METHOD AND MANUFACTURING PLANT FOR THE PRODUCTION OF A THERMALLY INSULATED PIPELINE

Description

background

[0001] The invention relates to a method for the continuous production of a thermally insulated pipe and a production plant for carrying out the method according to the respective independent claim. State of the art

[0002] WO2019 / 214954 A1 discloses a method for the continuous production of a thermally insulated pipe. The finished thermally insulated pipe comprises a corrugated plastic outer pipe, at least one inner pipe arranged within the outer pipe, and a cured insulating foam between the inner and outer pipes. This method has proven successful and results in high-quality thermally insulated pipes. Pipes produced using this method are used, for example, in local and district heating systems or in industrial applications.

[0003] In this process, a foil sleeve is inserted between the inner and outer pipes. The material forming the insulating foam is inserted between the inner pipe and the foil sleeve and expands in this space after the outer pipe has been corrugated. The use of the foil sleeve makes it possible to limit the expansion of the insulating foam toward the outer pipe, so that the insulating foam cannot, or only partially, fill the corrugation of the outer pipe. This measure allows for increased flexibility in the finished conduit, in other words, small bending radii that vary depending on the pipe dimension. This simplifies the installation of the conduit.

[0004] A thermally insulated pipe for heat supply is known under the name CALPEX ®< and has, for example, a bending radius of 1.2 meters in a dimension with an outer pipe diameter of 162 mm.

[0005] Furthermore, EP3871873 A1 discloses a thermally insulated conduit pipe which is manufactured according to the method of the above-mentioned WO2019 / 214954 A1 and in which the bending radius can be further reduced, inter alia, by using special materials such as LD-PE or LLD-PE or mixtures thereof, which have a high flexibility or a low modulus of elasticity, for the outer pipe, also called outer jacket, in compliance with applicable standards.

[0006] With this type of production of the aforementioned pipe with an LD-PE or LLD-PE or LD-PE-containing or LLD-PE-containing outer pipe, the problem arises, firstly, due to the low rigidity of the corrugated outer pipe associated with the LD-PE or LLD-PE (in contrast to HD-PE outer pipes) and, secondly, due to the foaming of the insulating foam only after the corrugator, that the inner pipe cannot be centered relative to the outer pipe in the conventional way using a centering device. However, the most precise centering possible is desirable in order to achieve a uniform thickness of the insulating foam along the entire length of the finished pipe, thus ensuring consistent insulation and stability. Description of the invention

[0007] The invention is based on the object of providing a thermally insulated pipe which, while at the same time having the high flexibility of the pipes described above with LD-PE or LLD-PE or LD-PE-containing or LLD-PE-containing outer pipe, has at least the same accuracy of the uniformity of the thickness of the insulating foam or a maximum prescribed inner pipe coaxial deviation as in the case of the above-mentioned CALPEX ®< pipes.

[0008] The task is in a first aspectThe invention is achieved with the method mentioned above. In this method for the continuous production of a thermally insulated pipe using a production plant, the thermally insulated pipe in its finished state comprises an outer pipe made of LLD-PE or LLD-PE-containing plastic, at least one inner pipe arranged in the outer pipe, and a cured insulating foam between the inner pipe and the outer pipe. The production of the thermally insulated pipe is carried out in a substantially horizontal production direction x through various stations of the production plant. The method comprises the steps: a) Forming a film tube around the at least one inner pipe and introducing a foamable starting material into the film tube, which starting material expands into an insulating foam and the insulating foam hardens, wherein the hardened insulating foam fills at least part of the space between the inner pipe and the outer pipe in the finished conduit pipe, b) Passing the inner pipe with the film tube and the foamable starting material through an extrusion head, by means of which the outer pipe is extruded around the inner pipe with the film tube, so that a semi-finished product is created, c) Forming a corrugation of the outer pipe in a corrugator to produce a corrugated outer pipe, wherein the foamable starting material is formed before being introduced into the film tube in such a way that it essentially only begins to expand when the semi-finished product exits the corrugator, thereby forming a foam front,d) detecting a position of the longitudinal axis of the corrugated outer pipe relative to the position of the longitudinal axis of the at least one inner pipe by means of a detection device, e) in the event that in step d) the longitudinal axes are not arranged in a correct position relative to one another, adjusting the position of the corrugated outer pipe relative to the inner pipe by means of a positioning device until its longitudinal axis is arranged in the correct position relative to the longitudinal axis of the inner pipe, f) fixing the outer pipe in the correct position.

[0009] A second aspect The invention relates to a manufacturing plant for carrying out the method according to the first aspect of the invention. The manufacturing plant comprises the following stations, viewed in the direction of production x: an insulating foam preparation device comprising a forming shoulder for continuously wrapping the inner tube with the film tube and an injection head for introducing the foamable starting material between the film tube and the inner tube, an extruder for extruding the outer tube around the inner tube with the film tube and the foamable starting material, thus producing a semi-finished product, a corrugator for generating a corrugation in the outer tube, a protective tube for protecting the inner tube with the film tube and the foamable starting material during the extrusion and / or corrugation of the outer tube, a positioning device for adjusting the position of the outer tube relative to the inner tube, and a detection device for detecting a position of the longitudinal axis of the outer tube relative to the position of the longitudinal axis of the at least one inner tube.

[0010] In the present inventive manufacturing method and, accordingly, in the present inventive manufacturing system, the generally known method of centering the inner tube in the outer tube is abandoned. Instead, the inner tube is used as a reference, and the position of the corrugated outer tube is adjusted relative to the inner tube, which is reflected in step e) of the method or in the positioning device of the manufacturing system. Another difference from the known procedure is that the centering takes place after the corrugator, not before the corrugator.

[0011] The conduit pipe produced by the present inventive production method using the present inventive production plant is preferably used as a district heating pipe.

[0012] The present invention has the advantage that the finished conduit pipe can be manufactured with at least the same accuracy in centering the concentric pipes as previously known, but with increased flexibility at the same time. In other words, the above-mentioned permissible inner pipe coaxial deviation of a maximum of 3 mm, which applies to the above-mentioned CALPEX®< conduit pipe, is also maintained for the conduit pipe according to the present invention. This coaxial deviation means that the longitudinal axis of the inner pipe and the outer casing may deviate from each other by a maximum of 3 mm. Converted to the insulation layer thickness, this would mean that the insulation layer thickness varies up to a maximum of 6 mm. This provides a conduit pipe that, with regard to inner pipe centricity, meets at least the accuracy of known comparable conduit pipes and is simultaneously more flexible. Short description of the drawings

[0013] Further embodiments, advantages, and applications of the invention will become apparent from the dependent claims and the following description with reference to the figures. These show: Fig. 1 schematically shows a production plant according to the invention; Fig. 2 schematically a detailed view of section A from Fig. 1 ; Fig. 3 schematically in cross section along line B from Fig. 2 a line pipe manufactured using the method and the manufacturing plant according to the invention, with an inner pipe; and Fig. 4 schematically in cross section along line B from Fig. 2 a line pipe with two inner pipes manufactured using the method and the manufacturing plant according to the invention. Ways to implement the invention Definitions:

[0014] The manufacturing direction x is defined as horizontal, as in Fig. 1 marked. In Fig. 1The production facility is shown vertically for clarity only. Fig. 3 and 4 it is to be interpreted as protruding vertically from the plane of the drawing.

[0015] A first adjustment direction for the outer tube is the y-direction, which is also horizontal and perpendicular to the manufacturing direction x, as in Fig. 3 and 4 An "adjustment" of a position in the y-direction generally involves a shift in the +y-direction and / or -y-direction.

[0016] A second adjustment direction for the outer tube is the z-direction, which is vertical and perpendicular to the manufacturing direction x, as in Fig. 3 and 4 An "adjustment" of a position in the z-direction generally includes a shift in the +z-direction and / or -z-direction.

[0017] Pipe insulation is referred to differently depending on its state. A "foamable starting material" is defined as a liquid material that is not yet foaming. This type of material is well known and usually consists of a composition of at least two liquid components that can react with each other and foam in the process. Additional components may be added, e.g., components that delay the reaction to delay foam formation. In this context, "expanding insulation foam" refers to a mixture that is already in a state of chemical reaction, which manifests itself in foam formation with a slow expansion. The reaction is assumed to be incomplete, and the foam is still expanding in all directions that offer free space."Cured insulating foam" here means that the reaction between the two liquid components is complete and the foam has reached a dry, solid state and can no longer expand on its own. "Foam front" refers to a position in the x-direction of production at which the still-expanding insulating foam has reached the top of the film tube described below. The foam front advances in the x-direction, continuously expanding the insulating foam.

[0018] A finished line pipe is defined as the line pipe that can be wound onto a drum for delivery. Until this point, the line pipe is defined, among other things, as a semi-finished product, whereby in the course of the description, reference is made only to the components of the semi-finished product that are relevant in the respective context. The term "semi-finished product" is considered to be redefined after each manufacturing step, with the additional properties of that final manufacturing step.

[0019] The "increased flexibility" of the inventive pipe refers to a comparison with a prior-art HDPE pipe of the same dimensions. The measure of flexibility used here is the modulus of elasticity (E-modulus). HDPE pipes are known to have an E-modulus between 900 MPa and 1500 MPa. Using the inventive method, pipes of the invention with an E-modulus of less than 700 MPa can be achieved, which represents significantly greater flexibility.

[0020] Fig. 1 shows a simplified schematic of a production plant H for producing a heat-insulated pipe 18, which has a number of different stations in the production direction x. With reference to Fig. 3The finished pipe 18 comprises a corrugated outer pipe 1, an inner pipe 2, and a cured insulating foam 1a between the two pipes 1, 2. The previously mentioned foil sleeve, which also remains in the finished pipe, is not shown. The medium to be transported, e.g., hot water for district heating, flows through the inner pipe, which is also called the carrier pipe.

[0021] Again with reference to Fig. 1In a first step, an inner tube 2 is continuously unwound from a supply roll 3 by means of an unwinder 4 known to those skilled in the art and fed to the production line H. Alternatively, inner tube rods of a specific length can be fed to the production line, which are then connected to form a continuous tube. The inner tube can be a plastic tube or a metal tube, and it can be smooth or corrugated. In particular, an inner tube 2 made of cross-linked polyethylene is used. The inner tube 2 is guided through a braking track 5, the purpose of which will be explained later.

[0022] In a further optional but preferred sub-step, the inner tube 2 is held in an expected centered position before the next step by means of a centering device 5a. The inner tube should be roughly positioned so that its longitudinal axis is arranged as centrally as possible in the later extruded outer tube. This centering is only roughly possible because the outer tube is not yet present at this point. Such a centering device is known and comprises, for example, centering jaws. The reason for this sub-step is, among other things, to enable the liquid foamable material introduced in the next step to flow around the inner tube. With inner tubes made of plastic, this avoids the possibility of the inner tube becoming a blockage for the foamable material due to unavoidable sagging at the bottom.This step can be omitted for metal inner tubes as they are inherently stiff and sag only slightly.

[0023] In the next step, a plastic film 6, in particular a polyethylene film, is pulled off a supply spool and guided over a forming shoulder 7. The forming shoulder 7 is designed such that it deflects the plastic film as a film tube 6 around the inner tube 2 concentrically to the latter. The film tube 6 is formed with a glued or welded longitudinal seam, and before this sealing, a foamable material, which is a liquid plastic mixture, is introduced into the interior of the film tube by means of a mixing head 8, in particular a PUR 2-component mixing head; this is known and will not be described in detail here. The film tube is, for example, a polyethylene-based plastic.By using the film tube 6, the subsequent outward expansion of the insulating foam located between the inner tube and the film tube is limited, so that the insulating foam cannot, or can only partially, fill the corrugation of the outer tube later created in a corrugator and harden there. Accordingly, the space between the inner tube and outer tube is only approximately 80% filled. This increases the flexibility of the finished conduit 18. "Subsequent expansion" means that the foamable starting material is formed before being introduced into the film tube 6 in such a way that it essentially only begins to expand when the semi-finished product exits the corrugator, thereby forming a foam front.

[0024] The semi-finished product, consisting of the inner tube, film tube, and foamable material between them, is introduced into a protective tube 9, which primarily serves to protect the semi-finished product from the elevated temperature occurring in the subsequent step, which is also known. It should be noted that the protective tube 9 extends through the extruder described below and into the corrugator described later.

[0025] In the next manufacturing step, the plastic outer tube 1 is extruded onto the semi-finished product using an extruder with an extrusion head 10. The extrusion head is preferably an extruder deflection head 10. The manufacturing step of extruding the outer tube 1 is known and will not be explained in detail.

[0026] Now, in the manufacturing sequence of the conduit 18, after the extrusion step, the outer pipe 1 is corrugated by means of a corrugator 11. A deep corrugation is introduced into the outer pipe using forming jaws. This corrugation is known and can normally be achieved in various ways, e.g., by pressing the corrugated form into the outer pipe or by vacuum-pulling the outer pipe, which is still very soft and thus deformable due to the process heat, outwards into appropriate shapes. For thin pipes, it is also possible to blow compressed air from the inside towards the outer pipe, so that the outer pipe is pressed outwards onto corresponding corrugated forming jaws. For the present application, only the second and third alternatives are used, since the insulating foam has not yet expanded at this point.For the first alternative, in which the mold jaws exert a force inwards from the outside, there is no counterpressure from the insulating foam in this process, so that a corrugation could not be introduced or could only be introduced insufficiently.

[0027] The protective tube 9 preferably ends approximately 50 cm after the point at which the corrugator's mold jaws close. The protective tube 9 must create a separation between the outer tube 1 and the film tube 6 up to the point at which the vacuum is applied. If the protective tube ends too early, the vacuum will attract not only the outer tube but also the foamable material, which must be avoided.

[0028] Upon exiting the corrugator 11, the semi-finished product comprises the inner tube 2, surrounded by the film tube 6 and the corrugated outer tube 1. At this point, the foamable material begins to foam, so that a foam front is formed, preferably directly upon entry into a subsequent positioning device 12. However, it is also possible that the foam front is formed somewhat later.

[0029] The semi-finished product now enters the positioning device 12, which adjusts the position of the outer tube relative to the inner tube. The outer tube is displaced such that its longitudinal axis is positioned in a correct position relative to the longitudinal axis of the inner tube. Of course, the outer tube is only displaced in the y-direction and / or z-direction if a deviation from the correct position has been detected.

[0030] This check of the position of the outer pipe is carried out by means of a detection device 13 arranged downstream of the positioning device in the production direction x. One such detection device is, for example, an X-ray device 13 known from EP0897788. With the aid of this device, the outer pipe 1 is continuously checked for an exactly central position in relation to the inner pipe 2 if it is a single inner pipe. In other words, the intended position is given by the fact that the longitudinal axes of the outer pipe and the inner pipe coincide. In the production of thermally insulated line pipes with more than one inner pipe, the position of the outer pipe is adjusted if the longitudinal axis of the outer pipe and a geometric center of gravity of the inner pipes are not in a proper relationship to one another, taking into account the specified position tolerances.In this case, it is preferable if the inner tubes are rigidly coupled together after the brake track 5 to prevent positional deviations of the inner tubes during subsequent manufacturing steps. For this purpose, spacer elements, preferably clips 1b, are used. ( Fig. 4 ),which are snapped onto the inner ears manually or automatically at specific intervals. For this purpose, the clips are flexible to a certain extent so that they can be pulled apart to overcome the diameter of the respective inner ear. The X-ray device 13 further comprises or is connectable to a control unit of the production plant. A cross-section of the semi-finished product is visualized on a display and any deviations from the intended position are indicated. Optionally, an audio signal can also be generated if the deviation goes outside the permissible tolerances. It is preferred if the distance of the X-ray device 13 from the positioning device is changeable in order to achieve the most representative detection possible, e.g. depending on the diameter of the conduit to be produced, e.g. with regard to different sagging behavior of the semi-finished product after the positioning device.Since this is a continuous manufacturing process, a certain amount of time is required after the production line has started up due to the position of the X-ray device 13 after the positioning device, until the feedback is effectively established between the determined position of the outer tube and the adjustment of this position by the positioning device within the permissible tolerances. The X-ray device can optionally also be coupled to the centering device 5a to also optimize the rough positioning of the inner tube, so that following a corresponding adjustment of the centering device, the positioning device only needs to correct minor deviations.

[0031] In a further step, the semi-finished product, now filled with foam, is secured in its intended position using a fixation device 23 arranged in front of the X-ray device 13 to prevent further deviation from the intended position due to sagging of the outer pipe. Such sagging could occur because the insulating foam may not have cured at this point, or may not have cured sufficiently to counteract the sagging. The position of the fixation device can also be adjusted in the x-direction depending on the pipe to be manufactured.

[0032] After the X-ray device 13, the semi-finished product is preferably transported through a cooling device 14, which accelerates the cooling of the outer pipe and the insulating foam. After the cooling device, which preferably, but not limited to, operates with cold water, the thermally insulated pipe 18 is finished.

[0033] If a cooling device is provided, a pulling bead 15 is provided after this, otherwise after the X-ray device 13. This pulling bead 15, in conjunction with the braking bead 5 mentioned above, ensures that the line pipe to be produced is aligned as straight and taut as possible from the inlet to the outlet of the production plant H. The braking bead acts mechanically on the inner pipe fed to the production plant, and the pulling bead acts mechanically on the finished line pipe leaving the production plant. The braking bead interacts with the pulling bead in such a way that the beads tension the inner pipe in the production direction x with a specified maximum sagging tolerance along the stations of the production plant. To exert the mechanical effect, the braking bead and the pulling bead each have guide elements which are in contact with the inner pipe orthe finished pipe and are designed in such a way that they vary a sliding friction in order to set a specified tension of the inner pipe.

[0034] Finally, the finished pipe is wound onto a drum 17 using a winding device 16. Alternatively, the finished pipe can be cut to length in bars.

[0035] Now, the positioning device 12 will be described in detail in the context of Fig. 2 explained. Fig. 2 shows a schematic detail view of section A from Fig. 1 It is expressly noted at this point that during the step of adjusting the position of the outer pipe using the positioning device, the pressure is applied directly exclusively to the outer pipe. Any indirect effect on the inner pipe via the expanding insulation foam is neglected.

[0036] The positioning device 12 comprises a guide rail 21 arranged directly at the output of the corrugator 11, which guides the semi-finished product horizontally transversely to the production direction x or holds it in position. Transversely to the production direction x, i.e. in the + / - y direction, means that the guide rail prevents the semi-finished product from shifting excessively in this direction. The guide rail 21 can also be an independent device of the production device or part of the corrugator. The guide rail is preferably designed as an upwardly open U-profile on which the semi-finished product rests. The lateral width of the U-profile can preferably be adapted to the diameter of the semi-finished product. It has been shown that when producing the outer pipe from plastic containing LD-PE or LLD-PE, the semi-finished product is more difficult to hold in position due to the greater flexibility of the outer pipe, i.e.The semi-finished product can shift more easily transversely to the production direction, i.e., in the y-direction, which is undesirable. The guide rail 21 effectively compensates for this behavior by holding the semi-finished product in the desired position in the y-direction due to its shape.

[0037] As already mentioned, the foamable starting material is formed before being introduced into the film tube 6 in such a way that the foam front is already formed when the semi-finished product enters the positioning device. The formation of the foam front can begin either when it reaches the guide rail 21 or only when it enters another element of the positioning device. The advantage of the foam only beginning to expand at this point is that it is not yet too viscous. As the viscosity increases until the insulating foam hardens, the effect of the displacement device described below on the outer pipe has a significant indirect effect on the inner pipe itself, so that this would consequently also shift.Due to the initially low viscosity of the insulating foam in this phase, a shift in the position of the outer pipe causes no or only a negligible shift in the inner pipe, so that an alignment of the outer pipe to the inner pipe with the required precision is possible.

[0038] This element of the positioning device is a displacement device 22 for adjusting the position of the outer tube in the y-direction and / or in the z-direction. The displacement device is arranged downstream of the guide rail in the production direction x at a first, adjustable distance from the guide rail 21. Advantageously, the first, adjustable distance provides increased flexibility in minimizing the offset in the y-direction for different diameters of the semi-finished product. The further the displacement device is from the guide rail, the more the position-correcting effect of the guide rail would deteriorate, depending on the diameter of the semi-finished product. It has been shown that a first distance of approximately 150 mm is advantageous for outer tube diameters of 70 mm to 150 mm.Even if a renewed offset in the y-direction can subsequently be compensated in the corresponding displacement device, it is desirable that such a renewed offset be kept as small as possible.

[0039] In a first embodiment, the displacement device can be the Fig. 2 Shown are a first displacement unit 22a for adjusting the position of the outer tube in the y-direction and a second displacement unit 22b for adjusting the position of the outer tube in the z-direction. The first displacement unit and the second displacement unit are arranged one after the other in the production direction x, different from one another, and at a second, variable distance from one another. The order is arbitrary, but due to the aforementioned offset in the y-direction, the arrangement of the displacement unit in the y-direction before the displacement unit in the z-direction is preferred.

[0040] Alternatively, the displacement device may comprise a single displacement unit for adjusting the position of the outer tube in the y-direction and in the z-direction.

[0041] Regardless of the above alternatives, the displacement device comprises at least two V-grooves or rollers, one for the y-direction and one for the z-direction. These V-grooves or rollers are connected to each other for each of the two directions and arranged opposite one another on either side of the outer tube, so that the outer tube is held in place with as little play as possible. These pairs of V-grooves or pairs of rollers are designed such that they can hold outer tubes of different diameters; in other words, the distance between the V-grooves or rollers is variable. They are aligned such that, in order to adjust the position of the outer tube, they move it in the respective y-direction and the opposite y-direction, or the z-direction and the opposite z-direction.

[0042] In the first alternative, the adjustment of the position of the outer tube can be carried out by means of at least one drive successively in the y-direction and z-direction or vice versa individually for each direction or, in the second alternative, combined as a simultaneous displacement in the y-direction and in the z-direction.

[0043] During the step of adjusting the position of the outer tube using the positioning device, at least one of the following two sub-steps is carried out. If a specified position in the y-direction does not already exist, the position of the outer tube is adjusted in the y-direction by the outer tube being displaced accordingly using the displacement device or the corresponding displacement unit until the specified position is reached in the y-direction. If a specified position in the z-direction does not already exist, the position of the outer tube is adjusted in the z-direction by the outer tube being displaced accordingly using the displacement device or the corresponding displacement unit until the specified position is reached in the z-direction. As mentioned, the order of the steps is arbitrary, or the steps can be carried out simultaneously.The adjustment of the position of the outer tube is triggered when specified position tolerances are exceeded when detecting the position of the longitudinal axis of the outer tube relative to the position of the longitudinal axis of at least one inner tube.

[0044] In embodiments, when adjusting the position of the outer tube in the z-direction, this position is set with a vertical offset from the intended position in the z-direction. The offset compensates for a deviation of the position of the outer tube from the intended position of the outer tube in the z-direction due to at least one of the following factors: weight of the inner tube, viscosity of the insulating foam, degree of curing of the insulating foam, temperature of the inner tube, material of the inner tube, temperature of the outer tube. This is explained using the example of the weight of the inner tube. Ideally, the inner tube would not sag, but this obviously cannot be the case, since the inner tube always sags more or less depending on its condition. As a result, its longitudinal axis can change further along, e.g.Depending on the viscous nature of the insulation foam and how it "supports" the inner pipe, the outer pipe could shift, and the previous positioning of the outer pipe would be incorrect because the longitudinal axis of the outer pipe would no longer coincide with the longitudinal axis of the inner pipe. This offset can be compensated for with the above measure, whereby the factors listed above can be considered individually or in any combination.

[0045] The positioning device preferably has adjustment elements (not shown) for setting a reference position of the displacement device, which can be operated manually or automatically using corresponding servomotors. This allows the displacement device or the V-channel or rollers to be adjusted at the start of the process such that an imaginary, expected, intended longitudinal axis of the semi-finished product is centered within the V-channel or rollers, and the V-channel or rollers are adjusted to the correct outer pipe diameter. This advantageously reduces the subsequent continuous adjustment of the position of the outer pipe during the process to a minimal offset of the adjusting elements of the displacement device.

[0046] Furthermore, the positioning device 12 preferably comprises a fixing device 23 for holding the outer pipe in the adjusted (intended) position at a third variable distance downstream of the displacement device 22 in the production direction x. The fixing device can be formed from one fixing element or from at least two successively arranged fixing elements 23a, 23b. The second alternative shown in the figure is preferable to a single-point fixing as a two-point fixing. The fixing device ensures that the adjusted, intended position of the outer pipe relative to the inner pipe is not distorted after exiting the displacement device. This could happen because the insulating foam may not yet be fully cured at this point and the semi-finished product is still relatively flexible. Another factor is the flexibility of the outer pipe comprising LLD-PE.

[0047] The second and third distances mentioned can be used to advantage, as with the first distance already described, to optimize the manufacturing process with regard to the precision of adjusting the position of the outer tube, depending on the semi-finished product.

[0048] In embodiments, the position of the foam front in the production direction x is optically detected by initially leaving the outer tube transparent and then coloring it with pigments only after the position of the foam front has been detected. Pigmentation is preferably carried out by adding a color masterbatch in the extruder so that the coloring becomes visible with a delay only after the foam front has been detected. This advantageously allows the start and progress of the foaming process to be easily monitored continuously during production.

[0049] Fig. 3 shows schematically in cross section along the line B from Fig. 2a conduit pipe 18 manufactured using the method and the manufacturing plant according to the invention, with a single inner pipe 2 through which the medium to be insulated flows, concentrically thereto the outer pipe 1 (the corrugation of the outer pipe not being shown for the sake of simplicity) and the cured insulating foam 1a in between.

[0050] Fig. 4 shows schematically in cross section along the line B from Fig. 2a conduit 18 manufactured using the method and the manufacturing plant according to the invention, comprising two inner pipes 2a, 2b through which the media(s) to be insulated flow, the outer pipe 1 concentrically arranged therewith (the corrugation of the outer pipe not being shown for the sake of simplicity), and the cured insulating foam 1a between them. Also illustrated is the previously described spacer element 1b, which remains as a lost element in the finished conduit and is preferably made of plastic.

[0051] The present invention solves the problem that, with more flexible conduits made of LLD-PE (Linear Low Density Polyethylene) or plastic containing LLD-PE, exact centering of the outer and inner pipes relative to one another could not be achieved with the required accuracy using the methods previously used due to this flexibility. Because the inner pipe is no longer centered in the existing outer pipe, but rather only the outer pipe is acted upon, it is possible to compensate for the increased flexibility of the outer pipe in this regard. It should be noted that the aforementioned curing of the insulating foam does not mean that the conduit is completely rigid. Rather, the increased flexibility of the conduit is to be regarded as increased within the applicable characteristic values ​​for such thermally insulated conduit pipes.

[0052] A further advantage of the invention is that positioning accuracy can be increased more easily during the ongoing process, since the position adjustment takes place at the end of the manufacturing process rather than at the beginning. This is achieved because the insulating foam only expands shortly before the positioning device and is not yet cured at the time of the position adjustment. In contrast, the known position adjustment at the beginning of the manufacturing process with foaming at the beginning of the process has the disadvantage that subsequent manufacturing steps, particularly corrugation, during which increased forces can act on the semi-finished product, can distort the previously achieved positioning.

[0053] Although preferred embodiments of the invention have been described, it is understood that the invention may be practiced in other ways within the scope of the following claims. Terms used in the description such as "preferred," "particularly," "advantageous," etc., refer only to optional and exemplary embodiments.

Claims

1. Method for the continuous production of a thermally insulated line pipe (18) by means of a production plant (H), wherein the thermally insulated line pipe (18) comprises, in the finished state, an outer pipe (1) made of LLD-PE or LLD-PE-containing plastic, at least one inner pipe (2) arranged in the outer pipe (1) and a hardened insulating foam (1a) between the inner pipe (2) and the outer pipe (1), wherein the production of the thermally insulated line pipe (18) is carried out in a substantially horizontal production direction x through various stations of the production plant (H), wherein the method comprises the steps of a) forming a foil tube (6) around the at least one inner pipe (1) and introducing a foamable starting material into the foil tube (6), which starting material expands to form an insulating foam and the insulating foam hardens, wherein the hardened insulating foam (1a) fills at least part of the space between the inner pipe (2) and the outer pipe (1) in the finished line pipe (18), b) passing the inner pipe (2) with the foil tube (6) and the foamable starting material through an extrusion head (10), by means of which the outer pipe (1) is extruded around the inner pipe (2) with the foil tube (6), so that a semi-finished product is formed, c) forming a corrugation of the outer pipe in a corrugator (11) to produce a corrugated outer pipe (1), wherein the foamable starting material is formed before being introduced into the foil tube (6) in such a way that it essentially only begins to expand when the semi-finished product emerges from the corrugator (11), thereby forming a foam front, characterized by the steps of d) detecting a position of the longitudinal axis of the corrugated outer pipe (11) relative to the position of the longitudinal axis of the at least one inner pipe (2) by means of a detection device (13), e) in the event that in step d) the longitudinal axes are not arranged in an intended position relative to one another, adjusting the position of the corrugated outer pipe (1) relative to the inner pipe (2) by means of a positioning device (12) until its longitudinal axis is arranged in the intended position relative to the longitudinal axis of the inner pipe (2), f) fix the outer pipe (1) in the intended position.

2. Method according to claim 1, wherein in the step of adjusting the position of the outer pipe (1) by means of the positioning device (12), action is exerted exclusively on the outer pipe (1).

3. Method according to claim 1 or 2, wherein the inner pipe (2) is held clamped in the manufacturing plant (H) in the manufacturing direction x by means of a brake bead (5) in cooperation with a traction bead (15).

4. Method according to one of the preceding claims, wherein the foamable starting material is formed before being introduced into the foil tube (6) in such a way that the foam front only begins to form or has already formed when the semi-finished product enters the positioning device (12).

5. Method according to one of the preceding claims, wherein in the step of adjusting the position of the outer pipe (1) by means of the positioning device (12) at least one of the two sub-steps is carried out: e1) adjusting the position of the outer pipe (1) in a y-direction horizontally perpendicular to the direction of manufacture x, if an intended position in the y-direction does not already exist, by carrying out a corresponding displacement of the outer pipe (1) by means of at least one first displacement unit (22a) until the intended position in the y-direction is reached, and / or e2) adjusting the position of the outer pipe (1) in a z-direction vertically perpendicular to the manufacturing direction x, if an intended position in the z-direction does not already exist, by carrying out a corresponding displacement of the outer pipe (1) by means of at least one second displacement unit (22b) until the intended position in the z-direction is reached, where steps e1 and e2 can be carried out in any order or steps e1 and e2 can be carried out simultaneously.

6. Method according to claim 5, wherein when adjusting the position of the outer pipe (1) in the z-direction, this position is set with a vertical offset from the intended position in the z-direction, wherein with the offset a deviation of the position of the outer pipe (1) from the intended position of the outer pipe (1) in the z-direction due to at least one of the following factors: weight of the inner pipe, viscosity of the insulating foam, degree of hardening of the insulating foam, temperature of the inner pipe, material of the inner pipe, temperature of the outer pipe is compensated for.

7. Method according to one of the preceding claims, wherein the inner pipe (2) is roughly centered with a predetermined tolerance in the outer pipe (1) by means of a centering device (5a) before the outer pipe (1) with the inner pipe (2) enters the corrugator (11).

8. Method according to one of the preceding claims, wherein the semi-finished product is guided or held in position horizontally transversely to the production direction x immediately after leaving the corrugator (11), in particular continuously, by means of a guide rail (21).

9. Method according to one of the preceding claims, wherein the adjustment of the position of the outer pipe (1) is triggered if, when detecting the position of the longitudinal axis of the outer pipe (1) relative to the position of the longitudinal axis of the at least one inner pipe (2), defined position tolerances of the position of the longitudinal axis of the outer pipe (1) relative to the position of the longitudinal axis of the inner pipe (2) are exceeded.

10. Method according to claim 9, wherein, during manufacture of thermally insulated line pipes (18) with exactly one inner pipe (2), the position of the outer pipe (1) is adjusted if the longitudinal axes of the outer pipe (1) and the inner pipe (2) are not identical, taking into account the specified positional tolerances, or wherein, during manufacture of thermally insulated line pipes (18) with more than one inner pipe (2a, 2b), the position of the outer pipe (1) is adjusted if the longitudinal axis of the outer pipe (1) and a geometric center of gravity of the inner pipes (2a, 2b), which are in particular rigidly coupled to one another, are not in an intended relationship to one another, taking into account the specified positional tolerances.

11. Method according to one of the preceding claims, wherein the position of the foam front in the direction of manufacture x is optically detected by initially leaving the outer pipe (1) transparent and only coloring it by means of pigments after the position of the foam front has been detected.

12. Method according to one of the preceding claims, wherein, if a plurality of inner pipes (2a, 2b) are present, these are connected to one another by means of spacer elements (1b) before the foil tube (6) is formed in such a way that they have a rigid configuration relative to one another, wherein spacer elements (1b) are attached continuously at a predefined distance along the inner pipes (2a, 2b), in particular are snapped in as a clip around the inner pipes (2a, 2b).

13. Manufacturing plant (H) for carrying out the method according to one of the preceding claims, comprising the following stations, viewed in succession in the manufacturing direction x: an insulating foam preparation device comprising a forming shoulder (7) for continuously wrapping the inner pipe (2) with the foil tube (6) and an injection head (8) for introducing the foamable starting material between the foil tube (6) and the inner pipe (2), an extrusion head (10) for extruding the outer pipe (1) around the inner pipe (2) with the foil tube (6) and the foamable starting material, a corrugator (11) for generating a corrugation in the outer pipe (11), a protective tube (9) for protecting the inner pipe (2) with the foil tube (6) and the foamable starting material during extrusion and / or corrugation of the outer pipe (1), a positioning device (12) for adjusting the position of the outer pipe (1) relative to the inner pipe (2), a detection device (13) for detecting a position of the longitudinal axis of the outer pipe (1) relative to the position of the longitudinal axis of the at least one inner pipe (2), and a cooling device (14) for cooling the finished line pipe (18).

14. Manufacturing plant according to claim 13, wherein the positioning device (12) is arranged downstream of the corrugator (11) in the manufacturing direction x.

15. Manufacturing plant according to one of the claims 13 or 14, wherein the positioning device (12) comprises a guide rail (21) arranged directly at the outlet of the corrugator (11), which guides or holds the semi-finished product in position horizontally transversely to the manufacturing direction x.

16. Manufacturing plant according to claim 13 or 14 and claim 15, wherein the positioning device (12) further comprises a displacement device (22; 22a, 22b) for adjusting the position of the outer pipe (1) in the y-direction and / or in the z-direction, wherein the displacement device (22; 22a, 22b) is arranged in the manufacturing direction x downstream of the guide rail (21) at a first changeable distance from the guide rail (21) .

17. Manufacturing plant according to claim 16, wherein the displacement device (22; 22a, 22b) comprises either a first displacement unit (22a) for adjusting the position of the outer pipe (1) in the y-direction and a second displacement unit (22b) for adjusting the position of the outer pipe (1) in the z-direction, wherein the first displacement unit (22a) and the second displacement unit (22b) are different from each other and are arranged at a second changeable distance from each other in the manufacturing direction x in any order one after the other, or comprises a single displacement unit (22) for adjusting the position of the outer pipe (1) in the y-direction and in the z-direction, in particular wherein the displacement device (22; 22a, 22b) comprises at least two V-channels or rollers for the y-direction and for the z-direction, respectively, which V-channels or rollers for each of the two directions are connected to each other and arranged opposite each other on one side of the outer pipe (1) and aligned in such a way that they displace the outer pipe (1) in the respective y-direction and y-counter-direction or z-direction and z-counter-direction to be adjusted in order to adjust the position of the outer pipe (1), and the position of the outer pipe (1) is adjustable by means of at least one drive successively in the y-direction and z-direction or vice versa individually for each direction or combined as a simultaneous displacement in the y-direction and in the z-direction.

18. Manufacturing plant according to one of claims 13 to 17 and claim 16, wherein the positioning device (22; 22a, 22b) further comprises adjustment elements for setting a reference position of the displacement device (22; 22a, 22b), which adjustment elements can be operated manually or automatically by means of corresponding servomotors.

19. Manufacturing plant according to one of claims 13 to 18 and claim 16, wherein the positioning device (12) comprises a fixing device (23; 23a, 23b) for holding the outer pipe (1) in the adapted position in the manufacturing direction x at a third changeable distance after the displacement device (22; 22a, 22b), wherein the fixing device (23; 23a, 23b) is formed from one fixing element (23) or from at least two successively arranged fixing elements (23a, 23b).

20. Manufacturing plant according to one of claims 13 to 19, wherein a brake bead (5) is provided before the insulating foam preparation device and a traction bead (15) is provided after the cooling device (14) for tensioning the inner pipe (2) in manufacturing direction x, wherein the brake bead (5) acts mechanically on the inner pipe (2) fed to the manufacturing plant (H) and the traction bead (15) acts mechanically on the finished line pipe (18) leaving the manufacturing plant (H), and the brake bead (5) and the traction bead (15) interact in such a way that they tension the inner pipe (2) in the manufacturing direction x with an intended maximum sag tolerance along the stations of the manufacturing plant (H), wherein the brake bead (5) and the traction bead (15) each has guide elements which are in contact with the inner pipe (2) and the finished line pipe (18), respectively, and are designed in such a way that they each vary a sliding friction in order to set an intended tension of the inner pipe (2).

21. Manufacturing plant according to one of claims 13 to 19, wherein the detection device (13) comprises an X-ray system by means of which the position of the longitudinal axis of the outer pipe (1) can be measured in relation to the position of the longitudinal axis of the at least one inner pipe (2), further comprising a display device by means of which the corresponding measurement results can be output, in particular graphically.