AU2014201808A1 - Pipe and pipe joining method - Google Patents

Abstract

A pipe having an internal coating (124) of anti-corrosive protective material and an outer coating (122) of anti-corrosive protective material, and a method for 5 providing protection against corrosion of a pipe joint (100) formed by the mating of complementary ends (106, 112) of two pipe portions (102, 104). A portion of the complementary ends (106, 112) include the internal coating (124) thereabout.

Description

Regulation 3.2 AUSTRALIA Patents Act 1990 Complete Specification Standard Patent Divisional APPLICANT: Orrcon Operations Pty Ltd Invention Title: PIPE AND PIPE JOINING METHOD The following statement is a full description of this invention, including the best method of performing it known to me: PIPE AND PIPE JOINING METHOD Field of the Invention 5 This invention relates to a pipe and a pipe joining method. Background of the Invention This invention has particular application to a method of joining steel pipes for 10 potable water reticulation, and for illustrative purposes the method will be described hereinafter with reference to this application. However, it is envisaged that this invention will find use in other pipe joining applications such as methods of pipe joining in recycled water, salt/bore waters, sewerage, slurry and mineral processes. 15 Steel pipe is the lowest-cost means of providing pipeline for pressurized-fluid handling. The disadvantage that steel has over polymer and concrete systems in some applications is its corrosion characteristics. All steel pipe for use in the conveyance of water or aqueous fluid flows must be protected from corrosion. 20 Previous corrosion protection methods for the outer surface of underground pipelines have included hot dipped galvanizing, bituminous enamels, various paints and cold galvanizing, single layer polyethylenes and over ditch tape wraps. Most of these methods of corrosion protection have been used in conjunction with cathodic protection systems. 25 Similarly, corrosion protection methods for the internal surface of underground pipelines have included hot dipped galvanizing, various paints, epoxies and urethane enamels, as well as cement linings for the preservation of the pipeline. 30 All of the above external corrosion protection systems are susceptible to "point corrosion" where accelerated local corrosion occurs to the steel substrate at any point where the external coating is damaged, either through abrasion or impact 1 during transportation, storage or laying of the pipes. It is generally accepted that the majority of pipeline failures occur at the pipe joints or junctions within pipe fittings where imperfect corrosion protection systems or application allows electrolytic or moisture driven corrosion to bring about failure. Cement linings in 5 addition have recognized water quality issues. It is therefore desirable that any corrosive protection system provides pipe joints with effective, long term corrosion resistance and an ability to inhibit moisture retention which will cause corrosive processes to occur. The absence of moisture 10 under the corrosion protection system will, by its nature, inhibit the establishment of any electrolytic reactions and corrosion processes. By far the most common form of pipeline joint has been that of the mating of a socket ended pipe (female end) and a spigot ended pipe (male end). To create 15 the desired seal, the socket end has generally contained an internal groove of one form or another which retains a rubber ring gasket which effects the seal. As such, to create a corrosive resistant system, it is paramount that the male and female components of the joint are fully coated and protected inside and out, ensuring that the ingress of moisture and corrosive materials is halted. To not 20 achieve this requirement will almost certainly lead to failure of such pipe joints. Typical of the system in ductile iron is the TYCO system, reproduced substantially in vinyl in the VINIDEX system, both of which are a reproduction of the joint described in Australian Standard AS1 579. 25 The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia. Summary 30 In one aspect the present invention resides broadly in a pipe joining method 2 including the steps of forming a corrosion-prone pipe element having a spigot end adapted to engage a socket end of a next adjacent corrosion-prone pipe element in a pipeline, providing each of the pipes with at least a single polymer corrosion protection lining on the inner surface thereof and a multilayer coating including at 5 least a corrosion protection layer and an abuse layer on the outer surface thereof, wherein the at least a single polymer corrosion protection lining extends about the pipe end to extend along the outer surface of the pipe at least as far as the spigot is inserted in the socket. 10 The corrosion-prone pipe elements may be of ductile iron, welded steel pipe, spiral welded steel pipe, or drawn steel tube. Of course, the pipe elements need not be of ferrous material, and in this context the expression "corrosion prone" may be taken to include a tendency to erosive and/or corrosive attack by the environment (natural or artificial) on the exterior surface of the pipe and erosive and/or 15 corrosive attack by the pipeline contents on the interior of the pipe. However, the following description is made in the context of ferrous pipe element systems particularly, such as welded steel pipe and tube, spiral welded steel pipe systems and ductile iron pipe systems. 20 The spigot end may be a plain end to the pipe or may be particularly adapted to the socket end. The socket end may include a bell-formed arrangement such as the TYCO or VINDEX form, being adapted to receive an internal annular sealing element to provide a sealing engagement with the plain-pipe spigot end. Particularly, the socket end may be a roll formed bell arrangement wherein a 25 rubber sealing element may be used in a manner analogous to the TYCO (Ductile Iron) and VINIDEX (PVC) systems. The bell-and-spigot arrangements have the advantage of accepting up to 50 of axial deviation, enabling the pipeline to curve in the horizontal plane and to follow terrain in the vertical plane. The invention is also suitable for use with other end configuration joints such as butt-welded, 30 shouldered or roll-grooved, ball and socket and spherical slip-in joint. 3 The bell-and-spigot arrangement may also be used in a welded pipeline system. For example, the outer end of the bell socket may be welded to the exposed portion of the spigot end, with or without additionally welding the outer end of the spigot to the inner surface of the socket portion. 5 The socket portion may include an expanded portion of the pipe end of a substantially parallel-sided, that is, cylindrical form, where the material of the pipe element permits plastic deformation to form the expanded end. Alternatively the spigot end may be cold-formed down to pass into the inner diameter (ID) of a plain 10 socket end of the pipe element. In another further embodiment, the socket end may be formed by fabricating a sleeve onto the end of a pipe element the ID of the sleeve being selected to accept the spigot end of the adjacent pipe element. Preferably the spigot and socket ends are formed on respective ends of a plurality 15 of identical pipe elements in order to form the majority of a pipeline. The at least a single polymer corrosion protection lining on the inner surface of the pipe elements will preferably be selected having regard to the nature of the material to be conveyed by the pipeline. For example, for potable water 20 distribution the coating may be a dip or spray application of a curable material such as epoxy resin or urethane, applied after appropriate treatment of at least the pipe element inner surface. In the case of steel pipe the treatment may include grit blasting or the like. Preferably an epoxy resin is a 100%-solids, curable epoxy resin based material such as spray-applied, high-build material. In other 25 applications the lining may include tank lining or other high-build, hard, mineral filled epoxy materials. The multilayer coating including at least a corrosion protection layer and an abuse layer on the outer surface thereof may take any form consistent with the 30 environment into which the pipeline is placed. For pipelines destined to be buried, the corrosion protection layer may include etch or other priming, adherent 4 and non-permeable polymer coatings, electrolytic or dip galvanizing or the like. The abuse layer may take any suitable form such as a relatively thick polyolefin layer. In one embodiment, the multilayer coating is formed as a trilaminate including a pipe-compatible fusion-bonded epoxy (FBE) layer which is cured off 5 before application of an extruded high-density polyethylene (HDPE) layer or sleeve, which is bonded to the epoxy layer by a secondary adhesive copolymer resin interlayer such as POLYGLUE LE149. The epoxy provides the long term base corrosion protection. The intermediate layer of chemical bonding poly adhesive maximizes the bond strength of the three layers and the final external 10 layer of high density polyethylene offers maximum abrasion, cutting and impact protection to the underlying FBE corrosion protective coating. The HDPE layer may be applied over the adhesive layer by any suitable means such as hot continuous extrusion, spiral winding of polymer film over the rotating pipe, or by heat shrinking a moderately and radially oriented HDPE layer or sleeve over the 15 pipe. Damage to the external HDPE layer does not necessarily impact on the performance of the overall pipeline protection system. The corrosion protection layer may extend to the ends of the pipe element and be overlain by the corrosion protection lining. The abuse layer stops short of the 20 spigot end of each pipe element. It may also stop short of the socket end of each pipe element. The internal protective coating not only covers the internal surface of the socket, but also extends around the socket and spigot ends, providing continuous protection to the inner and outer surface of the socket and spigot ends. The external surfaces of the socket and spigot ends are further corrosive 25 resistance enhanced by the fact that the liquid epoxy is underpinned by the initial layer of fusion bonded epoxy applied to the entire outer body of the pipe. The use of high quality liquid epoxies on the spigot and socket ends allows accurate control of film thicknesses and greatly assists control of manufacturing 30 tolerances required for the effective assembly of the pipe joint. The invention allows higher operating pressures than previously available and allows the use 5 of much longer pipes without increasing the difficulty of laying the pipeline. In embodiments where the join is welded internally, this may be done by robot (for diameters of less than 900 mm) or manually. Welding is preferably by fluxless 5 means such as inert gas welding (MIG or TIG). The at least a single polymer corrosion protection lining on the inner surface of the pipe elements is in this case selected to allow spot treatment of high integrity at the site of the internal weld. For example the preferred epoxy lining may be selected to form a stable and adherent char in the heat affected zone of the metal, whereby the weld may simply 10 be overcoated. Alternatively, the material may be selected whereby the heat affected zone may be readily removed before overcoating. In a further aspect this invention resides broadly in a method of forming a steel pipe element including the steps of: 15 a) cold expanding a pipe socket end on a plain welded steel pipe element at ambient temperature; b) cold rolling an externally-protruding circumferential groove into the expanded socket end at ambient temperature; c) testing the pipe socket end for predetermined dimensions, tolerances, weld 20 integrity and metallurgical structure; d) grit blasting of the pipe inner and outer surfaces; e) applying protective layer materials to the pipe body and the internal surfaces, including the socket and spigot ends; f) allowing the coating and lining to cure, and 25 g) testing the protective layers for pinholes, adhesion and other predetermined tests. In a further aspect this invention resides broadly in a method for forming coated pipe ends, the pipe having a socket end and a spigot end, with its inner surface 30 covered with a protective layer, extending the inner surface around the socket end, and providing protection to both the inner and outer surfaces of the socket 6 and spigot ends, the method generally including the steps of: a) producing a pipe with a collapsed spigot end shell having a diameter of a predetermined tolerance; 5 b) cold expanding and roll beading the pipe socket end at ambient temperature; c) testing the pipe socket and spigot ends for predetermined dimensions, tolerances, weld integrity and metallurgical structure; d) grit blasting of the pipe inner and outer surfaces in their entirety through in-line blast equipment; 10 e) applying protective layer materials to the pipe body and the internal surfaces, including the socket and spigot ends; f) allowing the coating and lining to cure, and g) testing the protective layers for pinholes, adhesion and other predetermined tests. 15 In a yet further aspect the invention provides a method for providing corrosion protection of a steel pipe joint which is formed by the mating of a socket end of one pipe with a matching spigot end of a second pipe, including the steps of: a) grit blasting of the pipe inner and outer surfaces in their entirety through in-line 20 blasting equipment; b) applying to the socket end and spigot end of each pipe an inner protective layer or coating of an epoxy or urethane material by a spray and cure function process, such that the protective layer covers all of the inner surface of each pipe and then passes continuously around the end extremities and along the 25 external surface, terminating at a predetermined distance from the ends; c) allowing the coating and lining to cure, and d) assembling the mating ends of each pipe to form a sealed corrosion resistant joint. 30 In another aspect the present invention provides a method for providing corrosion protection of a pipe joint which is formed by the mating of a socket end of 7 a first pipe with a spigot end of a second pipe, the method including applying a base layer of a substance suitable to protect said first pipe from corrosion along a portion of the surface of each of the spigot and socket ends; and applying an internal coating of protective material along a portion of the interior of each of the 5 first and second pipes and over a portion of the base layer of corrosion protection substance covering the spigot and socket ends. In another aspect the present invention provides a pipe including a body having an exterior surface, an interior surface, and a first end shaped for connection with an 10 end of another pipe; an internal coating of protective material extending along a portion of the interior surface of the body and along a portion of the exterior surface of the body about a portion of the first end; and an outer coating of protective material extending along a portion of the exterior surface of the body, the outer coating of material having a layer with a higher density than that of the 15 internal coating. In a further aspect the present invention provides a pipe including a body having an exterior surface, an interior surface, and a first end shaped for connection with an end of another pipe; an internal coating of protective material extending along a 20 portion of the interior surface of the body and along a portion of the exterior surface of the body about a portion of the first end; and an outer coating of protective material extending along a portion of the exterior surface of the body, the outer coating of material having a thickness greater than that of the internal coating 25 In one preferred embodiment, the pipe coating covers the inner and outer surfaces at the pipe ends so that the coating on the inner surface of the socket end totally surrounds the external surface of the spigot end which is coated in the identical protective layer. A rubber ring is then inserted into the groove and lubricated to 30 provide a pressure seal between the socket and spigot ends of the mating pipes. This process is performed in the pipe manufacturing plant and no further work 8 is required to be performed on the joint during pipe laying. Brief Description of the Figures 5 The invention is further described with reference to embodiments of the invention illustrated in the drawings. Fig. 1 is a partial cross sectional side view of a dissembled rubber ring joint for use with water in accordance with a preferred embodiment of the present invention. 10 Fig. 2 is a partial cross sectional view of the rubber ring joint of Fig. 1 assembled.. Fig. 3 is a partial cross sectional side view of the rubber ring joint of Fig. 1 assembled and showing the upper and lower surfaces of the pipes. 15 Fig. 4 is a partial cross sectional side view of the rubber ring joint of Fig. 1 assembled and in relation to exemplary contents. Fig. 5 is a partial cross sectional side view of a dissembled rubber ring joint for use 20 with mining or sewerage in accordance with another preferred embodiment of the present invention. Fig. 6 is a partial cross sectional side view of the rubber ring joint of Fig. 5 assembled. 25 Fig. 7 is a partial cross sectional side view of a dissembled ball and socket joint for use with water in accordance with another preferred embodiment of the present invention. 30 Fig. 8 is a partial cross sectional side view of the ball and socket joint of Fig. 7 assembled. 9 Fig. 9 is a partial cross sectional side view of a dissembled ball and socket joint for use with mining or sewerage in accordance with another preferred embodiment of the present invention. 5 Fig. 10 is a partial cross sectional side view of the ball and socket joint of Fig. 9 assembled. Fig. 11 is a partial cross sectional side view of a dissembled double sleeve joint for 10 use with water in accordance with another preferred embodiment of the present invention. Fig. 12 is a partial cross sectional side view of the double sleeve joint of Fig. 11 assembled. 15 Fig. 13 is a partial cross sectional side view of a dissembled double sleeve joint for use with mining or sewerage in accordance with another preferred embodiment of the present invention. 20 Fig. 14 is a partial cross sectional side view of the double sleeve joint of Fig. 13 assembled. Fig. 15 is a partial cross sectional side view of a dissembled spherical slip-in joint for use with water in accordance with another preferred embodiment of the present 25 invention. Fig. 16 is a partial cross sectional side view of the spherical slip-in joint of Fig. 15 assembled. 30 Fig. 17 is a partial cross sectional side view of a dissembled spherical slip-in joint for use with mining or sewerage in accordance with another preferred 10 embodiment of the present invention. Fig. 18 is a partial cross sectional side view of the spherical slip-in joint of Fig. 17 assembled. 5 Fig. 19 is a partial cross sectional side view of a dissembled sleeve joint for use with water in accordance with another preferred embodiment of the present invention. 10 Fig. 20 is a partial cross sectional side view of the sleeve joint of Fig. 19 assembled. Fig. 21 is a partial cross sectional side view of an assembled plain ended butt joint for use with water in accordance with another preferred embodiment of the present 15 invention. Fig. 21A is an enlarged side view of a field weld shown in section A of Fig. 21. Fig. 22 is a partial cross sectional side view of an assembled plain ended butt joint 20 for use with mining or sewerage in accordance with another preferred embodiment of the present invention. Fig. 22A is an enlarged side view of a field weld shown in section A of Fig. 22. 25 Fig. 23 is a partial cross sectional side view of an assembled plain flange joint for use with water in accordance with another preferred embodiment of the present invention. Fig. 24 is a partial cross sectional side view of an assembled angle flange joint for 30 use with water in accordance with another preferred embodiment of the present invention. 11 Fig. 25 is a partial cross sectional side view of an assembled plain flange joint for use with mining or sewerage in accordance with another preferred embodiment of the present invention. 5 Fig. 26 is a partial cross sectional side view of an assembled angle flange joint for use with mining or sewerage in accordance with another preferred embodiment of the present invention. 10 Fig. 27 is a partial side elevation view of an extended entry rubber ring joint in accordance with another preferred embodiment of the present invention. Fig. 28 is an end view of the extended entry rubber ring joint of Fig. 27. 15 Fig. 29 is an enlarged partial cross sectional side view of the extended entry rubber ring joint taken along section B in Fig. 27. Fig. 30 is a cutaway perspective view of the extended rubber ring joint of Fig. 27. 20 Fig. 31 is a perspective view of the extended rubber ring joint of Fig. 27. Fig. 32 is a partial side elevation view of a deep insertion socket joint in accordance with another preferred embodiment of the present invention. 25 Fig. 33 is an end view of the deep insertion socket joint of Fig. 32. Fig. 34 is an enlarged partial cross sectional side view of the deep insertion socket joint taken along section B in Fig. 32. 30 Fig. 35 is a cutaway perspective view of the deep insertion socket joint of Fig. 32. 12 Fig. 36 is a perspective view of the deep insertion socket joint of Fig. 32. Fig. 37 is a partial side elevation view of a rubber ring joint in accordance with 5 another preferred embodiment of the present invention. Fig. 38 is a cross sectional view of the rubber ring joint taken along section A in Fig. 37. 10 Fig. 39 is a partial cross sectional side view of the rubber ring joint taken along section B in Fig. 37. Fig. 40 is a cutaway perspective view of the rubber ring joint of Fig. 37. 15 Fig. 41 is a perspective view of the rubber ring joint of Fig. 37. Detailed Description of the Drawings 20 Alternative embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the claims which follow. Wherever possible, like numbers will refer to like parts. 25 The invention provides in at least one preferred embodiment an improved corrosive protection method for producing rubber ring jointed steel pipe as shown in Figs. 1 to 6. Figs. 1 to 4 show the joint in relation to pipe fittings for use with water while Figs. 5 and 6 show the joint in relation to pipe fittings for use with 30 mining or sewerage. As the structure of the joint for use with water is substantially the same or similar to that for use with mining or sewerage, the description in 13 relation to Figs. 1 to 4 will be understood to apply to Figs. 5 and 6. In Figs. 1 and 2, two views of a cross section of the pipe joint are shown, the first view showing the joint prior to assembly and the second following assembly of the 5 joint, with the coating on the internal and external surfaces shown. As shown in Figs. 1 and 2, joint 100 is preferably formed by combining the ends of first and second pipe bodies 102, 104. Pipe body 102 includes a spigot end 106 having an external surface 108 and an internal surface 110. Pipe body 104 10 preferably includes a socket end 112 having an external surface 114 and an internal surface 116 with a groove or recess 118. Recess 118 is preferably adapted to receive therein a rubber sealing ring 120 which may be subsequently lubricated. It is preferred to lubricate the rubber ring 120 prior to assembly to assist in assembly of the joint, eliminate damage to, or pull out of, the rubber ring 15 and provide a compressed watertight seal. The pipe bodies 102, 104 preferably include an external coating 122 extending to a predetermined distance from the ends. External coating 122 is preferably a trilaminate coating of a base layer of a powder fusion bonded epoxy (FBE) 20 substrate, an intermediate layer of a chemical bonding poly adhesive and an outer layer of a high density polyethylene (HDPE). The outer layer preferably acts as an abuse layer that is subject to the chipping and scrapping often accompanied by the joining of two pipe ends together. It will be appreciated that other protective materials may be used as an abuse layer. The abuse layer may take any suitable 25 form such as a relatively thick polyolefin layer. The FBE base layer preferably extends from end to end of each pipe body and beyond the predetermined stopping distance of external coating 122. Accordingly, in a preferred form external surface 108 of spigot end 106 and external surface 30 114 of socket end 112 will each include the FBE base layer while the remainder of the exterior surface of each pipe body will include the entire trilaminate coating 14 discussed above. It will be appreciated that other protective materials may be used as a corrosive protection base layer. In general, the base layer may include a number of powder applied thermoset resins which may include, but are not limited to epoxies, urethanes and ureas. For pipelines destined to be buried, the 5 corrosion protection layer may include etch or other priming, adherent and non permeable polymer coatings, electrolytic or dip galvanizing or the like. Pipe bodies 102, 104 preferably include an internal coating 124 including a liquid epoxy layer which wraps around the spigot and socket end extremities and over 10 the FBE base layer on the external end surfaces 108, 114. It will be appreciated that other materials may be used as an internal corrosive protection coating. In general, the internal coating may include liquid applied thermoset resins which may include, but are not limited to epoxies, urethanes and ureas. 15 The external coating 122 and the internal coating 124 are provided as corrosion resistant barriers for the steel pipes and their joint 100. The spigot end 106 of one pipe is joined to the socket end 112 of a second pipe. The internal coating 124 extends around the spigot and the socket ends 106, 112, 20 respectively, and continues onto the external surfaces 108, 114 of both ends, overlaying the FBE base layer and meeting up with the outer coating 122 of trilaminate at a predetermined points 126, 128. In a preferred form, predetermined point 126 is formed as a bevel proximate spigot end 106 with internal coating 124 partially overlapping outer coating 122. Predetermined point 128 is preferably 25 formed as a bevel proximate socket end 112 with outer coating 122 partially overlapping internal coating 124. The entire internal surface of each pipe may be protected by the internal coating if desired, which in a preferred form is a liquid epoxy coating. 30 The present invention has been described in relation to a rubber ring joint in Figs. 1 to 6. However it will be appreciated that the present invention is applicable to 15 other types of joints without departing from the scope of the present invention. For example, Figs. 7 to 10 show a joint 200 that is a ball and socket joint. Figs. 7 and 8 show joint 200 for use with water. Figs. 9 and 10 show joint 200 for use with mining or sewerage. Joint 200 preferably includes first and second field welds 5 230, 232 when assembled. Figs. 11 to 14 show a joint 300 that is a double sleeve joint. Figs. 11 and 12 show joint 300 for use with water. Figs. 13 and 14 show joint 300 for use with mining or sewerage. Preferred dimensions are included in Figs. 11 to 14. When 10 assembled, joint 300 preferably includes a combination of field weld 334 and shop welds 336 as shown in Figs. 12 and 14. Figs. 15 to 18 show a joint 400 that is a spherical slip-in joint. Figs. 15 and 16 show joint 400 for use with water. Figs. 17 and 18 show joint 400 for use with 15 mining or sewerage. Preferred dimensions are included in Figs. 15 to 18. When assembled, joint 400 preferably includes a field weld 438 as shown in Figs. 16 and 18. Figs. 19 and 20 show a joint 500 that is a sleeved joint. When assembled, joint 20 500 preferably includes a combination of a field weld 540 and shop welds 542 as shown in Fig. 20. Figs. 21, 21A, 22 and 22A show a joint 600 that is a plain ended butt joint. Figs. 21 and 21A show joint 600 for use with water. Figs. 22 and 22A show joint 600 for 25 use with mining or sewerage. When assembled, joint 600 preferably includes a field weld 644 as shown in Figs. 21A and 22A. Figs. 23 and 25 show a joint 700 that is a plain flange joint. Figs. 24 and 26 show a joint 800 that is an angle flange joint. Figs. 23 and 24 show the respective joint 30 for use with water. Figs. 25 and 26 show the respective joint for use with mining or sewerage. 16 Figs. 27 to 31 show a joint 900 that is an extended entry rubber ring joint. The ends of the pipe bodies 902, 904 are preferably elongated as shown in Fig. 29. The elongated ends advantageously provide an improved securement for the joint. 5 The elongation of spigot end 906 and socket end 912 are facilitated by the protection provided by the internal and external coatings. Preferred dimensions are shown in Fig. 29. Figs. 32 to 36 show a joint 1000 that is a deep insertion socket joint. Joint 1000 is 10 similar to joint 900 except that recess 1018 is preferably centrally positioned along the length of socket end 1012 as shown in Fig. 34. Also shown in Fig. 34, a distal portion 1048 of socket end 1012 and a proximal portion 1050 of spigot end 1006 preferably include a bare base metal surface that may be coated after the pipe portions are welded. 15 Figs. 37 to 41 show a joint 1100 that is a rubber ring joint. Joint 1100 is similar that described above in relation to Figs. 1 to 6 except there is less clearance between internal surface 1110 of socket end 1112 proximal of recess 1118 and external surface 1108 of spigot end 1106. 20 The methodology of the present invention improves the production of corrosion resistant jointed steel pipes as indicated above. EXAMPLE 1 25 Joint formation is carried out as follows: The pipe is produced as electric resistance welded pipe or sub arc welded spiral pipe to predetermined dimensions and tolerances. The male or spigot end of the pipe is collapsed in an end former to nominated dimensions and sized to mate with 30 the female (socket) end within predetermined tolerances. The collapsing (or internal swage) of the pipe occurs only at the extreme tip of the pipe without 17 affecting the pipe body, and is equal to the wall thickness of the pipe in its reduction, which permits ease of entry into the socket end during joint assembly. It is preferred that pipe diameter is not increased in the first 120mm of the pipe end 5 during the collapsing process, as this will inhibit field assembly of the joint. Similarly, too great a reduction during collapsing will reduce rubber gasket compression, potentially allow vegetation root penetration of the joint and chance of rubber ring blowout. 10 For both electric resistance welded pipe and spiral pipe that is manufactured to a larger tolerance specification, it may be necessary to expand the spigot end within the first 120mm of the pipe end region. To accommodate the increased diameter of the spigot, the inner diameter specification of the socket is increased accordingly. 15 The ovality dimensions of the socket for each individual pipe size are calculated to accommodate the outside diameter of the spigot end and the thicknesses and tolerances of the liquid epoxy corrosion protective coating. The female socket end is cold rolled to precise dimensions and tolerances, with the process ensuring 20 repetition manufacturing of the socket end. As the pipe is securely clamped during the cold expansion and roll beading, consistently accurate ends are achieved from the process. The use of ambient temperature rolling eliminates all of the temperature and control issues previously encountered in the hot formed spigot and socket production process. 25 PREPARING PIPE FOR COATING AND LINING In order to achieve a superior corrosion protection system, the steel pipe surfaces should be thoroughly prepared and free of moisture, solvents, dust, rust or steel scale. To achieve this, socket and spigot pipes are preferably passed along a fully 30 automated line which: 18 a) Pre-heats the pipe to remove all moisture; and b) Passes the pipe through a grit blast machine which cleans the pipe's external surface to clean white steel as per AS1 627 (Class 2.5 or better). 5 The pipe is then ready for immediate external coating. EXTERNAL PROTECTIVE COATING Following grit blasting, the pipe continues to travel through an induction heating oven, reaching predetermined temperature, at which time a primary or base layer 10 of thermosetting fusion bonded epoxy (FBE) powder is spray applied which adheres to the heated steel substrate providing corrosion protection to the pipe. Simultaneously, a secondary layer of adhesive polymer resin is applied which reacts chemically with the FBE base layer to create a bonding agent for the topcoat layer. Finally, an outer layer of high density polyethylene (HDPE) film is 15 spirally applied to the rotating pipe which bonds with the previously applied resin, providing the tough mechanical protection to the system. This layer stops a predetermined dimension from both ends of the pipe. The pipe is then cooled as it rotates through the final section of the coating 20 machine, after which it passes through an electric resistance unit which 100% tests the external coating for pinholes, scouring thickness of coating and any other damage. INTERNAL LINING AND SOCKET END PROTECTIVE COATING 25 The externally coated pipe is then transferred to the internal lining plant where the pipe is fully internally grit blasted to the relevant standard such as Class 2.5 or better, using a rotating grit spray lance. The pipe is then air blasted internally to remove any dust and grit particles, after which it is ready for immediate coating. 30 The internal liquid epoxy or urethane lining is then applied through a rotating spray lance which is withdrawn through the pipe at predetermined speeds, spray 19 rates and nozzle capacities. The liquid epoxy wraps around the pipe end extremities and onto the external surfaces of the socket and spigot over the previously applied FBE base layer until it reaches the HDPE outer layer at a predetermined point. The internal coating is then allowed to cure whilst rotating at 5 predetermined warm temperatures. The finally cured internal protective coating is then tested with an electric resistance unit which 100% tests the internal lining for any defects or coating variations. 10 COMPLETION OF THE JOINT To minimise additional activity in the field, predetermined and tested rubber rings of suitable substance and configuration are inserted into the socket end of the pipe and lubricated and provide the sealing mechanism of the pipe joint. 15 Apparatus and methods in accordance with the foregoing embodiments provide superior methods for producing corrosion resistant coated pipes with spigot and socket end joints. 20 The foregoing description is by way of example only, and may be varied considerably without departing from the scope of the present invention. For example only, the internal coating need not extend continuously around each end of the pipe body, but may be interrupted (see, e.g., Figs. 21 and 22). The outer coating may include only two layers or more than three layers as desired. The 25 internal coating may include more than one layer as desired. It is envisaged that chemical compositions other than that already described may be utilised for the purpose of protecting the pipe material from corrosion. The predetermined stopping points between the outer coating and the internal coating may be varied as desired. The stopping points may take forms other than a bevel, or if bevelled, 30 may include a slope that may be as steep or shallow as desired. One or more layers of each coating may be of the same material as desired. 20 The joint and its associated method(s) may be used with pipe portions having a metal component or non-metal component. For example, the extended entry rubber ring joint shown in Figs. 27 to 31 could be used with plastic pipe portions to 5 provide enhanced strength and/or protection to the joint. The features described with respect to one embodiment may be applied to other embodiments, or combined with or interchanged with the features other embodiments, as appropriate, without departing from the scope of the present 10 invention. It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within 15 the broad scope and ambit of the invention as herein set forth. 21

Claims (29)

1. A pipe joining method including the steps of: forming a corrosion-prone pipe element having a spigot end adapted to 5 engage a socket end of a next adjacent corrosion-prone pipe element in a pipeline; and providing each of said pipes with at least a single polymer corrosion protection lining on the inner surface thereof and a multilayer coating including at least a corrosion protection layer and an abuse layer on the outer surface thereof, 10 wherein said at least a single polymer corrosion protection lining extends about the pipe end to extend along the outer surface of the pipe at least as far as the spigot is inserted in said socket.

2. A method of forming a steel pipe element including the steps of: 15 cold expanding a pipe socket end on a plain welded steel pipe element at ambient temperature; cold rolling an externally-protruding circumferential groove into the expanded socket end at ambient temperature; testing the pipe socket end for predetermined dimensions, tolerances, weld 20 integrity and metallurgical structure; grit blasting of the pipe inner and outer surfaces; applying protective layer materials to the pipe body and the internal surfaces, including the socket and spigot ends; allowing the coating and lining to cure, and 25 performing one or more tests on the protective layers.

3. A method for forming coated pipe ends, the pipe having a socket end and a spigot end, with its inner surface covered with a protective layer, extending the inner surface around the socket end, and providing protection to both the inner 30 and outer surfaces of the socket and spigot ends, the method including the steps of: 22 producing a pipe with a collapsed spigot end shell having a diameter of a predetermined tolerance; cold expanding and roll beading the pipe socket end at ambient temperature; 5 testing the pipe socket and spigot ends for predetermined dimensions, tolerances, weld integrity and metallurgical structure; grit blasting of the pipe inner and outer surfaces in their entirety through in line blast equipment; applying protective layer materials to the pipe body and the internal 10 surfaces, including the socket and spigot ends; allowing the coating and lining to cure, and testing the protective layers for pinholes, adhesion and other predetermined tests. 15

4. A method for providing corrosion protection of a steel pipe joint which is formed by the mating of a socket end of one pipe with a matching spigot end of a second pipe, including the steps of: grit blasting of the pipe inner and outer surfaces in their entirety through in line blasting equipment; 20 applying to the socket end and spigot end of each pipe an inner protective layer or coating of an epoxy or urethane material by a spray and cure function process, such that the protective layer covers all of the inner surface of each pipe and then passes continuously around the end extremities and along the external surface, terminating at a predetermined distance from the ends; 25 allowing the coating and lining to cure; and assembling the mating ends of each pipe to form a sealed corrosion resistant joint.

5. A method for providing corrosion protection of a pipe joint which is formed 30 by the mating of a socket end of a first pipe with a spigot end of a second pipe, the method including: 23 applying a base layer of a substance suitable to protect said first pipe from corrosion along a portion of the surface of each of the spigot and socket ends; and applying an internal coating of protective material along a portion of the interior of each of the first and second pipes and over a portion of the base layer of 5 corrosion protection substance covering the spigot and socket ends.

6. The method of claim 5, wherein the base layer of the corrosion protection substance is applied over a majority of the exterior surface of each pipe, further including the step of applying an outer coat of protective material over a portion of 10 the base layer of the corrosion protection substance.

7. The method of claim 6, wherein the step of applying an outer coat of protective material is applied up to a predetermined point where the internal coating stops. 15

8. The method of claim 6, wherein the step of applying an outer coat of protective material includes applying an adhesive layer and an abuse layer.

9. The method of claim 8, wherein the abuse layer includes a high density 20 polyethylene.

10. The method of any one of claims 5 to 9, wherein the step of applying the base layer includes applying a fusion bonded epoxy. 25

11. The method of any one of claims 5 to 10, wherein the step of applying the internal coating includes applying a liquid epoxy.

12. The method of any one of claims 5 to 11, wherein the step of applying the internal coating includes spraying the internal coating onto the portion of each 30 pipe. 24

13. A pipe including: a body having an exterior surface, an interior surface, and a first end shaped for connection with an end of another pipe; an internal coating of protective material extending along a portion of the 5 interior surface of said body and along a portion of the exterior surface of said body about a portion of said first end; and an outer coating of protective material extending along a portion of the exterior surface of said body, said outer coating of material having a layer with a higher density than that of said internal coating. 10

14. A pipe including: a body having an exterior surface, an interior surface, and a first end shaped for connection with an end of another pipe; an internal coating of protective material extending along a portion of the 15 interior surface of said body and along a portion of the exterior surface of said body about a portion of said first end; and an outer coating of protective material extending along a portion of the exterior surface of said body, said outer coating of material having a thickness greater than that of said internal coating. 20

15. The pipe of either claim 13 or 14, wherein said outer coating of protective material is multi-layered.

16. The pipe of any one of claims 13 to 15, wherein said outer coating of 25 protective material includes at least three layers.

17. The pipe of any one of claims 13 to 16, wherein said outer coating includes a base layer, an intermediate adhesive layer, and an outer layer of protective material. 30

18. The pipe of claim 12, wherein said layer of higher density material 25 includes polyethylene.

19. The pipe of claim 17, wherein said base layer includes a fusion bonded epoxy. 5

20. The pipe of either claim 13 or 14, wherein a portion of said first end includes a base layer of a fusion bonded epoxy.

21. The pipe of claim 20, wherein said internal coating overlaps a portion of 10 said base layer of said fusion bonded epoxy.

22. The pipe of any one of claims 13 to 21, wherein said internal coating meets said outer coating at a predetermined point. 15

23. The pipe of claim 22, wherein said predetermined point is a bevel between said coatings.

24. The pipe of any one of claims 13 to 23, wherein said internal coating extends along the exterior surface of said body about said portion of said first end 20 a distance substantially equal to the insertion depth of said first end into the end of the other pipe.

25. The pipe of any one of claims 13 to 24, wherein said internal coating includes a liquid epoxy. 25

26. The pipe of claim 13, wherein said internal coating has a thickness less than said outer coating.

27. The pipe of any one of claims 13 to 26, wherein said first end is shaped as 30 a spigot. 26

28. The pipe of any one of claims 13 to 26, wherein said first end is shaped as a socket.

29. The pipe of any one of claims 17 to 19, wherein the base layer includes a 5 powder applied substance. 27