CH664433A5 - METHOD FOR REINSULATING A SHEET OF A HEAT-INSULATED PIPELINE. - Google Patents

Description

DESCRIPTION

The present invention relates to a method for the subsequent insulation of a bend in a heat-insulated pipeline, which consists of an inner tube carrying the medium, a jacket tube concentrically spacing the inner tube and a heat insulation layer made of foam arranged between the inner tube and the jacket tube, in which method the ends first the inner pipes of two pipeline sections which are opposite the insulation layer and the casing pipe are connected to one another, a shape resting on the ends of the casing pipes is placed over the connection point and the annular space between the connection point and the form is foamed with polyurethane foam.

From DE-OS 2 012 558 it is known to place two half-shells on the ends of the jacket pipes after connecting the inner tubes of two heat-insulated pipe sections running at an angle to one another and to firmly clamp these half-shells together. A foamable plastic mixture is filled through a filling opening located in one of the half-shells and foams the annular space between the inner tubes and the shape formed from the two half-shells. The half-shells are pressed firmly onto the jacket pipes so that foam does not escape through the gap between the mold and the jacket pipes. The connection of the two mold halves takes place by means of flanges which run in the parting plane and which are attached to the mold halves and which are screwed together. However, these flanges mean that the mold halves are very rigid and cannot be bent. If, for example, a change of direction is desired in the course of the pipeline, the procedure is as described above, but half-shells must also be used, which must be angled at the angle of the change in direction. When laying a heat-insulated pipeline, however, changes in direction can occur at any angle, so that the half-shells required for the post-insulation have to be stored for almost every angle.

Another way of making changes in direction in the course of a pipeline is to weld pre-insulated pipe elbows into the pipeline and to subsequently insulate the connection point. This procedure also requires

that different pipe elbows have to be stored for the different angles, although it is also possible to compensate for slight angle differences by messages from the pipe bend. In addition, the latter procedure has the disadvantage that two post-insulation points are required when the direction of the pipeline changes. These post-insulation points make the laying work more expensive and often lead to the insulation layer between the inner pipe and the casing pipe being moistened from the outside due to a leak in the area of the post-insulation. When laying a pipeline, one should strive to provide as few connection points as possible.

Both methods have in common that the exact angular mass of the deviation from the installation route is usually only determined during the installation, so that there are long waiting times, double journeys and possibly in the meantime flooding of the installation trenches and thus dampening of the insulation.

The object of the present invention is to improve the method of the type mentioned at the outset in such a way that there is no need to store pipe elbows or curved shapes and that the laying time for a pipe can be reduced to a minimum.

The method according to the invention is characterized in that first a flexible hose with an inner diameter approximately corresponding to the outer diameter of the casing pipe is pushed over the end of one of the pipe sections to be connected, that the ends of the inner pipes are connected to one another, that the hose is pushed over the connection point, until it rests on the jacket pipes of both pipe sections, that the hose is kept at a distance from the inner pipe by spacers and that the space between the hose and the inner pipe is foamed.

By using a flexible hose, any change of direction in the course of the pipeline can be carried out very quickly. On a mate5

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Rial-consuming stocking of contra-angle handpieces can be dispensed with. The spacers ensure that the same distance between the inner tube and the hose is maintained.

The method according to the invention can be used with particular advantage if the inner tubes are not welded directly to one another, but are connected by a bent tube piece. A bare metal pipe can therefore be precisely adapted to the pipe run using tools commonly used in pipe construction and welded to the ends. In order to prevent moisture from penetrating through the gap between the casing tubes and the hose, the gap is expediently sealed. Here, for example, there are shrink sleeves that lie both on the hose and on the jacket tube and seal the gap sustainably. However, it appears much more advantageous to use a corrugated plastic tube and to weld the ends of the tube to the jacket tube. The hose is welded to the jacket by electrical resistance heating with particular advantage. This is expediently done by introducing a plastic strip, in which a resistance wire is embedded, into the gap between the plastic tube and the jacket tube and passing electrical current through the resistance wire. As a result of the passage of current, the resistance wire heats up to the melting temperature of the plastic and welds the hose to the jacket tube.

A corrugated hose made of plastic, preferably made of polyethylene, can be used as the hose. Since the jacket pipe of the heat-insulated pipeline is also made of polyethylene, a permanent, liquid-tight weld seam is formed between the hose and the jacket pipe.

In order to obtain the largest possible contact surface between the hose and the jacket tube, it is advantageous to use a hose that is undulated at both ends.

An exemplary embodiment of the method according to the invention is described below using the schematic drawing.

Fig. I shows the pipeline with the bend to be insulated, and

Fig. 2 shows the same pipeline with the bend already insulated.

664433

In the figures, the ends of two pipe sections 1 and 2 are shown, which meet at an angle. The pipe sections 1 and 2 each consist of an inner pipe 3, e.g. made of steel, a casing tube 4, e.g. made of plastic, as well as a layer of foamed plastic arranged between the inner tube 3 and the jacket tube 4, which adheres to both the inner tube 3 and the jacket tube 4 and thus creates a force fit between the inner tube 3 and the jacket tube 4. Pipe systems of this type are referred to as composite pipes or plastic jacket pipes. To establish a conductive connection between the pipe sections 1 and 2, a corrugated plastic hose 5 is first drawn onto the end of one of the pipe sections - in this case onto the pipe section 2. The inner tubes 3 are connected to one another by a piece of tube 6, which is provided with the desired curvature on the construction site, by means of the weld seams 7. Spacers 8 are placed on the pipe section 6, preferably slices made of polyurethane foam, and the plastic hose 5 is pulled over the connection point so that its ends lie on the casing pipes 4 of the pipe sections 1 and 2. In the gap between the jacket tube 4 and the plastic tube 5, a plastic tape is inserted, in which a resistance wire is embedded. The resistance wire is then connected to a power source and heats up and thus leads to a melting of the plastic tape and to a welding of the jacket tube 4 with the plastic tube 5. The welding produced in this way certainly prevents the entry of moisture into the insulating layer.

After this work, an opening is preferably made at the highest point of the plastic hose 5 and a foamable plastic mixture based on polyurethane is introduced through this opening, which foams the annular space between the plastic hose 5 and the pipe section 6. As soon as the foam appears at the filling opening, the filling opening is closed with a plastic plug. The stopper and the filling opening are connected to each other by means of mirror welding.

By using a flexible plastic hose 5, any change in direction of the pipe run can be produced and reinsulated in a simple manner. It is no longer necessary to stock pre-insulated curvatures or curved shapes.

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1 sheet of drawings

Claims (7)

664433 1. A method for the subsequent insulation of a bend of a heat-insulated pipeline, which consists of an inner tube (3) carrying the medium, a jacket tube (4) concentrically spacing the inner tube and a heat insulation layer made of foam arranged between the inner tube and the jacket tube, in which method First the ends of the inner pipes (3) of two pipeline sections (1, 2) that protrude from the insulation layer and the casing pipe are connected to each other, a shape resting on the ends of the casing pipes (4) is placed over the connection point and the annular space between the connection point and the form is foamed with polyurethane foam, characterized in that first a flexible hose (5) with an inside diameter approximately corresponding to the outside diameter of the casing pipe (4) is pushed over the end of one of the pipe sections (2) to be connected so that the ends of the inside pipes (3) connected with each other n that the hose (5) is pushed over the connection point until it rests on the casing pipes (4) of both pipe sections (1, 2), that the hose (5) is kept at a distance from the inner pipe (3) by spacers (8) and that the space between the hose (5) and the inner tube (3) is foamed. 2. The method according to claim 1, characterized in that the ends of the inner tubes (3) are welded together. 2nd PATENT CLAIMS 3. The method according to claim 1, characterized in that the inner tubes (3) are connected by a bent tube piece (6) and that each end of the tube piece (6) is welded to one end of the inner tube. 4. The method according to claim 1, characterized in that the gaps between the casing tubes (4) and the hose (5) are sealed. 5. The method according to claim 1, characterized in that a corrugated plastic tube, preferably made of polyethylene, is used as the tube (5) and the ends of the tube are welded to the jacket tubes (4). 6. The method according to claim 5, characterized in that the ends of the hose (5) with the jacket tubes (4) are welded by electrical resistance heating. 7. The method according to claim 5, characterized in that a hose (5) is used as the hose (5), the two ends of which are not corrugated.