WO2018167736A2 - Method for lining by electrofusion joints of on-shore pipelines used for conveying fluids, formed by pipes externally lined with polyurethane foam and covered or enveloped with polyethylene sheets, and joint produced by this method - Google Patents

Abstract

Method and joint produced by this method, used for lining joints of pipes preferably intended for conveying any type of fluid that must be conveyed through thermally insulated pipelines, wherein the pipes, except for their ends, are already lined with a thermal insulation, polyurethane foam, and externally covered with a polyethylene sheet, the pipe ends being not lined in order to define zones that can be provided with any kind of lining and to allow the pipe ends to be joined.

Description

 "METHOD FOR COATING GASKETS BY ELECTROFUSION IN ON-SHORE DUCTS USED IN

DRIVING FLUIDS BUILT WITH EXTERNALLY COATED PIPES WITH POLYURETHANE FOAM, COATED OR ENCHAMED WITH POLYETHYLENE AND UNION

 OBTAINED BY SUCH METHOD "

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method, and to the joint obtained by it, for coating pipe joints preferably intended for the transport of any type of fluid that needs to be conducted through a thermally insulated pipe. Tubes that are supplied already coated with a thermal insulator, polyurethane foam, and externally jacketed with a lining or polyethylene jacket, except at the ends, areas where the tubes are free of any type of coating to allow the joining of the themselves (Board).

The proposed method makes it possible to achieve continuity between polyethylene liners or liners in the area where the pipes are joined together (Gasket) by using a sleeve or tubular body that is fixed overlapping by means of electrofusion welding between the Polyethylene coatings present at the ends of adjacent pipes to be joined. Once placed this shirt or tubular body: - cover the joint joint of said adjacent tubes and make contact at its ends with the first and second polyethylene liners or liners of the tubes.

 a perfectly sealed interior space or cavity will be generated, defined between the inner surfaces of the jacket and the tubes and into which polyurethane foam will be injected, thus covering the outer area of the welded joint.

STATE OF THE TECHNIQUE AND ADVANTAGES ON THE SAME

There are various devices and methods in the state of the art that use electro-fusion for joining pipes. US Patent 7,144,045 (Karl-Heinz Krah) discloses an electrofusion pipe joining system that includes a member capable of melting, such as the pipe itself or an intermediate piece, and a heating means attached to the pipe . There, fasteners are used to fix the aforementioned heating medium and it is connected to an external power source.

In US 6,680,464 (Krahe Ronald et al) a control device for a pipe joint by electro fusion is shown, where the pipes are preferably made of thermoplastic material and includes a means of coupling thereof and a means for attaching said coupling means to the pipes, and which in turn defines a fusible seal by means of electro fusion.

 US 6,375,226 (Dickinson Alan et al) refers to a multilayer thermoplastic pipe connector that has a hollow tubular cover capable of receiving the pipes, means for thermofusion, mechanical fastening means, and seal means.

 US Patent 6,127,662 (Katz Oded) discloses a device and method for joining a first pipe of plastic material to a second pipe whose material does not weld well with the material of the first pipe, and which uses a material electrofusion handle plastic that welds well with the first pipe of plastic material and includes a first heating coil in contact with the first pipe and a second coil in contact with the second pipe. Said handle includes at one end a link material capable of generating a good connection between the second pipe and the material of said handle.

Also among the elements, apparatus and systems of the prior art are the apparatus described in US Patent 5,798,021 (Stiles Terry); the pipe joining system of US Patent 5,127,116 (Greig John); the electrofusion joint of US Patent 5,116,082 (Handa Takayuki et al), US 4,929,817 (Mito Kazunori et al). In none of the aforementioned patents is it possible to solve the proposed problem of coating pipe or pipe joints on which a thermal insulation of polyurethane foam covered by a coating or jacket of polyethylene has been placed. The solutions to date used to solve this need do not ensure a perfect seal between the original polyethylene jacket or jacket of the tubes and the joint coating allowing the occurrence of leaks from the outside to the inside of the coating that can affect the normal performance and duration of the pipe

 In summary, among the methods of coating joints mentioned in the state of the art and the problems associated with each one, the following are to be mentioned:

1) Injection of polyurethane foam into a temporary mold made of steel or Teflon, placed in the area of the joint to be coated. The mold is then removed and the polyurethane foam is covered with a heat shrinkable polyethylene blanket. In these cases, the sealing obtained with the heat shrinkable blanket on the linings or polyethylene jacket of the tubes is not efficient enough, moisture leaks can occur from the outside into the joint, significantly affecting the quality of the thermal insulation and its integrity over time. 2) Injection of polyurethane foam into a temporary mold made of steel or Teflon, placed in the area of the joint to be coated. The mold is then removed and the polyurethane foam is covered with a self-adhesive polyolefin tape. As in the previous case, a perfect seal cannot be ensured, resulting in consequences similar to those caused in point 1), that is, possible leaks which, directly and notably, will affect the integrity of the joint coating.

 3) Placing two half polyurethane foam rods over the area of the joint to be coated, fixed together and then covered with a shrinkable thermo blanket or a self-adhesive polyolefin tape. In this case, the coexistence of a clear triple problem is possible, namely:

 a- On the one hand, the lack of security in the perfect seal from the use of both the thermo shrinkable polyethylene blanket and the self-adhesive polyolefin tape;

 b- On the other, the absolute lack of adhesion between the two half rods is added to each other and with respect to the substrate;

 c- Finally, the lengths of the half rods must be adapted to each particular joint.

They generally have lengths slightly different, which gives rise to extra work in the field, with the consequent lack of precision required for perfect thermal insulation.

It is therefore one of the objectives of the present invention to achieve the following two purposes:

 Ensure perfect continuity between the polyethylene liners or linings that cover the thermal insulation of polyurethane foam from the pipes to be joined and that originally come with them.

 - Insulate the area of the joint generated from the welding of the tubes preventing any possibility of filtration into the injected polyurethane foam lining after fixing the jacket to the ends of the tubes.

 - Ensure that all the space or cavity that surrounds the joint generated when welding is perfectly defined and delimited to then be able to inject polyurethane foam into it. The polyurethane injection involves filling the cavity in its entirety without the need to remove any mold as in the state of the art, thus obtaining the thermal insulation required in this type of joints.

BRIEF SUMMARY OF THE INVENTION: The present invention provides a method of coating externally coated pipe joints with thermal insulation of polyurethane foam covered with a polyethylene coating or jacket and having the following characteristics:

 - Use of a jacket of the same type of polyolefins (Polyethylene) and with a thickness similar to that of the original coatings or liners that act as a coating for the foam of the tubes, so that continuity can be granted to them.

 - Placing a jacket or tubular body, which has a length that allows it to overlap with the original polyethylene liners or linings of the tubes.

- Use of an electrofusion process as a connection system between pre-existing polyethylene liners or linings in the original thermal coating of two consecutive tubes and the tubular jacket or body placed in the area of the joint to be coated. This ensures a perfect weld resulting in optimum continuity between both linings or Polyethylene sheaths, preventing any type of filtration from the outside to the inside of the coated joint. - Sealing the hole through which the joint is filled with polyurethane foam by means of a thermo fusion welded polyethylene plug which ensures a perfect seal preventing any type of filtration.

 The mentioned method will bring:

 - Simplification of the method used in the field ensuring a unique and constant quality in all coated joints. This is achievable from the management of a complex technology, reliable with respect to the results and derived from the electro fusion welding process using bonding parts as heating agents, which may be: electrical resistors, metal meshes or metal meshes embedded in polymers of polyolefinic origin.

 - Reduction of the time spent in the manufacture of the lining of the joints, it being no longer necessary to place and then remove temporary molds for the injection of polyurethane foam.

- Obtaining optimum adhesion values in the overlapping areas between the pre-existing polyethylene liners or linings in the tubes and the new jacket or semi-shirts used to cover the polyurethane foam coating applied on the joint. BRIEF DESCRIPTION OF THE FIGURES

In order to achieve a better understanding of the present invention and a greater understanding of the advantages discussed, the detailed description of some preferred embodiments of the present invention is given below. For this, the attached figures are taken into account, in which:

 Figure 1 shows a longitudinal section of two tubes joined by a joint in which a sleeve or tubular body is threaded into one of them, over its coating or jacket of original polyethylene.

 Figure 2 shows a longitudinal section of the two tubes to be joined, with the sleeve or tubular body already positioned in the area of the joint to be coated, and overlapped at each end with the original polyethylene coating or jacket of each tube.

Figure 3 shows the positioning of an equipment to preheat and compress the area where welding is to be carried out by means of an electrical resistor, metal mesh or connecting piece between the new polyethylene sleeve or tubular body and the original coating or jacket of the same material with which the tubes to be joined are coated.

 Figure 4 shows the longitudinal section of the two tubes to be joined, the polyurethane foam filling of the cavity or surrounding space of the welded joint having already been carried out.

 Figure 5 shows two half shirts to be used in those cases where the joint to be coated already has the welded tubes and therefore it is impossible to thread a single-piece shirt.

 In all figures the same reference numbers correspond to identical elements of the invention.

DETAILED DESCRIPTION OF THE INVENTION

We see in Figure 1 the tubes 1 and 2, which have a first coating 3 of polyurethane foam and a second coating or jacket of polyethylene 4, already welded and held by a joint 5, thus leaving a portion of tubes 1 and 2 which will be closed and isolated by the method of the present invention. It is shown in this figure the respective connecting pieces 6, already installed on the ends of the original linings or linings of the tubes 1 and 2, and a sleeve or tubular body 7, intended to cover the joint 5 and made in a whole piece , already threaded over the coating or jacket of polyethylene 4 of one of said tubes, and prior to welding of two consecutive tubes.

 In Figure 2, it is observed how the tubular jacket or body 7 is positioned overlappingly over each connecting piece 6, said jacket 7 having an upper perforation 7a, capable of allowing the injection of polyurethane foam and consequently the filling of the cavity 8 .

 In figure 3 you can see the positioning of a preheating and compressing equipment 9, the area where welding is to be carried out by means of the connecting pieces 6, between the polyethylene sleeve or tubular body 7 and the lining or jacket original 4, of the same material with which tubes 1 and 2 are joined together.

 It is observed in Figure 4, that after electrofusion of the jacket 7 with the second coatings 4 of each tube, the cavity 8 has been filled with polyurethane foam, then a polyethylene plug 10, welded by thermo fusion in the opening 7a of the sleeve or tubular body 7.

The achievement of the final objective of this invention can then be observed which corresponds to the perfect and definitive sealing of the surrounding area of the joint of the tubes 1 and 2, giving continuity to both the original thermal insulation 3 of the tubes and the protection provided by the original 4 polyethylene liners or liners of each tube.

 Therefore, in the preferred form of graphic embodiment, the use of:

 a) A polyethylene jacket 7 which has a perforation 7a in the center considered radially allowing injection of the polyurethane foam. The length (preferred) of this jacket 7 is equal to the length of the joint 5 to be coated more than twice the length of overlap between it and the linings or linings 3 and 4, existing in tubes 1 and 2. Its inner diameter it is slightly larger than the outer diameter of the pre-existing original linings 3 and 4 on the tubes 1 and 2 in order to allow threading on the original tubes, their thickness being similar to their thickness.

 They arise according to the moment in which the method of the present invention must be carried out, two modalities of placement and structure of the shirt 7. Namely:

1) That it is conformed by a single tubular piece with the shape and dimensions depending on the tubes to be joined. This piece is used in the process of forming a new pipe when two consecutive tubes have not yet been subjected to the welding process, allowing this jacket 7 to be threaded over one of them for its subsequent use, as illustrated in figures 1 to 4.

) That it is formed by two half sleeves lia and 11b, as can be seen in figure 5. These must be joined in longitudinal form by means of electrofusion welding for the definitive dimensional conformation. They are used when the tubes are already welded and it is not possible to thread a jacket 7 over one of them, as is the case in forming a new pipe.

b) A polyethylene plug 10 which, after the injection of the polyurethane foam into the space 8 of the joint, will be welded by thermo fusion, perfectly sealing the perforation 7a existing in the jacket 7 and described in the previous point "a ".

c) Two linkage pieces 6, which will be used to carry out electro fusion welding between the jacket 7 corresponding to the joint 5 and the original polyethylene liners or casings 4 of the tubes 1 and 2. These linkage parts 6 consist of an electrical resistor or a heating mesh may or may not be embedded in polyolefin material (polyethylene) with their respective terminals incorporated to connect it to the power supply equipment during The welding process. They are of sufficient length to fully cover the outer perimeter of the sheaths or sheaths of polyethylene pipes.

 d) Stretch polyethylene tapes that will be used for temporary fixing of the bonding pieces 6 on the preexisting polyethylene sheaths or shells 4 typical of the original coating in the areas of overlap with the new gasket jacket.

II) The tools necessary for the placement and welding by electro fusion of the 7th and 11b shirts:

 • System for longitudinal electrofusion welding when the forming of the jacket results from the union of two half sleeves (lia and 11b).

 • Simultaneous heating and compression system 9, which will be used to raise the temperature and apply the consolidation pressure to the new jacket in the area of overlap with the existing liners in the lining of the tubes during the electro fusion welding process.

• Power generating equipment that will be connected to the heating elements (resistors, metal meshes or polymer embedded meshes) of the Bonding parts during the electrofusion welding process.

 • Thermo fusion equipment used to heat the plug and the hole surface of the polyethylene jacket used for polyurethane injection at the time of sealing it.

Detailed description of the proposed method:

In the process of forming pipes and before welding two consecutive tubes 1 and 2, a polyethylene jacket 7 is threaded on one of them. This operation is feasible since the inner diameter of the jacket 7 is slightly larger than the diameter exterior of the pre-existing liners or linings 4 in the tubes. In turn, it travels in a length considered sufficient and necessary to not be affected and in turn compromise the welding process of the tubes (Figure 1). When the tubes are already welded and it is impossible to carry out the threading operation of the new shirt over that of one of them for later use, the methodology is based on two half shirts lia and 11b, which will be joined longitudinally by means of two also longitudinal welds, as shown in Figure 5. This shirt formed by two half shirts lia and 11b will result in a whole similar to that described in the previous point. The following steps, and as explained, will be common for both specified procedures.

 Once the welding of two consecutive tubes is carried out, if necessary, the external anticorrosive coating of the joint 5 is carried out, by any of the procedures normally used in this type of processes, for example, epoxy coatings or with heat shrinkable blankets. Once the anticorrosive coating is finished, the overlap zone between the jacket 7, or half sleeves lia and 11b, and the pre-existing linings or linings of the tubes is perfectly cleaned. Bonding pieces 6 are placed in the overlapping areas by wrapping them on the pre-existing polyethylene liners or sheets 4 and securing them by means of stretch polyethylene tapes (Figure 1). The polyethylene jacket 7 is moved to the correct position, placing the perforation for the injection of the polyurethane on the upper part (figure 2).

The heating and compression system 9 is placed. A preheating of the preset zone is started to heat up to a temperature that allows the softening of the jacket area 7 to be welded. Ultimately allowing perfect contact with the bonding piece 6. The bonding pieces 6 are then energized while maintaining the consolidation pressure producing the final weld.

 The heating and compression equipment 9 is removed and the polyurethane foam is injected through the pre-established hole 7a and oriented for this purpose in the upper part of the jacket 7.

 Once the injection process is finished and once the foam has hardened, the surface of the hole 7a is cleaned and the corresponding plug 10 is welded by thermo fusion.

Claims

CLAIMS Having described and specified the nature and scope of the invention and how to put it into practice, it is claimed to claim ownership and exclusive right: 1.- Method for the thermal coating of joints made for the union of two externally coated tubes (1, 2), and close to their joining ends, by a first coating (3) of polyurethane foam and by a second coating or jacketed (4) polyethylene, located externally to the first lining (3), characterized by comprising the steps of:  a) Position at the end of one of said tubes (1, 2), and outside said second outer shell (4), a hollow cylindrical jacket or body (7) of polyolefin material and which has a hole (7a) on its surface, proceeding to make the welding joint between the ends of said tubes (1, 2); b) If the tubes are already welded and it is not possible to perform the positioning referred to in point "a" of a shirt (7) over one of them, two half shirts (lia and 11b) will be incorporated, which should be longitudinally joined by electrofusion welding for forming dimensional dimension resulting in a whole similar to the shirt (7).  c) Move the jacket (7) towards the joint of the tubes (1), until its end is close to the joint, which overlaps in the second lining (4) of the remaining tube (2);  d) Assemble, by electrofusion welding and through the use of connecting pieces (6), the ends of said jacket (7) with the second coatings (4) present in the tubes (1, 2);  e) injecting through said at least one hole (7a) of the jacket (7), polyurethane foam (8) in order to fill the defined space or cavity inside said jacket (7);  f) proceed to seal the polyurethane injection hole (7a) of point "e" by means of a polyethylene plug (10) welded by thermo fusion.  2. Method for thermal coating of joints made for joining two tubes (1, 2), according to claim 1, characterized in that said hollow cylindrical jacket or body (7) to be positioned at the end of one of the tubes (1,2), is a whole piece. 3. Method for thermal coating of joints made for joining two tubes (1, 2), according to claim 1, characterized in that said hollow cylindrical jacket or body (7), to be positioned at the end of one of the tubes (1,2), it is formed from two half shirts (lia, 11b).  4. Method for thermal coating of joints made for joining two tubes (1, 2), according to claim 1, characterized in that said electrofusion welding is carried out with a heating and compression system in the two zones overlapping, with a weld between the polyolefinic material (polyethylene) of each end of the jacket (7) and the second lining or jacket of polyethylene (4) of each tube, where:  a) The areas of superposition to be welded are preheated and compressed;  b) Electro fusion welding of adjacent and previously defined surfaces is carried out.  c) Once point "b" has been successfully completed, interrupt the energy supply by allowing the area covered in the welding process to cool to a predetermined temperature,  d) disassemble the heating and compression application system. 5. Method for thermal coating of joints made for joining two tubes (1, 2), according to claim 1, characterized in that an anticorrosive outer coating is made on the joint. 6. Method for coating joints according to claim 1, characterized in that the connecting parts (6), present in the areas of jacket overlap (7) and second coatings (4), are temporarily secured by means of a Stretch type polyethylene tape.  7. Method for thermal coating with polyurethane foam according to claim 1, characterized in that the connecting pieces (6) are electrical resistors, metal meshes or metal meshes embedded in polyethylene and have connectors enabling their connection to energy sources capable of enabling the fusion of adjacent material. 8. Method for thermal coating with polyurethane foam according to claim 1, characterized in that the electro fusion welding is carried out by means of bonding pieces (6), the same being located between the second coating ( 4) and the ends of the jacket (7), and being energized maintaining the consolidation pressure until the electro-fusion welding of the jacket (7) and the second polyethylene coating (4) of the tube (1,2) are obtained. 9. Method for thermal coating with polyurethane foam according to claim 1, characterized in that said hole (7a) is located in the central part of said jacket (7), the same being positioned on top of the mentioned shirt (7).  10. A union with thermal coating of pipe joints, formed according to some of the preceding claims, characterized by comprising: a) Two tubes (1, 2) coated externally by a first coating (3) of polyurethane foam and a second coating or jacket (4) of polyethylene, located externally to the first coating (3), said tubes being joined by a welding joint (5); b) A hollow jacket or body (7) positioned around said joint (5) and overlapping outside said second linings (4) of the ends of each tube (1,2), being attached to them by electrofusion welding ; c) polyurethane foam (8) located inside said hollow jacket or body (7); d) a plug (10) one hole sealant (7a) having said hollow jacket or body (7).  11. A thermally clad joint of tube seals formed according to claim 9, characterized in that the jacket (7) is formed by welding of two half sleeves (lia, 11b).