EP1152879A1

EP1152879A1 - Method and device for the discontinuous production of heat-insulated pipes

Info

Publication number: EP1152879A1
Application number: EP00909130A
Authority: EP
Inventors: Rainer Welte; Karl-Dieter Kreuer; Reiner Napp; Helmut Duschanek; Wolfgang Müller; Patrick BRÜNINGHAUS
Original assignee: Bayer AG; Hennecke GmbH
Current assignee: Bayer AG; Hennecke GmbH
Priority date: 1999-02-09
Filing date: 2000-02-01
Publication date: 2001-11-14
Also published as: AU3152000A; NO20013567L; NO20013567D0; WO2000047387A1; PL350578A1; DE19905275A1

Abstract

The invention relates to so-called heat-insulated double pipes (5, 6) which have a heat-insulating layer (15) consisting of rigid expanded polyurethane. Pipes of this type can be produced with an improved insulation effect and without heat bridges or cold bridges by positioning the pipes (5, 6) separately from each other before the intermediate space (11) between them is filled with foam in order to eliminate any deflection that has arisen as a result of their previous storage, and by filling the intermediate space (11) of the finished double pipe (5, 6) with rigid expanded polyurethane only.

Description

Method and device for the discontinuous production of thermally insulated pipes

The invention relates to a method and a device for the discontinuous production of thermally insulated pipes with a thermal insulation layer made of rigid polyurethane foam produced by foaming in the space between an outer pipe and an inner pipe, the pipes being centered and mechanically fixed in their position relative to one another before the foaming are and wherein at least one pullable mixing head is introduced into the intermediate space, which, when pulled out, ejects a reaction mixture forming a rigid polyurethane foam, which foams to form the thermal insulation layer, and a heat-insulated tube with a thermal insulation layer which fills the space between an outer tube and an inner tube and is produced by foaming made of rigid polyurethane foam.

It is generally known to use pipes with thermal insulation made of rigid polyurethane foam for the transport of warm or cold liquids or gases to be kept at the same temperature, the inner pipe, which is usually made of steel, being used to conduct the temperature-controlled medium. The outer tube, which is generally made of polyethylene, essentially has the function of a protective cover and is therefore also called “cladding tube”. Such heat-insulating tubes are also referred to in technical terms as “double tubes”.

In the past, the ends of both pipes were clamped concentrically to each other in the simplest way and the gap was foamed. Before the double pipe was manufactured, the individual pipes were generally stored and usually suffered a deflection due to this storage and transport. Another one

The problem is the elastic deflection of the pipes during the foaming process by its own weight. This resulted in an inhomogeneous thermal insulation layer when foaming depending on the condition of the inner and outer pipe. In other words, this was possibly of different thickness, which had a disadvantageous effect on the thermal insulation properties. The deflection due to the weight of the pipes is particularly unpleasant in the case of longer pipes, ie pipes over a length of about 6 m.

Therefore, in the manufacture of such pipes, spacers were introduced into this space between the outer pipe and the inner pipe before foaming with rigid polyurethane foam, which, in addition to the centering of the spacing, also took on the task of aligning (plastic manual volume 7, "Polyurethane" , 3rd edition, Carl Hanser Verlag Munich-Vienna, page 283, ISBN 3.446-16263-1) Alignment is necessary because, as described above, the individual tubes often warp during the previous storage, especially bend It is obvious that the insertion of such spacers is associated with lengthy and complex manual work. Due to the narrowness of the space, the insertion and correct placement are associated with many uncertainties, in particular inaccuracies, which means that exact alignment with one another is only possible to a limited extent and also from the Number of spacers is dependent, so of course a The desired homogeneous thermal insulation along the pipe length is also questioned. In order to absorb the sometimes considerable forces, these spacers are made of solid and stable material, such as metal or plastic. This material, which differs from that of the thermal insulation layer made of rigid polyurethane foam, creates heat or cold bridges which adversely affect the thermal insulation effect.

The object of the invention is to provide a method and a device for producing heat-insulated pipes with a heat-insulating layer made of rigid polyurethane foam produced by foaming between an outer pipe and an inner pipe, and a heat-insulated pipe, the alignment of the two pipes themselves and with respect to one another faster and safer with less manual labor takes place so that the heat-insulated pipe produced in this way has improved insulation properties which are homogeneous over its length, and in particular in the case of longer pipes the deflection caused by its own weight is compensated for.

According to the invention, this object is achieved by a method in which, prior to the foaming, both tubes are mechanically aligned, centered and fixed in position relative to one another about a common central axis.

“Separately from one another” is to be understood here to mean that the alignment, centering and fixing at the location of the subsequent foaming, that is to say in a device in this regard, takes place independently of one another and acts on the two pipes which do not have any contact with one another External tube acted on from outside, and on the inner tube from the inside, so that the space to be foamed remains free.

This reduces the amount of manual work required for pipes up to around 6 m in length and, thanks to the improved alignment, achieves a homogeneous thermal insulation effect over the entire length of the pipe because, on the one hand, the distance between the two pipes is constant over the length and, on the other hand, no heat or cold bridges causing spacers are present. The inner tube is also adequately aligned with the outer tube by avoiding or compensating for deflections. The deflections caused by storage and transport can be aligned linearly before processing, which is, of course, an additional work step. The pipes or their deviations from an imaginary linear center line can also be measured before being introduced into the device for foaming, and then deformations existing in the foaming device can be compensated for by means of a program control. Otherwise, the new method is centering, aligning and fixing as

Processes often more or less intertwined. Align and center accomplish this, for example, by touch-free scanning of the positions, in particular of the inner tube, at certain measuring points and the action of the alignment elements based thereon.

The outer tube is preferably centered, aligned and fixed from the outside by means of supporting surfaces.

This can advantageously be accomplished by means of appropriate machine elements. These support surfaces are preferably attached to the pipe ends or near the pipe ends. As a result, the outer tube is centered and aligned in its position at its ends, and in particular with longer tube lengths, additional support surfaces that can be attached over the length of the outer tube ensure exact alignment and positioning of the tube. It goes without saying that the support surfaces assigned to the ends can be so far away from them that there is no longer any deflection in the case of short outer tubes between them. In order for larger ones

To avoid bending in the middle area of the outer tube, it is aligned and supported at a sufficient number of points. In extreme cases, the outer tube is supported continuously over its entire length. In addition to avoiding or eliminating deflections, the support surfaces serve as a counter pressure bearing for the foaming pressure that occurs during foaming.

The inner tube is preferably centered, aligned and fixed at its ends by clamping holders.

Alignment is carried out by applying a bending moment which compensates for existing deflections, for which purpose the deflection is carried out by mechanical scanning or scanning with rays, and depending on this, a counter-bending is generated until both tubes are aligned linearly.

Suitable machine elements are also used for this. According to a further advantageous embodiment of the new method, tensioning elements are introduced into the ends of the inner tube, optionally in addition to tensioning holders, and each of them is arranged at least 0.1 m from the associated tube end, and by means of these tensioning elements, the inner tube is centered, aligned and fixed.

If necessary, a bending moment which counteracts an existing deflection of the inner tube is also exerted here by the tensioning elements and / or tensioning holders.

It is understood that the spacing of the centering elements from the pipe ends is to be set such that any unwanted deflections that are created with them for alignment are compensated for.

A prefabricated spacer is preferably made before foaming

Rigid polyurethane foam is arranged in the space and this space is foamed with two counter-rotating mixing heads.

Since this spacer is made of rigid foam with preferably the same inherent shade as the remaining thermal insulation layer produced by foaming, it is essentially homogeneous in an advantageous manner compared to conventional spacers used in the intermediate space, which consist of materials other than the rigid polyurethane foam thermal insulation layer the insulation properties of the thermal insulation layer achieved. It is particularly advantageous, however, that by inserting such a spacer, the tube length is quasi halved with regard to the inherent deflection, because at the point below the rigid foam core, the tubes can be jointly supported from below so that the inherent deflection can be compensated for by pressing up. The linear alignment at this point can be achieved, for example, by means of a light barrier, which is placed on the upper outer edge of the envelope. tube responds and at the appropriate time aborts the process of pushing up the support device.

The distance between the outer tube and inner tube is preferably maintained by the mixing head.

Ie, the outer circumference of the mixing head or a part of it designed as a spacer is matched to the outer diameter of the inner tube and the inner diameter of the outer tube in such a way that it fulfills the function of a spacer on the one hand and can be pulled out of the intermediate space without significant additional effort when foaming . The expelled, rapidly foaming reaction mixture then ensures that the correct distance between the tubes is maintained. This design of the mixing head is particularly advantageous if the outer tube consists of a less dimensionally stable polyethylene sheath.

The new device for the discontinuous production of thermally insulated pipes with a thermal insulation layer made of rigid polyurethane foam in the intermediate space between an outer pipe and an inner pipe, with the outer pipe and inner pipe being centered in relation to one another, starts from

Brackets for the pipes and at least one mixing head that can be pulled through the intermediate space to produce the thermal barrier coating.

What is new is that separate but coordinated alignment elements are provided for both the outer tube and the inner tube for alignment.

As far as the deflection due to storage and transport is not already expensive

In this way, by individually aligning the tubes before inserting them into the foaming device, the two tubes can be centered, aligned and fixed independently of one another about a common central axis. The holding As a rule, structures serve all of these processes, more or less simultaneously. This has the advantage that there is no need to insert spacers in the narrow space between the tubes, which would also represent undesirable thermal bridges. Since the alignment process of the two pipes takes place independently of one another, the elimination through the previous storage of any existing bends is possible more precisely. In particular, a deflection occurring in the device due to the weight of the pipes can be compensated. This also allows the so-called double pipe to be produced without bending, because when using the known spacers, the pipes can only be aligned with one another by this, and in extreme cases existing bending of both pipes could add up in a particularly undesirable manner. Since these alignment elements for both pipes, which due to their construction generally also take over the centering and fixing of the pipes, are coordinated with one another in terms of their positions and functions, further sources of error are excluded.

Support surfaces are preferably arranged as alignment elements towards the outside of the outer tube near each tube end.

These are usually arranged in such a way that the outer tube is immediately centered in its position at the attachment points of the support surfaces. The possible pivoting moments of the supporting surfaces can be used to generate the bending moments that are required for alignment and thus align the outer tube and center it overall about the central axis.

According to a special embodiment, further centering and aligning support surfaces are assigned to the outer tube.

Such additional support surfaces are particularly advantageous for long pipes. They are designed so that they participate in the alignment. Another one

They need a design - due to the appropriate distance from the outer tube - not to be involved in the alignment itself, and only at the last moment, so to speak, do the support surfaces attack, help with the rest of the alignment, center and fix the outer tube in its final position before foaming the gap. In the extreme case, a single or several support surface (s) distributed over the circumference of the tube extends in one piece over the entire length of the tube. In this case, alignment is primarily done by applying pressure.

The support surfaces preferably consist of prisms.

Such prisms make it possible, to a certain extent, to process outer tubes of different diameters on the same device.

According to a particular embodiment, tensioning elements which are movable, in particular pivotable, are provided for the tube ends of the inner tube as alignment elements for generating a bending moment transversely to the central axis.

Here too, centering, aligning and fixing in the end position run more or less simultaneously, through the action of these appropriately designed clamping elements.

As an alternative or at the same time as the previous embodiment, tensioning elements which can be inserted into the inner tube are provided as alignment elements and can be moved transversely to the central axis in order to generate a bending moment.

For centering, aligning and fixing the inner tube, essentially the same aspects apply with regard to the mode of operation as are described for the clamping holders that can be attached to the ends of the inner tube. Both the clamping holders for the pipe ends and the clamping elements that can be inserted into the inner pipe are advantageously designed, for example, as clamping blocks with a spreading effect.

According to a special embodiment, two counter-rotating mixing heads are provided.

This ensures that when foaming the space with a central insert made of rigid polyurethane foam, both mixing heads can be withdrawn almost simultaneously from the center of the tube, thereby reducing the time of the

Foaming process is cut in half. In addition, the resulting double tube is always symmetrically loaded with the foam pressure that occurs. It is of particular advantage, however, that this halving of the entire pipe length creates almost two pipe lengths with significantly less inherent deflection, so that larger pipe lengths, i.e. also about

6 m, can be processed.

According to a further special embodiment, the mixing head itself is designed as a spacer.

This is to be understood to mean that the circumference of the mixing head or a corresponding part of it is matched to the inside diameter of the outer tube and the outside diameter of the inner tube in such a way that the mixing head can still be pulled out without too much effort when expelling the reaction mixture, and on the other hand its task, to ensure that the two tubes are equally spaced from one another while passing through the intermediate space. Due to the ejected reaction mixture, which foams up quickly behind the mixing head, the thermal insulation layer generated maintains this distance or fixes it. The new thermally insulated pipe is based on a thermal insulation layer made of rigid polyurethane foam and arranged in the space between an outer pipe and an inner pipe.

What is new is that the tubes are aligned linearly and concentrically to each other around a common central axis and that the space between the outer tube and inner tube contains only rigid polyurethane foam.

Since there are no spacers in the gap between the materials, there are no undesirable thermal bridges, and due to the pipes that have become free of deflection due to the separate alignment, the pipe spacing is constant over the length of the double pipe and forms the basis for homogeneous thermal insulation.

According to a particular embodiment, a space in front of the

Foaming placed spacers placed on half the length of the tube, which spacer consists of rigid polyurethane foam.

The placement of this spacer does not necessarily have to be half length. However, this is advantageous because on the one hand the distance at the

Extreme point is pre-fixed and because then on the other hand mixing heads can be inserted and withdrawn on both sides at the same time

Have to travel. It goes without saying that the prefabricated spacer should consist at least approximately of the same rigid polyurethane foam as the thermal insulation layer produced from the reaction mixture, because the insulation properties are then the same. At least theoretically, before

Foaming also several prefabricated from rigid polyurethane foam

Spacers are used. But then they have to be designed in such a way that the reaction mixture expelled from the mixing head through openings in the spacers in good time before foaming in the between the

Spacers can flow space. In the drawing, the new device is shown purely schematically and together with the double tube to be foamed in section and explained in more detail below. Show it:

1 shows the device with a double tube with a spacer and two mixing heads, but without a thermal barrier coating,

2 shows the device with a double tube according to FIG. 1, namely with a spacer, two mixing heads and the reaction mixture foaming to form a thermal barrier coating,

3 shows a section along line A-B in FIG. 1,

4 shows a section along line C-D in FIG. 1.

1 to 4, the device consists of individual, but coordinated alignment and fixing elements 1, 2, 3, 4, which are functionally assigned to an outer tube 5 made of polyethylene and an inner tube 6 made of steel. Both tubes 5, 6 have a common central axis 7. To the desired bending moments on the

To be able to exercise pipes 5, 6, these alignment and fixing elements 1, 2, 3, 4 can be pivoted and fixed transversely to the central axis 7. The alignment and fixing elements 1, 2 of the outer tube 5 can engage on the outer side 8 of the outer tube 5 and consist of support surfaces 1, 2 designed as prisms 1, 2. Of which the prisms 1 are assigned to the ends 9 of the outer tube 5, the prisms 2 as further support surfaces

2 of the center of the outer tube 5. The alignment and fixing elements 3, 4 of the inner tube 6 consist of clamping brackets 3 which engage the tube ends 10 of the inner tube 6 and (or or) clamping elements 4 which engage in the inner tube 6 at a distance from the tube ends 10 The space between the outer tube 5 and the inner tube 6 is designated by 11. Two mixing heads 12, 13 are provided with a device, not shown, for supplying polyurethane reaction components connected. These mixing heads 12, 13 can be moved into the intermediate space 11 in opposite directions. They are therefore simultaneously pulled out in the opposite direction and thereby expel a polyurethane reaction mixture 14. This foams into a thermal insulation layer 15 made of rigid polyurethane foam that completely fills the space 11. A prefabricated spacer 16 made of rigid polyurethane foam is arranged in the intermediate space 11 over half the length of the tube and has the same thermal insulation properties as the remaining thermal insulation layer 15 produced by foaming.

The simplified embodiment of the device with only one mixing head without

Spacers made of rigid polyurethane foam are on hand and their functionality is easy to understand. Here the mixing head is placed at one end of the space to be foamed and pulled through it when the space is foamed. It is understood that the end sides of the space are preferably sealed to prevent contamination of the

Avoid parts of the device with a reacting reaction mixture.

Claims

claims

1. A method for the discontinuous production of thermally insulated pipes with a thermal insulation layer (15) made of rigid polyurethane foam in an intermediate space (11) between an outer pipe (5) and an inner pipe (6), the pipes (5, 6) in front the foaming is centered in its position relative to one another and mechanically fixed, and at least one pullable mixing head (12, 13) is inserted into the intermediate space (11), which, when pulled out, ejects a reaction mixture (14) forming rigid polyurethane foam, which leads to the insulating layer (15) foams, characterized in that before the foaming, both tubes (5, 6) are mechanically aligned, centered and fixed in their position relative to one another about a common central axis (7).

2. The method according to claim 1, characterized in that the outer tube (5) by means of support surfaces (1, 2) is centered, aligned and fixed from the outside.

3. The method according to claim 1 or 2, characterized in that the inner tube (6) at its ends (10) by clamping holder (3) is centered, aligned and fixed.

4. The method according to claim 1, 2 or 3, characterized in that in the ends (10) of the inner tube (6) clamping elements (4) are inserted and each of them with at least 0.1 m distance from the associated

Tube end (10) is arranged and that the inner tube (6) is centered, aligned and fixed by means of these clamping elements (4).

5. The method according to any one of claims 1 to 4, characterized in that a prefabricated spacer (16) from before foaming

Rigid polyurethane foam is arranged in the intermediate space (11) and that the space (11) is foamed with two counter-rotating mixing heads (12, 13).

6. The method according to any one of claims 1 to 5, characterized in that the distance between the outer tube (5) and inner tube (6) through the mixing head

(12, 13) is held.

7. Device for the discontinuous production of thermally insulated pipes with a thermal insulation layer produced by foaming in an intermediate space (11) between an outer pipe (5) and an inner pipe (6)

(15) made of rigid polyurethane foam, the outer tube (5) and inner tube (6) being centered and fixed to one another, consisting of brackets (1, 3, 4) for the tubes (5, 6) and at least one through the intermediate space (11 ) pullable mixing head (12, 13) for producing the thermal barrier coating (15), characterized in that both for the outer tube (5) and for the

Inner tube (6) for aligning separate but coordinated alignment elements (1, 2, 3, 4) are provided.

8. The device according to claim 7, characterized in that to the outside (8) of the outer tube (5) near each tube end (9) as alignment elements

(1) support surfaces (1) are arranged.

9. The device according to claim 8, characterized in that the outer tube (5) on the outside further centering and aligning support surfaces (2) are assigned.

10. The device according to claim 7, 8 or 9, characterized in that the support surfaces (1, 2) consist of prisms (1, 2).

11. The device according to claims 7 to 10, characterized in that for the

Tube ends (10) of the inner tube (6) as for generating a bending moment Alignment elements (3), clamping elements (3) movable transversely to the central axis (7) are provided.

12. Device according to claims 7 to 11, characterized in that clamping elements (4) which can be inserted into the inner tube (6) are provided as alignment elements (4) and are movable transversely to the central axis (7) in order to generate a bending moment.

13. Device according to one of claims 7 to 12, characterized in that two counter-rotating mixing heads (12, 13) are provided.

14. Device according to one of claims 7 to 13, characterized in that the mixing head (12, 13) itself is designed as a spacer (12, 13).

15. Insulated pipe with an in an intermediate space (11) between an outer tube (5) and an inner tube (6) arranged by foaming generated heat insulation layer (15) made of rigid polyurethane foam, characterized in that the tubes (5, 6) around a common central axis (7) are aligned linearly and concentrically to one another about a common central axis (11) and that the intermediate space (11) between

Outer tube (5) and inner tube (6) contains only rigid polyurethane foam.

16. Thermally insulated pipe according to claim 15, characterized in that in the intermediate space (11) a spacer (16) placed before the foaming, placed on half the length of the pipe is arranged and that this

Spacers (16) made of rigid polyurethane foam.