SE468827B - PROCEDURE AND DEVICE FOR PREPARATION OF HEAT-INSULATING PIPES - Google Patents

Description

15 20 25 30 35 40 468 827 z In contrast to these continuous processes, therefore, a discontinuous process has been carried out in practice, in particular in the case of pipes with lengths of 6-12 m and diameters of 20-60 mm, in which case the pipe is first spacers are provided with foam-permeable spacers and covered with a relatively thick plastic hose. The unit prepared in this way is then gradually filled with foam at an oblique position. The thickness of the plastic hose in this process depends on the foam pressure occurring, since the plastic hose not only has the task of forming an outer jacket but also functions as a "mold". Therefore, the plastic hose must be so strong that it can absorb the resulting foam pressures. A disadvantage of this method is not only the necessary use of a thick space hose, but also the fact. that when foamed in an inclined position no uniform foam is obtained and that the foam also has a relatively high density. In addition, a discontinuous procedure is not economical. The object of the present invention is therefore to provide a method, by means of which it is possible to continuously produce pipes in an economical manner. even those with larger diameters, with simultaneous saving of material for the outer jacket and the achievement of a uniform foam with low density in the heat-insulating layer.

This is solved according to the invention by (a) as a pipe, which is to be heat insulated. uses rigid. non-flexible tubes of larger diameter. preferably with a diameter of 20-60 mm and a length of 6-18 m, which pipes are connected by means of pipe connecting piece and which seemingly endless string is passed through the strip installation with double mold block chains, the pipe connecting pieces being cylinders with axially projecting recesses from both ends, the diameter of the recesses corresponds to the outer diameter of the tubes and the outer diameter of the cylinders corresponds to the inner diameter of the cavity in the strip installation with double mold block chains, (b) the foamable plastic mixture adjusts so. that the last time the pipe was to be bent down due to its own weight is so hardened that it exerts a carrying function on the pipe and (c) on the pipe surrounded by foam, when it has left the strip the installation with double mold block chains, by means of an optionally cooled, vacuum-calibrated extruder with a ring nozzle extrudes a high-density foamed plastic protective jacket.

The strip plant with double mold block chains used according to the invention is known per se and constitutes an example of continuous production of longitudinally slit cellular plastic insulation pipes according to DE-AS-1 266 485 resp. for continuous production of two hinge-like connected, collapsible, foamed tube half-bowls according to DE-PS-2 503 425 by means of an outer foil.

During the continuous production of longitudinally slit cellular plastic insulation pipes according to DE-AS-1 266 485, special difficulties arose with the retention of the core. which extends over the entire length of the mold channel formed by the two movable mold block chains and which is necessary for creating the internal space in the cellular plastic insulation pipe. Namely, it has been found that even if the core is firmly clamped at both ends, it is in the mold channel of the foam that the pressure is so strong. that the core cannot be kept centered over its entire length. To avoid such deflections, the core was therefore provided over its entire length with a supporting retaining plate, which projected radially into the mold channel between the mutually arranged mold blocks.

The same applies to the deflection of the core also with respect to another known plant, which has a fixed mandrel as inner core, which mandrel is attached only to the inlet end of the plant and projects freely into the stationary or rotating outer shape. Here again, the mandrel only clamped at one end has sufficient stability to be able to absorb the pressures occurring during foaming without deflection.

Reference is made in this connection to what is stated in the above-mentioned DE-PS-2 503 425, column 3, line 49 and the following. Due to the above-mentioned problems with deflection of the mandrel, it is proposed at another known plant according to DE-AS-2 165 584 that the deflection of the mandrel be monitored by means of a laser beam and regulated by means of control and control elements. By means of this auxiliary device, however, an objection-free alignment of the solid inner core (mandrel) is achieved only with difficulty. completely apart from the fact that the whole plant is very complicated and very sensitive to disturbance.

In view of the experience gained in the case of double strip plants with double mold block chains in connection with the production of longitudinally slit cellular plastic insulation pipes, it must be considered as completely surprising that in the process according to the invention using a belt plant with double mold block chains obtained with cellular plastics tubes, where even large diameter tubes are position-fixed concentrically in the foam even without the use of spacers.

The continuous process, which is possible through the use of the belt plant with double mold block chains, results in a continuous foaming around the pipes. which has the advantage that the cellular plastic casing over the entire length has a homogeneous cell image without blisters and with low density, whereby not only a uniform mechanical strength is obtained but also a better lambda value.

With the aid of the extrusion device connected to the belt assembly with double mold block chains and the associated vacuum calibration device, it is also possible to economically achieve the foamed plastic protective jacket with a high density and smooth outer surface and with an accurate shape. In addition, in the process according to the invention, the plastic protective jacket can be designed considerably thinner than in the initially discontinuous process, since the pressures occurring during the formation of the heat-insulating foam layer do not have to be absorbed by the plastic protective jacket. Thereby, the function of the plastic protective jacket according to the method according to the invention is reduced to diffusion tightness and protection against damage during transport and laying. The foamed 10 15 20 25 30 35 n 5 46 'e 827 protective jacket lowers the weight and price and increases flexibility. It preferably consists of a foamed polyethylene, polypropylene, polyvinyl chloride or the like and preferably has a density of 500 - 800 kg / m 3.

Since the plant according to the invention is designed in such a way that the pipes are automatically concentric in relation to the outer jacket, it is also possible to dispense with all distance resp. centering means, which were necessary in the prior art procedures. This has the additional advantage that the many cold bridges are eliminated, whereby the heat-insulated pipe produced in accordance with the invention is further improved and made cheaper.

The method according to the invention is suitable for all pipes to be thermally insulated. such as, for example, copper, steel or plastic pipes. In the case of copper or plastic pipes, these can be fed at smaller diameters, for example at diameters of 22 mm, according to the corresponding rectilinear alignment, with the strip system with double mold block chains practically endless from the roll on which they are delivered in lengths of 50 m or more after being surrounded by foam and provided with the plastic protective jacket can be rewound on a roll.

In the case of larger diameter plastic pipes, these are best produced directly in front of the device according to the invention by extrusion, so that the handling of the pipes is avoided. After the outlet of the device according to the invention, the tubes are cut, which cannot be wound up into a roll. 1 heat-insulated pipe with the desired length.

Rigid pipes, for example steel pipes or other metal pipes, are suitably used in lengths of 15-18 m, which shortly before insertion into the device according to the invention are connected by means of special plastic sleeves to an "endless string" and then practically "endlessly" surrounded by foam and jacket in After arranging the jacket, the pipes are then separated with a special saw at the sleeves, ie the pipe connecting pieces.

The pipe connectors are designed in such a way that, after removal during the laying of the heat-insulated pipes, they release pipe ends without cellular plastic insulation, so that the pipes can then be connected tightly and permanently to ordinary pipe connectors and subsequently insulated.

To provide the heat-insulating foam layer, any suitable plasticizer with blowing agents or equivalent starting components can be used. which forms the plastic in question.

Depending on the area of use, the foam in the heat-insulating layer can be more or less flexible or rigid.

For example, it is convenient to use flexible materials in cases where the "endless" heat-insulated pipes are wound on a roll when they leave the device according to the invention. In contrast to rigid pipes, it can be an advantage to use a harder material.

Suitable foams preferably include polyurethane foam, polyisocyanate foam, polyolefin foam. in particular polyethylene or polypropylene foams or foams of the corresponding copolymeris thereof, as well as polystyrene foams.

In the production of polyurethane foam, regardless of whether it is flexible or rigid. the use of a release foil is required, which together with the tube is inserted into the strip plant with double mold block chains in such a way that it will abut against the mold blocks. The annular space between the release foil and the tube is then filled with foam.

As a release foil, you can use any foil. for example a foil of paper, plastic or metal. To achieve a clean release effect, it is sufficient to use paper or a plastic foil as a release foil. However, if additional effects are desired, such as, for example, heat reflection or a vapor barrier, it is advantageous to use a metal foil, for example a single-sided or double-sided coated aluminum foil with paper or plastic. f; ' 10 15 20 25 30 35 'D 7 468 0'7 _; In contrast to certain types of foam, such as those made of polyethylene or polystyrene, it is possible to work without release film, in which case it may be sufficient for the mold block chains to be treated with a regular mold release agent on their return. extra cooled mold block chains, it can even be achieved with a suitable procedure to obtain a relatively firm, largely homogeneous surface skin, so that the outer plastic protective jacket can possibly also be dispensed with.

The introduction of the foamable mixture into the annular space between the tube and the release foil resp. The mold block chains take place in the usual way, for example as described in the initial DE-OS-3 307 865, in which case the foamable mixture is applied to the release foil before joining to a foil hose. The foam can be adjusted, preferably components A and B to form polyurethane foam, in such a way that the cellular plastic already shortly after the introduction of the foam-shaped, hose-shaped release foil into the strip plant with double mold block chains fills the annular space between the tube and the release foil while at the same time keeping the tube concentric by the meanwhile resilient foam. The efforts required to achieve this are known to those skilled in the art resp. can be calculated without difficulty.

If desired, one or more sensing lines at a distance from the pipe can be embedded in the vicinity of the tube with foam.

These sensing lines are intended to detect and locate moisture penetrating into the foam layer.

The method according to the invention of course also enables simultaneous embedding of several tubes insulated against each other in foam, the tubes then being surrounded by a common plastic protective jacket.

Advantageously, two pipes are arranged in a plastic protective jacket and the pipes are insulated against each other, a cross-section through such a combination unit preferably not being round, but oval.

This device can, for example, be used as a branch line 10 15 20 25 30 35 * + 68 827 8 from the main line to the users, so that flow and backflow are achieved in one unit, whereby one can reduce the transport and laying costs.

The present invention is described in more detail below with reference to Figs. 1-4, which show particularly suitable embodiments without limiting the invention thereto.

Fig. 1 shows a schematic plan view of the main part of a device for carrying out the method according to the invention.

Fig. 2 schematically shows a cross section through the mold blocks (Sa, Sh, 5a ', Sb'), which form the strip plant (5) with double mold block chains, along the line A-A in Fig. 1.

Pig. 3 shows a cross section through a heat-insulated pipe 7 according to the invention.

Pig. 4 shows a pipe connecting piece 12 in cross section.

In Figs. 1 - 4 and the following description, the following reference numerals are used: 1 Pipe 2 Storage roll for release foil 3 Release foil 4 Foam machine 5 Belt system with double mold block chains Sa. 5b, 5a '. 5b 'Mold blocks forming the mold block chains 6 Vacuum-calibrated extruder 7 Heat-insulated pipe 8 The mold channel formed by the mold blocks Sa, Sb 9 Support for guiding the mold block chains 10 Heat-insulating foam plastic layer ll Foamed plastic protective jacket in the formwork , which in the longitudinal direction are divided into separate shape blocks Sa, 5b, 5a ', 5b' and which move at the same speed along a straight line. The separate mold blocks Sa, 5b, when pressed close to each other, form the required mold channel and are redirected and returned outside the production area as separate mold blocks 5a ', Sb' (see Fig. 2) in a manner known per se. a governing aid 9.

Form blocks 5a. 5b can be exchanged for adaptation to the current, desired diameter of the pipes resp. of the thermally insulating foam jacket to be produced.

According to a preferred embodiment of the present invention, for example a flexible copper pipe or a flexible plastic pipe is supplied from a supply roll by means of a pipe supply and holding device via a straightening tool to the belt assembly 5 with double mold block chains together with a release foil from the supply roll. 3 before insertion into the belt plant 5 with double mold block chains by means of the foaming machine 4, the foamable mixture is provided and formed into a hose. After the outlet from the belt plant 5, the tube 1 provided with the foam plastic layer 10 is passed through the extruder 6 provided with vacuum calibration device, where the actual high-density foamed plastic protective jacket 11 is applied to the release foil 3. The heat-insulated tube 7 thus completed (Fig. 3). ) is then wound on a transport roll and transported to the place of use, where it is laid from the roll.

According to another preferred embodiment of the invention, rigid, non-flexible pipes 1, in particular those of larger diameter, in lengths of 6-18 m, preferably 12-18 m, are supplied from a storage position not shown in Fig. 1 by means of the likewise non-flexible showed the pipe supply and holding device to the belt plant 5 with double mold block chains together with the release foil 3 and the foamable mixture in the manner described above. In order to effect a continuous process, the pipes 1 to be insulated are connected one after the other by means of pipe connecting pieces 12 in accordance with Figs. 4 and 10. The belt installation 5 is supplied as a kind of endless string. The pipe connecting pieces 12 are adapted with respect to outer and inner diameters to the relevant pipes 1 and the desired heat-insulating foam layer 10. After the outlet from the extruder 6 provided with vacuum calibration device and after application of the plastic protective jacket 11, the pipe is visually transparent. 12 by means of a guided saw across the longitudinal axis. The heat-insulated pipes 7 re-separated in this way are supplied over a storage rack, packaging resp. the bundling unit. The sawn-through pipe connectors are advantageously left connected to the heat-insulated pipes up to the laying and installation and are only removed just before the installation of the pipes.

Of course, however, the heat-insulated pipes 7 emerging from the vacuum calibration device 6 of the extruder 6 can also be separated from the pipe connectors 12, so that these non-sawn pipe connectors 12 can be reused after removal of the coated release foil 3 and the plastic protective jacket 11. The heat-insulated pipes 7 freed from the pipe connecting pieces 12 can then be provided with other protective covers for transport up to the assembly, if this should be desired.

Another advantage obtained when using the pipe connecting pieces 12 according to the invention is that after removal of the pipe connecting pieces 12 the pipe ends are immediately free of the latter required, ordinary, durable and tight pipe socket connection.

Claims (4)

10 15 20 25 30 ll .Ps C 'Cr J ï Patentkrgv Process for the continuous production of a heat-insulated pipe with a plastic protective jacket for the transport of liquid or gaseous, heated or cooled media, wherein the pipe (1) to be heat-insulated is continuous in the axial direction. centrally in a tubular cavity (8) formed by a strip installation (5) with double mold block chains under simultaneous environment with a plastic foam, the tube being fixed in position by the foam plastic, and providing the tube with a plastic protective jacket. k ä n n e t e c k n a t a) b) C) 2. by using rigid, non-flexible pipes of larger diameter as pipes (1), which are to be heat-insulated. preferably with a diameter of 20-60 mm and a length of 6-18 m, which pipes are connected by means of pipe connecting pieces (12) and which seemingly endless string is passed through the strip installation (5) with double mold block chains, the pipe connecting pieces (12) being formed of cylinders with axially projecting recesses from both ends, the diameter of the recesses corresponding to the outer diameter of the tubes and the outer diameter of the cylinders corresponding to the inner diameter of the cavity in the strip plant with double mold block chains, the foamable plastic mixture weight should be bent down so hardened that it exerts a carrying function on the tube (1) and on the foam-surrounded tube (1). when this has left the belt assembly (5) with double mold block chains, by means of an optionally cooled, vacuum-calibrated extruder (6) with a ring nozzle, a high-density foamed plastic protective jacket (II) is extruded. characterized in that the method according to claim 1, prior to foaming in the space between the tube (1) and the mold blocks (5a, 5b) in the strip installation (5), introduces one at the inlet of the strip installation (5) into a hose formed release foil (3), preferably of paper. of aluminum foil or paper-coated aluminum foil or of plastic, and only then does the annular space between the tube (1) and the release foil (3) foam fill. 3. A method according to claims 1 and 2, characterized in that the gap between the tube (1) and the release foil (3) is filled with a starting mixture which forms a polyurethane foam. 4. A method according to claims 1 and 2, characterized in that a polyolefin provided with blowing agent is used for the production of the foamed plastic protective jacket (11). preferably polyethylene or PVC. uk