System with a device for manufacturing a piping unit and method for manufacturing a piping unit

Abstract

The present invention relates to a system (1) comprising an apparatus (2) for producing a piping unit (5) from a piping (3) having an outer piping surface (8) and a pipe fitting (4) having an outer pipe fitting surface (13), and a method for producing the system (1).

Description

[Technical field]

[0001] The present invention relates to a system that includes an apparatus for fabricating a piping unit from piping having an outer piping surface and a pipe fitting having an outer pipe fitting surface.

[0002] The present invention further relates to a method for manufacturing a piping unit. [Background technology]

[0003] Conventionally, pressure-loaded pipe assemblies are realized in accordance with DIN 11864-3 by grooved and notched clamp fittings, which are respectively welded to the pipe ends. The weld seams of pressure-loaded pipe assemblies must then be subjected to costly post-processing and inspection. A seal, in particular an O-ring, is inserted into the grooved clamp fitting. A clamping device connects the grooved and notched clamp fittings, and a mechanical stop arranged in the grooved clamp fitting ensures that the O-ring is pressed in a defined way. Due to the pressing pressure, the O-ring is partially pushed out of the groove, so that a defined transition is created inside the pipe assembly between the grooved and notched clamp fittings.

[0004] According to another pipe assembly produced in accordance with DIN 32676, the pipe assembly is realized by two welded joints which accommodate a seal. One disadvantage of this pipe assembly is that the weld seams of the pipe assembly, which are under pressure, must subsequently be subjected to a laborious post-processing and inspection. A further disadvantage is that the seals do not have a defined crimping pressure, which is determined by the clamping device.

[0005] It is also known to roll a pipe fitting onto a pipe and to accordingly lock the pipe fitting in place. A method for this is disclosed in DE 10 200 43 336. For this purpose, holes or recesses in the inner wall are provided at individual points in the pipe section of the pipe fitting, into which the pipe engages with a bulge extruded from the inside. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] DE 484 005 A Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is therefore to provide a system with an apparatus for manufacturing a piping unit and a method for manufacturing a piping unit. [Means for solving the problem]

[0008] The object is achieved in a system of the type mentioned at the beginning, in which the device has an annularly structured stress receiving device with a longitudinal central axis and a radially inward stress receiving device inner surface, which is adapted to the outer surface of the pipe and / or the outer surface of the pipe fitting, so that in the operating state the pipe unit to be produced can be at least partially accommodated, and the stress receiving device surrounds the pressing tool in the operating state, so that in the operating state the pipe unit to be produced can be supported during expansion of the pipe by the pressing tool. Advantageously, the system supports the pipe unit, in particular the pipe and / or the pipe fitting, during expansion of the pipe by the pressing tool, expediently a rolling tool, so that the formation of the pipe unit consisting of the combination of the pipe unit and the pipe fitting is carried out in an improved manner. In the simplest case, the system consists only of a stress receiving device.

[0009] Expediently, the system comprises a piping unit having piping and pipe fittings.

[0010] Furthermore, the system expediently also comprises a pressure tool for expanding the pipes.

[0011] According to an additional advantageous configuration of the system, the inner surface of the stressed device is stepped, which provides the possibility for the inner surface of the stressed device to be adapted to different contours and / or areas of the piping units produced from the pipes and the pipe fittings.

[0012] Furthermore, in a preferred development, the system comprises a stressed device, which has a stressed device ring body, which has two ring body elements which together form the stressed device inner surface, each having a first end section and a second end section, the first end sections being arranged pivotally relative to one another and on each second end section a coupling element is arranged, which coupling elements are suitable for cooperating with one another to detachably couple the second end sections. Such a preferred development has the advantage that the stressed device can be easily arranged on pipes and pipe fittings.

[0013] More preferably, the inner surface of the stress receiving device has at least one annular groove for at least partially accommodating the fitting, which axially positions and holds the fitting, and thus at least indirectly the piping, in this position.

[0014] Advantageously, the stress-receiving device accordingly forms a radially inwardly extending annular projection, which is defined on the one hand by the first axial stress-receiving device end face and on the other hand by a lateral groove-defining surface of at least one annular groove, remote from the first axial stress-receiving device end face. According to one development of the system in this respect, the radially inwardly extending annular projection extends radially inwardly to such an extent that it forms a stop for the pipe to be inserted into the pipe joint. The radially inwardly extending annular projection formed as a stop allows for easy positioning and / or fixing of the pipe during expansion of the pipe by means of a pressure tool.

[0015] In addition, according to an additional preferred configuration of the system, the stress-receiving device has a second axial stress-receiving device end face facing away from the first axial stress-receiving device end face, which is stepped to form an annular stress-receiving device collar for radially supporting the pipe inserted into the flush, whereby the pipe is additionally supported by the stress-receiving device in an improved manner.

[0016] The problem is further solved by a method of the type mentioned at the beginning, which method comprises the steps of claims 1 to 5. 6In order to produce a piping unit using the system according to any one of claims 1 to 5, the method includes the method steps of preparing a piping, preparing a pipe fitting, arranging the pipe fitting on the piping, preparing a stressed device, placing the piping unit to be produced from the piping and the pipe fitting in the stressed device and closing the stressed device, preparing a pressure tool, inserting the pressure tool into the piping so that the stressed device surrounds the pressure tool in the operating state, expanding the piping, thereby connecting the piping and the pipe fitting by an interference fit to form a piping unit, removing the pressure tool from the piping, and releasing the stressed device and removing the piping unit produced from the piping and the pipe fitting. Advantageously, by the above method, the system, in particular the pipe fitting, is supported during the expansion of the piping by the pressure tool, so that the formation of the piping unit by connecting the piping unit and the pipe fitting is performed in an improved manner.

[0017] The present invention will now be described in detail with reference to the accompanying drawings. [Brief description of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view of an embodiment of a system including an apparatus for fabricating a piping unit. [Diagram 2] 1 is a cross-sectional view of a piping unit to be produced from a pipe and a pipe joint by radially expanding the pipe. [Diagram 3] 3 is a cross-sectional view of the piping unit shown in FIG. 2 produced from piping and pipe joints by radially expanding the piping. [Figure 4] FIG. 2 is a cross-sectional view of a piping assembly having two piping units. [Diagram 5] FIG. 2 is a perspective view of an embodiment of a stressed device in a closed state. [Figure 6] FIG. 6 is a front view of the stress receiving device shown in FIG. 5. [Figure 7] FIG. 6 is a side view from the right of the stress receiving device shown in FIG. 5. [Figure 8] FIG. 6 is a rear view of the stress-receiving device shown in FIG. 5 in an open state. [Figure 9] FIG. 6 is a perspective view of a first ring body element of the stress receiving device shown in FIG. 5. [Figure 10] FIG. 10 is a rear view of the first ring body element shown in FIG. 9. [Figure 11] FIG. 10 is a front view of the first ring body element shown in FIG. 9. [Figure 12] FIG. 10 is a left side view of the first ring body element shown in FIG. 9. [Figure 13] FIG. 2 is a cross-sectional view of a first ring body element along section AA. [Figure 14] FIG. 6 is a perspective view of a second ring body element of the stress receiving device shown in FIG. 5. [Figure 15] 15 is a rear view of the second ring body element shown in FIG. 14 of the stress receiving device shown in FIG. 5 . [Figure 16] FIG. 15 is a front view of the second ring body element shown in FIG. [Figure 17] FIG. 15 is a side view in partial cross section of the second ring body element shown in FIG. 14. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Unless otherwise stated, the following description relates to all embodiments shown in the drawings of a system 1 comprising an apparatus 2 for producing a piping unit 5 having piping 3 and pipe fittings 4 .

[0020] The system 1 with the device 2 for producing a piping unit 5 comprises in the illustrated embodiment a piping 3, a pipe fitting 4, a stress receiving device 6 and a pressing tool 7, which is expediently configured as a rolling tool. The piping 3, the pipe fitting 4, the stress receiving device 6 and the pressing tool 7 have a central longitudinal axis XX, to which they are aligned in the operating state.

[0021] The pipe 3 has a pipe outer surface 8, a pipe end surface 9, and a pipe outer diameter 10. Furthermore, the pipe 3 is formed according to set values ​​regarding the pipe length and pipe bends, and in this embodiment, a straight pipe 3 is used.

[0022] The pipe fitting 4 has a pipe section 11 and a flange section 12, a pipe fitting outer surface 13, a pipe fitting inner diameter 14 and a pipe fitting inner surface 15. The pipe fitting inner surface 15 is provided with a structure 16 in the form of a protrusion 17. In another embodiment, not shown, the pipe outer surface 8 and / or the pipe fitting inner surface 15 are at least partially structured before the radial expansion of the pipe 3. The structure 16 does not necessarily have to be provided in the form of a protrusion 17, but can also be provided, for example, in the form of a recess, valley, groove or the like. The structure 16 arranged on the pipe fitting inner surface 15 provides a form-fit in addition to a force-fit between the pipe 3 and the pipe fitting 4 by expanding the pipe 3.

[0023] Additionally, the flange section 12 of the pipe fitting 4 has a flange section end face 18 that defines a groove 19 that partially receives a seal 20 .

[0024] In the illustrated embodiment, the pipe outer diameter 10 of the pipe 3 and the pipe fitting inner diameter 14 of the pipe fitting 4 are approximately the same size.

[0025] In another embodiment, not shown, the outer pipe diameter 10 of the pipe 3 is larger than the inner pipe fitting diameter 14 of the pipe fitting 4. Expediently, the difference is minimal, so that an interference fit is directly formed when the pipe fitting 4 is axially pulled onto the pipe 3. Such an interference fit forms a force connection between the pipe 3 and the pipe fitting 4.

[0026] Preferably, the fitting 4 is heated and / or the pipe 3 is cooled before slipping the fitting 4 onto the pipe 3. Cooling the fitting 4 and / or heating the pipe 3 are also possible in this context.

[0027] The piping assembly 21 has two piping units 5, each having a pipe fitting 4 axially fitted onto the piping 3, and a seal 20 having a seal insert 22 is arranged axially between these piping units 5.

[0028] The two pipe units 5 of the pipe assembly 21 are in this embodiment axially clamped to one another by means of a clamping device 23. For this purpose, the flange sections 12 of the pipe fittings 4 of the two pipe units 5 are axially clamped to one another by means of a clamping device 23. In this embodiment, the clamping device 23 is expediently configured as a hinge clamp 24. With the clamping device 23 configured as a hinge clamp 24, the pressing force acting on the seal 20 corresponds in terms of the surface to a pressing pressure and can additionally be adjusted, for example, by means of a wing nut or the like which closes the hinge clamp 24.

[0029] Alternatively, standard items, such as measuring instruments, valves and flaps or the like, may in this case be used as preformed piping units 5 and together with another second piping unit 5 according to this embodiment form one piping assembly 21.

[0030] The piping assembly 21 comprises a seal 20, which is axially arranged between the flange section end faces 18 formed in the flange sections 12 of the pipe fitting 4. The seal 20 is configured to form a defined transition 25 between two piping units 5 that are clamped together. The defined transition 25 is formed by a pressing force acting on the seal 20 during clamping.

[0031] With the defined transition 25, the buildup of residue or solids in one type of media flowing through the piping assembly 21, or in multiple types of media flowing through the piping assembly 21, is reduced or eliminated.

[0032] In addition, the seal 20 has a seal insert 22. The seal insert 22 defines a minimum axial distance 26 between the two piping units 5, and therefore the pressure force to which the two piping units 5 are exposed when the piping assembly 21 is tightened is determined by the minimum axial distance 26 determined based on the seal insert 22.

[0033] The seal 20 is preferably formed as a flat seal, and the seal material is, for example, elastomer, compressed fiber, aramid fiber, carbon fiber, mineral fiber, metal, copper, etc. Jacketed seals 20, in particular jacketed flat seals, are also preferred. Jacketed seals 20, in particular jacketed flat seals, have a core (any flat seal material, for example fiber composite, PTFE, etc.) covered by a PTFE or metal jacket, preferably steel or a corrosion-resistant nickel alloy. The jacket protects the core from chemical attack of the medium to be sealed.

[0034] The seal insert 22 of the seal 20 has a seal insert end face 28 formed as a seal stop 27. By means of the seal insert 22, an axial minimum distance 26 can be defined or is defined between the two piping units 5. The pipe end face 9 and / or the flange section end face 18 adjoins the seal insert end face 28 of the seal insert 22 of the seal 20 in the clamped state of the piping assembly 21. As a result, the minimum distance 26 between the two piping units 5 of the piping assembly 21 and therefore also the pressing force acting on the seal 20 can be precisely adjusted.

[0035] The transition section 25, determined by the pressing force established by the sealing insert 22, is preferably configured in such a way that the bulge 29 forms an obtuse angle α with the expanded pipe inner diameter 30. Particularly preferably, the obtuse angle α has an angle α between 100° and 170°, very particularly preferably between 120° and 150°. This achieves a reduction or prevention of the residue of a medium flowing through the pipe assembly 21 or of a plurality of media flowing through the pipe assembly 21.

[0036] The device 2 comprises an annularly structured stress-receiving device 6, which has a longitudinal central axis XX. The stress-receiving device 6 comprises at least one annular groove 31, whereby the radially inwardly directed stress-receiving device inner surface 32 is stepped in order to at least partially accommodate, in the operating state, the piping unit 5 to be produced, in particular but at least the pipe fitting 4. Expediently, the stress-receiving device inner surface 32 is therefore adapted to the pipe outer surface 8 and / or the pipe fitting outer surface 13. In the illustrated embodiment, the stress-receiving device comprises two annular grooves 31a and 31b, which are offset from one another, as best shown in Figs. 13 and 17. In this case, the annular groove 31a is suitable for accommodating the pipe section 11 of the pipe fitting 4, and the annular groove 31b is suitable for accommodating the flange section 12.

[0037] The stress-receiving device 6 comprises a stress-receiving device ring body 33, which in turn comprises two ring body elements 34, which together form the stress-receiving device inner surface 32. Each of the ring body elements 34 comprises a first end section 35 and a second end section 36, which are arranged so as to be pivotable relative to each other about a pivot axis YY, which extends parallel to the longitudinal center axis XX. A coupling element 37 is arranged on each second end section 36, which coupling elements 37 are suitable for cooperating with each other to releasably connect the second end sections 36. Each coupling element 37 has a coupling hole 56, which has a bearing hole center axis WW. The two coupling elements 37 are connected to each other by means of fastening elements (not shown), for example screw fasteners, cotter bolts or the like, arranged in the aligned coupling holes 56. In order to facilitate distinction, the reference numerals of the ring body element 34, the first and second end sections 35, 36 and the coupling element 37 are designated by a lower case letter a or b, respectively.

[0038] In addition, the stress-receiving device 6 forms a radially inwardly extending annular projection 38, which is defined on the one hand by a first axial stress-receiving device end face 39 and on the other hand by a lateral groove-defining surface 40 of the at least one annular groove 31, which is remote from the first axial stress-receiving device end face 39. Expediently, the radially inwardly extending annular projection 38 extends radially inwardly to such an extent that it forms a stop 41 for the pipe 3 that is inserted into the pipe fitting 4. This ensures that the pipe end face 9 and the flange section end face 18 are aligned flush with one another during expansion by the pressing tool 7.

[0039] The ring body element 34a has, in the region of the first end section 35a, a bearing fork 50 with two bearing legs 49. Each bearing leg 49 has a bearing hole 51 which are aligned with one another based on a swing axis YY which is used as the bearing hole central axis.

[0040] In contrast to the ring body element 34a, the ring body element 34b has in the region of the first end section 35b a bearing eye 54 with a bearing bore 53 which is arranged in the bearing body 52. ​​The bearing bore 53 also uses the oscillating axis YY as the bearing bore central axis.

[0041] The two ring body elements 34a and 34b, which are arranged to be freely pivotable relative to each other around the pivot axis YY, are connected to each other via a bearing bolt 55 in the illustrated embodiment, which may be configured, for example, as a cotter bolt.

[0042] The stress receiving device 6 surrounds the pressing tool 7 in the operating state, so that in the operating state the pipe unit 5 to be produced can be supported during the expansion of the pipe 3 by the pressing tool 7. The pressing tool 7 has for this purpose a pressing mandrel 43, which is arranged in a housing 42, is conically shaped and is movable in the axial direction about a central longitudinal axis XX. This pressing mandrel 43 is surrounded in the circumferential direction by a force transmission element 44, in particular a crown 45 with a force transmission roller, which in the operating state rotates about the pressing mandrel 43 and about the central longitudinal axis XX. The force transmission element 44 is also rotatably supported in the crown 45 on a rotation axis ZZ. Due to the axial movement of the pressing mandrel 43, the force transmission element 44 is pressed radially outwards and the simultaneous rotation of the force transmission element 44 about the rotation axis ZZ expands the pipe 3. In this embodiment, the pipe 3 is expanded to reduce the pipe wall thickness, thereby forming a pipe unit 5.

[0043] The radial expansion is achieved by a pressing tool 7, expediently a rolling tool, also referred to as fixation expansion or roller expansion of the pipe 3. After the radial expansion, the cross-sectional area of ​​the pipe 3 in the area of ​​the expansion is larger than the original cross-sectional area of ​​the pipe 3. Thus, due to the radial expansion of the pipe 3, in the area where the pipe 3 and the pipe fitting 4 overlap, the expanded pipe inner diameter 46 is larger than the original pipe inner diameter 30.

[0044] In the illustrated embodiment, the stress receiver 6 further has a second axial stress receiver end face 47 facing away from the first axial stress receiver end face 39, which is stepped to form an annular stress receiver collar 48 for radially supporting the pipe 3 inserted into the pipe fitting 4. The stress receiver collar 48 is formed in order to provide an additional support for the pipe 3 of the pipe unit 5 to be produced when the pipe 3 is expanded by the pressure tool 7 in the operating state.

[0045] The method for producing a piping unit 5 using the system 1 includes, as a preparation method step, the steps of preparing a pipe 3, preparing a pipe fitting 4, and then placing the pipe fitting 4 on the pipe 3. Then, a device 2 is prepared, which has a stress-receiving device 6 and receives the piping unit 5 to be produced from the pipe 3 and the pipe fitting 4. After receiving the piping unit 5, the stress-receiving device is closed. Then, the prepared pressurizing tool 7 is introduced into the pipe 3. As a result, the stress-receiving device 6 at least partially surrounds the pressurizing tool 7 in the operating state. The pipe 3 is then expanded by the pressurizing tool 7, so that the pipe unit 5 can be produced from the pipe 3 and the pipe fitting 4 by interference fit, and the pipe 3 and the pipe fitting 4 can be connected by fixation expansion. Finally, the pressurizing tool 7 is then removed from the pipe 3 and the stress-receiving device 6 is opened. This allows the piping unit 5 produced from the pipe 3 and the pipe fitting 4 to be taken out. This application relates to the invention described in the claims, but also includes the following as other aspects. 1. 1. A system (1) comprising a device (2) for producing a piping unit (5) from a pipe (3) having a piping outer surface (8) and a pipe fitting (4) having a pipe fitting outer surface (13), characterized in that the device (2) comprises an annularly structured stress-receiving device (6) having a longitudinal central axis (XX) and a radially inwardly directed stress-receiving device inner surface (32) which is adapted to the pipe outer surface (8) and / or the pipe fitting outer surface (13) and which is thereby capable of at least partially accommodating in an operational state the piping unit (5) to be produced, and in that the stress-receiving device (6) surrounds a pressure tool (7) in an operational state and thus is capable of supporting in an operational state the piping unit (5) to be produced when the pipe (3) is expanded by the pressure tool (7). 2. The system (1) according to claim 1, characterized in that it comprises the piping unit (5) having the piping (3) and the pipe joint (4). 3. 3. The system (1) according to claim 1 or 2, characterized in that the system (1) includes the pressurizing tool (7) for expanding the pipe (3). 4. 4. The system (1) according to any one of claims 1 to 3, characterized in that the inner surface (32) of the stress-receiving device is formed in a stepped shape. 5. 5. The system (1) according to any one of claims 1 to 4, characterized in that the stress-receiving device (6) comprises a stress-receiving device ring body (33) which comprises two ring body elements (34) which together form the stress-receiving device inner surface (32), each of the ring body elements (34) having one first end section (35) and one second end section (36), the first end sections (35) being arranged so as to be pivotable relative to one another about a pivot axis (YY), and each second end section (36) being provided with a coupling element (37), the coupling elements (37) being suitable for cooperating with one another to detachably couple the second end sections (36). 6. 6. The system (1) according to any one of claims 1 to 5, characterized in that the stress-receiving device inner surface (32) has at least one annular groove (31) which at least partially accommodates the pipe fitting (4). 7. 6. System (1) according to claim 6, characterized in that the stress-receiving device (6) forms a radially inwardly extending annular projection (38) which is defined, on the one hand, by a first axial stress-receiving device end face (39) and, on the other hand, by a lateral groove-defining surface (40) of at least one of the annular grooves (31), which is spaced away from the first axial stress-receiving device end face (39). 8. 7. The system (1) of claim 7, wherein the annular protrusion (38) extends radially inward to such an extent that the annular protrusion (38) forms a stopper (41) for the pipe (3) inserted into the pipe fitting (4). 9. 9. The system (1) according to any one of claims 1 to 8, characterized in that the stress-receiving device (6) has a second axial stress-receiving device end face (47) facing opposite to the first axial stress-receiving device end face (39), the second axial stress-receiving device end face (47) being formed in a stepped shape, thereby forming an annular stress-receiving device collar (48) that radially supports the pipe (3) inserted into the pipe fitting (4). 10. A method for manufacturing a piping unit (5) using any one of the systems (1) according to 1 to 9, comprising the steps of: - method steps for preparing the piping (3); - a method for preparing a pipe fitting (4), - a method step of placing said pipe fitting (4) in said pipe (3); - the method steps of providing a stress receiving device (6), - the method steps of placing the piping unit (5) to be produced from piping (3) and pipe fittings (4) in the stress receiving device (6) and closing the stress receiving device (6); - a method step of providing a pressure tool (7); - inserting said pressure tool (7) into said pipe (3), so that said stress-receiving device (6) at least partially surrounds said pressure tool (7) in an operational state; - expanding the pipe (3), thereby connecting the pipe (3) to a pipe fitting (4) by means of an interference fit to form the pipe unit (5); - a method step of withdrawing said pressure tool (7) from said pipe (3); - opening the stress receiving device (6) and removing the piping unit (5) made of piping (3) and pipe fittings (4), A method for manufacturing a piping unit (5), comprising:

Claims

1. A system (1) comprising an apparatus (2) for producing a piping unit (5) from a pipe (3) having a piping outer surface (8) and a pipe fitting (4) having a pipe fitting outer surface (13), said apparatus (2) having an annularly structured stress receiving device (6) having a longitudinal central axis (X-X) and a radially inwardly directed stress receiving device inner surface (32) adapted to said pipe outer surface (8) and / or to said pipe fitting outer surface (13) so as to at least partially accommodate said piping unit (5) to be produced in an operational state, said stress receiving device (6) surrounding a pressure tool (7) in an operational state so as to support said piping unit (5) to be produced during expansion of said pipe (3) by said pressure tool (7) in an operational state, the stress-receiving device (6) comprises a stress-receiving device ring body (33) which comprises two ring body elements (34) which together form the stress-receiving device inner surface (32), each of the ring body elements (34) having a first end section (35) and a second end section (36), the first end sections (35) being arranged so as to be pivotable relative to one another about a pivot axis (Y-Y), each second end section (36) being provided with a coupling element (37) which is suitable for cooperating with one another to releasably couple the second end sections (36), the stress receiving device inner surface (32) has at least one annular groove (31) for at least partially receiving the pipe fitting (4); The stress-receiving device (6) has a first axial stress-receiving device end face (39) and a second axial stress-receiving device end face (47) facing opposite to the first axial stress-receiving device end face (39), the second axial stress-receiving device end face (47) being stepped to form an annular stress-receiving device collar (48) for radially supporting the pipe (3) inserted into the pipe joint (4). A system (1) comprising an apparatus (2) for producing a piping unit (5),

2. The system (1) according to claim 1, characterized in that the system (1) comprises a piping unit (5) having the piping (3) and the pipe fittings (4).

3. The system (1) according to claim 1 or 2, characterized in that the system (1) comprises a pressurizing tool (7) for expanding the pipe (3).

4. The system (1) according to any one of claims 1 to 3, characterized in that the stress receiving device inner surface (32) is stepped.

5. 2. The system (1) according to claim 1, characterized in that the stress-receiving device (6) forms a radially inwardly extending annular projection (38) which is defined, on the one hand, by a first axial stress-receiving device end face (39) and, on the other hand, by a lateral groove-defining surface (40) of at least one annular groove (31), which is remote from the first axial stress-receiving device end face (39).

6. 6. The system (1) according to claim 5, characterized in that the annular protrusion (38) extending radially inwardly extends to such an extent that the annular protrusion (38) forms a stopper (41) for the pipe (3) that is inserted into the pipe fitting (4).

7. A method for manufacturing a piping unit (5) using a system (1) according to any one of claims 1 to 6, comprising the steps of: - the method steps of providing a pipe (3), - the method steps of preparing a pipe fitting (4), - a method step of placing said fitting (4) in said pipe (3); - the method steps of providing a stress receiving device (6), - the method steps of placing said piping unit (5) to be produced from piping (3) and pipe fittings (4) in said stress receiving device (6) and closing said stress receiving device (6), - the method steps of providing a pressure tool (7), - inserting said pressure tool (7) into said pipe (3), so that said stress receiving device (6) at least partially surrounds said pressure tool (7) in the operational state; - expanding said pipe (3), thereby connecting said pipe (3) with a pipe fitting (4) by means of an interference fit to form said pipe unit (5); - a method step of withdrawing said pressure tool (7) from said pipe (3); - the method step of opening said stress receiving device (6) and removing said piping unit (5) made from piping (3) and pipe fittings (4), A method for manufacturing a piping unit (5), comprising:

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