Sealed pipe connection for connecting a pipeline, and method for producing same

Abstract

The invention relates to a pipe connection (1) for connecting a pipeline (2), comprising the pipeline (2), a connection element (3) and a clamping element (4), wherein the pipeline (2) has an outer circumferential surface (AU), an inner circumferential surface (IU), an end-side face (SF) and at least one connecting portion (5) which is formed in an end region of the pipeline (2) and has at least one sealing surface (6, 7), said connection element (3) having at least one receiving portion (8) for receiving at least part of the connecting portion (5). A sealing connection between the pipeline (2) and the connection element (3) can be established by clamping the connecting portion (5) between the connection element (3) and the clamping element (4). In order to ensure an improved sealing effect in such a pipe connection (1) with little manufacturing effort, it is proposed that the at least one sealing surface (6) is formed by the end-side face (SF) of the pipeline (2).

Description

[0001] "Sealed pipe connection for connecting a pipeline and method for its manufacture"

[0002] The present invention relates to a sealed pipe connection for connecting a pipeline. The pipe connection comprises the pipeline, a connection element, and a clamping element. The pipeline has an outer circumferential surface, an inner circumferential surface, and an end face, as well as at least one connection section, wherein the connection section is formed in an end region of the pipeline. The connection section has at least one sealing surface. The connection element of the pipe connection has a receiving section for receiving at least a portion of the connection section of the pipeline. A sealing connection between the pipeline and the connection element can be established with the clamping element by clamping the connection section between the connection element and the clamping element.

[0003] Furthermore, the invention relates to a method for producing a pipe connection by connecting a pipeline, wherein the pipe connection comprises the pipeline, a connection element and a clamping element, wherein the pipeline has an outer circumferential surface, an inner circumferential surface and an end face as well as at least one connection section which is formed in an end region of the pipeline and has at least one sealing surface, wherein the connection element has a receiving section for receiving at least a part of the connection section, wherein a sealing connection between the pipeline and the connection element is produced by clamping the connection section between the connection element and the clamping element.The clamping is achieved in particular by an externally applied torque which acts on the clamping element equipped with a thread, whereby this thread interacts with a corresponding counter thread of the connecting element.

[0004] A generic pipe connection and a method of the aforementioned type are known from EP 3 390 881 B1. In particular, it is provided that the at least one sealing surface is located on the outer circumference of the pipeline and is inclined towards the end region, tapering in a frustoconical shape, at least partially, towards the end region of the pipeline, and that a sealing projection is formed as a protrusion in the end face. The sealing projection is continuous, in particular rotationally symmetrical, and is formed in an edge region, preferably a radially outer edge region, of the end face, such that at least one of its flanks transitions directly into the inclined sealing surface of the connection section.The shape, which tapers towards the end of the pipeline, is produced by a forming process using a special upsetting tool, which is also intended to smooth out any scratches or grooves present in the conical, circumferential sealing surface of the pipeline, whereby such longitudinal grooves in the undeformed pipeline can unavoidably have a depth of up to 10 pm due to its manufacturing process.

[0005] The well-known pipe joint has proven its worth in practice; however, it has also become apparent that smoothing existing scratches or grooves during the forming process is not always reliable or achievable with the desired smoothness when damage is significant, thus reducing the sealing effect of the sealing surface. However, additional mechanical smoothing of the pipe's circumferential surface before forming, such as by grinding, sandblasting, or similar processes, is technically complex and should be carried out to avoid this problem.

[0006] The present invention is therefore based on the objective of providing a pipe connection of the type mentioned above and a method for manufacturing it, with which an improved sealing effect can be ensured with minimal manufacturing effort.

[0007] This problem is solved according to the invention by a generic pipe connection with the feature of the characterizing part of claim 1 and by a generic method with the feature of the characterizing part of claim 15.

[0008] Accordingly, it is provided that the at least one sealing surface is formed by the end face of the pipeline, or that the end face of the pipeline is used as the at least one sealing surface.

[0009] It is possible that the sealing surface formed by the end face of the pipeline is the only sealing surface.

[0010] However, it is also possible to provide a second sealing surface on the outer circumference of the pipeline, inclined towards the end region. In this case, the end face must be designed such that the sealing effect of the sealing surface it forms is greater than the sealing effect of the sealing surface on the outer circumference of the pipeline. This can be achieved, in particular, by ensuring that the sealing surface formed by the end face has a lower roughness than the sealing surface on the outer circumference of the pipeline.

[0011] To achieve this, a precision cutting process, in particular precision cutting grinding, can preferably be used, by which the end face of the pipeline is produced dry or in particular wet without burrs, wherein the cutting surface, in particular the ground cut surface, enables a gap-free joining with a counter-sealing surface of the connection element.

[0012] The connecting element can be another pipeline, a hydraulic or pneumatic unit, or an adapter part that can be connected to another pipeline or to a hydraulic or pneumatic unit.

[0013] In a preferred embodiment, the end face may have a sealing projection and / or a sealing recess. The sealing surface, and in particular the sealing projection and / or the sealing recess of the end face, may, in a preferred embodiment, have a radial distance from the outer circumferential surface and, optionally, a radial distance from the inner circumferential surface. This ensures that longitudinal grooves on the outer circumferential surface do not extend into the sealing surface on the end face of the pipeline.

[0014] The connecting element preferably has a counter-sealing surface to the sealing surface on the end face of the pipeline, wherein the counter-sealing surface in particular has a shape complementary to the contour of the sealing surface on the end face of the pipeline.

[0015] According to the inventive method for manufacturing the pipe connection, it is preferably provided that, during an assembly process, the end face of the pipeline – starting from a pressureless assembly start position, in which it is already in contact with the counter-sealing surface of the connection element – ​​is pressed into an assembly end position by means of the clamping element against the counter-sealing surface of the connection element. In this assembly end position, local surface pressures significantly above the yield strength, up to values ​​of 2000 N / mm², are exerted between the sealing surface of the end face and the counter-sealing surface. 2This process results in plastic deformation and surface smoothing of these sealing surfaces, or - if not already present - a flattening of the sealing projection and / or the sealing recess.

[0016] Alternatively, the sealing protrusion and / or the sealing recess can also be formed only during assembly because the material begins to flow when the pipe and connection element are compressed together.

[0017] In detail, there are numerous possibilities for designing and further developing the pipe connection and the method according to the invention.

[0018] The invention is particularly suitable for highly demanding applications of fluids, such as hydrogen or natural gas (e.g. LNC or GNC), in the field of newer drive technologies, where the highest requirements are placed on the tightness of the systems.

[0019] In particular, reference is made to the dependent patent claims and the following description for further technical features and their respective advantages - in conjunction with the drawing.

[0020] The drawing shows:

[0021] Fig. 1 in cutaway side view, a first embodiment of a pipe connection according to the invention in an assembly starting position,

[0022] Fig. 2 shows an enlarged section from Fig. 1 ,

[0023] Fig. 3 in a cutaway side view, the embodiment according to Fig. 1 in a final assembly position, Fig. 4 an enlarged section from Fig. 3,

[0024] Fig. 5 in cutaway side view, a second embodiment of a pipe connection according to the invention in an assembly starting position,

[0025] Fig. 6 shows an enlarged section from Fig. 5,

[0026] Fig. 7 in a cutaway side view, the embodiment according to Fig. 5 in a final assembly position,

[0027] Fig. 8 shows an enlarged section from Fig. 7,

[0028] Fig. 9 in cutaway side view, a third embodiment of a pipe connection according to the invention in an assembly starting position,

[0029] Fig. 10 shows an enlarged section from Fig. 9,

[0030] Fig. 11 in cutaway side view, a fourth embodiment of a pipe connection according to the invention in an assembly starting position,

[0031] Fig. 12 shows an enlarged section of Fig. 11.

[0032] In the various figures of the drawing, identical parts are always provided with the same reference symbols and are therefore usually only described once below.

[0033] In the following description, it is deemed to be disclosed as essential to the invention that the invention is not limited to the exemplary embodiments and not to all or several features of the described combinations of features; rather, each individual partial feature of the exemplary embodiment(s) can also have an inventive significance independently of the partial features described in connection with it, both on its own and in combination with any features of another exemplary embodiment, as well as independently of the combinations of features and cross-references of the claims, namely in combination with the features of claims 1 and 13.

[0034] As can be seen from Figures 1 to 4, the pipe connection 1 according to the invention serves to connect a pipeline 2, wherein the pipe connection 1 comprises the pipeline 2, a connecting element 3 and a clamping element 4, and wherein the pipeline 2 has an outer circumferential surface AU, an inner circumferential surface IU and an end face SF as well as at least one connecting section 5 which is formed in an end region of the pipeline 2 and has at least one sealing surface 6, 7. The end face SF is considered to be the surface which runs longitudinally to a flat base surface, which is characterized by the line BB in Figures 2, 4, 6, 8, 10 and 12. The line BB begins and ends at the points where the circular cross-section of the pipe 2 meets the junction of the pipe connection 2 and the clamping element 4.The circular shape of the outer circumferential surface AU and the inner circumferential surface IU - in other words: the hollow cylindrical shape of the wall of the pipe 2, which runs exactly equidistant between the outer circumferential surface AU and the inner circumferential surface IU within the usual tolerances - ends or changes.

[0035] The connecting element 3, which may be another pipeline, a hydraulic or pneumatic unit, or an adapter part connectable to another pipeline or a hydraulic or pneumatic unit, has a receiving section 8 for receiving at least a part of the connecting section 5. A sealing connection between the pipeline 2 and the connecting element 3 can be established by clamping the connecting section 5 between the connecting element 3 and the clamping element 4. The pipe connection 1 according to the invention transitions from the assembly starting position shown in Figures 1 and 2 to the assembly end position shown in Figures 3 and 4. A free flow cross-section A2 of the pipeline 2 is then fluidically connected to a free flow cross-section A3 of the connecting element 3.

[0036] According to the invention, the at least one sealing surface 6, 7 is formed by the end face SF of the pipeline 2.

[0037] This sealing surface 6 formed by the end face SF of the pipe 2 can be the only sealing surface 6 of the pipe connection 1 according to the invention; however, in the embodiments shown in Figs. 1 to 4 and Figs. 9 to 12, there is also a second secondary sealing surface 7 inclined towards the end region on the outer circumferential surface AU of the pipe 2.

[0038] The end face SF is designed in such a way that the sealing effect of the sealing surface 6 formed by the end face SF is greater than the sealing effect of the sealing surface 7 on the outer circumference AU of the pipeline 2. For this purpose, the primary sealing surface 6 formed by the end face SF may preferably have a lower roughness than the secondary sealing surface 7 on the outer circumference AU of the pipeline 2.

[0039] As further shown in Figures 1 to 4, the end face 6 has a sealing projection 10 and a sealing recess 20. The sealing projection 10 and the sealing recess 20 are defined by the flat base surface. The sealing projection 10 is convex with respect to the plane BB, and the sealing recess 20 is concave with respect to the plane BB. The sealing surface 6, and in particular the sealing projection 10 and / or the sealing recess 20, may preferably have a radial distance AA (indicated only in Figure 4) from the outer circumferential surface AU and also a radial distance AI from the inner circumferential surface IU of the pipeline 2. This distance AA (and / or AI) can, for example, be in the range of 20 pm to 200 pm, so that on the one hand it is greater than the depth of any grooves in the outer circumferential surface AU (and / or in the outer circumferential surface IU) of the pipe 2, but on the other hand does not excessively reduce the sealing surface 6 in relation to the end face SF.

[0040] The connecting element 3 can preferably have a counter-sealing surface 9 to the sealing surface 6 on the end face SF of the pipeline 2, as shown, wherein the counter-sealing surface 9 in particular has a shape complementary to the contour of the sealing surface 6 on the end face SF of the pipeline 2.

[0041] The clamping element 4 can preferably be a screw-in body. The connecting element 3 has a connecting thread 11 onto which the clamping element 4 is screwed with a corresponding thread 12 serving the clamping function. The thread 12 can be an external or an internal thread, depending on the connecting thread 11. A torque applied to the clamping shoulder 13 generates a force on the clamping element 4, essentially parallel to the longitudinal axis XX, acting on the pipe 2. This clamps the pipe 2 between the connecting element 3 and the clamping element 4; in particular, the connecting section 5 is pressed against the receiving section 8 of the connecting element 3.

[0042] According to the inventive method for producing the pipe connection 1, the end face SF of the pipe 2 is pressed from a pressureless assembly starting position (Figs. 1, 2) against a counter-sealing surface 9 of the connection element 3 into an assembly end position (Figs. 3, 4) by means of the clamping element 4. Advantageously, high surface pressures can be generated between the sealing surface 6 of the end face SF and the counter-sealing surface 9 until the assembly end position is reached, such that plastic deformation occurs in the connection section 5 and the surface of the end face SF is smoothed.Knowing the yield strength of the material of the pipe 2 and the geometry of the end face SF, a defined force can be applied via the torque by means of the screw connection of the connecting element 3 and the clamping element 4. This force achieves the desired feed of the pipe 2 along its longitudinal axis XX with the highest accuracy, corresponding to the thread pitch of the connecting thread 11 and the corresponding clamping thread 12. Corrosion-resistant steels are preferably used as materials for the pipe 2. Typically, so-called stainless steel pipes, such as VA 1.4404 annealed (soft) or cold-drawn (hard), exhibit a yield strength of 200 N / mm² or higher. 2 up to 500 N / mm 2 a flow can occur.

[0043] Regarding the tightening torques required to apply the defined force, these are generally highly dependent on the pipe size. For example, they can range from 15 Nm to 150 Nm for pipe diameters from 6 mm to 22 mm, with smaller pipe diameters correspondingly lower tightening torques. For hydraulic fittings, tightening torques from 12 Nm to 1000 Nm are possible for pipe diameters from 6 mm to 42 mm.

[0044] The end face SF of the pipe 2 can preferably already have a high surface quality before assembly, provided that it is produced burr-free, preferably by a precision cutting process, particularly preferably by precision grinding, either dry or especially wet, wherein the surface quality of the end face SF is higher than the surface quality on the outer circumferential surface AU, where grooves running longitudinally along the pipe 2 may still be present due to the pipe manufacturing process, as mentioned above. Machines for carrying out the aforementioned precision cutting processes are commercially available.

[0045] The invention therefore does not aim to further level the grooves already present on the outer circumferential surface AU, which would be obvious, but offers a technical solution at a different point of action, namely at the primary sealing surface 6 located on the end face SF.

[0046] Therefore, it is advantageously and easily possible to use an upsetting tool, such as that known from EP 3 390 881 B1, to form the connection section 5 located in the end region of the pipeline 2. Accordingly, a force is exerted on the end face SF of the pipeline 2 by a die, whereby the material of the pipeline 2 is pressed towards the outer circumferential surface AU of the pipeline 2 to form the secondary sealing surface 7, causing the material to flow and allowing the sealing projection 10 and / or the sealing recess 20 to be formed. The direction of action of the force on the end face SF of the pipeline 2 can be expediently aligned precisely, e.g.The design provides that the die has an inclined base surface, and that a force is also exerted from the inclined base surface, in particular from a curved second section of the base surface, on the end face of the die in the direction of the outer circumferential surface AU of the pipeline 2. Consequently, the base surface of the die not only generates a force parallel to the neutral axis of the pipeline 2, but also a force that runs obliquely to it, i.e., is directed obliquely towards the end face SF. This causes the end face SF to curve, and the sealing projection 10 forms outwards and / or the sealing recess 20 forms inwards. Advantageously, this also simultaneously—though not completely as desired—results in a smoothing of the secondary sealing surface 7 on the outer circumferential surface AU.The secondary sealing surface 7 comprises, in particular, a section 7a which is inclined in a frustoconical shape at an angle α to the longitudinal axis XX of the pipe 2. Apart from the more or less significant sealing effect of the secondary sealing surface 7, the frustoconical section 7a prevents the pipe 2 from rotating during assembly by means of frictional engagement with the connection element 3 and centers the pipe 2 in the connection element 3.

[0047] In particular, sealing projections 10 and sealing recesses 20 have the advantage that very high surface pressures can be generated in these areas, thus generating additional smoothing effects that have a positive effect on the sealing behavior. The parting surface on the end face of the pipe 2, which is designed in particular as a ground cut surface, then enables a gap-free joining with the counter-sealing surface 9 of the connection element 3, wherein in the assembly start position the sealing surface 6 of the end face SF and the counter-sealing surface 9 adjacent to it at no pressure on the connection element 3 have a contact surface KFA (Fig. 2) which is less than 50%, preferably less than 35%, particularly preferably less than 20% of the end face SF, and which in the assembly end position has a contact surface KFE (Fig.4) exhibit a surface area greater than 50%, preferably greater than 65%, particularly preferably greater than 80% of the end face SF, thereby achieving the excellent high sealing effect of the sealing surface 6 of the end face SF.

[0048] The second embodiment of a pipe connection 1 according to the invention, shown in Figures 5 to 8, differs from the first embodiment in that, firstly, there is no sealing recess 20 in the end face SF, but only a sealing projection 10, and secondly, it also does not have a secondary sealing surface 7, but only the primary sealing surface 6 on the end face SF of the pipe 2. Otherwise, the design is the same as in the first embodiment.

[0049] As in all other embodiments, the inventive method for connecting the pipeline 2 is used to produce the pipe connection 1, wherein the pipe connection 1 comprises the pipeline 2, a connection element 3, and a clamping element 4, wherein the pipeline 2 has an outer circumferential surface AU, an inner circumferential surface IU, and an end face SF, as well as at least one connection section 5, which is formed in an end region of the pipeline 2, and has at least one sealing surface 6, wherein the connection element 3 has a receiving section 8 for receiving at least a part of the connection section 5. A sealing connection between the pipeline 2 and the connection element 3 is established by clamping the connection section 5 between the connection element 3 and the clamping element 4, wherein the end face SF of the pipeline 2 provides the at least one sealing surface 6.

[0050] For the third and fourth embodiments of a pipe connection 1 according to the invention, shown in Figures 9 to 12, it is characteristic that an additional sealing insert 30 is arranged in the receiving section 8 of the connecting element 3 for the connecting section 5 of the pipe 2 on the end face SF of the pipe 2. Such a sealing insert 30 can, in particular, be made of a material, e.g., surface-hardened steel, that has a higher strength, especially a higher yield strength, than both the material of the connecting element 3 and the material of the pipe 2. Any plastic deformation that preferably occurs during assembly in the sealing area then occurs in the material of the connecting element 3 and in the material of the pipe 2, but not in the sealing insert 30. Such a sealing insert 30 therefore does not need to be replaced during reassembly, but can be reused.

[0051] However, it is also possible that the sealing insert 30 has a lower strength than the material of the connecting element 3 and the pipe 2, for example, by being made of copper or brass. This causes plastic deformation in the sealing insert, and during reassembly, the initial state of the first assembly can be restored by replacing the relatively small and inexpensive sealing insert.

[0052] According to the third and fourth embodiments of the pipe connection 1 according to the invention, the end face SF of the pipe 2 is designed in the same way as in the first embodiment of the invention. It thus has a sealing projection 10 and a sealing recess 20 in the sealing surface 6. By means of a complementary contouring of the end face of the sealing insert 30 facing the pipe, the latter provides the counter-sealing surface 9 for the primary sealing surface 6. The sealing insert 30 can preferably be designed in a cap-like manner – as can be seen particularly from Figures 10 and 12 – such that it also provides a complementary counter-sealing surface 31 to the secondary sealing surface 7 of the pipe 2, or at least prevents the pipe 2 from rotating during its installation.

[0053] The special feature of the fourth embodiment of a pipe connection 1 according to the invention is that, in addition to the presence of the sealing insert 30, soft seals 40, preferably O-rings, are optionally provided. This counteracts the fact that the presence of the sealing insert 30 increases the total number of gaps in the sealing area, which could potentially impair the seal. The soft seals 40 are located in grooves 32, 33, one groove 32 being on the end face of the sealing insert 30 facing the connection element 3, and one groove 33 being on the inner side of the sealing insert 30 facing the outer circumferential surface AU of the pipe 2. Alternatively, only one soft seal 40 may be provided.

[0054] The invention is not limited to the embodiments illustrated and described, but also includes all embodiments that have the same effect within the meaning of the invention. It is expressly emphasized that the embodiments are not limited to all features in combination; rather, each individual feature can have inventive significance independently of all other features. Furthermore, the invention is not yet limited to the combinations of features defined in claims 1 and 15, but can also be defined by any other combination of specific features from all disclosed individual features. This means that, in principle, virtually any individual feature of the independent claims can be omitted or replaced by at least one individual feature disclosed elsewhere in the application.

[0055] Reference symbol list

[0056] 1 pipe connection

[0057] 2 pipelines from 1

[0058] 3 connection elements of 1

[0059] 4 clamping elements of 1

[0060] 5 connecting section of 2

[0061] 6 primary sealing surface from 2 to SF

[0062] 7 secondary sealing surface from 2 to AU

[0063] 7a frustoconical section of 2

[0064] 8 Recording section of 3 for 5

[0065] 9 counter-sealing surface to 6 of 3 / 30

[0066] 10 density advantage in SF

[0067] 11 connection threads of 3

[0068] 12 clamping threads of 4

[0069] 13 tension shoulders out of 4

[0070] 20 density rebounds in SF

[0071] 30 sealing inserts between 2 and 3 in 8

[0072] 31 counter-sealing surface for 7 in 30

[0073] 32 Nut in 30 for 40

[0074] 33 Nut in 30 for 40

[0075] 40 soft seals in 1

[0076] AA radial distance of 10 to AU

[0077] AI radial distance of 10 to IU

[0078] AU outer perimeter area of ​​2

[0079] A2 free flow cross-section of 2

[0080] A3 free flow cross-section of 3

[0081] IU Inner circumferential surface of 2 KFA Contact surface of 6 and 9 in assembly start position of 2 (Fig. 2) KFE Contact surface of 6 and 9 in assembly end position of 2 (Fig. 4)

[0082] SF front surface of 2

[0083] XX Longitudinal axis of 1, 2 a Angle between 7a and XX

Claims

Claims 1. Pipe connection (1) for connecting a pipeline (2), comprising the pipeline (2), a connection element (3) and a clamping element (4), wherein the pipeline (2) has an outer circumferential surface (AU), an inner circumferential surface (IU) and an end face (SF) as well as at least one connection section (5) which is formed in an end region of the pipeline (2) and has at least one sealing surface (6, 7), wherein the connection element (3) has a receiving section (8) for receiving at least a part of the connection section (5), wherein a sealing connection between the pipeline (2) and the connection element (3) can be established by clamping the connection section (5) between the connection element (3) and the clamping element (4), characterized in that the at least one sealing surface (6) is formed by the end face (SF) of the pipeline (2).

2. Pipe connection (1 ) according to claim 1 , characterized in that the sealing surface (6) formed by the end face (SF) of the pipeline (2) is the only sealing surface (6).

3. Pipe connection (1) according to claim 1, characterized by a second sealing surface (7) inclined towards the end region on the outer circumferential surface (AU) of the pipeline (2).

4. Pipe connection (1 ) according to claim 3, characterized in that the end face (SF) is designed such that the sealing effect of the sealing surface (6) formed by it is greater than the sealing effect of the sealing surface (7) on the outer circumference (AU) of the pipeline (2).

5. Pipe connection (1 ) according to claim 4, characterized in that the sealing surface (6) formed by the end face (SF) has a lower roughness than the sealing surface (7) on the outer circumference (AU) of the pipeline (2).

6. Pipe connection (1 ) according to one of claims 1 to 5, characterized in that the end face (6) has a sealing projection (10) and / or a sealing recess (20).

7. Pipe connection (1 ) according to claim 6, characterized in that the sealing surface (6), in particular also the sealing projection (10) and / or the sealing recess of the end face (SF) has a radial distance (AA) from the outer circumferential surface (AU) and optionally a radial distance (AI) from the inner circumferential surface (IU).

8. Pipe connection (1) according to one of the preceding claims, characterized in that the connecting element (3) is a further pipeline, a hydraulic or pneumatic unit or an adapter part connectable to a further pipeline or to a hydraulic or pneumatic unit.

9. Pipe connection (1 ) according to one of the preceding claims, characterized in that the connecting element (3) has a counter-sealing surface (9) to the sealing surface (6) on the end face (SF) of the pipeline (2), wherein the counter-sealing surface (9) in particular has a shape complementary to the contour of the sealing surface (6) on the end face (SF) of the pipeline (2).

10. Pipe connection (1) according to one of the preceding claims, characterized in that the clamping element (4) is a screwing body, wherein the clamping is effected in particular by a torque introduced from the outside, which acts on the clamping element (4) equipped with a thread (12), such as an internal thread or in particular an external thread, wherein the thread (12) interacts with a corresponding mating thread (11), in particular an internal thread, of the connecting element (3).

11. Pipe connection (1) according to one of the preceding claims, characterized in that in an assembly starting position in which the end face (SF) of the pipeline (2) rests without pressure against a counter-sealing surface (9) of the connection element (3), the sealing surface (6) of the end face (SF) and the counter-sealing surface (9) on the connection element (3) have a contact area (KFA) which is less than 50%, preferably less than 35%, particularly preferably less than 20% of the end face (SF).

12. Pipe connection (1 ) according to one of the preceding claims, characterized in that in an assembly end position the sealing surface (6) of the end face (SF) and the counter-sealing surface (9) on the connection element (3) have a contact area (KFE) which is larger than 50%, preferably larger than 65%, particularly preferably larger than 80% of the end face (SF).

13. Pipe connection (1 ) according to one of the preceding claims, characterized in that an additional sealing insert (30) is arranged in the receiving section (8) of the connection element (3) for the connection section (5) of the pipeline (2) on the end face (SF) of the pipeline (2), wherein the material of the sealing insert (30) preferably has a higher strength than both the material of the connection element (3) and the material of the pipeline (2).

14. Pipe connection (1 ) according to claim 13, characterized in that (a) soft seal(s) (40) is / are arranged between the sealing insert (30) and the pipeline (2) and / or the connecting element (3).

15. Method for producing a pipe connection (1) by connecting a pipeline (2), wherein the pipe connection (1) comprises the pipeline (2), a connection element (3) and a clamping element (4), wherein the pipeline (2) has an outer circumferential surface (AU), an inner circumferential surface (IU) and an end face (SF) as well as at least one connection section (5) which is formed in an end region of the pipeline (2) and has at least one sealing surface (6, 7), wherein the connection element (3) has a receiving section (8) for receiving at least a part of the connection section (5), wherein a sealing connection between the pipeline (2) and the connection element (3) is produced by clamping the connection section (5) between the connection element (3) and the clamping element (4), characterized in that the end face (SF) of the pipeline (2) is used as the at least one sealing surface (6).

16. Method according to claim 15, characterized in that, to produce the pipe connection (1), the end face (SF) of the pipeline (2) is pressed into an assembly end position from a pressureless assembly starting position by means of the clamping element (4) against a counter-sealing surface (9) of the connection element (3), wherein in the assembly end position, surface pressures of up to 2000 N / mm² are exerted between the sealing surface (6) of the end face (SF) and the counter-sealing surface (9). 2 are generated, which lead to plastic deformation in the connection section (5) and to surface smoothing of the sealing surface (6) and / or the counter surface (9).

17. Method according to claim 15 or 16, characterized in that the end face (SF) of the pipeline (2) is produced burr-free by a precision cutting process, either dry or, in particular, wet, wherein the cutting surface enables gap-free joining with a counter-sealing surface (9) of the connection element (3), and wherein the surface quality of the end face (SF) is higher than the surface quality on the outer circumferential surface (AU).

18. Method according to claim 16 or 17 characterized in that, in the assembly start position, the sealing surface (6) of the end face (SF) and the counter-sealing surface (9) on the connection element (3) have a contact area (KFA) that is less than 50%, preferably less than 35%, particularly preferably less than 20% of the end face (SF), and in the assembly end position, they have a contact area (KFE) that is greater than 50%, preferably greater than 65%, particularly preferably greater than 80% of the end face (SF).

19. Method according to one of claims 15 to 18, characterized in that the clamping is effected by an externally applied torque which acts on the clamping element (4) equipped with a thread (12), in particular an external thread, wherein the thread (12) interacts with a corresponding counter thread (11), in particular an internal thread, of the connecting element (3).

20. Method according to claim 19, characterized in that during clamping by the torque introduced from the outside a deformation of the end face (SF) of the pipeline (2) and / or - at the connection element (3) - of a counter sealing surface (9) to the sealing surface (6) on the end face (SF) of the pipeline (2) takes place.

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