WO2024147769A1

WO2024147769A1 - A method for welding of thermoplastic pipes

Info

Publication number: WO2024147769A1
Application number: PCT/TR2023/050012
Authority: WO
Inventors: Volkan UÇAR; Esra MIRMAHMUTOGULLARI; Ezgi Uçar; Mustafa Dogu
Original assignee: Mir Arastirma Ve Gelistirme Anonim Sirketi
Priority date: 2023-01-06
Filing date: 2023-01-06
Publication date: 2024-07-11

Abstract

The present application proposes a method for fusion welding without damaging the geometric structure of a thin-walled thermoplastic pipe. The present application further proposes a system (100) for implementation of the method. The teaching of the present application provides an increased wall thickness to a pipe end (11) of a thermoplastic pipe (1) with a main axis (A), a pipe face (11) at an end of the pipe (1) with regard to the main axis (A), an inner diameter (Di) orthogonal to the main axis (A), and a pipe wall thickness (W1) in radial directions with regard to the main axis (A). The system (100) includes an end piece (2) that is formed from a thermoplastic building material. The end piece (2) comprises a tubular first end (21) for being introduced into the pipe (1) along the main axis (A). The first end (21) has an outer diameter (Do1) that matches said inner diameter (Di) for provision of a circumferential contact in-between the pipe (1) and said first end (21). The end piece (2) further comprises a tubular second end (22) distal to the first end (21) with regard to the main axis (A). The second end (22) has a second end wall thickness (W2) that is greater than the pipe wall thickness (W1) in radial directions with regard to the main axis (A). The method encompasses arrangement of the measures in relation with the system (100).

Description

A METHOD FOR WELDING OF THERMOPLASTIC PIPES

Technical Field

The present application relates to an improvement in welding of thermoplastic pipes. In particular, the present application relates to a system and method for damage-free fusion welding of a thermoplastic pipe that has a low extent of original wall thickness.

Background

Thermoplastic pipes have various advantages such as low thermal conductivity, high chemical resistance, galvanic corrosion resistance, flexibility and low density. Extension by end-to-end connection of thermoplastic pipes can be easily performed using simple welding machines. There are numerous methods available for use in connection of pipes that are made of thermoplastic materials and various other materials. Gluing and mechanical attachment can be used on any plastics, whereas the welding can be used only in thermoplastics. Welding is known to provide a comparatively increased extent of stability.

Extension of thermoplastic pipes for sanitary piping is performed by connecting the pipes with each other by end-to-end connection methods, thereby forming a pipeline.

In welding of thermoplastic pipes using a thermal source, two thermoplastic surfaces are heated into a fused state, and welded to each other by exertion of mechanical pressure. This procedure results in a homogeneous attachment inbetween the two welded surfaces. US 2014/0375047 Al discloses several methods that are used in connecting thermoplastic pipes, including socket fusion welding, butt fusion and electro fusion welding. Electrofusion includes the cleaning of corresponding ends of two pipes, preparation with stripping said ends, and introduction of the ends into a connecting socket that is provided with a heating coil. This is followed by mechanical matching of the ends, and provision of a voltage to the coil to heat and partially fuse the outer surfaces of the ends along with the inner surface of the socket. The fused portions are then cooled to form a stable connection between the pipes (Gierulski et al., "Electrofusion welding and reinforced thermoplastic pipes - A review", Journal of Reinforced Plastics and Composites, 2022, Vol.41(3-4) 147-163; DOI: 10.1177/07316844211051207). Electrofusion bears a high equipment cost and an increased difficulty in terms of complexity.

As a method that finds a wide industrial use, butt fusion is used for connecting pipes with outer diameters between 50 mm and 2500 mm. This method includes the heating of opposing surfaces of the ends of two corresponding pipes into a fused state, followed by axial compression of the two pipes towards each other. In butt fusion, the opposing ends of two corresponding pipes are required to be geometrically identical. According to US 2014/0375047 Al, the main shortcoming of the method is the head loss caused by the internal bead of thermoplastic material formed at the joint seam.

Socket fusion welding, or socket welding is a method used on polymers such as polypropylene (PP), polyethylene (PE), polybutylene and polyvinylidene fluoride (PVDF) that are employed in chemical process applications. The method employs a welding machine with a heating element. The heating element has a socket as a first side to receive and heat an outer surface of a first pipe, and a spigot as a second side to be introduced into a second pipe for heating an inner surface thereof. Upon heating into a fused state, the first and second pipes are removed from the heating element, and introduced to one another, thereby the fused outer surface of the first pipe is welded to the fused inner surface of the second pipe. For achieving the extension, the outer diameter of the first pipe is to be substantially identical to the inner diameter of the second pipe. This method is not suitable for use in welding of pipes that have low wall thicknesses such as lower than 2 mm, for instance, 1 mm. This is because such thin-walled thermoplastic pipes deform at introducing to one another when at a fused state.

Butt fusion and socket fusion generally require the use of pipes with high wall thicknesses and high extent of pressure stability, therefore increasing the overall cost of the pipeline.

US 7,601,931 B2 discloses a method for production of end connections with a minimized labour and decreased material consumption. A flange ring is provided around an end of a pipe. The flange ring is obtained by cutting a small length of plastic pipe that has an inner diameter corresponding to the outer diameter of the pipe on which the flange ring is to be coaxially disposed.

US 3,013,925 A discloses a method and means for butt welding of thermoplastic pipes. The publication aims to provide an unaffected inner diameter at the connection zone.

Unfortunately, these methods do not allow a flawless welding of thermoplastic pipes with low wall thicknesses with a simple equipment and procedure. Such pipes tend to deform under axial compression when at fused or softened state. This result in discrepancies in terms of reproducibility of welding, mechanical stability, uniformity in flow path cross-sectional area and flow characteristics at the extension zone.

Thin-walled pipes are usually connected to each other via multi-part mechanical fitting components that are made of various building materials different from those of the respective pipes. By being formed from numerous different building materials that can also include metals, the thermal expansion behaviour thereof in radial directions differ from that of the thermoplastic material of the respective pipes. This results in leakages at variable temperatures. Furthermore, the fitting components are expensive and dramatically increase the overall cost of the respective pipeline.

Accordingly, structural solutions shall be sought for enabling and enhancing the extension of thin-walled thermoplastic pipes by decreasing the process difficulty and overall costs.

Summary

Primary object of the present application is to overcome the above-mentioned shortcomings of the prior art. Another object of the present application is to propose a method for extension of thin-walled thermoplastic pipes that bears minimized extent of costs and complexity.

The present application achieves these objects by the technical features that constitute the appended independent claim. The present application accordingly proposes a system and method.

The system proposed in the present application is arranged for provision of an increased wall thickness to a pipe end of a thermoplastic pipe. Within the present context, the pipe has a main axis, a pipe face at an end of the pipe with regard to the main axis, an inner diameter orthogonal to the main axis, and a pipe wall thickness in radial directions with regard to the main axis. The system includes an end piece that is formed from a thermoplastic building material.

The end piece comprises a tubular first end for being introduced into the pipe along the main axis. The first end has an outer diameter that matches said inner diameter of the pipe, for provision of a circumferential contact in-between the pipe and said first end. The end piece further comprises a tubular second end distal to the first end with regard to the main axis. The second end has a second end wall thickness that is greater than the pipe wall thickness in radial directions with regard to the main axis. In a preferred embodiment, the system further comprises a welding mandrel. The welding mandrel has a mandrel tip for being introduced into the first end through the second end along the main axis. The mandrel tip has an outer wall for geometrically matching with an inner wall of the first end around the main axis when in use.

Preferably, the mandrel tip is provided with a shaft that extends along the main axis when in use.

Preferably, the system further comprises a threaded nut around the shaft, and the second end of the end piece is provided with corresponding threads for releasably engaging with the threaded nut.

Preferably, the system further comprises a spigot and a socket for sandwiching a heating means. The spigot and socket are arranged for conducting heat for fusion of respective thermoplastic building materials of the pipe and end piece, from the heating means. The spigot and the socket are shaped and sized to geometrically match with the inner wall of the pipe and the outer wall of the first end of the end piece, respectively.

Preferably, the system further comprises a welding die that is shaped and sized to sandwich the pipe. The welding die is arranged for geometrically matching an outer wall of the pipe. Thus, the welding die is inevitably further arranged for supporting the pipe against radial forces exerted onto the inner wall of the pipe away from the main axis when in use.

Accordingly, the present application also proposes a method for extending a pipe that is formed from a thermoplastic building material. Within the present context, the pipe is arranged to have a main axis, a pipe face at an end of the pipe with regard to the main axis, an inner diameter orthogonal to the main axis, and a pipe wall thickness in radial directions with regard to the main axis. The method includes the following steps: step (a): provision of an end piece that is formed from a thermoplastic building material; provision of the end piece with a tubular first end for being introduced into the pipe along the main axis; arrangement of the first end with an outer diameter that matches said inner diameter for provision of a circumferential contact in-between the pipe and said first end; and step (b): arrangement of the end piece with a tubular second end distal to the first end with regard to the main axis; arrangement of the second end with a second end wall thickness that is greater than the pipe wall thickness in radial directions with regard to the main axis.

The method can further include the following sequential steps: step (c): heating an inner wall of the pipe and an outer wall of the first end of the end piece to respective fusion temperature(s) of the thermoplastic building materials of the pipe and the end piece; and then step (d): introduction of the first end into the pipe for provision of a circumferential fusion welding in-between the pipe and the end piece.

Preferably, the method includes the arrangement of the pipe wall thickness to be 1 mm or higher, preferably within a range between 1 mm and 2.5 mm; and the arrangement of the second end wall thickness to be 3 mm or higher.

As a preparative step prior to the step (c), the method can include the formation of pipe face by cutting the pipe orthogonal to the main axis to form a pipe end having a substantially planar, annular surface extending on a radial direction with regard to said main axis. Such method can further include arrangement of the end piece with an abutting surface around the first end, for matching and covering the pipe face, upon complete introduction of the first end into the pipe.

The method can preferably include the arrangement of the first end of the end piece with a frusto-conical side surface that is radially narrower in diameter at a tip portion distal to the second end with regard to the main axis.

In a preferred variation, the method includes the selection of the thermoplastic building materials of the pipe and end piece to have overlapping fusion temperatures; more preferably, to have identical fusion temperatures.

The method can preferably include the provision of a welding mandrel with a mandrel tip that is arranged for being introduced into the first end through the second end along the main axis.

Preferably, the method further includes the provision of the mandrel tip with an outer wall around the main axis to geometrically match with an inner wall of the first end.

Preferably, the method further includes the provision of the mandrel tip with a shaft that is arranged to extend along the main axis when in use. Preferably, the method further includes the provision of a threaded nut around the shaft, and the provision of the second end of the end piece with corresponding threads for releasable attachment between the nut and the end piece.

The method can preferably include the arrangement of a spigot and a socket for sandwiching a heating means. Such method further includes the arrangement of the spigot and socket for conducting heat for fusion of the respective thermoplastic building materials of the pipe and end piece, from the heating means; arrangement of the shapes and sizes of the spigot and of the socket to geometrically match with the inner wall of the pipe and the outer wall of the first end of the end piece, respectively.

The method can preferably further include the arrangement of a welding die that is shaped and sized for sandwiching the pipe, that is, for geometrically matching an outer wall of the pipe, and thus for supporting the pipe against radial forces exerted onto the inner wall of the pipe away from the main axis. Within this context, the welding die can be formed from a rigid material that retains its geometry at fusion temperature of the pipe.

Brief Description of Figures

The figures, whose brief explanations are herewith provided, are solely intended for providing a better understanding of the present invention and are as such not intended to define the scope of protection or the context in which the scope is to be interpreted in the absence of the description.

Fig. la is section view of an exemplary end piece according to the present application, adapted for a pipe with an inner diameter.

Fig. lb is section view of another exemplary end piece according to the present application, adapted for another pipe with a greater inner diameter in comparison with that considered in connection with Fig. la.

Fig.2a is section view of an exemplary mandrel tip for use with the end piece that is shown in Fig. la.

Fig.2b is section view of another exemplary mandrel tip for use with the end piece that is shown in Fig. lb. Fig.3a is section view of an exemplary socket for use with an end piece within the context of the present application.

Fig.3b is section view of an exemplary spigot for being matched and releasably attached with the socket shown in Fig.3a, using a threaded bolt for axially connecting the socket to the spigot.

Fig.4a is section view of another exemplary socket for use with an end piece within the context of the present application.

Fig.4b is section view of an exemplary spigot for being matched and releasably attached with the socket shown in Fig.4a, using a threaded bolt for axially connecting the socket to the spigot.

Fig.5a is section view of another exemplary socket for use with an end piece within the context of the present application.

Fig.5b is section view of an exemplary spigot for being matched and releasably attached with the socket shown in Fig.5a, using a threaded bolt for axially connecting the socket to the spigot.

Fig.6a is exploded perspective view of an exemplary system for implementing the method within the context of the present application.

Fig.6b is exploded perspective view of another exemplary system for implementing the method within the context of the present application. Here, the system is provided with a welding die.

Fig.7a represents the preparation of the system that is shown in Fig.6a, for implementation of the method. Fig.7b represents the preparation of the system that is shown in Fig.6b, for implementation of the method.

Fig.8a represents the implementation of the step (c) of the method using the system that is shown in Fig.6a.

Fig.8b represents the implementation of the step (c) of the method using the system that is shown in Fig.6b.

Fig.9a represents the implementation of the step (d), after the step (c) of the method within the context of the present application.

Fig.9b represents the implementation of the step (d), after the step (c) of the method within the context of the present application, that includes the use of welding die.

Fig.10 is side view of the pipe that is fusion welded with the end piece upon the step (d). As a result, a second wall thickness is available at the extended pipe, instead of the relatively smaller original pipe wall thickness.

Fig.11 exemplifies a preparation for attaching of the thick-walled second end that is integrated to the pipe, with an exemplary further piping element, using fusion welding.

Fig.12 shows the heating of corresponding surfaces on the exemplary further piping element and on the second end of that is integrated to the pipe, using a respective couple of spigot and socket that sandwich a heating means of a fusion welding device.

Fig. 13a shows a section view of the exemplary further piping element that is fusion welded to the thick-walled second end that is integrated to the pipe. Fig. 13b show a side view based on the section view that is shown in Fig.13a.

Detailed Description

Referring to the figures described above, the present application proposes a method for extending a thermoplastic pipe (1) with a main axis (A), a pipe face (11) at an end of the pipe (1) with regard to the main axis (A), an inner diameter (Di) orthogonal to the main axis (A), and a pipe wall thickness (Wl) in radial directions with regard to the main axis (A). The method can be considered to include the provision of such pipe (1) as a step (a). Within the context of the present application, the pipe wall thickness (Wl) corresponds to an "original wall thickness" of the pipe (1).

The method further includes provision of an end piece (2) that is formed from a thermoplastic material. Fig. la shows section view of an exemplary end piece (2) according to the present application, adapted for a pipe (1) with an inner diameter (Di). Fig. lb shows section view of another exemplary end piece (2) according to the present application, adapted for another pipe (1) with a greater inner diameter (Di) in comparison with that considered in connection with Fig. la.

The end piece (2) is provided with a tubular first end (21) for being introduced into such respective pipe (1) along the main axis (A). The first end (21) is arranged with an outer diameter (Doi) that matches said inner diameter (Di) for provision of a circumferential contact in-between the pipe (1) and said first end (21).

The end piece (2) further comprises a tubular second end (22) distal to the first end (21) with regard to the main axis (A). The second end (22) is arranged to have a second end wall thickness (W2) that is greater than the pipe wall thickness (Wl) in radial directions with regard to the main axis (A). The method can be considered to include the provision of such end piece (2) as a step (b).

The method further includes the following sequential steps of heating an inner wall of the pipe (1) and an outer wall of the first end (21) to respective fusion temperature(s) of the thermoplastic building materials of the pipe (1) and the end piece (2); and then introduction of the first end (21) into the pipe (1) for provision of a circumferential fusion welding in-between the pipe (1) and the end piece (2). These sequential steps can be considered as a step (c) and step (d), respectively. In step (d), said circumferential fusion welding can be performed by compressing of the end piece (2) towards the pipe (1) along the main axis (A), until the temperatures of the inner wall of the pipe (1) in contact with the outer wall of the first end (21) drop below said respective fusion temperatures; which can be considered to require only a few seconds. Said fusion temperature(s) can be considered as melting points or melting temperature ranges of the respective thermoplastic building materials of the pipe (1) and end piece (2).

The method results in obtention of a pipe (1) that is integrated (here: fused) to an end piece (2) with a second end wall thickness (W2) that is greater than the original pipe wall thickness (Wl). So, upon the fusion, the pipe (1) is practically provided with a new thermoplastic end (here, second end (22)) that has an increased extent of wall thickness that allows a safe and flawless further extension using thermal processes such as fusion welding.

In a preferred exemplary variation of the method, the pipe wall thickness (Wl) is arranged to be 1 mm or higher, for instance within a range between 1 mm and 2.5 mm; and the second end wall thickness (W2) is arranged to be 3 mm or higher.

The pipe face (11) can be obtained by cutting the pipe (1) orthogonal to the main axis (A) to form a pipe end (in other terms, a butt) having a substantially planar, annular surface extending on a radial direction with regard to said main axis (A). The end piece (2) can be configured to have an abutting surface (23) around the first end (21), arranged to match and cover the pipe face (11) when the first end (21) is completely received by the pipe (1).

The first end (21) of the end piece (2) can be arranged with a frusto-conical side surface that is radially narrower in diameter at a tip portion distal to the second end (22) with regard to the main axis (A). That is, in such embodiment, the first end has a tubular structure with an outer diameter that decreases in an axial direction away from the second end (22). This embodiment allows a facilitated introduction of the first end (21) into the pipe (1).

Thermoplastic building materials of the pipe (1) and end piece (2) can be arranged to have overlapping fusion temperatures, or identical fusion temperatures. Here, the fusion temperature corresponds to a melting point or melting temperature range of respective thermoplastic building material(s) of the pipe (1) and end piece (2). For instance, the building materials of the pipe (1) and end piece (2) can include same thermoplastics with each other.

The method can further include the provision of a welding mandrel (3) with a mandrel tip (31), for being introduced into the first end (21) through the second end (22) along the main axis (A). Fig.2a is section view of an exemplary mandrel tip (31) for use with the end piece (2) that is shown in Fig. la. Fig.2b is section view of another exemplary mandrel tip (31) for use with the end piece (2) that is shown in Fig. lb.

The mandrel tip (31) can be arranged from a building material that retains its geometric shape at temperatures used in the step (c). For instance, the mandrel tip (31) can be formed from a metallic material or an alloy. The mandrel tip (31) is provided with an outer wall (311) around the main axis (A) to geometrically match with an inner wall (211) of the first end (21). Such introduction of the mandrel tip (31) into the end piece (2) can be performed as a preparation to the step (c) and/or to the step (d). This measure provides support to the first end (21) against deformations under radial forces that are onto the first end (21) towards the main axis (A) at the step (c) and step (d) discussed above.

The mandrel tip (31) can be arranged with a shaft (32) extending along the main axis (A) when in use. The introduction and removal of the mandrel tip (31) into/from the end piece (2) can be performed over the shaft (32).

Preferably, a threaded nut (33) can be provided around the shaft (32), and the second end (22) of the end piece (2) can be provided with corresponding threads (24) for releasable attachment between the nut (33) and the end piece (2). Accordingly, the method can include attaching the nut (33) to the end piece (2) as a preparation to the step (c); and detaching the nut (33) from the end piece (2) after completion of the step (d). Removal of the mandrel tip (31) from the end piece (2) after the step (d) can be safely performed by an operator; by gripping the nut (33) with a hand, and then translating the shaft (32) along the main axis (A) away from the end piece (2), without necessitating the manual exertion of radial force components to the mandrel tip (31). Thus, inner walls of the end piece (2), particularly at the first end (21), are protected from mechanical damage during the operation.

The method can be considered to include the provision of a spigot (41) and a socket (42) that are arranged for sandwiching a heating element (4) that can be an electric-powered fusion melting heater. The spigot (41) and socket (42) are further arranged for conducting heat for fusion of the respective thermoplastic building materials of the pipe (1) and end piece (2), from the heating element (4). To this end, the spigot (41) and socket (42) can be formed from a metallic material. The spigot (41) is shaped and sized to geometrically match with the inner wall of the pipe (1). and the socket (42) is shaped and sized to geometrically match the outer wall of the first end (21) of the end piece (2). Fig.3a is section view of an exemplary socket (42) for use with an end piece (2) within the context of the present application. Fig.3b is section view of an exemplary spigot (41) for being matched and releasably attached with the socket (42) shown in Fig.3a; e.g., using a threaded bolt for axially connecting the socket (42) to the spigot (41). Fig.4a is section view of another exemplary socket (42) for use with an end piece (2) within the context of the present application. Fig.4b is section view of an exemplary spigot (41) for being matched and releasably attached with the socket (42) shown in Fig.4a; e.g., using a threaded bolt for axially connecting the socket (42) to the spigot (41). Fig.5a is section view of another exemplary socket (42) for use with an end piece (2) within the context of the present application. Fig.5b is section view of an exemplary spigot (41) for being matched and releasably attached with the socket (42) shown in Fig.5a, using a threaded bolt for axially connecting the socket (42) to the spigot (41).

Fig.6a is exploded perspective view of an exemplary system (100) for implementing the method within the context of the present application. Fig.7a visualizes an exemplary preparation of the system (100) that is shown in Fig.6a. Here, the end piece (2) is engaged with a welding mandrel (3) for facilitated and stabilized axial introduction of the first end (21) of the end piece (2) into the socket (42). The pipe (1) is aligned with the spigot (41) for axially receiving the spigot (41).

Fig.8a represents the implementation of the step (c) of the method using the system (100) that is shown in Fig.6a. Here, the first end (21) of the end piece (2) that is engaged with the welding mandrel (3) is axially introduced into the socket (42). The spigot (41) is axially introduced into the pipe (1).

Fig.9a visualizes the implementation of the step (d), after the step (c) of the method within the context of the present application. Here, the first end (21) of the end piece (2) is introduced into the pipe (1) and the end piece (2) is axially compressed towards/into the pipe (1) using the welding mandrel (3). The geometric form of the first end (21) of the end piece (2) is retained by means of the corresponding outer geometric form of the mandrel tip (31), against inwardly exerted radial pressures from the pipe (1).

In a preferred variation, the method can further include the use of a welding die (5) that is shaped and sized to sandwich the pipe (1), during the step (c) and step (d). It can be thus considered that the welding die (5) is arranged for geometrically matching an outer wall of the pipe (1), as well as for supporting the pipe (1) against radial forces exerted onto the inner wall of the pipe (1) away from the main axis (A), during the step (c) and step (d). Fig.6b is exploded perspective view of an exemplary system (100) that is provided with a welding die (5).

Preferably, the welding die (5) can include a first part (51) and a complementary second part (52), that have corresponding C-shaped radial sections along the main axis (A) when in use. Thus, the outer wall of the pipe (1) is sandwiched and circumferentially contacted by opposing complementary inner surfaces of the first part (51) and second part (52) along an axial length of the welding die (5) with regard to the main axis (A). The first part (51) and second part (52) can be arranged to be pivotally connected to each other through a hinge; for instance, over a respective couple of arms that are secured (e.g., welded) to the first part (51) and second part (52).

Fig.7b represents the preparation of the system (100) that is shown in Fig.6b, for implementation of the method in provision of a non-reinforced thermoplastic pipe (1) that has a low original pipe wall thickness (Wl), with a higher wall thickness (W2) using fusion welding. Here, the end piece (2) is engaged with a welding mandrel (3) for facilitated and stabilized axial introduction of the first end (21) of the end piece (2) into the socket (42). The pipe (1) is aligned with the spigot (41) for axially receiving the spigot (41). An end portion of the pipe that includes the pipe face (11) is sandwiched in-between the opposing first part (51) and second part (52) of the welding die (5).

Fig.8b visualizes the implementation of the step (c) of the method using the system (100) that is shown in Fig.6b. Here, the first end (21) of the end piece (2) that is engaged with the welding mandrel (3) is axially introduced into the socket (42). The spigot (41) is axially introduced into the pipe (1). The pipe (1) is protected by the welding die (5), against outwardly exerted radial forces from the heated spigot (41), to eliminate potential geometric damages when the pipe (1) is softened at the respective fusion temperature.

Fig.9b visualizes the implementation of the step (d), after the step (c) of the method within the context of the present application, that includes the use of welding die (5). Here, the first end (21) of the end piece (2) is introduced into the pipe (1) and the end piece (2) is axially compressed towards the pipe (1) using the welding mandrel (3). The geometric form of the first end (21) of the end piece (2) is retained by means of the corresponding outer geometric form of the mandrel tip (31), against inwardly exerted radial pressures from the pipe (1) and from the welding die (5).

In an exemplary case, the pipe (1) can be arranged with a single wall or single layer formed from a thermoplastic material; that is, the pipe (1) can be a nonreinforced thermoplastic pipe. In such case, the use of welding die (5) facilitates or possibly, even enables the retention of the pipe geometry, even when the pipe has a very low thickness such as that within the range between 1 mm and 2 mm; e.g., 1 mm.

In an alternative case where the pipe (1) is provided with one or more means for reinforcement that is arranged for retaining the geometry of the pipe (1) against radial forces away from the main axis (A), the geometry of the pipe (1) is retained even in the absence of the welding die (5). Fig.10 is exemplary side view of the pipe (1) that is fusion welded with the end piece (2) upon the step (d). As a result, a second wall thickness (W2) is available by extension of the pipe (1) with the end piece (2), instead of the relatively smaller original pipe wall thickness (Wl). The extension is provided by the end piece (2) that has the second end (22) with the second end wall thickness (W2) that is comparatively greater than the original pipe wall thickness (Wl). Thus, the thick-walled second end (22) that is integrated to the pipe (1) is easily attachable to a further piping element (6) using fusion welding without suffering geometric damage.

Fig.11 visualizes an exemplary preparation for attaching of the thick-walled second end (22) that is integrated to the pipe (1), with an exemplary further piping element (6), using fusion welding.

Fig.12 shows the heating of corresponding surfaces on the exemplary further piping element (6) and on the second end (22) that is integrated to the pipe (1), using a respective couple of spigot (41) and socket (42) that sandwich a heating element (4) of a fusion welding device.

Fig. 13a is a section view that shows the exemplary further piping element (6) fusion welded to the thick-walled second end (22) of the end piece (2) that is integrated to the pipe (1). Fig. 13b show a side view based on the section view that is shown in Fig.13a.

In accordance with the considerations above, the present invention also proposes a system (100) for implementation of the method discussed above. Hence, the system (100) is for provision of an increased wall thickness to a pipe end (11) of a thermoplastic pipe (1) with a main axis (A), a pipe face (11) at an end of the pipe (1) with regard to the main axis (A), an inner diameter (Di) orthogonal to the main axis (A), and a pipe wall thickness (Wl) in radial directions with regard to the main axis (A). The system (100) includes an end piece (2) that is formed from a thermoplastic building material.

The end piece (2) comprises a tubular first end (21) for being introduced into the pipe (1) along the main axis (A). The first end (21) has an outer diameter (Doi) that matches said inner diameter (Di) for provision of a circumferential contact in-between the pipe (1) and said first end (21).

The end piece (2) further comprises a tubular second end (22) distal to the first end (21) with regard to the main axis (A). The second end (22) has a second end wall thickness (W2) that is greater than the pipe wall thickness (Wl) in radial directions with regard to the main axis (A)

The system (100) can further comprise a welding mandrel (3) that is provided with a mandrel tip (31) for being introduced into the first end (21) through the second end (22) along the main axis (A). The mandrel tip (31) has an outer wall for geometrically matching with an inner wall of the first end (21) around the main axis (A) when in use.

The mandrel tip (31) can be provided with a shaft (32) that extends along the main axis (A) when in use.

The system (100) can further comprise a threaded nut (33) around the shaft (32), and the second end (22) of the end piece (2) can be provided with corresponding threads (24) for releasably engaging with the threaded nut (33).

The system (100) can further comprise a spigot (41) and a socket (42) for sandwiching a heating element (4). The spigot (41) and socket (42) can be arranged for conducting heat for fusion of respective thermoplastic building materials of the pipe (1) and end piece (2), from the heating element (4). The spigot (41) and the socket (42) can be shaped and sized to geometrically match with the inner wall of the pipe (1) and the outer wall of the first end (21) of the end piece (2), respectively.

The system (100) can comprise a welding die (5) that is shaped and sized for sandwiching the pipe (1), that is, for geometrically matching an outer wall of the pipe (1), and thus, for supporting the pipe (1) against radial forces exerted onto the inner wall of the pipe (1) away from the main axis (A) when in use.

It can be considered that, prior to the implementation of the method, a pipe face (11) can be formed by cutting the pipe (1) orthogonal to the main axis (A), thereby obtaining a pipe end with a substantially planar, annular surface extending on a radial direction with regard to said main axis (A). In a preferred embodiment according to this consideration; the end piece (2) can comprise an abutting surface (23) around the first end (21), arranged for matching and covering the pipe face (11), upon complete introduction of the first end (21) into the pipe (1).

The first end (21) of the end piece (2) can have a frusto-conical side surface (that is, outer surface) diameter of which radially decreases towards at a tip portion distal to the second end (22) with regard to the main axis (A).

The thermoplastic building materials of the pipe (1) and end piece (2) to can have overlapping fusion temperatures; more preferably, to have identical fusion temperatures. This provides a simultaneous softening or melting of the corresponding surfaces of the pipe (1) and end piece (2) to be subjected to fusion welding with each other. Reference si'

1 Pipe 11 pipe face

2 end piece

21 first end 211 inner wall (of the first end) 22 second end

23 abutting surface

24 threads 3 welding mandrel

31 mandrel tip 311 outer wall (of the mandrel) 32 shaft

33 nut 4 heating element 41 spigot

42 socket 5 welding die

51 first part

52 second part 6 further piping element

100 system A main axis Di inner diameter (of the pipe)

Doi outer diameter (of the first end) W1 (original) pipe wall thickness W2 second end wall thickness

Claims

1. A system (100) for provision of an increased wall thickness to a pipe end (11) of a thermoplastic pipe (1) with a main axis (A), a pipe face (11) at an end of the pipe (1) with regard to the main axis (A), an inner diameter (Di) orthogonal to the main axis (A), and a pipe wall thickness (Wl) in radial directions with regard to the main axis (A); wherein the system (100) includes an end piece (2) that is formed from a thermoplastic building material; the end piece (2) comprises a tubular first end (21) for being introduced into the pipe (1) along the main axis (A); the first end (21) having an outer diameter (Doi) that matches said inner diameter (Di) for provision of a circumferential contact in-between the pipe (1) and said first end (21); the end piece (2) further comprises a tubular second end (22) distal to the first end (21) with regard to the main axis (A); the second end (22) has a second end wall thickness (W2) that is greater than the pipe wall thickness (Wl) in radial directions with regard to the main axis (A).

2. System (100) according to claim 1, further comprising a welding mandrel (3) having a mandrel tip (31) for being introduced into the first end (21) through the second end (22) along the main axis (A); wherein the mandrel tip (31) has an outer wall for geometrically matching with an inner wall of the first end (21) around the main axis (A) when in use.

3. System (100) according to claim 2, wherein the mandrel tip (31) is provided with a shaft (32) that extends along the main axis (A) when in use.

4. System (100) according to any of claims 2 or 3, further comprising a threaded nut (33) around the shaft (32), and the second end (22) of the end piece (2) is provided with corresponding threads (24) for releasably engaging with the threaded nut (33).

5. System (100) according to any of claims 1 to 4, further comprising a spigot (41) and a socket (42) for sandwiching a heating element (4); wherein the spigot (41) and socket (42) are arranged for conducting heat for fusion of respective thermoplastic building materials of the pipe (1) and end piece (2), from the heating element (4); the spigot (41) and the socket (42) are shaped and sized to geometrically match with the inner wall of the pipe (1) and the outer wall of the first end (21) of the end piece (2), respectively.

6. System (100) according to any of claims 1 to 5, further comprising a welding die (5) shaped and sized to sandwich the pipe (1), for geometrically matching an outer wall of the pipe (1), and for supporting the pipe (1) against radial forces exerted onto the inner wall of the pipe (1) away from the main axis (A) when in use.

7. A method for extending a pipe (1) that is formed from a thermoplastic building material; the pipe being arranged to have a main axis (A), a pipe face (11) at an end of the pipe (1) with regard to the main axis (A), an inner diameter (Di) orthogonal to the main axis (A), and a pipe wall thickness (Wl) in radial directions with regard to the main axis (A); wherein the method includes the following steps: step (a): provision of an end piece (2) that is formed from a thermoplastic building material; provision of the end piece (2) with a tubular first end (21) for being introduced into the pipe (1) along the main axis (A); arrangement of the first end (21) with an outer diameter (Doi) that matches said inner diameter (Di) for provision of a circumferential contact in-between the pipe (1) and said first end (21); step (b): arrangement of the end piece (2) with a tubular second end (22) distal to the first end (21) with regard to the main axis (A); arrangement of the second end (22) with a second end wall thickness (W2) that is greater than the pipe wall thickness (Wl) in radial directions with regard to the main axis (A).

8. Method according to claim 7, further including the following sequential steps: step (c): heating an inner wall of the pipe (1) and an outer wall of the first end (21) of the end piece to respective fusion temperature(s) of the thermoplastic building materials of the pipe (1) and the end piece (2); step (d): introduction of the first end (21) into the pipe (1) for provision of a circumferential fusion welding in-between the pipe (1) and the end piece (2).

9. Method according to any of claims 7 or 8, including the arrangement of the pipe wall thickness (Wl) to be 1 mm or higher, preferably within a range between 1 mm and 2.5 mm; and the arrangement of the second end wall thickness (W2) to be 3 mm or higher.

10. Method according to any of claims 7 to 9, including the provision of a welding mandrel (3) with a mandrel tip (31), for being introduced into the first end (21) through the second end (22) along the main axis (A).

11. Method according to claim 10, further including the provision of the mandrel tip (31) with an outer wall around the main axis (A) to geometrically match with an inner wall of the first end (21).

12. Method according to any of claims 10 or 11, further including provision of the mandrel tip (31) with a shaft (32) extending along the main axis (A) when in use.

13. Method according to claim 12, including the provision of a threaded nut (33) around the shaft (32), and provision of the second end (22) of the end piece (2) with corresponding threads (24) for releasable attachment between the nut (33) and the end piece (2).

14. Method according to any of claims 7 to 13, further including the arrangement of a spigot (41) and a socket (42) for sandwiching a heating element (4); wherein the method further includes the arrangement of the spigot (41) and socket (42) for conducting heat for fusion of the respective thermoplastic building materials of the pipe (1) and end piece (2), from the heating element (4); arrangement of the shapes and sizes of the spigot (41) and of the socket (42) to geometrically match with the inner wall of the pipe (1) and the outer wall of the first end (21) of the end piece (2), respectively.

15. Method according to any of claims 7 to 14, further including the arrangement of a welding die (5) that is shaped and sized to sandwich the pipe (1), for geometrically matching an outer wall of the pipe (1), and for supporting the pipe (1) against radial forces exerted onto the inner wall of the pipe (1) away from the main axis (A).