CH703167A2 - Composite pipe for use in remote heating pipeline above ditch on road for guiding of two separated fluid stream at different temperature, has thermal insulation layer arranged between fluid flow channels and guiding elements - Google Patents

Abstract

The pipe (10) has an inner pipe (11) arranged in a center pipe (12) that is arranged in an outer pipe (13) such that a cavity is formed between an external wall of the inner pipe and an inner wall of the center pipe and between the external wall of the center pipe and the inner wall of the outer pipe. A thermal insulation layer (15) is arranged in a cavity between the inner pipe and the center pipe such that fluid flow channels (101, 102) are formed in the inner pipe and between the center pipe and the outer pipe. The layer is arranged between the channels and guiding elements (14). The thermal insulation layer covers polyurethane foam pipes or glass fiber pipes that are covered with an aluminum foil. Independent claims are also included for the following: (1) a pipeline comprising an individual exterior fixed bearing (2) a method for setting line distance of a composite pipe.

Description

The present invention relates to a composite pipe according to the preamble of claim 1. It further relates to a pipeline, which is carried out using such a composite pipe, an internal fixed point, as well as the use of the composite pipe.

Known piping systems, such as e.g. the channel, steel jacket pipe and plastic composite jacket pipe (KVMR) -Verlegung have each a flow and return line, which are arranged in pairs, juxtaposed or one above the other. The temperature-related length expansions are usually recorded in the form of U, L, Z-arc or compensators. Another possibility is the thermal or mechanical preload. In the sewer design, the supply and return line is stored separately on slide, roller or guide bearings and insulated. Consequently, it is free in its thermal dynamics. The actual duct takes over the mechanical and moisture protection of the cables and can also be used for operating temperatures above 130 ° C.

In the case of the steel jacket pipe method, the supply and return lines are each located in a e.g. Polyethylene (PE) coated and additionally cathodically protected steel protective tube arranged. The annular space serves as a spacer by roller bearings and heat insulation. External loads are taken over by the jacket pipe alone and provide optimal moisture protection of the thermal insulation. Operating temperatures above 130 ° C are permissible.

When KVMR system, carrier pipe and casing pipe are continuously connected by the polyurethane (PUR) foam. Traffic and earth loads act on the PUR foam and the medium pipe via the jacket pipe. In addition to the thermal bias and the known so-called cold laying is applied, which causes large Erstdehnwege and in the detention area high compressive stresses. The PUR thermal insulation has a temperature resistance up to approx. 130 ° C. The KVMR has achieved great market significance.

The known systems require in part a large civil engineering volume, are space consuming and time consuming to implement or have to protect the pipes a security system consisting essentially of equipment, which must be maintained, or the temperature rating is only up to about 130 ° C.

It is an object of the invention to provide a pipe system and a pipe of the type mentioned.

According to one aspect of the invention, the device should be specified so that the disadvantages of the prior art are avoided. Thus, according to one aspect, the technology of the piping systems is to be simplified and improved so as to reduce, for example, the heat losses into the soil, the construction period, the traffic obstruction and the total costs. It is a cold laid, non-positive and slim district heating pipe, hereinafter also referred to as compact pipe, from rigid pipes with high flow temperature up to, for example, 200 ° C or depending on steel quality and above for main, distribution and domestic service lines indicated. This, in addition to a variety of other advantageous properties, is able to afford the composite pipe according to claim 1.

It is further indicated a pipeline, which is created using the described composite pipe, a method for assembling a line section of such a pipeline and uses of the composite pipe or the pipeline. Further embodiments of the invention will become apparent from the dependent claims.

The described composite pipe for guiding two separate fluid streams, in particular at different temperature of the fluid streams, therefore comprises an inner tube, an outer tube and a central tube. The inner diameter of the central tube is greater than the outer diameter of the inner tube and the inner diameter of the outer tube is larger than the outer diameter of the central tube. The inner tube is arranged in the central tube and the central tube is arranged in the outer tube; such that in each case a cavity is formed between the outer wall of the inner tube and the inner wall of the central tube and between the outer wall of the central tube and the inner wall of the outer tube. In the cavity formed between the inner tube and the center tube, a heat insulating layer is disposed. In each case a fluid flow channel is formed in the inner tube and between the central tube and the outer tube, wherein the two fluid flow channels are thermally insulated from one another.

A tube is in the context of this disclosure, a tube with a cross section in principle of any geometry. Tubes with a circular cross-section represent a specific and advantageous embodiment. In the case of tubes with a non-circular cross-section, the person skilled in the art will readily be able to read the term "diameter" in general as a cross-sectional dimension.

In one embodiment, the tubes are arranged concentrically with each other.

In one embodiment of the composite tube, the inner diameter of the outer tube and the outer diameter of the central tube are chosen so that in the channel formed between the central tube and outer tube is able to flow the same mass flow of a given fluid as in the inner tube at the same pressure drop. In this case, narrowing of the flow cross-section between the central tube and the outer tube by the spacer elements and the branches described below are to be considered.

With these features results in a slim pipe construction and it is possible to consistently use proven materials. The pipe system can be used universally in the creation of pipelines, for example, for main, distribution and service lines. In this case, pipes of different sizes or nominal masses can be used, in such a way that a larger mass is used for main lines than for distribution lines and there again a larger size than for house connection lines. Due to the specified slender and compact composite pipe trench volume, road maintenance, traffic obstruction during installation are significantly reduced. The reduced space, material, energy and time required simplifies the laying of a pipeline and results in lower costs for construction, installation, operation and maintenance, without compromising operational safety. The space requirement of such a compact line is less than when supply and return line are led side by side. The design in a single tube makes it possible to discharge branches laterally, which reduces the necessary coverage height of the lines and thus again the civil engineering volume and the cost of laying. The composite pipe appears outwardly as a single-jacket pipe, and ultimately reduces the number of jacket pipe joints exposed to the environment by 50%. Furthermore, in a laid line from this composite pipe traffic and earth loads act on the outer tube. The inner tube, which is thermally stressed, for example, as a flow of a district heating pipe, and the associated insulation remain mechanically unloaded and are protected against other external influences.

A further development of the composite pipe is characterized in that the outer tube is a KVMR, which comprises a media-carrying tube having an outer insulation made of PUR foam, which in turn has a jacket tube surrounding the insulation. The jacket tube consists for example of hard polyethylene, short HDPE. The media-carrying pipe, the insulation and the jacket pipe are non-positively connected with each other. The use of the known and proven KVMR as an outer tube results in a high reliability, water resistance and robustness. As described below, the mechanical and thermal loading of the KVMR, in particular the PUR foam and the outer jacket, compared to conventional cold-laid KVMR lines is reduced by the application of the technical teaching taught here and thus increases the expected life and reliability even more.

In one embodiment of the composite tube axially spaced apart guide elements are arranged between the central tube and the inner tube, which are made specifically for the operational temperatures and forces. For example, these are arranged on the circumference of the inner tube. The guide elements are arranged in an exemplary embodiment, in particular at regular or at least substantially regular axial distances. The guide elements thereby effect a radial and in particular centric, thermal bridge-free guidance and storage of the inner tube in the central tube. They are at least axially displaceable relative to the inner tube and / or the middle tube, such that an axially displaceable movable bearing of inner tube and middle tube results. This ensures the displaceability of the pipes during assembly of the compact pipe and the relative movements between the inner, middle and outer pipe can be accommodated. Axial between the guide elements, the heat insulating layer is arranged. The axial distance between the guide elements is smaller than the critical buckling length of the inner tube. The guide elements preferably have a sufficiently high strength to ensure a secure and stable radial bearing, and at the same time a sufficiently low thermal conductivity to avoid the formation of pronounced thermal bridges between inner and central tube.

In a further development of the composite tube spacer holding elements are arranged between the center tube and the outer tube, which cause a radial and concentric guidance of the center tube in the outer tube, wherein in the region of the spacer holding elements a flow cross-section remains, and wherein the distance holding elements relative to the central tube and / or are axially displaceable relative to the outer tube in order to obtain an axially displaceable storage here, too. The dimensions and the distances of the spacer elements are determined according to the operational requirements resulting in the respective desired operation.

The guide elements and / or the spacer elements are advantageously adapted to the geometry of the tubes, and have, for example, in particular in circular tube cross-sections, an annular basic geometry or are designed annular. These are then guide rings and / or spacer rings. In particular, a guide element in an exemplary embodiment substantially completely fills the entire space between the inner tube and the central tube in the radial direction, while the spacer holding elements must imperatively release a flow cross section between the central tube and the outer tube. The spacer elements are, for example, in a manner described in more detail below star-shaped, and are made for example of flat steel. In one embodiment, the guide elements and / or the spacer elements are circumferentially interrupted at one location to achieve some flexibility and adaptability of the radial mass; this facilitates, for example, the assembly and facilitates adaptation to radial thermal expansion during operation.

If a line section is constructed with a composite tube of the type described above, an internal fixed point is arranged in one embodiment at the end of the line route. At this the inner tube and the center tube and the outer tube are mounted axially fixed or limited and in particular well-defined axial clearance, wherein both in the inner tube and between the central tube and the outer tube, a flow channel is maintained. This is called inside fixed point, because at this point the individual tubes of the composite tube are internally mounted against each other. The cold laid line can be due to the special structure in principle arbitrarily long. The line is limited if, due to external boundary conditions, such as terrain and / or obstacles, a bending of the composite pipe would be necessary, the one determined by the geometry of the pipeline, the materials used, the intended operating temperatures, pressures and voltages, and the like dependent critical bending radius.

The fixed point is also referred to as non-positive return medium leading internal fixed point.

Due to the solid bond between inner, middle and outer tube by means of the return medium leading, internal fixed point accounts for the laying of a pipeline with the composite pipe described, for example, roller guide bearing and the concrete structures for external benchmarks. Due to the solid composite of the three steel pipes at the pipe ends and the arrangement of the return medium between the middle and outer pipe, the large initial strains and the material stresses in the so-called cold laying, which will be described below, reduced and it can be saved considerable amounts of Dehnpolstermaterial.

In one embodiment, the fixed point is a single assembly, which have larger pipe wall thicknesses in the region of the fixed point construction for the introduction of compressive and tensile forces than in the rest of the line region and which can be connected in particular by welding with the pipes. Inserted flameproof thermal insulation pieces reduce the heat transfer from the inner and central tube in an exemplary embodiment. In a further development, the fixed point comprises an inner component, an outer component, and a middle component, wherein the inner component can be arranged within the middle component and the middle component within the outer component can be arranged, and wherein in the assembled state in the inner component and between the middle component and the outer component Flow channel is formed. In this case, for example, the inner component, the middle component and the outer component, in particular in a manner similar to a bayonet lock axially locked against each other, and further, in a further embodiment, the axial dimension of the outer component is greater than the axial dimension of the central component, and the axial dimension of the central component is greater than that of the inner component, such that in the assembled state the axial ends of the inner component come to lie within the middle component and the axial ends of the middle component come to rest within the outer component. This design allows a particularly efficient method of mounting the fixed point to the pipes, which comprises the inner component of the fixed point is firmly connected to one end of the inner tube, the center component of the fixed point is pushed axially over the inner component, the center component is brought by rotation about the tube axis in a position in which it is axially mounted against the inner component, the middle component is firmly connected to one end of the central tube, the outer component of the fixed point is pushed axially over the middle component, the outer component is brought by rotation about the tube axis in a position in which it is axially mounted against the central component, and the outer component is firmly connected to one end of the outer tube, wherein the compounds are produced in particular by welding.

These steps are preferably carried out in the order given, which of course also here not explicated further steps between the steps described can be performed.

A method for assembling a line section from the composite pipe described comprises joining elements of the composite pipe of the type described together; insert branch elements if required; and to arrange an inboard anchor point at each conduit end in the manner described above. In a further embodiment, the line section is bent as needed to a maximum of the critical bending radius of the composite tube.

In the arrangement of an internal fixed point at each end of a line route, the supply and return lines, or the inner tube, the center tube, and the outer tube, not move differently due to different thermal expansions, and there is a balance of power between the tubes a, which in turn results in shorter Gleitbereichslängen.

Due to the permanent bond between the inner, middle and outer tube, and in the above-described use of the KVMR also of media-carrying pipe and PUR foam or PUR foam and HDPE jacket, the line acts as a complete unit. This means that the occurring forces are transmitted and distributed to all components of the line. Due to the coaxial arrangement of the fixed point, a deflection of the line due to a bi-metal effect is prevented.

The heat insulation layer arranged between the inner tube and the central tube comprises PUR foam tubes and / or glass fiber tubes in exemplary embodiments, the insulating tubes being wrapped in particular with aluminum foil. For example, unslotted PUR foam tubes and glass fiber tubes are used. The embodiment with PUR foam tubes allows operation up to flow temperatures of approx. 130 ° C, while with water-repellent glass fiber tubes operating flow temperatures up to over 200 ° C are provided. In principle, other materials are suitable with a suitable heat resistance and heat insulation, since the insulation layer is mechanically unloaded; the forces are carried by the guide elements. With suitable materials both for the heat insulation and the guide elements as well as for the pipes, in principle higher flow temperatures than the 200 ° C mentioned by way of example can be provided.

Of course, the described embodiments of the composite tube can be combined.

A pipeline using the above-mentioned composite pipe comprises at least one pipe section constructed of a composite pipe of the type described above. The composite pipe has a critical bending radius. This is determined by various parameters, such as the materials used, the tube cross-sectional dimensions, and the like, and its determination is explained in more detail below in an embodiment. Globally, the critical bend radius is when, when bending the composite pipe of this radius or a narrower radius, the stresses that occur due to bending in the pipes, in one of the pipes, allowing for a safety factor and material and u.U. reach or exceed the maximum permissible voltage dependent on the operating parameters. Overall, the determination of the critical bending radius is familiar to the expert. On any route on which the line is currently laid or the critical bending radius is not exceeded, a single line section is arranged, is arranged exclusively at the ends of the line each an internal fixed point in which the axial displaceability of the inner tube, the Middle tube, and the outer tube are obstructed against each other, while in the intermediate region of the conduit route, the tubes are arranged free of an internal mutual axial bearing. In particular, no expansion compensators, arches, or other length compensation elements and devices for compensating the thermal expansions must be arranged, such that the pipeline is advantageously designed free of such elements. When laying the described pipeline or the described composite pipe no systemic changes in direction are made or built compensators, nor is the pipe thermally or mechanically biased. Due to the operational self-prestressing, the laying can be done in a straight line as long as the terrain and / or obstacles allow and the residual displacements in the subsequent pipe bending areas can be accommodated. If directional changes have to be made by arches, then a non-positive, return-medium-guiding, internal fixed point of the type described above is to be arranged and thus the termination of the line route.

Due to the properties of the composite pipe, it is possible that branch off laterally in the region of a line section.

In a further development of the pipeline, a single fixed bearing is arranged in particular in the middle of a line route, in particular a line section without adhesive area, in which the outer tube is mounted axially fixed against the environment. This counteracts an uncontrolled shift in the overall system. Other external benchmarks are not required. An adhesive area, where the friction of the environment is sufficient to prevent a displacement of the pipe, acts as a natural benchmark.

In the inner tube, the warmer flow medium is performed, which is for example water or other suitable for energy transport fluid. Between the central tube and the outer tube, the colder return medium is guided. Heat losses to the soil surrounding the pipe are thus effectively reduced.

The outer tube is not subjected to the flow medium high temperature, resulting in particular when using the KVMR, as an outer tube in a low aging of the plastics used. A critical PE jacket tube temperature, for example, 50 ° C is not achieved due to thinner Dehnpolster at the expansion zone and just at limited return temperatures, for example, 60 ° C. The use of a KVMR pipe with PUR insulation as the outer pipe is possible without restriction if these temperature limits are taken into account. Another advantage of this operation is that cold deflection results in reduced axial stresses in the adhesion area. Due to the reduced, temperature-induced axial stresses, in particular in the outer tube (KVMR), the build-up safety is also increased and the permissible lateral clearance lengths are similar to a thermally prestressed KVMR line.

Depending on the design of the insulation between the inner and central tube and the material quality of the inner tube, the line for flow temperatures up to about 130 ° C, 200 ° C, or even suitable. In an exemplary use of the composite tube, the return temperature is limited to 60 ° C to limit the total linear expansion of the conduit. This limitation also offers advantages when using a KVMR with PUR insulation as outer pipe.

Finally, in the context of the present disclosure, an internal fixed point of the type described above and the embodiments specified there are described and claimed.

Of course, the above-described embodiments and developments of the composite pipe, the pipeline, the fixed point and the assembly process can be combined with each other. In this sense, combinations of the features of the subclaims are disclosed among each other, even if a combination in the back covers of the claims was not explicitly specified.

The invention will be explained in more detail with reference to an embodiment illustrated in the drawing. Show in detail <Tb> FIG. 1 <sep> an example of a conduit using the composite tube described; <Tb> FIG. Figure 2 is a more detailed illustration of the structure of an exemplary embodiment of the composite tube; <Tb> FIG. 3 <sep> a cross section through the composite tube of Fig. 2; <Tb> FIG. 4 <sep> an exemplary guide ring for thermal bridge-free storage of inner tube and center tube; <Tb> FIG. 5 <sep> an embodiment of a spacer element for use between the middle and outer tube; <Tb> FIG. FIG. 6 shows an example of the arrangement of a line with the illustrated composite pipe in a heavily used cross-section of a road; FIG. <Tb> FIG. 7 <sep> the connection of a branch line; and <Tb> FIG. 8 <sep> an exemplary embodiment of a fixed point for terminating a line route.

For the understanding of the invention, not immediately essential details have been omitted in the drawing. The following description of the embodiment and the drawings serve to better understand the invention, and are not to be used to limit the invention characterized in the claims.

In Fig. 1, an exemplary pipeline is shown in a highly schematic representation, which is constructed of a composite tube of the type described above. A straight or bent to a critical bending radius line 1 is assembled in a manner not shown from axially successive elements of the composite tube. An inner tube 11 is arranged in a central tube 12 and this in an outer tube 13. In the inner tube an inner flow channel 101 is formed, which is used for example as a flow line for guiding hot water for a district heating supply. Between the outer tube and the central tube, an outer flow channel 102 is formed, which is used for example as a return line for returning the fluid from the consumer. Between the inner tube and the outer tube, not shown in this illustration, an insulating layer, and arranged at axial intervals radially acting guide elements. These are provided so that axial movements between the inner tube and the center tube are not hindered. Likewise, not shown spacer support elements are also arranged for the radial mounting of the outer tube and center tube, which also ensure a free axial mobility of central tube and outer tube. The limitation of such a line route arises when line bends 3 or the like must be provided, i. the bending radius is smaller than the critical bending radius. The line section is then terminated by internal fixed points 2 at which the inner tube against the central tube and the central tube against the outer tube are axially fixed. To the outside, at most an outer bearing 40 is recommended, on which the outer tube is mounted against the environment, if the friction surrounding the soil laid in the ground pipe is insufficient to prevent uncontrolled displacement of the line section 1. When laying the pipeline in the ground or for example a sand bed creates a friction between the outer tube and the environment, which counteracts a displacement of the pipeline and hinders the thermal expansion. This frictional force is all the greater, the longer the line piece lying in the sand bed, for example. From one end of the line takes the frictional force and thus the obstruction of the temperature-induced expansion of the line to the line center towards. From a certain distance, the strain in the center of the line is completely obstructed, and the pipeline can no longer slide in the environment, such as, for example, a sand bed with filling material. This area of the pipeline, in which the movement of the pipeline is completely prevented, is called the adhesion area. The line sections at the end of a line route in which the expansion is not completely hindered, in which the force due to the thermal expansion is greater than the static friction between the outer tube and the surrounding area, is called a sliding area. If an adhesive area is present, this acts as a natural fixed point, and the arrangement of a special fixed bearing in the middle of the line is not absolutely necessary.

Due to the rigid connection of inner, middle and outer tube with an internal and return medium leading fixed point at the line end results in the initial startup by the well-known technique «operational self-bias» the following: The inner tube 11 wants to increase with rising temperatures up to maximum Extend operating temperature in length, but is hampered by the fixed points 2 and the axial bearing on the middle and outer tube - which indeed have much lower temperatures - in its longitudinal extent, and is biased by uniform flow when reaching the yield strength. This Dehnbehinderung is caused by the resistance of the middle and outer tube and by the friction between the outer tube and the soil. The return flow flowing between the central tube and the outer tube causes small, temperature-dependent voltage variables in the outer and middle tubes and the risk of buckling of the conduit system is counteracted.

In Fig. 2 is a detail of a line section of the example shown in Fig. 1 a district heating compact pipe section shown in more detail. The composite tube used by way of example and shown comprises an inner tube 11, which is designed for transmitting a hot flow medium as a steel tube, a central tube 12 and an outer tube 13. Within the inner tube, a flow channel 101 is formed which serves as a flow channel for flowing to a consumer flow medium while an annular space 102 between the central tube and the outer tube serves as a return channel for flowing back from the consumer medium. The annular cavity between the inner tube and central tube can be used in one embodiment by means of monitoring wires or sensors and by means of positive or negative pressure to control the moisture or water attack. In this cavity is also the insulating material, such as unslotted PUR foam tubes up to flow temperatures of 130 ° C, or, for example, 200 ° C or beyond, for example, unslotted, especially water-repellent glass fiber tubes with a thermal conductivity of 0.035 W / mK at + 50 ° C, which can still be wrapped with an aluminum foil. The inner tube is mounted in the center tube by means of guide elements, guide rings 14 over the entire length of the line route at axial intervals, wherein between the guide elements 14, the insulating material 15 is arranged. Due to the design of the guide elements 14 made of a thermal insulation material, the storage is free of thermal bridges or without pronounced thermal bridges. In principle, there is a great freedom of choice in the selection of the insulating material, since the storage of the tubes is taken over each other by the guide rings 14 and the insulating material 15 is mechanically unloaded. The center tube, consisting of steel, is externally loaded by the return medium and supported by star-shaped metal support rings 16 in the outer tube 13, wherein the annular cavity between the central tube and outer tube is used to transfer the return medium. The outer tube is designed as KVMR with or without diffusion barrier and with different insulation thicknesses. A steel tube 131 is encased by a plastic jacket tube 133 made of HDPE, the annular space between the steel tube 131 and the plastic jacket tube 133 with, for example, with PUR foam 132, with a thermal conductivity of about 0.026 W / mK at + 50 ° C, and complete frictionally filled with foam. It is known that leak warning and locating cables can be inserted in the PUR foam to monitor for leaks or moisture drops. The storage of the tubes into each other by means of the guide elements 14 and the spacer elements 16 is carried out such that an axial displaceability of the tubes is not hindered against each other. The heat loss from the flow medium is absorbed by the return medium, thereby the heat loss to the ground is reduced by about 50% compared to a juxtaposition of flow and return line. When creating a line section shown in FIG. 1, axial elements of limited length are preferably prefabricated with the described construction and welded together on site.

Fig. 3 shows an exemplary cross section, vertical to the longitudinal axis of a described herein and claimed compact tube for a line according to Fig. 1 and 2. The guide rings 14 are hidden in this cross section of the insulation 15 and not shown. Inner tube 11, the insulating material 15, the guide rings 14, not shown, the center tube 12, the star-shaped spacer element 16, and the outer tube 13, comprising the media-carrying tube 131, the polyurethane foam 132 and the jacket tube 133 are prefabricated as a unit.

The installation of a pipe from the described composite pipe, so a compact pipe, is very simple, because the pipes and other moldings are prefabricated, so that on the site largely only straight connections are executed. If the local conditions allow, it is in any case more advantageous to weld the items outside or above the trench to longer sections to perform the pressure and tightness test, nachisolieren the joints and then with the so-called and the person skilled in per se known pipeline technology on the lower prepared sand bed.

A curved pipe section can be made by welding a straight pipe section and then elastic bending of the pipe when laying in the trench. This can be done by successively bending a free end of the line, if necessary by means such as e.g. Winches. If the pipe bending stress in the KVMR with steel pipe diameter DN 225 is limited to 140 N / mm <2>, for example, a safety factor of 1.5 against the hot yielding limit will result in a radius of curvature of 181 meters. The size of the values for the bending stress and the safety must be decided by the project managers. For narrower radii of curvature, the line must be terminated in the manner described by means of the internal fixed points and a bow line to be connected.

With the first operational start from the tension-free mounting state of the cold-laid line to the nominal operating temperature, the inner tube (flow) wants to expand, but finds no free expansion, because inner, middle and outer tube are rigid by the inner, return medium leading point fixed to each other connected. A steadily increasing equilibrium of forces between inner tube on the one hand and middle resp. Outer tube on the other hand arises. The steel area cross-sections of the center and outer tubes are much larger in relation to the inner tube, i. the tensions in it are much smaller. The axial compressive stress in the inner tube is not equal to the full temperature stress, as under the assumption of purely elastic deformations, but is equal to the yield strength and thus smaller than the full temperature stress. The tension in the inner tube reaches the flow limit before reaching the operating temperature. As a result, the inner tube is plastically compressed by uniform flow. When cooled to ambient temperature, the inner tube now has a tensile prestressing force and the middle and outer tubes have a compressive force of the same size. Each subsequent heating causes an elastic deformation.

The self-prestressed compact tubing with, for example, an inner tube diameter of 114.3 mm from St. 37.0, a center tube diameter of 193.7 mm from St. 37.0 and an outer tube diameter of 244.5 mm from St. 37.2, KVMR Da = 400 mm, for an operating flow temperature of 180 ° C at a max. Operating pressure of 32 bar and a return temperature of 60 ° C and a pipe peak coverage of 0.6 m, resulting in the first start a line displacement of Al = 40 mm. After self-prestressing, the normal stress in the inner tube (flow) at maximum operating temperature is 34% below the hot yield point.

With the reduced initial expansions and the practically constant return temperatures, the jacket pipe connections, except when starting and stopping, exposed only insignificant changing temperature-related displacements, which in turn has an advantageous effect on the tightness of the socket joints and the shear stress of the polyurethane foam. Thus, the statically stressed plastics in the KVMR will be subject to much less aging under the influence of the return temperature. This also extends the technical life, and it also increases the security of the system. The heat loss from the flow goes into the return and the approximately 50% lower heat loss to the ground in comparison to the leadership of the flow medium in a single-installed KVMR or in other systems, the operating costs decrease accordingly. The arrangement of the return in the outer space of the cold laid composite pipe, the axial stresses are not fully utilized and therefore allow a more flexible wiring.

In order to avoid the risk of cyclic plasticizing, it is necessary at higher operating temperatures and larger pipe dimensions and economic wall thicknesses to use steels with corresponding yield strength, in particular from a non-alloyed or low-alloy, welded, ferritic steel pipe according to DIN 1626; an unalloyed or low-alloy, seamless, ferritic steel pipe according to DIN 1629; an unalloyed or low-alloy, seamless, ferritic, heat-resistant steel tube (boiler tubes), for example St. 35.8 or St. 45.8, according to DIN 17175; a fine grain steel, for example according to DIN: WStE 51 material number 1.8937), WStE 420 (material number 1.8932) WStE 460 (material number 1.8935) or StE 690 (material number 1.8928 and 1.6919); a stainless, acid-resistant and austenitic tubular steel, for example XIOCrNiTi 189 or X2CrNiMo 1810 according to DIN 17440.

Fig. 4 shows a guide ring 14 which centrally superimposed in the described composite tube, the inner tube in the central tube and is disposed between the mechanically unloaded insulation material. The guide ring is made of a pressure-resistant thermal insulation material, which is manufactured specifically for the operational temperatures and forces. The guide ring has in this embodiment, a leak water cutout 141 and two radial holes 142 which are symmetrical to the leak water cutout at an angle of, for example, 120 ° to each other. The holes serve to clamp the guide ring on the inner tube, which is particularly useful during assembly.

As a material for the guide elements or the guide ring comes a thermally insulating and pressure-resistant material in question. In order to ensure a sufficient guiding and centering function on straight pipe sections, the compressive strength should be at least 10 MPa. Specifically, the required minimum values result from the specific system configuration. It goes without saying that the material must also have the appropriate mechanical strength values at the desired operating temperatures, loads and forces.

Fig. 5 shows a star-shaped metal ring 16, which serves as a spacer element between the middle and the outer tube and the center tube centered in the outer tube. The construction shown by way of example, which leaves a flow cross section for the return medium free, is made for example of flat steel. The illustrated construction with a circumferential gap ensures elasticity in the circumferential direction.

FIG. 6 shows an exemplary cross-section of a compact pipeline integrated into the road superstructure of a main road or intersection. In this area, the compact pipeline is embedded in concrete, so that the high loads from road traffic can be absorbed with a minimum overlap.

Fig. 7 shows a partial longitudinal section (in the lower half of the tube shown) by a laterally outgoing connection compact pipe, for example, a service line. This also comprises an inner tube 11, a central tube 12, and an outer tube 13, which in the manner already described as KVMR with the media tube 131, a jacket tube 133, and the PUR insulation 132 is constructed. Inner, middle and outer tubes are connected to the respective corresponding tubes of the conduit shown in cross-section, for example, welded. Between the inner and middle tube also an insulating layer 15, and at axial intervals guide elements 14 is arranged. Between the center and outer tube spacer elements, not shown, are arranged in the manner described above. 101 and 102 designate the flow channels which are in fluid communication with the respective corresponding flow channels 101 and 102 of the main conduit. The length of the house connection line is included inside the building. Inside the building, the pipes carrying the return pipe are tightly welded to a ring and the return pipe is discharged laterally.

Such outgoing lines, e.g. House connections, can be created laterally and can be realized over the entire length of the route. Branches in the sliding area experience smaller displacements with cold laid compact piping than with conventional laying of KVMR. It should be noted that when starting and stopping the composite pipe, a relative movement between the inner, middle and outer pipe is established. In order to prevent that the branches are claimed inadmissible by relative displacements, the heating gradient and the flow rate of the medium should be selected so that the relative movements can be recorded in the interstices of the outlet lines. So that no greater stresses occur in the cross-sectional area than in the longitudinal section, the diameter ratio of the base pipe to the reinforced outlet nozzle must generally be greater than 1.5.

Fig. 8 shows in various views an example of a three mutually rotatable parts fixed point 2, which are welded from the inside to the outside of the existing lines to terminate a line route and mutual axial support of the three tubes of the composite pipe described create. The fixed point comprises an inner component 50, a middle component 60, and an outer component 70. Their diameter can correspond in each case to the diameter of the corresponding tube or require the fixed point components to use larger tubes for constructional reasons. The inner component has a number of lugs on its outer circumference, for example in the axial center position. Likewise, the outer component has on its inner circumference in the interior of the tube projecting noses. In this case, these noses cover only a part of the circumference, and leave space between them, in order, as will be described later, to release a flow cross-section between the middle and outer components. The middle component has at two axial positions lugs 61 and 62, which protrude both inwardly and outwardly. These are arranged with respect to their circumferential positions on the outside of the central component analogous to those of the lugs of the outer component, and on the inside of the middle component analogous to those of the inner component. In the present example, the circumferential positions on the inner and outer components are identical, but this is not mandatory in terms of number and arrangement. In the axial position, the tabs of the central component are complementary to those of the inner and outer components, respectively, such that the tabs 51 and 71 of the inner and outer components can be axially arranged between the tabs 61 and 62 of the central component. This can be seen in particular in FIGS. 8a and 8d. The result of this arrangement is that the components of the fixed point can be axially locked against one another in the manner of a bayonet closure as follows: The middle component is brought into a coaxial circumferential position relative to the inner component, in which the inner noses of the central component lie in the circumferential direction between the noses of the inner component come. Thereafter, the middle component is axially guided over the inner component until the lugs of the inner component lie axially between the inner lugs of the central component. Then the components are rotated in the circumferential direction against each other so that the lugs of the inner component comes to lie axially between the inner lugs of the central component. As a result, inner and middle components with at most a small and defined game are axially fixed against each other. In this position, for example, a circumferential fixation by welding the components with the corresponding tubes of the composite tube; In particular, the inner component is firmly connected to the inner tube from the beginning. Then the outer component is pushed in an analogous manner axially over the middle component, and the lugs 71 of the outer component are brought into engagement with the outer noses of the middle component by twisting, and finally the circumferential position is fixed. In this way, a composite of axially against each other supporting components, which are connected to the composite tube, and the tubes of the composite tube at the end of a line route axially against each other. Due to the increasing from the inside to the outside axial dimension of the components of the fixed point, the joints of the pipes to be connected are each free to assembly, for example, for welding, accessible before the respective outermost component is pushed over. As can be seen in particular in FIGS. 8b and 8c, an outer flow channel 102 remains in the circumferential direction between the lugs, which corresponds to the annular channel between the outer tube and the central tube of the composite tube and is preferably supplied with return medium during operation. The channel 101 within the inner component is supplied, for example, with the flow.

The arrangement and number of noses can of course be deviating from the illustrated as long as the described bayonet function is achieved and the strength of the lugs ensures the axial support. In particular, axially spaced lugs may be arranged on the inner component, engage between the corresponding individual lugs on the inside of the central component. Likewise, axially spaced lugs may be arranged on the outer component, engage between the corresponding individual lugs on the outside of the central component.

Although the invention is explained with reference to specific embodiments, the invention as set forth in the claims is in no way limited to these embodiments. The person skilled in the art will readily be aware of further embodiments and applications of the composite pipe according to the invention on the basis of the description and explanation of the invention given above.

LIST OF REFERENCE NUMBERS

[0057] <Tb> 1 <sep> line route <Tb> 2 <sep> Fixed Points <Tb> 3 <sep> pipe bends <Tb> 10 <sep> composite pipe <tb> 11, 11 <sep> Inner tube <tb> 12, 12 <sep> Middle tube <tb> 13,13 <sep> outer tube <tb> 14, 14 <sep> Guide element, guide ring <tb> 15, 15 <sep> Isolation <tb> 16, 16 <sep> Distance element, distance ring <tb> 40 <sep> outer warehouse <tb> 50 <sep> Inner component of a fixed point <tb> 51 <sep> Nose, Axialveriegelungselement <tb> 60 <sep> Middle component of a fixed point <tb> 61 <sep> Nose, Axialveriegelungselement <tb> 62 <sep> Nose, Axialveriegelungselement <tb> 70 <sep> Outer component of a fixed point <tb> 71 <sep> Nose, Axialveriegelungselement <tb> 101, 101, 101 <sep> inner flow channel; forward channel <tb> 102, 102, 102 <sep> outer flow channel, return channel <tb> 131, 131 <sep> Media pipe of a composite pipe <tb> 132, 132 <sep> Insulation; Insulation of a composite pipe, PUR insulation <tb> 133, 133 <sep> Jacket tube <Tb> 141 <sep> leakage water cut <Tb> 142 <sep> Hole

Claims (14)

1. A composite pipe for guiding two separate fluid streams, in particular at different temperature of the fluid streams, comprising an inner tube (11), an outer tube (13) and a central tube (12), wherein the inner diameter of the central tube is greater than the outer diameter of the inner tube and the Inner diameter of the outer tube is greater than the outer diameter of the central tube, and wherein the inner tube is arranged in the central tube and the central tube is arranged in the outer tube, such that between the outer wall of the inner tube and the inner wall of the central tube and between the outer wall of the central tube and the inner wall of the A heat insulation layer (15) is further arranged in the cavity formed between the inner tube and the central tube, such that in each case a fluid flow channel (101, 102) is formed in the inner tube and between the central tube and the outer tube , where between the b eiden fluid flow channels an insulating layer is arranged. 2. A composite pipe according to claim 1, characterized in that between the central tube and the inner tube axially spaced and in particular substantially regular axial spacing guide elements (14) are arranged, which for a radial and in particular centric, guide and radial mounting of the inner tube in the center tube are provided, wherein the guide elements are axially displaceable at least relative to the inner tube and / or the central tube, and wherein the heat insulating layer is arranged axially between the guide elements, wherein the guide elements in particular consist of an insulating material and further in particular of a pressure-resistant insulating material, such that a thermal bridge-free guidance and storage is made. 3. A composite pipe according to one of the preceding claims, characterized in that between the central tube and the outer tube spacer elements (16) are arranged, which cause a radial and concentric guidance of the central tube in the outer tube, wherein in the region of the spacer elements, a flow cross section between the central tube and the outer tube remains, and wherein the spacer elements are axially displaceable relative to the central tube and / or relative to the outer tube. 4. The composite pipe according to one of the preceding claims, characterized in that the heat insulation layer (15) comprises PU foam tubes and / or glass fiber tubes, which are wrapped in particular with aluminum foil. 5. A composite pipe according to one of the preceding claims, characterized in that at the end of a line section (1) an internal fixed point (2) is provided, on which the inner tube against the central tube and the central tube against the outer tube mounted axially fixed or with limited axial play is, wherein both in the inner tube and between the central tube and the outer tube, a flow channel is maintained. 6. A composite pipe according to claim 5, characterized in that the fixed point is a single assembly, which is connectable in particular by welding with the tubes. 7. A composite pipe according to claim 6, characterized in that the fixed point (2) comprises an inner component (50), an outer component, (70) and a central component (60), wherein the inner component within the central component can be arranged and the central component within the outer component can be arranged, and wherein in the assembled state in the inner component and between the central component and the outer component, a flow channel (101, 102) is formed. 8. A composite pipe according to claim 7, characterized in that the inner component, the middle component and the outer component are axially locked against each other, wherein the axial locking is carried out in particular in the manner of a bayonet closure. 9. Pipe, comprising at least one line section (1), which is formed from a composite pipe (10) according to one of the present claims, characterized in that on any route, on which in particular a critical bending radius of the composite pipe is not exceeded, a single Conductor line is arranged, in which exclusively at the ends of the line section depending an internal fixed point (2) is arranged, in which the axial displaceability of the inner tube, the center tube, and the outer tube are obstructed against each other, while in the intermediate region of the line section, the tubes free an internal mutual axial bearing are arranged. 10. Pipe according to claim 9, characterized in that branch off laterally in the region of a line section. 11. Pipe according to one of claims 9 or 10, characterized in that in particular in the middle of a line route, a single outer fixed bearing (40) is arranged, in which the outer tube is axially fixed against the environment. 12. Inboard fixed point (2) characterized by the internal fixed point features of one of claims 5 to 8. 13. A method for assembling a pipe section of a composite pipe according to one of claims 1 to 8, comprising line elements according to one of claims 1 to 8 join together and connect; inserting branch elements as needed; to arrange an inside fixed point at each line end by - The inner component of the fixed point is firmly connected to one end of the inner tube, the middle component of the fixed point is pushed axially over the inner component, - The middle component is brought by rotation about the tube axis in a position in which it is axially mounted against the inner component, - The middle component is firmly connected to one end of the central tube, the external component of the fixed point is pushed axially over the middle component, - The outer component is brought by rotation about the tube axis in a position in which it is axially mounted against the central component, and - The outer component is firmly connected to one end of the outer tube, wherein the compounds are produced in particular by welding, and which method further comprises in one embodiment in particular to bend the line route, if necessary, up to the critical bending radius of the composite tube. 14. A composite pipe according to one of claims 1 to 8 for media management, in particular as a district heating line, wherein in the inner tube, the flow medium is guided and between the central tube and the outer tube, the return medium is guided.