DE3110503A1 - Process for producing a joint for heat-insulated conduit pipes - Google Patents

Abstract

In a process for producing a joint for heat-insulated conduit pipes, first of all the medium-carrying inner pipes are welded. A sleeve is pushed over the joint and, at its end, is seated on the case of the insulated pipes and here is sealed by means of shrink tubes. Subsequently the annular space between the sleeve and the inner pipes is filled by foaming with a foamable plastic. To ensure complete, unhindered foaming, 2-10 mm diameter bores are made in the direct vicinity of the shrink tubes before the plastic is introduced into the sleeve, through which bores the air can escape from the annular space. After the plastic has been introduced, the introduction opening is provisionally closed and after the foam has cured, both the introduction opening and the vent bores are permanently sealed.

Description

Method of making a joint for

heat-insulated conduit pipes The invention relates to a method to create a connection point for preferably buried thermally insulated Line pipes, which consist of an inner pipe carrying the medium and a concentric inner pipe surrounding plastic jacket and one between the inner tube and the jacket arranged heat insulating layer exist, in which the pipe ends free of insulating material are first welded, a tubular sleeve over the connection point Plastic is pushed, which rests on the jacket of the pipes to be connected, the ends of the sleeve through both the ends of the sleeve and on the jacket Sealed shrink tubing on top, and then by one in the sleeve attach a foamable plastic mixture to the cavity is filled between the inner pipe and the socket.

District heating networks are largely made from factory pre-insulated Assembled pipe sections, in which the medium-carrying inner pipes come together on site welds, and the connection points are then reinsulated. When re-insulating two processes are in use, namely foaming under low pressure and foaming under pressure. In the case of pressure-free foaming, a sleeve is placed over the Connection point pushed, placing them on the sheaths of the connected pipe ends rests.

After filling in the foamable plastic mixture, the displaced by the rising foam. Air through the annular gap between the Casing pipe and socket pipe escape. With this method, the volume weight of the foam are not clearly adhered to, as too much foam is often caused by the Annular gap escapes. With subsequent intentions of the socket pipe compared to the Sheath diffused through shrink tubing due to the heating of the shrink tubing Freeze out the oxygen so that the heat shrink tubing is puffed up and not seals sufficiently against moisture or pressurized water.

Another major disadvantage of this process is it too see that a pressure test for tightness of the shrink tubing is not possible is.

When foaming under pressure, the sleeve is pushed over the plastic jacket is sealed against the socket pipe with shrink tubing. After this sealing, a pressure test can be carried out. The required volume weight of the foam is determined by the amount of foam due to the cavity to be filled. Since no foam can escape, this quality parameter is easy to comply with. The sleeves previously used for this purpose have two openings that are used to fill the Foam and serve for ventilation. In practice, however, it turns out that this Ventilation is only sufficient for the socket space, but compressed air in the annular gap remaining These enclosed air cushions have a pressure that is greater than the peeling pressure of the shrink tube. It is coming thus to the Lifting off the shrink sleeve.

The present invention is based on the object last to improve said method to the effect that a lifting of the shrink tubing is avoided, and thus a permanent seal between the socket pipe and the plastic jacket is guaranteed.

This object is achieved in that prior to filling the plastic mixture in the socket in the immediate vicinity of the ends of the shrink tubing at least one 2 to 10 mm, preferably 3 to 6 mm, diameter is drilled, that the plastic mixture is filled into the cavity in a precisely dosed amount, and the filling opening is temporarily closed with a plug or the like, and after the cavity has been filled with foam, both the ventilation holes and the Filling openings are permanently closed, preferably by so-called mirror welding will. Through ventilation holes made in the immediate vicinity of the shrink tube ends the air escapes without it entering the annular gap between the socket pipe and the Plastic sheath penetrates.

The bore diameter from 2 to 10, preferably from 3 to 6 mm Diameter ensures that no foam can escape. Due to the A foam plug forms a relatively narrow cross-section, the vent holes closes after the annular space has been completely filled with foam.

Then both the vent holes and the filling opening sealed liquid-tight. For this purpose, it is expedient to use the per se well-known mirror welding process, in which the r æer of the bores and the edges are heated by plastic discs so far that the plastic material plastic will. The plastic plastic disks are then inserted into the bore and connect to the sleeve material. With special advantage the ventilation holes are in the. Sleeve inserted that the ventilation holes are located at the highest level of the socket. The filling opening is around 1/4 up to 1/8 of the sleeve circumference offset to it. This creates the advantage that the air can escape until the plastic foam rising from below has completely filled the annulus.

Because the filling opening is 1/4 to 1/8 of the sleeve circumference is arranged offset to the ventilation holes, the foamable plastic mixture arrives directly onto the inner surface of the sleeve and can settle evenly at the bottom of the sleeve distribute and thus a uniformly foamed plastic can be produced.

The invention also relates to a sleeve for carrying out the method, which is characterized by the fact that, in addition to the filling opening, it is in the immediate vicinity Near their ends at least one vent hole with a diameter between 2 and 6 mm.

The invention is shown schematically on the basis of the figure Embodiment explained in more detail.

The pipes 1 and 2 that are to be connected at the factory are pre-insulated from a medium-carrying inner tube 3, preferably made of steel, a heat insulating layer 4, preferably made of foamed polyurethane, and an outer jacket 5 made of polyethylene. The pipes 1 and 2 are usually delivered to the site that the Ends of the inner tubes 3 protrude from the insulating layer.

To create the connection point, proceed as follows: About one of the pipes 1 or 2, for example via the pipe 2, a socket pipe 6 is made thermoplastic plastic and a shrink tube 7 pushed. About the other A shrink tube 8 is pushed into tube 1. the Ends of the inner tubes 3 are now welded to one another as shown at 9. After welding the inner pipe 3, the sleeve 6 is pushed over the connection point and their Ends with respect to the plastic jacket 5 mi 'the shrink tubing 7 and 8 sealed. The sleeve 6 preferably has a filling opening 10 in the middle.

After sealing by means of the shrink tubes 7 and 8, a Pressure test carried out for leaks, for example by using the filler opening 10 generates an overpressure in the annular space between the inner pipe 3 and the sleeve 6 will. In the immediate vicinity of the ends of the shrink tubing 7 and 8 are then from above into the sleeve 6 vent holes 11 and 12 with a diameter of 2 to 3 mm brought in. In a container 13, the components of the polyurethane foam are mixed with one another stirred and filled through the filling opening 10 into the annular space, so that the Liquid at the bottom of the sleeve 6 is evenly distributed.

Now the filling opening 10, for example by means of a stopper temporarily closed. The air compressed by the rising foam escapes through the vent holes 11 and 12 until the foam enters the Vent holes 11 and 12 has penetrated. Because of the narrow cross-section The foam solidifies or hardens and prevents it from settling through the ventilation holes Further amounts of foam bulging out. Finally, both the filler opening 10 as well as the ventilation bores 11 and 12 with a mirror welding device known per se welded liquid-tight.

The main advantage of the invention is that with Exactly meterable amounts of foam allow the annular space to be completely filled without leaking large amounts of foam.

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Claims (3)

Method for producing a connection point for thermally insulated conduit pipes, preferably buried in the ground, consisting of a medium-carrying Inner tube, a plastic jacket concentrically surrounding the inner tube, and consist of a thermal insulation layer arranged between the inner tube and the jacket, in which the pipe ends free of insulating material are first welded over the connection point is pushed a tubular sleeve made of plastic, which rests on the jacket of the pipes to be connected, the ends of the socket through both shrink tubing on the ends of the sleeve as well as on the jacket is sealed, and finally a foamable one through a filling opening in the sleeve Plastic mixture filled into the cavity between the inner pipe and the socket is, characterized in that prior to filling the plastic mixture in the Socket in the immediate vicinity of the shrink tube ends at least one hole each from 2 to 10 mm, preferably 3 to 6 mm in diameter is introduced that the plastic mixture in exactly dosed amount filled into the cavity, and the filling opening with a Stopper or similar is temporarily closed, and after the foaming of the Cavity both the ventilation holes and the filling opening permanently is preferably sealed by the so-called mirror welding. 2. The method according to claim 1, characterized in that the bores be introduced into the socket in such a way that the holes are at the highest spatial level of the socket, and the filling opening by about 1/4 to 1/8 of the socket circumference is arranged offset to it. 3. sleeve for carrying out the method according to claim 1 or 2, characterized characterized in that the sleeve {6) in addition to the filling opening (10) in the immediate Near each of their ends at least one vent hole (11, 12) with one diameter between 2 and 6 mm.