MXPA97006344A - Union of pieces of tube revesti - Google Patents

Abstract

The present invention relates to a method for joining two pieces of pipe comprising joining, at the ends of each piece, a metal tubular connection, each connection has an internal surface formed of corrosion-resistant metal that extends to the free end of the connection and the inner surface has grooves separated by crenellations or teeth, lining the parts with thermoplastic linings, introducing a respective corrosion-resistant metal ring in each connection to compress the liner and push it into the grooves of the connection; and join the connections by soldadu

Description

UNION OF COATED PIPE PARTS FIELD OF THE INVENTION The invention relates to the joining of coated tube parts and to tube connections that are used in this joint.

BACKGROUND OF THE ART In particular, the invention relates to the joining of tubes having a liner, particularly a forced fit liner, made of polyethylene or other thermoplastic material. The tubes can, for example, be used for the transportation, in particular, of liquid hydrocarbons containing carbon dioxide, hydrogen sulfide, methane or hydrocarbons. The transported liquid may be at a temperature of, for example, up to 160 ° C and may be at a pressure of, for example, up to 5,000 pounds per square inch. The liquid transported can include exclusively or in conjunction with the hydrocarbons, non-deaerated water or brine. In general, the tubes can be used for the transport of liquids which have a very detrimental effect on the material normally used for the production of the tubes. That material is usually metal, for example, ferrous metals that can be steel or iron E'l i7 q7MX casting. Therefore, the tubes have adapted a lining of thermoplastic material to reduce the effect of the liquid transported in the tube. These coated tubes have to be joined at intervals, in order to allow a long pipe to be constructed. At the ends of these pipes, the pipe includes other tube-like parts, such as valves. In this specification, the term "tube part" means tubes and other tube-like parts, such as valves. An object of the present invention is to provide: a method for joining two pieces of metal tube; the two pieces of metal tube joined by that method and a connection for metal tube for use in that method, wherein a piece of tube or a connection for tube may be formed of ferrous metals, for example, steel or cast iron. U.S. Patent No. 5009737 (Lescaut - assigned to Atochem) discloses a method for producing a pipeline arrangement comprising placing pipes in end-to-end relationship, having an inner shell terminating axially inward from the ends axial, to define an uncovered inner wall section located between the longitudinal end E'1375 / '-? 7MX adjacent decks; solder the ends of the tubes; introducing radially, inside the uncovered wall section, a strip of meltable material and heating the strip while applying a pressure directed radially outwardly on the strip, to push the strip against the wall section not covered in order to reduce the thickness of the strip and increase the longitudinal width of the strip and cause the strip to contact the adjacent ends of the covers and to completely cover the uncovered wall section and to weld the strip to the covers. In the example described in U.S. Patent No. 5009737, each of the adjacent tubes has a cover composed of a thermoplastic polyamide material. The end of each end adjacent tube is free from the cover. The two adjacent ends of the tubes are welded. The strip is also composed of thermoplastic polyamide material and has an initial thickness of 6 mm and is 80 mm wide. The ends of the adjacent tubes are heated by an induction heating unit, to a temperature of 200 ° C, while a pressure of 20 kPa is applied to the inner face of the strip. As soon as the temperature reaches 200 ° C, the heating is interrupted and the E'l i7c, / > 1TMX applies a forced cooling until the temperature drops to 100 ° C, and the pressure exerted on the strip is no longer applied. As a result, the strip is brought to a molten state and widens and solders at the ends of the covers of the two tubes. The pressure is applied to the strip by four blades that move radially by means of four hydraulic rams in a self-propelled cart that moves inside the tubes. This car is equipped with a means to detect the part of the tubes (inside which the car is traveling) that is free or lacking in the cover. For example, the medium could be a radioactive isotope or a mechanical probe. Although the description mentions polyethylene as a cover material, it is not considered that U.S. Patent No. 5009737 contemplates the use of a liner as a cover. A liner is a one-piece tube type member that is fitted or inserted into the steel tube. In contrast, the tire described in U.S. Patent No. 5009737 is a tire that is progressively applied to the tube in particulate form. Alternative forms of cover are mentioned, including centrifuged cement and bitumens. The methods described in U.S. Patent No. 5009737 primarily comprise the E 1) 7c) / 't7 X joining of the metal tubes by welding, followed by fusion welding of the strip to the covers of the two tubes, using a tool that operates inside the tubes. U.S. Patent No. 4611833 (of Lescuat - assigned to Atochem) describes a pipe internally coated with heat sensitive material to protect the inside of the pipe against corrosion or abrasion and comprises at least two sections of pipe connected by a welded joint, where the inside of each pipe metallic is covered with a stainless steel alloy for a distance of from half a diameter to three diameters of the tube from the end of the tube and there is a reserved area at the end of the tube, which is free of heat sensitive material, the coating heat sensitive overlaps the coating of the stainless steel alloy by at least 20 millimeters from the end of the pipe, the edge of each section will be coated with the stainless alloy and will constitute the welded joint between the two sections of pipe, the sections of tube will be joined by means of the union formed by the stainless alloy with the edges of the tube and join In addition, by an external welding of the metal which is substantially the same metal as the metal of which the tube is formed.

Pl 37 / 07MX In this United States Patent, the stainless ferrochrome alloy with a thickness of 500 microns is applied to the inner wall and to the edge of a tube of 200 mm in diameter, over a length of 120 mm measured from from the end of the tube. The cover is not a liner but it is a cover composed of polyamide-11 deposited in an electrostatic way until reaching a thickness of 600 microns, leaving a non-coated reserve zone of 80 mm from the end of the tube section. The method described in U.S. Patent No. 4611833 requires access, over the entire length of each tube, to the inner surface of the tube in order to apply the covers to the inner surfaces of the tubes. It is clear that the methods described in U.S. Patent Nos. 5009737 and 4611833 are not applicable for joining pipe pieces in order to manufacture a long pipe of the type described above. In particular, in the Patent of the States No. 5009737, the two steel tubes are first joined by welding. Subsequently, the joining of the linings of the tubes requires the use of a machine that works inside the tubes. It is evident that there is a limit on the length of the tubes that PI? ^ MX allow the operation to be performed. The applicants assume that these operations could be carried out only when each tube has, at most, approximately 15 m in length and that the operation of joining the liner is made each time a tube length is added to the preceding tubes. Additionally, the described method includes the use of an induction unit arranged or arranged around the tubes at each joint. Again, this presupposes that each joint will be made every 15 m or less along the tube. U.S. Patent No. 4611833, describes a process that requires the internal deposition of a stainless metal coating at the end of each tube, followed by deposition by an electrostatic process or by dipping or spin casting. Again, this process requires that the length of the tube be limited to a length more or less than 15 m. Therefore, the joints will have to be made every 15 m in order to manufacture a pipe. According to the invention, the method for joining two pieces of pipe comprises joining to the ends of each piece a tubular metal connection, each having an internal surface formed of corrosion-resistant metal, which extends to the free end of the pipe. connection, the inner surface has separate slots E'1J7 / C »7MX by means of a crenellation or toothing; lining the pieces with thermoplastic linings; forcefully introduce a respective corrosion-resistant metal ring into each connection, to compress the liner and force it into the slots of the connection, and join the connections by welding. Instead of using a respective ring that is forcedly inserted into the connection, an alternative method uses a smaller respective ring that is housed in each connection and, subsequently, the ring is pushed out to compress the liner and push it towards the ends. connection slots. The connection can have an external flange at its free end and, instead of joining the connections by welding, the connections are joined with screws that pass through the flanges of the connections. One of the pieces of tube can be made of corrosion-resistant metal and can have an external flange, the connection and a piece of tube are joined by screws that pass through the eyelashes, the piece of tube does not contain a liner or a ring. According to the invention, the tube connection used in the method comprises a section of corrosion-resistant metal tube, whose internal surface has grooves separated by crenellations or teeth and a ring P1 J75 / 97MX corrosion-resistant metal that has a smaller diameter than the internal diameter of the pipe section, the connection is joined during use by welding it to one of the pieces of pipe, later the piece of pipe and the connection are coated by a thermoplastic liner, then the ring is located within the liner opposite the slots and pushes the liner towards the slots and, the connection is joined by welding to a similar connection. The connection may have an integral external flange, the connection shall be attached to a similar connection or to another piece of tube having an integral external flange, by screws passing through the flanges. Alternatively, a pipe connection according to the invention, for use in the method, comprises a length of metal pipe having an internal plating of corrosion-resistant metal, the plating extends to a first end of the connection, the inner surface of the plating has grooves separated by crenellations or teeth and, a corrosion-resistant metal ring has a smaller diameter than the inner diameter of the tube section, the connection will be joined, at its opposite end to the first end in use, To one of the pieces of tube, then the piece of tube and the connection are coated with a thermoplastic lining, then the ring is located inside the liner opposite the slots and E'1J75 / < * 7 X pushes the liner into the slots and, the connection is joined by welding to a similar connection. This connection may have an integral external flange having screw holes and a working face extending outwardly from the first end of the connection and having an annular • groove formed, the plating extends over the face including the groove , wherein the plating also provides an annular groove which, during use, admits or partially houses an annular seal which, during use, can be compressed against the groove in the flange of a connection or other similar tube part by the action of the screws that pass through the screw holes of the two tabs. The invention also includes two pieces of tube joined by the method according to the invention. When the piece of pipe or pipe connection is formed by fiery casting and has to be welded to another cast iron or some other weldable metal, the welding has to be carried out with some caution, as is already known in the welding technique of the iron strained.

BRIEF DESCRIPTION OF THE DRAWINGS The modalities of the methods for joining two pieces of tube will be described below as a way of P137 07MX example with reference to the accompanying drawings, in which: Figures 1A and IB are a longitudinal section through a part of the first form of union between two pieces of tube, - Figure 2 is a partial section, in enlarged scale, showing the grooves and the crenellations or teeth shown in Figures 1A and IB; Figure 3 is a vertical section through a connection used in a second form of connection, - Figure 4 is a longitudinal section through part of the connection shown in Figure 3 (this is shown only by way of example, in the same way a connection of the type shown in Figures 1A or IB or in Figure 7) attached to a piece of tube could be used and showing the apparatus by which the ring is forcedly inserted into the connection; Figure 5 is a longitudinal section corresponding to Figure 4 but showing an alternative form of ring and apparatus by means of which the ring is expanded, - Figure 6 is a longitudinal section corresponding to Figure 5 but showing a additional alternative to the apparatus by means of which the ring expands; and you < 7 r, / 1"> ~ M Figure 7 is a section corresponding to Figure 1 but showing an alternative form of connection having an external flange.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Figures 1A and IB show one of the two pieces of tube 10. In this case, each piece is a steel tube. The other tube (not shown) is attached to the right side of a right connection shown in the Figure and described later. The tube 10 and the other tube are composed of carbon steel. Each tube 10 is attached to a tubular connection 12 of carbon steel by an annular circumferential weld 14. The two connections 12 are joined by an annular circumferential weld 15. The interior of each connection 12 is recessed 16 and the plating material is High alloy and corrosion resistant 18 is deposited as a weld deposit in the connection 12. The material is, for example, Inconel welding reservoir material 625. The inner surface of the material 18 is subsequently machined to form a series of annular grooves. internal 20 separated by crenellations or internal annular teeth 22. Between the internal end of the released area 16 and the annular teeth or tops 22, the internal surface of the material 18 is machined to provide a wider groove 24. Beyond the battlements or teeth 22 and directly to the end of the connection 12, the inner surface of the material 18 is machined to provide a recess 26. Each tube 10 contains a tubular liner 30. In this example, the liners 30 are composite of medium density polyethylene. The liners 30 have a tight fit inside the tubes 10 and are installed by any method to install linings with tight fit. The preferred method is the "Swagelining" process. "Swagelining" is a registered trademark of British Gas pie. In this process, the polyethylene liner is pulled and passed through a die that reduces the diameter of the liner. Then the liner is passed through the steel tube. It is allowed to relax from the lining and, after a period of time, the liner returns to its original diameter and is tightly fitted inside the tube. Each liner 30 is compressed in the region of the grooves 20 and the battlements or teeth 22 by a ring 32, which may be of a suitable metal having an external corrosion resistant coating 33 formed, for example, of a plating Inconel 625 solder deposit material. In an alternative method, ring 32 is composed entirely of stainless steel. Each ring 32 has been inserted into connection 12 and E'l '"/' • MX. pushes the liner 30 into the slots 20. Each liner 30 terminates shortly after the end of the connection 12 and a ring 40 of the lining material is housed in the space between the ends of the liners 30. The ring 40 has a slot external annular 42 in which an annular body 44 of thermal insulation material is received. The preferred material is obtained from Burnstone Ceramic Limited of 19 Redgates, Walkington, Beverly, North Humberside HU17 8TS, United Kingdom, under the description Refractory Sheet Type A Moldable. The material comprises a mixture of aluminum oxide and aluminum silicate fibers with approximately 35-40% water, which is lost when dried, 1% organic binder and traces of ammonia. The material as received in the form of a rectangular strip is easily formed in an annular body 44 and the two ends are pressed. After forming and molding the ends of the strip, the strip can be heated to dryness, after which a hard body 44 is obtained. The body 44 jumps the annular circumferential weld 15 between the connections 12 and protects the underlying ring 40 from material of lining. The procedure for joining the two tubes 10 is as follows: (a) the connections 12 are joined by welding them to the tubes, - E'l) 7r? / 17 X (b) the tubes 10 are lined, each, using the process "Swagelining" by passing a polyethylene liner 30 through a die and through the tube 10 and the connection 12. After a relaxation period of 24 hours, the polyethylene liner 30 is cut slightly longer than the tube and the Connection; (c) the compression ring 32 is forcibly inserted into each connection 12. The polyethylene liner 30 is compressed between say 10 and 20% and pushed to enter the slots 20 in the connection 12 and against the battlements or teeth 22 Any surplus polyethylene that is pushed by the insertion of the ring 32 into the connection 12, in any case, is admitted by the long groove 24 machined on the inner surface of the plating material 18; (d) the polyethylene liners 30 are cut to the final length leaving a section of each connection 12 free or lacking the liner; (e) the ring of the lining material 40 is located in one of the connections 12 and the other connection 12 is stretched over it; (f) the two connections 12 are joined by an annular circumferential weld 15. The process used is welding with inert gas-tungsten and a E'l i'S '' 1- X support rod compatible with the veneering material 18, so that the weld is completely resistant to corrosion and free of cracks. The insulation material 44 protects the ring 40 during welding. Figure 2 shows details of the slots 20 and of the battlements or teeth 22 in the connections 12. In Figure 2, the following are the values of the listed features: Particularities Value Angle A 30 ° Width of the battlement or tooth B 3 millimeters Pass or light of the battlement or tooth C 9.3 millimeters Radius of the battlement or tooth D 1.0 mm In the example described above, the tubes 10 have an external diameter of 219.1 mm and an internal diameter of 200 mm. Each connection 12 is 500 mm long. In this example, the tubes 10 are, each, of 0. 5 to 1.0 kilometers long. During the construction of a pipe, a typical requirement would be a total of 2 or 3 joints between the coated pipes. The advantage of the method according to the invention is that this pipe is manufactured using the majority of carbon steel E 1J7 '- > 7M? which is much cheaper than using pure high alloy steel (Duplex) or using corrosion inhibitors. During the operation of the pipe fabricated using the method according to the invention for joining pipes, the corrosive product carried by the pipe eventually permeates through the liner 30. Then a very small amount of corrosion on the inner surface of the pipe occurs. of steel 10. However, after a period of time, this corrosive action ceases or stops, due to the accumulation of corrosion products. The corrosive product that reaches the internal surface of the plating 18 on the connections .12 does not cause corrosion. Each liner 30 is compressed and pushed against the plating 18, so that there is no path for the corrosive product, carried by the pipe, between the plating 18 and the liner 30. The use of the ring 40 described above is. optional. It is included due to the possibility that a scraper is used in the pipe and when the scraper goes through the space between the end of the liners 30 (in the absence of the ring 40) some damage to the scraper may be caused. If it is known that the scraper is not required, then the ring 40 can be omitted. Figure 3 shows a modified form of the E'l? V ^ M connection 50. Connection 50 is composed entirely of duplex stainless steel or other corrosion-resistant metal. Two connections 50 are joined to the tubes 10 by welding instead of using the connections 12. The welds at 14 are fabricated using filler or filler material that is compatible with the duplex steel and the weld at 15 is fabricated from a filler material. filling or adequate contribution, between the two duplex connections. Figure 4 shows tube 10 and the connection 50 joined to it by welding 14. The liner 30 has already been inserted through the tube 10 and the connection 50. The ring 32 has an outer diameter larger than the internal diameter of the liner 30. When the ring 32 reaches a position opposite the slots 20 in the connection 50, the ring 32 compresses the liner 30 between itself and the battlements or teeth 22 and pushes the liner 30 towards the slots 20. The parts of Figure 4 are shown in their positions immediately before that the ring is inserted into the liner 30. The ring 32 is pushed into place using a hydraulic cylinder 60 which reacts against a plate 62 connected by connecting rods 64 to a clamping unit 66, arranged or arranged around the connection E'l J7 / r > 7MX 50. The unit 66 includes shims 68, connected to the tie rods 64 and which react against the internal shims 70 and engage with the connection 50. The rod 72 of the cylinder piston 60 acts on a loading plate 74 which is it engages with the ring 32. On the outside of the ring 32 silicone grease is smeared, which reduces friction and makes the insertion of the ring 32 in the liner 30 relatively easy and greatly reduces the force necessary to compress the liner 30 and push it into the slots 20. After the ring 32 has been pushed towards its final position opposite the slots 20, the liner 30 is cut to its final length, i.e. at level with the free end of the connection 50. If instead of the connection 50 the connection type 12 shown is used in Figure 1, the liner 30 would be cut to its final length inside the connection, as shown in the Figure. Figure 5 shows an alternative form of ring used to compress the liner 30 and push it into the slots 20. In this case, the ring 80 is initially of an outer diameter smaller than the inside diameter of the liner 30. The parts are shown in Figure 5 in the positions they occupy immediately before the ring is expanded to compress the liner 30. The ring is placed opposite the 'i í7"i &nt; nMy. slots 20 if a hydraulic cylinder 82 is used to cut the ring 80 outwards. The ring 80 deforms beyond its elastic limit and compresses the liner 30 between itself and the crenellations or teeth 22 of the connection 50. The ring 80 is made of stainless steel or other corrosion resistant metal. The cylinder 82 has a piston rod 84 connected to the wedges 86 (of which only one is shown). The wedges 86 act on the additional wedges 88 (of which only one is shown). The wedges 88 act on the ring 80. When the rod 84 of the piston moves to the left (as seen in the Figure) the wedges 88 move outwards, which in turn pushes the ring 80 outwards, beyond of its elastic limit. Figure 6 shows another alternative method of using a ring to push liner 30 into slots 20 in connection 50. Ring 90 initially has an outside diameter smaller than the inside diameter of liner 30. In Figure 6 , the parts are shown immediately before the ring expands. As soon as anything, a mandrel 91 is inserted into the liner 30. The far left side (as seen in Figure 6) of the mandrel 91 has a diameter approximately equal to the internal diameter of the liner 30. The mandrel 91 is connected to a pull rod 92 connected to a hydraulic cylindrical (not shown). Next, the ring 90 is placed in the opposite position to the slots 20 and, then, a tubular member 94 of steel of the same outer diameter as the ring 90, is placed to the right of the ring 90 as seen in the Figure. The member 94 is restricted against movement to the right. Next, the hydraulic cylinder is operated to push the mandrel 91 to the right (as seen in Figure 6) on the ring 90. The ring 90 expands outward beyond its elastic limit. The thickness of the ring 90 is selected such that, when it has been expanded by the mandrel 91, it compresses the liner 30 between itself and the battlements or teeth 22 and pushes the liner 30 into the slots 20. After the mandrel 91 has expanded to the ring 90, the member 94 is removed from the liner 30 and then the mandrel 91 can also be removed from the liner 30. Figure 7 shows a modified form of connection that can be used, wherein the tube is required to to some other piece of tube type, such as for example a valve. In this case, it is required that the union be by means of a screwed unit instead of E'137"M" join the parts by welding The connection 100 in this case has an integral external flange 102 having a working face or front 104 extending radially outwardly from the end of the connection remote from the end which it is welded at 14 to the tube 10. The connection 100 is recessed at 116 and the high-alloy corrosion-resistant plating material 118 is deposited as a weld deposit on the connection 100 in the area of the recess 116. The connection 100 also it is recessed at 120 on the working face or front 120, including the formation of an annular groove 122. The plating 118 is deposited in a contiguous layer not only on the area 116 but also on the recess area 120 that includes the groove 122. The plating 118 also forms an annular groove 124 on the groove 122. The groove 124 partially accommodates or accommodates a ring-type steel joint 126. This gasket is also partially ad The other piece of tube 132 may be identical to the connection 10T. Alternatively, the other piece of tube 132 can be made entirely of corrosion-resistant metal, such as, for example, stainless steel.

J1ci / 07MX The tab 102 has screw holes 136 (of which only one is shown). The connection 100 is connected to the other connection 132 or to the other piece of tube 132, by means of screws (not shown) passing through screw holes 136 adapted with nuts (not shown) and tightened. The steel gasket 126 is compressed between the flanges. As a further alternative to the construction shown in Figure 7, the entire connection can be made of corrosion-resistant metal (e.g., stainless steel). In this case, of course plating would not be used. Although the connection shown in Figure 7 has been described as being used to join a tube with some other type of tube-like part, the connection shown in Figure 7 can of course be used to join two tubes. As a matter of choice with the different connections described herein, any of the methods described with reference to Figures 1, 4, 5, 6 and 7 can be used to use a ring to push the liner into the grooves. In the foregoing, any of the pieces of tube 10 or connections 12, 50 or 100 may be cast iron and any weld including pieces of cast iron shall be made in the proper manner known for the cast iron.

E'l j7"-, / 7MX

Claims (11)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. A method for joining two pieces of tube that comprises joining, at the ends of Each piece, a metallic tubular connection, each connection has an internal surface formed of corrosion resistant metal that extends to the free end of the connection and the inner surface has grooves separated by crenellations or teeth; lining the parts with thermoplastic liners, insert a respective corrosion-resistant metal ring in each connection to compress the liner and push it into the grooves of the connection, - and join the connections by welding. A method according to claim 1, wherein after each piece of tube has been lined, in each case the liner is allowed to relax for a period, subsequently a respective ring is pushed towards each connection, then the lining , in each case, it is cut to the final length. 3. A method according to claim 1 or 2, wherein the lining, in the case of each piece of tube, is cut within the connection leaving a connecting section without < 1 i7 / • 'MX lining; subsequently and before the connections are joined by welding, within a connection a ring of lining material is placed and extended from it to the other connection and stretched over the ring, the ring has an external slot that admits a annular body of insulation material that protects the underlying ring to the lining material when the connections are subsequently joined by welding. A method according to any of claims 1 to 3, wherein instead of using a respective ring that is forcedly inserted into the connection, a respective ring of smaller size is housed in each connection and, then, the ring is Forced outwardly to compress the liner and push it into the grooves of the connection. 5. A method according to any of claims 1 to 4, wherein each connection has an external flange at its free end and in which instead of joining the connections by welding, the connections are joined with screws that pass to through the tabs of the connections, or one of the two pieces of tube is made of corrosion-resistant metal and does not have a connection but has an external flange, and the connection and the piece of tube are joined by screws passing them through of the eyelashes, the piece of tube does not contain a liner or a E i '7r, / 17MX ring. A pipe connection for use in the method according to claim 1, comprises a length of corrosion-resistant metal pipe and whose internal surface has grooves separated by crenellations or teeth and a corrosion-resistant metal ring having a diameter smaller than the internal diameter of the tube section, during use the connection will be joined by welding to one of the pieces of tube, then, the piece of tube and the connection are lined with a thermoplastic lining, the ring is located inside the lining opposite the slots and pushes the liner into the slots and the connection is welded to a similar connection. A pipe connection according to claim 6, wherein the connection has an integral external flange, the connection will be attached to a similar connection or to another piece of pipe having an integral external flange, by screws passing through the flanges. eyelashes . A pipe connection for use in the method according to claim 1, comprising a length of metal pipe having an internal plating of corrosion-resistant metal, the plating extends to a first end of the connection, the inner surface of the plating has grooves separated by crenellations or teeth and t'l 17 ^, 1 MX a corrosion-resistant metal ring has a smaller diameter than the inner diameter of the pipe section, the connection will be joined, at its opposite end to the first end in use, to one of the pieces of tube, subsequently, the piece of tube and the connection are lined with a thermoplastic lining, then the ring is located inside the lining opposite to the slots and pushes the liner into the slots and the connection is welded to a similar connection. A pipe connection according to claim 8, wherein the connection has an integral external flange having screw holes and a working face extending outwardly from the first end of the connection and having an annular groove formed therein. , the plating extends over the face including the groove in which the plating also provides an annular groove which, during use, partially houses an annular seal which, in use, is compressible against a groove in the flange of the connection similar or another piece of tube, through the action of the screws that pass through the screw holes of the two tabs. 10. Two tube pieces joined by the method according to claim 1, each will be welded to a tubular metal connection having an inner surface E? L? 7r? / P7MX formed of corrosion resistant metal, the surface has internal grooves separated by crenellations or teeth and the two connections will be joined by welding and each one contains a lining of thermoplastic material, each lining is compressed in each connection through a respective metal ring resistant to corrosion, the lining in each case is pushed into the slots in the connection. 11. Two pieces of pipe joined by the method according to claim 10, the two linings are separated by a ring of lining material having an external groove that houses an annular body of insulation material that jumps to the welded joint between the two. connections E'l 17 < 5 / Q7MX