150 that is not provided with bolt holes like in the first to fifth embodiments. Instead the jacket flange 150 is configured so that when a pair of jacket flanges 150 are in mating engagement, as seen in figures 16a and 16b, then together they define a keyway 160 into which an elongate locking key in the form of a square or rectangular cross-section rod can be inserted so as to secure the mating jacket flanges to each other. This arrangement can provided a faster installation method than for the earlier first to fifth embodiments, avoiding the need for the installation of multiple bolts.

Turning to figures 15a and 15b, the elongate jacket flange 150, which is formed from HDPE, has a continuous weld slot section 151 of a rectangular form and a first width W5 taken transverse to the length of the jacket flange. In this continuous lower section 131 there is provided a weld slot 157 of the same configuration as figures 11, 11a, llb and 12, which will be used as described above in relation to the fifth embodiment. The weld slot 157 extends lengthwise along the jacket flange 150 for the whole or substantially the whole length of the jacket flange 150. The weld slot 157 could be configured as in any of the first to fourth embodiments and used as described above in relation to those embodiments.

The jacket flange 150 is also provided with a plurality of keyway sections 152 spaced apart lengthwise along the length of the elongate jacket flange 150. They are integral with the weld slot section 151. Typically the jacket flange 150 will be formed as an extrusion and then the spaced apart keyway sections 152 are formed by a machining operation. Each keyway section 152 is generally U-shaped in cross-section transverse -23 -to the longitudinal axis of the jacket flange 150, each keyway section 152 having: a first part 153 which extends from the weld slot section 151 perpendicular to the weld slot section 151; a side part 154 which extends perpendicular to the part 153 and in a plane parallel to and spaced apart from the plane of the face of lower weld slot section 151 in which the weld slot opening is present; and a third part 155 which extends perpendicular to the side part 154 and parallel to and spaced apart from the lower part 133. In other embodiments the keyway sections could be configured with a T-shaped or Triangular cross-section (or other shape) instead of a U-shape.

A U-shaped channel is defined by the parts 153, 154, 155 with an opening on the same side face of the jacket flange 150 as the opening of the weld slot 157. The face of the U-shaped channel opposite the opening of the weld slot 157 is planar. The U-shaped channels of the keyway sections 152 are aligned when the jacket flange 150 is viewed end on. The keyway sections 152 have a width W6, transverse to the length of the jacket flange 150, which is greater than the width W5. The keyway sections 152 provide castellations spaced along the length of the jacket flange 150, i.e. the jacket flange 150 is castellated by the provision of the plurality of keyway sections 152 along its length.

Each pair of opposed faces of adjacent keyway sections 152 define a keyway socket therebetween for receiving a keyway section of a second jacket flange 150. The opposed faces are flat and inclined relative to the longitudinal axis of the jacket flange 150. The inclination of these faces is arranged so that the width of the keyway socket (taken lengthwise along the length of the jacket flange 150) tapers linearly from a maximum width W7 at a face on a side of the jacket flange 150 opposite to the face with the opening of the weld slot 157, to a minimum width W8 at the face of the jacket flange 150 in which the opening of the weld slot 157 is also provided (see Figure 15b).

The lengths the keyway sections 151 match the lengths of the keyway sockets defined between the keyway sections 151. Hence two jacket flanges 150 can be brought together in mating engagement with the keyway sections 151 of one inserted into the keyway sockets defined between the keyway sections 151 of the other (with one jacket flange 150 inverted with respect to the other). This is shown in figures 16a and 16b. During the insertion of the keyway sections of one jacket flange 150 into the keyway -24 -sockets of the other jacket flange 150, the inclined faces of the keyway sections 150 slidingly engage with each other with the interaction of the inclined surfaces serving to allow the two jacket flanges 150 to be brought into final mating engagement without the need for initial exact lengthwise alignment. The assembly is thereby self-aligning. The keyway sections 152 of the two jacket flanges 150 when in mating engagement as illustrated in figures 16a and 16b define a keyway 160 into which can be inserted a locking key (not shown) in the form of an elongate rod of square or rectangular transverse (transverse to its length) cross-section (another cross-section could be chosen; circular has already been mentioned above, but hexagonal would be possible, or octagonal, etc.). Since the openings of the U-shaped keyway sections of one jacket flange 150 face in one direction and the openings of the other U-shaped keyway sections of the other jacket flange 150 face in the opposite direction, the inserted locking key engages with the keyway sections of both jacket flanges 150 to prevent them being disengaged from each other and to thereby lock them together. In other embodiments with keyway sections of e.g. a T-shaped or triangular shaped transverse cross-section then the keyway defined by the keyway sections will have a transverse cross-section defined by such T-shaped or triangular shaped cross-sections and the locking key will have a matching transverse cross-section.

The jacket flanges 150 will be used with a jacket as illustrated in figure 1 in place of the flanges 16, 17 illustrated in the figure. The method of installation and method of protection of the pile from corrosion will be the same as previously described with e.g. the steps of application of primer, then optionally mastic, then tape and then the assembly of the jacket. As described above, a hydraulic clamp is used to during installation of the jacket. The clamp has jaws which engage the adjacent jacket flanges 150 and then hydraulic pressure is used to force the jacket flanges 150 into engagement. Then the locking key is inserted through the keyway provided by the keyway sections 152 of engaged jacket flanges 150. The hydraulic clamp is removed once the locking key has been installed. Compared with first to fifth embodiments, the use of the key speeds assembly since there is no need to install bolts and tighten nuts. Also the key can be made of HDPE (or another plastic) to be less susceptible to corrosion than steel bolts. Typically the key will be inserted vertically downwards and -25 -will have an enlarged head to act as an end stop limiting insertion of the key and keeping the key from sliding further under gravity when installed.

Whilst above the invention has been described with reference to its use with jetty piles, the invention can also be used with sheet steel piling as used in quay walls, jetties and other seaboard structures, and as shown as 171 in figure 17. Sheet piling 171 is a corrugated structure made from a number of metal sections which interlock with each other and which are driven into a seabed 172. Corrosion of such piling is a problem, particularly over the zone which is alternately wet and dry, as it is covered and uncovered by the tide.

In an eighth embodiment of the invention there is provided a method of protecting a structure, namely sheet piling, comprising: coating the sheet piling with a primer; optionally smoothing irregularities with a mastic; applying a tape covering over the primer and any mastic that has been applied; and then covering the tape with a jacket comprising a water impermeable sheet provided with jacket flanges as described above; fastening sheet sections together using the jacket flanges; affixing the jacket to the piling via the jacket flanges.

As shown in figure 17, the cladding sheet sections 174 of the jacket are stretched over the sheet piling 171. This piling 171 will have been covered with primer and tape although this is not specifically shown in the figure. Preferably, the sheet sections 174 can have a height greater than the exposed height of the sheet piling 171 and the lower edges of the jacket sheet sections 174 buried along the line 175. Alternatively, the jacket sheet sections 174 could be weighted along their lower edges, i.e. weights attached to hold the lower edges against the seabed.

The embodiment will use jacket flanges (30, 50, 70, 90, 110, 130, 150) as described above in the earlier embodiments, shown as 176 in the figure 17 (any of the previously described jacket flanges will work) and these jacket flanges 176 are placed into the corners of the channels provided in the corrugated sheet piling 171 (in the figure only two pairs of jacket flanges 176 are shown, but a pair will be provided for each channel in the piling 171).

-26 -In this embodiment, the jacket flanges 176 are provided with fastener holes through which bolts 178 are inserted to secure the jacket flanges 176 to the piling 171, with the nuts 179 tightened on to the bolts 178. When the jacket sheet sections 174 are interconnected via the jacket flanges 176 and the jacket flanges affixed to the piling 171, then the jacket flanges 176 apply a tensioning force to the jacket sheet sections 174 between them, drawing the jacket sheet sections 174 into tight engagement with the taped surface underneath.

Profiles may be inserted in the channels of the corrugated sheet piling, after the tape is applied to partially to fill them. These profiles can be used to provide for the jacket sheets 174 an underlying surface more gently contoured than the sheet piling itself. The profiles can be formed of foamed thermoplastic material. The profiles can be used instead of or as well as the mastic described above.

Looking at Figure 18a, there can be seen in the figure an elongate jacket flange 180 according to a ninth embodiment of the invention. The jacket flange 180 is formed as an HOPE extrusion with a cross-section formed generally as a rectangle, providing four faces. There are two parallel planar faces 181 and 182 (see figure 18b). There are two parallel planar faces 183 and 184 which lie in a plane perpendicular to the planes of the faces 181 and 182.

A series of regularly spaced bolt holes 185 are provided in the jacket flange 180 spaced along the length of the jacket flange 180, each bolt hole 186 extending between the faces 183 and 184.

The jacket flange 180 is provided with a weld slot 187 in the face 181. The weld slot 187 can be formed during the extrusion of the jacket flange or machined in the face 181 after initial formation of the face 181 by extrusion. The weld slot 187 extends perpendicular to the face 181, as can be clearly seen in figure 19, and extends lengthwise along the jacket flange 180, along the whole or substantially the whole of the length of the jacket flange 180. It can also be seen in figure 19 that the weld slot 187 has a cross section with a shape of a trapezoid (American English) or trapezium (English), with a flat end surface 187c lying in a plane parallel to and spaced apart from the surface 182. The end surface 187c is wider than the opening of the weld slot 187 -27 -which it faces (these width measurements being taken in a plane perpendicular to the longitudinal axis of the jacket flange 180). Two side surfaces 187a and 187b extend from the edges of the end surface 187c to the opening of the weld slot, with the side surfaces 187a and 187b non-perpendicular and inclined relative to the end surface 187c so that the slot 187 narrows in width from the top 187c towards the opening. The opening typically has a 5mm minimum width. The weld slot 187 is provided to facilitate the welding of the jacket flange 180 to a flexible HDPE sheet 188 which forms a jacket part of the anti-corrosion apparatus. This jacket part will be similar to the jacket part 15 or 14 shown in figure 1.

In figure 19 there can be seen weld material 189 used to fix the jacket flange 180 to the HDPE sheet 188. The weld material 189 extends into and fills the weld slot 187 and extends between the jacket flange 180 and the HDPE sheet 188 to join one to the other. HOPE is a thermoplastic well suited to welding. However, an acceptable alternative would be to use an adhesive to affix the jacket flange 180 to the sheet 188, with the slot 187 in this case not being a weld slot, but nevertheless providing an increased surface area for adhering the flange 180 to the sheet 188.

When comparing the weld of figure 19 with the weld of figure 2, it can be seen that the weld slot 187 provides an increased surface area for engagement by the weld material 189. The trapezoid/trapezium shape of the weld slot 187 provides a strong interference fit for the weld material when solidified. Furthermore, due to the improved engagement, the HDPE sheet 188 may only contact a surface of a single face of the flange 180, and there is no need to wrap the HDPE sheet 188 around the jacket flange 180, unlike in figure 2, so there is avoided the stress placed on the HDPE in the corner region 29 of figure 2. In the weld of Figure 19, the weld slot 187 is provided in the same face 181 that has a surface in contact with the HDPE sheet 188. The HDPE sheet 188 contacts the surface of the face 181 adjacent to the weld slot 187, with the weld material extending from the weld slot 187 to engage a surface of the HDPE sheet 188 (by extending from the weld slot onto the surface of the HDPE sheet 188 opposite the surface to which the flange 180 is in contact).

An additional HDPE sheet 191 can be affixed to HDPE sheet 188 by way of weld material 190, to provide an overlap region 192 which can lie under the HDPE sheet of a -28 -mating jacket part engaged with the jacket flange 180. Typically each jacket part of this embodiment of the invention will have one end as shown in figure 19 provided with an overlap region and then a second end which is as shown in figure 19 except that no overlap region is provided and the jacket flange is provided coincident with the face 183. As another alternative, both ends of the jacket part can be as shown in figure 19, but one overlap region 192 is sandwiched between opposing abutment faces 183 of a pair of jacket flanges 180 instead of underlying an adjacent jacket sheet. It is advantageous to provide for an overlap region in order to minimise ingress of water and other material into the region between the jacket and the jetty pile.

The weld slot 187 is a feature easily inspected for quality assurance purposes. For instance a light can be shone along the weld slot 187 to make sure there are no obstructions to block the passage of the light.

In use the jacket flange 180 of a first jacket part will be brought into engagement with an identical jacket flange 180 of a second jacket part, with abutment faces 183 of the jacket flanges 180 engaging and abutting each other. The jacket flanges 180 and thereby the jacket parts are secured together by nuts and bolts, with the bolts passing through the bolt holes 185. The surfaces 181 of the jacket flanges 180 will be the surfaces facing the cylindrical outer surface of the jetty pile. This is advantageous in comparison with the figure 2 arrangement since it minimises the percentage of the flat surfaces that are not in engagement with the cylindrical surface of the tape wrapping immediately underneath the jacket. The use of the weld slot 187 means that there is sufficient surface area for engagement by the weld material despite the reduced width of the surfaces 181.

The jacket part of figure 2 comprising the jacket flange 180 will be used in a system as illustrated in figure 1 with the jacket flanges 16 and 17 of figure 1 each replaced with a jacket flange 180 according to the invention.

The invention provides a method of protecting a structure such as a metal jetty pile from corrosion, in which the external cylindrical surface of the jetty pile 10 is first prepared by removing weld spatter, sharp points and edges as well as removing marine growth, loose rut, loose paint and foreign matter from the cylindrical outer -29 -surface 11 of the jetty pile 10. This will be done by hand or with power tools. For instance, a hydraulic whirl away or high pressure water blasting may be used to prepare the surface.

Next the prepared surface is coated with a primer 12. This will typically comprise saturated petroleum hydrocarbons (petrolatum), inert fillers and passivating agents. The primer 12 is used to displace moisture, passivate the surface and fill surface imperfections on corroded areas. It is important to coat all areas of the cylindrical surface with corrosion pits greater than 2mm diameter. The primer 12 will fill such pits.

The primer 12 is applied by hand. When the primer 12 is applied underwater then the worker applying the primer 12 will use a gloved hand to displace water and slowly rub the primer 12 on to the cylindrical surface and fill the pits.

The next (optional) step is to use a mastic (not shown) to smooth surface irregularities.

For instance in the protection of complex surfaces with configurations such as brackets and flanges, the mastic is used to fill and pack to achieve a smooth contour to which tape can be applied without bridging or voids. The mastic is also used to fill in cavities at the interface between the jetty pile 10 and a pile cap (not shown). The mastic will typically comprise saturated petroleum hydrocarbons (petrolatum), inert fillers, reinforcing fibres and thermal extenders and may contain beads of cellular polymer and/or flow control additives. The mastic is cold applied by hand around irregular shaped fittings to provide a suitable profile for the subsequent use of a tape wrapping 13.

Next the primed surface (with mastic applied, if appropriate) is spirally wrapped with tape 13, with a 55% overlap, which will provide a double thickness of tape along the length of the pile. The tape 13 is applied starting at a vertically highest point and then wound downwards. The end of the tape 13 is firmly pressed against the starting point and then the tape 13 unrolled while keeping the tape 13 close to the primed surface, applying sufficient tension to provide continuous adhesion without stretching of the tape. During application of the tape 13 all folds and air pockets should be pressed out. Typically the tape 13 is applied by hand, but a tape application machine can be used. The tape 13 is formed from a non-woven synthetic fibre carrier fully impregnated and coated with a neutral saturated petroleum hydrocarbon (petrolatum) based composition -30 -having inert siliceous fillers, water displacing agents and corrosion inhibitors. The tape 13 has an HDPE film backing. The tape 13 is stable in composition and plasticity over a wide temperature range and is non-hardening and non-cracking. The tape 13 can accommodate vibration and movement of the jetty pile. The tape 13 is resistant to mineral acids and alkalis.

The HDPE sheets used to make the jacket 15 are substantially seamless and substantially uniform and substantially free from cracks, creases, bubbles and other defects. The jacket 15 prevents damage to the underlying tape 13. The jacket 15 will be custom engineered to provide the correct fit for the diameter of the jetty pile 10. The jacket flanges 30 of the jacket 15 (used in place of the jacket flanges 16 and 17 illustrated in figure 2) are secured together by the use of M12 x 90 mm hexagon bolts of 316 stainless steel and M12 hexagon nuts, also of stainless steel. Two flat washers and one split washer will be used for each nut and bolt, the flat washers being M12 x 24mm x 2.5mm washers of 316 stainless steel and the split washers being M12 washers of 316 stainless steel.

Figures 18 to 26 show variants of what has already been described above. For brevity for each of the figures 18 to 26 embodiments not all of the above description will be repeated, but it should be understood that the above description applies equally to each of the ninth to thirteenth embodiments. Each of the ninth to thirteenth illustrated embodiments is a different variant of jacket flange. Each of the different variants of jacket flange (180, 193, 206, 219) will be used in a jacket arrangement as shown in -31 -figure 1 in place of the jacket flanges 16, 17 shown in that figure; otherwise all other aspects of the jacket arrangement will remain as illustrated in figure 1 and described above. The steps of the method of installation will remain as described above. The reference numerals selected show correspondence. They are based on the figure numbers. For instance the reference numeral 180 is used for the jacket flange of figure 18 and 185 for the bolt holes, while reference numeral 206 is used for the jacket flange of figure 22 and 211 for the bolt holes, reference numeral 219 is used for the jacket flange of figure 24 and 224 for the bolt holes, and so on.

Looking at Figure 20a, there can be seen in the figure an elongate jacket flange 193 according to a tenth embodiment of the invention. The jacket flange 193 is formed as an HDPE extrusion with a cross-section formed generally as a rectangle, providing four faces. There are two parallel planar faces 194 and 195 (see figure 20b). There are two parallel planar faces 196 and 197 which lie in a plane perpendicular to the planes of the faces 194 and 195.

A series of regularly spaced bolt holes 198 are provided in the jacket flange 193 spaced along the length of the jacket flange 193, each bolt hole 199 extending between the faces 196 and 197.

The jacket flange 193 is provided with a weld slot 200 in the face 194. The weld slot 200 can be formed during the extrusion of the jacket flange or machined in the face 194 after initial formation of the face 194 by extrusion. The weld slot 200 extends perpendicular to the face 194, as can be clearly seen in figure 21, and extends lengthwise along the jacket flange 193, along the whole or substantially the whole of the length of the jacket flange 193. It can also be seen in figure 21 that the weld slot 200 has a rectangular cross section, with two parallel side surfaces 200a and 200b extending perpendicular to a flat end surface 200c, which faces the opening of the weld slot 200. The opening typically has a 5mm minimum width. The weld slot 200 is provided to facilitate the welding of the jacket flange 193 to a flexible HDPE jacket sheet 201 which forms a jacket section of the anti-corrosion apparatus. This jacket part will be similar to the jacket part 15 or 14 shown in figure 1.

-32 -In figure 21 there can be seen weld material 202 used to fix the jacket flange 193 to the HDPE sheet 201. The weld material 201 extends into and fills the weld slot 200 and extends between the jacket flange 193 and the HDPE sheet 201 to join one to the other. HDPE is a thermoplastic well suited to welding. However, an acceptable alternative would be to use an adhesive to affix the jacket flange 193 to the sheet 201, with the slot 200 in this case not being a weld slot, but nevertheless providing an increased surface area for adhering the flange 193 to the sheet 201.

When comparing the weld of figure 21 with the weld of figure 2, it can be seen that the weld slot 200 provides an increased surface area for engagement by the weld material 202 and also an undercut to provide an interference fit for the weld material 202 when solidified. Furthermore, due to the improved engagement, the HDPE sheet 201 may only contact a surface of a single face of the flange 193, and there is no need to wrap the HDPE sheet around the jacket flange 193, unlike in figure 2, so there is avoided the stress placed on the HDPE in the corner region 29 of figure 2. In the weld of Figure 21, the weld slot 200 is provided in the same face 194 that has a surface in contact with the HDPE sheet 201. The HDPE sheet 201 contacts the surface of the face 194 adjacent to the weld slot, with the weld material extending from the weld slot 200 to engage a surface of the HDPE sheet 201 (by extending from the weld slot 200 onto the surface of the HDPE sheet 201 opposite the surface to which the flange 193 is in contact).

An additional HDPE sheet 204 can be affixed to HDPE sheet 201 by way of weld material 203, to provide an overlap region 205 which can lie under the HDPE sheet of a mating jacket part engaged with the jacket flange 193. Typically each jacket part of this embodiment of the invention will have one end as shown in figure 21 provided with an overlap region and then a second end which is as shown in figure 21 except that no overlap region is provided and the jacket flange is provided coincident with the face 196. As another alternative, both ends of the jacket part can be as shown in figure 21, but one overlap region 205 is sandwiched between opposing abutment faces 196 of a pair of jacket flanges 193 instead of underlying an adjacent jacket sheet. It is advantageous to provide for an overlap region in order to minimise ingress of water and other material into the region between the jacket and the jetty pile.

-33 -The weld slot 200 is a feature easily inspected for quality assurance purposes. For instance a light can be shone along to the weld slot 200 to make sure there are no obstructions to block the passage of the light.

In use the jacket flange 193 of a first jacket part will be brought into engagement with an identical jacket flange 193 of a second jacket part, with abutment faces 196 of the jacket flanges 193 engaging and abutting each other. The jacket flanges 193 and thereby the jacket parts are secured together by nuts and bolts, with the bolts passing through the bolt holes 198. The narrow width surfaces 194 of the jacket flanges 193 will be the surfaces facing the cylindrical outer surface of the jetty pile. This is advantageous in comparison with the figure 2 arrangement since it minimises the percentage of the flat surfaces that are not in engagement with the cylindrical surface of the tape wrapping immediately underneath the jacket. Nevertheless it is important that the jacket flange has an overall size sufficient to bear the clamping loads. The use of the weld slot 200 means that there is sufficient surface area for engagement by the weld material despite the reduced width of the surfaces 194.

Turning now to Figure 22a, there can be seen in the figure an elongate jacket flange 206 according to a eleventh embodiment of the invention. The jacket flange 206 is formed as an HDPE extrusion with a cross-section formed generally as a rectangle, providing four faces. There are two parallel planar faces 207 and 208 (see figure 22b). There are two parallel planar faces 209 and 210 which lie in a plane perpendicular to the planes of the faces 207 and 208.

A series of regularly spaced bolt holes 211 are provided in the jacket flange 206 spaced along the length of the jacket flange 206, each bolt hole 211 extending between the faces 209 and 210.

The jacket flange 206 is provided with a weld slot 213 in the face 207. The weld slot 213 can be formed during the extrusion of the jacket flange or machined in the face 207 after initial formation of the face 207 by extrusion. The weld slot 213 extends perpendicular to the face 207, as can be clearly seen in figure 23, and extends lengthwise along the jacket flange 206, along the whole or substantially the whole of the length of the jacket flange 206. The shape of the weld slot 213 makes it very -34 -suitable for machining. It can be seen in figure 23 that the weld slot 213 has a cross section with a circular section 213a (which can be formed by a milling or drilling operation) and a straight-sided neck section 213b (which can be formed by a milling operation) extending from the circular section 213a to the slot opening. The circular section 213a has a diameter greater that the width of the neck section 213b, whose width is the same as that of the opening of the weld slot 213. The opening typically has a 5mm minimum width. The weld slot 213 is provided to facilitate the welding of the jacket flange 206 to a flexible HDPE sheet 214 which forms a jacket part of the anticorrosion apparatus. This jacket part will be similar to the jacket part 15 or 14 shown in figure 1.

In figure 23 there can be seen weld material 215 used to fix the jacket flange 206 to the HDPE sheet 214. The weld material 215 extends into and fills the weld slot 213 and extends between the jacket flange 206 and the HDPE sheet 214 to join one to the other. As mentioned above, HDPE is a thermoplastic well suited to welding. However, an acceptable alternative would be to use an adhesive to affix the jacket flange 206 to the sheet 214, with the slot 213 in this case not being a weld slot, but nevertheless providing an increased surface area for adhering the flange 206 to the sheet 214.

When comparing the weld of figure 23 with the weld of figure 2, it can be seen that the weld slot 213 provides an increased surface area for engagement by the weld material 215. The circular section 213a of the slot 213, since it has a diameter greater than the width of the neck portion 213b, provides a strong interference fit for the weld material 215 when solidified. Furthermore, due to the improved engagement, the HDPE sheet 214 may only contact a surface of a single face of the flange 206, and there is no need to wrap the HDPE sheet 214 around the jacket flange 206, unlike in figure 2, so there is avoided the stress placed on the HDPE in the corner region 29 of figure 2. In the weld of Figure 23, the weld slot 213 is provided in the same face 207 that has a surface in contact with the HDPE sheet 214. The HDPE sheet 214 contacts the surface of the face 207 adjacent to the weld slot 213, with the weld material extending from the weld slot 213 to engage a surface of the HOPE sheet 214 (by extending from the weld slot 213 onto the surface of the HDPE sheet 214 opposite the surface to which the flange 206 is in contact).

-35 -An additional HDPE sheet 217 can be affixed to HOPE sheet 214 by way of weld material 216, to provide an overlap region 218 which can lie under the HOPE sheet of a mating jacket part engaged with the jacket flange 213.

The weld slot 213 is a feature easily inspected for quality assurance purposes. For instance a light can be shone along to the weld slot 213 to make sure there are no obstructions to block the passage of the light.

In use, the jacket flange 206 of a first jacket part will be brought into engagement with an identical jacket flange 206 of a second jacket part, with abutment faces 209 of the jacket flanges 206 engaging and abutting each other. The jacket flanges 206 and thereby the jacket parts are secured together by nuts and bolts, with the bolts passing through the bolt holes 211. The narrow width surfaces 207 of the jacket flanges 206 will be the surfaces facing the cylindrical outer surface of the jetty pile. This is advantageous in comparison with the figure 2 arrangement since it minimises the percentage of the flat surfaces that are not in engagement with the cylindrical surface of the tape wrapping immediately underneath the jacket. Nevertheless it is important that the jacket flange 206 has an overall size sufficient to bear the clamping loads. The use of the weld slot 213 means that there is sufficient surface area for engagement by the weld material despite the reduced width of the surfaces 207.

Turning now to Figure 24a, there can be seen in the figure an elongate jacket flange 219 according to a twelfth embodiment of the invention. The jacket flange 219 is formed as an HOPE extrusion with a cross-section formed generally as a rectangle, providing four faces. There are two parallel planar faces 220 and 221 (see figure 24b).

There are two parallel planar faces 222 and 223 which lie in a plane perpendicular to the planes of the faces 220 and 221.

A series of regularly spaced bolt holes 224 are provided in the jacket flange 219 spaced along the length of the jacket flange 219, each bolt hole 224 extending between the faces 222 and 223.

The jacket flange 219 is provided with a weld slot 226 in the face 220. The weld slot 226 can be formed during the extrusion of the jacket flange or machined in the face 220 -36 -after initial formation of the face 220 by extrusion. The weld slot 226 extends lengthwise along the elongate jacket flange 219, for the whole or substantially the whole of the length of the elongate jacket flange 219. It can be seen in figure 25 that the weld slot 226 has a T-shaped cross section with a head section 226a and a tail section 226b extending from the head section 226a to the slot opening. The head section 226a has a width greater that the width of the slot opening, the width of the slot opening being equal in width to the width of the tail section 226b (the widths measured in a plane perpendicular to the longitudinal axis of the jacket flange 90). The opening typically has a 5mm minimum width. The weld slot 226 is provided to facilitate the welding of the jacket flange 219 to a flexible HDPE sheet 227 which forms a jacket part of the anti-corrosion apparatus. This jacket part will be similar to the jacket part 15 or 14 shown in figure 1.

In figure 25 there can be seen weld material 228 used to fix the jacket flange 219 to the HDPE sheet 227. The weld material 228 extends into and fills the weld slot 226 and extends between the jacket flange 219 and the HDPE sheet 227 to join one to the other. As mentioned above, HDPE is a thermoplastic well suited to welding. However, an acceptable alternative would be to use an adhesive to affix the jacket flange 219 to the sheet 227, with the slot 226 in this case not being a weld slot, but nevertheless providing an increased surface area for adhering the flange 219 to the sheet 227.

When comparing the weld of figure 25 with the weld of figure 2, it can be seen that the weld slot 226 provides an increased surface area for engagement by the weld material 228. The head section 226a of the slot 226, since it has a width greater than the width of the tail portion 226b, provides a strong interference fit for the weld material 228 when solidified. Furthermore, due to the improved engagement, the HDPE sheet 227 may only contact a surface of a single face of the flange 219, and there is no need to wrap the HDPE sheet 227 around the jacket flange 219, unlike in figure 2, so there is avoided the stress placed on the HDPE in the corner region 29 of figure 2. In the weld of Figure 25, the weld slot 226 is provided in the same face 220 that has a surface in contact with the HDPE sheet 227. The HDPE sheet 227 contacts the surface of the face 220 adjacent to the weld slot 226, with the weld material extending from the weld slot 226 to engage a surface of the HOPE sheet 227 (by extending from the weld slot -37 - 226 onto the surface of the HDPE sheet 227 opposite the surface to which the flange 219 is in contact).

An additional HDPE sheet 230 can be affixed to HDPE sheet 227 by way of weld material 229, to provide an overlap region 231 which can lie under the HOPE sheet of a mating jacket part engaged with the jacket flange 219.

The weld slot 226 is a feature easily inspected for quality assurance purposes. For instance a light can be shone along to the weld slot 226 to make sure there are no obstructions to block the passage of the light.

In use the jacket flange 219 of a first jacket part will be brought into engagement with an identical jacket flange 219 of a second jacket part, with abutment faces 222 of the jacket flanges 219 engaging and abutting each other. The jacket flanges 219 and thereby the jacket parts are secured together by nuts and bolts, with the bolts passing through the bolt holes 224. The narrow width surfaces 220 of the jacket flanges 219 will be the surfaces facing the cylindrical outer surface of the jetty pile. This is advantageous in comparison with the figure 2 arrangement since it minimises the percentage of the flat surfaces that are not in engagement with the cylindrical surface of the tape wrapping immediately underneath the jacket. Nevertheless it is important that the jacket flange 219 has an overall size sufficient to bear the clamping loads. The use of the weld slot 226 means that there is sufficient surface area for engagement by the weld material despite the reduced width of the surfaces 220.

Turning now to Figure 26, the jacket flange 180 from figure 18 can be clearly seen.

The jacket flange 180 is provided with a weld slot 187 in the face 181. The weld slot 187 can be formed during the extrusion of the jacket flange or machined in the face 181 after initial formation of the face 181 by extrusion. The weld slot 187 extends perpendicular to the face 181, as can be clearly seen in figure 19, and extends lengthwise along the jacket flange 180, along the whole or substantially the whole of the length of the jacket flange 180. It can also be seen in figure 26 that the weld slot 187 has a cross section with a shape of a trapezoid (American English) or trapezium (English), with a flat end surface 187c lying in a plane parallel to and spaced apart from the surface 182. The end surface 187c is wider than the opening of the weld slot 187 -38 -which it faces (these width measurements being taken in a plane perpendicular to the longitudinal axis of the jacket flange 180). Two side surfaces 187a and 187b extend from the edges of the end surface 187c to the opening of the weld slot, with the side surfaces 187a and 187b non-perpendicular and inclined relative to the end surface 187c so that the slot 187 narrows in width from the top 187c towards the opening. The opening typically has a 5mm minimum width. The weld slot 187 is provided to facilitate the welding of the jacket flange 180 to a flexible HDPE sheet 188 which forms a jacket part of the anti-corrosion apparatus. This jacket part will be similar to the jacket part 15 or 14 shown in figure 1.

In Figure 26, the HDPE sheet 188 is provided with apertures, which may be in the form of slot, slots or holes, to enable weld material to pass through the HDPE sheet 188 and fill the weld slot 187. These apertures are provided along the HDPE sheet 188 in direction parallel to the longitudinal axis of the jacket flange.

In figure 26 there can be seen weld material 189 used to fix the jacket flange 180 to the HDPE sheet 188. The weld material 189 extends into and fills the weld slot 187 and extends from the jacket flange 180 to engage a surface of the HDPE sheet 188 to join the jacket flange to the HDPE sheet 188. The weld material 189 extends through the apertures in the HDPE sheet and then onto the surface of the HDPE sheet opposite the surface to which the flange 180 is in contact. HDPE is a thermoplastic well suited to welding. However, an acceptable alternative would be to use an adhesive to affix the jacket flange 180 to the sheet 188, with the slot 187 in this case not being a weld slot, but nevertheless providing an increased surface area for adhering the flange 180 to the sheet 188.

When comparing the weld of figure 26 with the weld of figure 2, it can be seen that the weld slot 187 provides an increased surface area for engagement by the weld material 189. The trapezoid/trapezium shape of the weld slot 187 provides a strong interference fit for the weld material when solidified. Furthermore, due to the improved engagement, the HDPE sheet 188 may only contact a surface of a single face of the flange 180, and there is no need to wrap the HDPE sheet 188 around the jacket flange 180, unlike in figure 2, so there is avoided the stress placed on the HDPE in the corner region 29 of figure 2. Additionally, the HDPE sheet 188 can provide an overlap region 192 which -39 -can lie under the HDPE sheet of a mating jacket part engaged with the jacket flange 180.

Figure 26 illustrates the attachment of an HDPE sheet 188 to a flange 180 of Figure 18.

However, it will be understood that flanges 193, 206 and 219 as illustrated in Figures and 22 and 24 respectively may instead be used and attached to the HDPE sheet 188 in the manner described above in connection with the flange 180 of Figure 18. In particular, in such alternative embodiments, the HDPE sheet 188 is again provided with apertures in alignment with the weld slot of the associated flange and weld material extends from to engage a surface of the jacket sheet, by extending through the apertures in the HDPE sheet.

Claims

-40 -CLAIMS: 1. Apparatus for protecting a structure from corrosion comprising a jacket for cladding the structure, the jacket comprising: a jacket sheet; and one or more jacket flange(s) for the jacket sheet; wherein each jacket flange is elongate and has a slot running lengthwise along the jacket flange; and each jacket flange is joined to the jacket sheet by weld material or an adhesive with the weld material or adhesive filling or substantially filling the slot in the jacket flange and extending from the slot to engage a surface of the jacket sheet.
2 Apparatus as claimed in claim 1 wherein the jacket comprises: a plurality of jacket sheets; one or more jacket flange(s) for each jacket sheet; wherein each jacket flange is elongate and has a slot running lengthwise along the jacket flange; and each jacket flange is joined to a respective jacket sheet by weld material or an adhesive with the weld material or adhesive filling or substantially filling the slot in the jacket flange and extending from the slot to engage a surface of the respective jacket sheet.
3. Apparatus as claimed in claim 1, wherein the jacket sheet has a first surface and a second surface opposing the first surface, wherein each jacket flange is in contact with the first surface of the jacket sheet and wherein the weld material extends from the slot to engage the second surface of the jacket sheet.
4. Apparatus as claimed in claim 1 or claim 2 wherein each slot is rectangular in a cross-section taken perpendicular to a longitudinal axis of the jacket flange.
-41 - 5. Apparatus as claimed in claim 4 wherein each slot has an opening and has a pair of opposed walls extending from the opening perpendicular to a face of the jacket flange in which the opening is present.
6. Apparatus as claimed in claim 4 wherein each slot has an opening and has a pair of opposed walls extending from the opening at an acute angle to and non-perpendicular to a face of the jacket flange in which the opening is present.
7 Apparatus as claimed in claim 1 or claim 2 wherein each slot has a cross-section taken perpendicular to a longitudinal axis of the jacket flange which is shaped as a trapezium or trapezoid, with an end face of the slot facing an opening of the slot having a width greater that a width of the slot.
8. Apparatus as claimed in claim 1 or claim 2 wherein each slot has a cross-section taken perpendicular to a longitudinal axis of the jacket flange which comprises a circular portion having a diameter and a straight-sided neck portion extending from the circular portion to an opening of the slot in a face of the jacket flange, the straight-sided neck portion having a pair of opposed walls spaced by a width less than the diameter of the circular portion.
9. Apparatus as claimed in claim 1 or claim 2 wherein each slot is has a cross-section taken perpendicular to a longitudinal axis of the jacket flange which is T-shaped, with the a head portion of the T-shaped cross-section joined to an opening of the slot in a face of the jacket flange by a tail portion of the T-shaped cross-section.
10. Apparatus as claimed in any one of the preceding claims wherein each jacket flange is provided with a plurality of bolt holes to allow each jacket flange to be connected to another jacket flange by a plurality of bolts.
11. Apparatus as claimed in claim 10 wherein: each jacket flange has a perimeter which when viewed in a cross-section transverse to a longitudinal axis of the jacket flange has a shape of a -42 -truncated right-angled triangle, having a first abutment face and a second face perpendicular to each other and an inclined face lying in a plane at an acute angle to planes of the first and second faces; the bolt holes extend from the inclined surface to the abutment surface; and the abutment face of each jacket flange is the surface which engages and abuts an adjacent jacket flange when two jacket flanges are bolted together.
12. Apparatus as claimed in claim 11 wherein the right-angled triangle shape of perimeter is truncated by an apex of the triangle, other than the apex with the right-angle, being cut-off to provide for each jacket flange a planar engagement surface for engaging a surface of the structure underneath the jacket either directly or with a respective jacket sheet interposed.
13. Apparatus as claimed in any one of claims 1 to 9 comprising additionally an elongate locking key wherein: each jacket flange is provided with a plurality of lengthwise spaced apart keyway sections; each jacket flange is provided with a plurality of lengthwise spaced apart keyway sockets, each keyway socket defined in part by opposed faces of adjacent keyway sections and each keyway socket configured to receive a keyway section of another jacket flange; and each keyway section has an aperture extending therethrough in a direction lengthwise of the jacket flange and the apertures of all the keyway sections are aligned; whereby a pair of jacket flanges can be brought together into mating engagement, with the keyway sections of one jacket flange fitting into the keyway sockets of the other jacket flange and the apertures of the keyway sections of both jacket flanges aligning to form a keyway into which the elongate locking key can be inserted to lock both jacket flanges together.
14. Apparatus as claimed in claim 13 wherein the aperture in each keyway socket is provided by a generally U-shaped channel formed in the keyway socket.
-43 - 15. Apparatus as claimed in claim 13 or claim 14 wherein the opposed faces of the adjacent keyway sections are inclined relative to the longitudinal axis of the jacket flange whereby each keyway socket has a tapering width, the width taken lengthwise along the jacket flange.
16. Apparatus as claimed in any one of the preceding claims wherein each a jacket sheet is a flexible sheet of impermeable material and each jacket flange is rigid, substantially rigid or semi-rigid.
17. A method of protecting a structure from corrosion comprising in which the structure is clad by the jacket of the apparatus of any one of the preceding claims.
18. A method as claimed in claim 17 wherein the structure is a jetty pile and the method comprises: wrapping the jetty pile with one or a plurality of the jacket sheets; and securing the locking flanges in engagement together in pairs using bolts or one or more locking keys; wherein a clamp is used to force the jacket flanges of at least one pair of jacket flanges into engagement with other and to thereby apply a tension on the jacket sheet(s) acting to draw the jacket sheet(s) into engagement with an underlying surface; the clamp is used to hold the pair of jacket flanges together while the pair jacket flanges are secured in engagement with each other using bolts or a locking key.
19. A method as claimed in claim 18 in which: an external surface of the jetty pile is coated with a primer before the jetty pile is wrapped with the jacket.
20. A method as claimed in claim 19 in which the primed surface of the jetty pile is wrapped with an anti-corrosion tape before the jetty pile is wrapped with the jacket, whereby the tape underlies the jacket.
-44 - 21. A method as claimed in claim 20 in which mastic is applied to the external surface of the jetty pile before or after the surface is coated with primer and before the jetty pile is wrapped with the anti-corrosion tape, with the mastic used to smooth out surface irregularities prior to the wrapping of the jetty pile with anti-corrosion tape.
22. A method as claimed in claim 17 wherein the structure is sheet piling and the method comprises: cladding the sheet piling with a plurality of the jacket sheets; and securing the locking flanges attached to adjacent jacket sheets in engagement together in pairs of locking flanges using bolts or one or more locking keys; and securing the interengaged locking flanges to the sheet piling; wherein: a clamp is used to force the jacket flanges of at least one pair of jacket flanges into engagement with other and to thereby apply a tension on the jacket sheets acting to draw the jacket sheets into engagement with an underlying surface; the clamp is used to hold the pair of jacket flanges together while the pair jacket flanges are secured in engagement with each other using bolts or a locking key.
23. A method as claimed in claim 22 in which: an external surface of the sheet piling is coated with a primer before the sheet piling is clad with the jacket.
24. A method as claimed in claim 23 in which an anti-corrosion tape is applied to the coated surface before the sheet piling is clad with the jacket, whereby the tape underlies the jacket.
25. A method as claimed in claim 24 in which mastic is applied to the external surface of the sheet piling before or after the surface is coated with primer and before the anti-corrosion tape is applied, with the mastic used to smooth out surface irregularities prior to the applying the anti-corrosion tape to the sheet piling.
-45 - 26. A method of manufacture of the apparatus of any one of claims 1 to 16 wherein the jacket flange(s) is/are formed by extrusion and then machining.
27. A method as claimed in claim 26 wherein the slot(s) is/are formed in the jacket flange(s) by the extrusion process.
28. A method as claimed in claim 26 wherein the slot(s) is/are machined in the jacket flange(s). 10
29. Apparatus for protecting a structure from corrosion comprising a jacket for cladding the structure, the jacket comprising: a jacket sheet; and a pair of jacket flanges for the jacket sheet; wherein each jacket flange is elongate; each jacket flange is joined to the jacket sheet by welding or adhesively or by mechanical fasteners; each jacket flange is provided with a plurality of lengthwise spaced apart keyway sections; each jacket flange is provided with a plurality of lengthwise spaced apart keyway sockets, each keyway socket defined in part by opposed faces of adjacent keyway sections and each keyway socket configured to receive a keyway section of another jacket flange; and each keyway section has an aperture extending therethrough in a direction lengthwise of the jacket flange and the apertures of all the keyway sections are aligned; whereby a pair of jacket flanges can be brought together into mating engagement, with the keyway sections of one jacket flange fitting into the keyway sockets of the other jacket flange and the apertures of the keyway sections of both jacket flanges aligning to form a keyway into which the elongate locking key can be inserted to lock both jacket flanges together.
30. Apparatus as claimed in claim 29 wherein the jacket comprises: a plurality of jacket sheets; -46 -a pair of jacket flanges for each jacket sheet; wherein each jacket flange is elongate; and each jacket flange is joined to a respective jacket sheet by weld material or an adhesive.
31. Apparatus as claimed in claim 29 or claim 30 wherein the aperture in each keyway socket is provided by a generally U-shaped channel formed in the keyway socket.
32. Apparatus as claimed in any one of claims 29 to 31 wherein the opposed faces of the adjacent keyway sections are inclined relative to the longitudinal axis of the jacket flange whereby each keyway socket has a tapering width, the width taken lengthwise along the jacket flange.
33. Apparatus as claimed in any one claims 29 to 32 wherein each jacket sheet is a flexible sheet of impermeable material and each jacket flange is rigid, substantially rigid or semi-rigid.
34. A method of protecting a structure from corrosion in which the structure is clad by the jacket of the apparatus of any one of claims 29 to 33. 20
35. A method as claimed in claim 34 wherein the structure is a jetty pile.
36. A method as claimed in claim 34 wherein the structure is sheet piling.