DE3720577A1 - Weld sleeve for producing a pipe connection, and use of said weld sleeve - Google Patents

Abstract

The sleeve (11) is formed as an open, flexible or pliant ring from loops (13) which rest one against the other in a meandering manner in the circumferential direction of the ring and comprise an insulated heating wire (14). In a sub-region (17) of one abutment end, said loops (13) terminate such that they are set back with respect to the other abutment end and, in the opposite region (20) of the other abutment end, they jut out in the manner of a tongue. The heating wire (14) is electrically insulated by a sheathing (16) of a thermoplastic material of the same specification as that of the pipe parts which are to be welded. The sleeve (11) is intended to be arranged in the overlap gap of two pipe parts, pushed one over the other, of plastic of the same specification, in order to weld said pipe parts to one another by connecting their heating wire to a power source. <IMAGE>

Description

The invention relates to a welding sleeve according to the Preamble of claim 1 and a use of Welding sleeve according to the invention for the production a socket connection at the joint of two pipes sections of a thermally insulated pipe.

For pipe connections at the joint of two pipe sections a thermally insulated line, especially an underground one Pipe in which the pipe sections are made of a plastic jacket pipe and this one with the interposition of a ver foamed thermal insulation penetrating medium Inner tube exist, the are at the connection point projecting inner tube ends welded together and the cavity between them and one, on the ends supporting the jacket pipes and bridging the joint the sleeve to complete the thermal insulation foams.

It is particularly useful when it is laid directly in the ground Pipes important to prevent moisture from outside through the annular gap between the sleeve and the of which the casing pipe end is enclosed in the connection point can penetrate. Already slight traces of moisture  The junction can cause damage, but also too trigger leakage protection devices, although there are no leaks in the medium-carrying pipes.

In order to achieve such a seal, it is e.g. known from DE-A-32 17 820 or CH-A-3 96 536 to arrange a resistance wire on the inside of the socket ends nen. The sealing between the casing pipe and the socket is made then by directly melting the material together Sleeve and the casing tube ends when the heating wires are heated. With these known methods, however, the game is allowed between sleeve and casing pipe for understandable reasons not be too big. Your application is so small limited to medium pipe diameter.

From EP-A-36 963 and EP-A-75 901 it is also known closed between the sleeve and the casing pipe Arrange welding ring with inserted heating wire. To EP-A-75 901 is a welding ring on the casing tube ends pushed from a thermoplastic in which the heating wire winding from a spiral wound resistor wire is embedded. According to EP-A-36 963 there is sweat ring from a spiral winding one with thermo plastic material covered resistance wire, where the covering of each turn of the winding by welding solution with the sheathing of the next following turn is connected and thus forms a compact sleeve. The winding is fixed by partial shrinking with the sleeve  connected, the sleeve a frozen latent radia le has residual shrinkage stress, which at a heating radial play between the welding process Eliminate winding and jacket tube parts and the Should generate welding pressure.

However, as is known, commercially available jacket pipes with larger diameters, such as are required, for example, in underground district heating pipes, sometimes have large ovality and dimensional tolerances of the outside diameter. In order to be able to move the sleeve on the jacket pipe into its position bridging the joint in such jacket pipes and under the difficult conditions in the open trench, the free play between the sleeve or welding ring and the jacket pipe must be chosen so large that the overlap gap to be sealed for a sealing device by melting together in the manner described is too large. The aforementioned irregularity of the outer dimensions of commercially available casings was previously also the application of the known welding rings on the mantle pipe ends - held in the sleeve ends - contrary.

Rather, it has been used so far in such cases fen (e.g. EP-A-30 776) around the for welding the necessary contact pressure using a strap or to be able to effect clamping tool, first along split, adjust to the circumference, then over the connection place to fold and weld in the longitudinal direction.  

This sleeve technology is complex and requires great craftsmanship skills on the part of the fitters. This The disadvantage is small to medium pipe dimensions particularly uncomfortable for cost reasons.

The invention has for its object a Schweissman to design a chain of the type mentioned at the beginning, that even with extreme deviations from outside knife and shape of the inner tube parts, in particular of Jacket pipes with heat-insulated lines, with little effort in time and work and without special aids too can be used in a pipe trench and a reliable permanent and permanent sealing of the welded together Pipe parts, especially seamless welding guaranteed over the entire scope of these pipe parts.

According to the invention, this task is accomplished by welding cuff with the in the characterizing part of claim 1 specified features solved.

Because the cuff according to the invention as an open, flexible or flexible ring is formed, it leaves lying around the outside surface without any problems apply to a pipe part. The comb-like interlocking The pushing ends of the cuff ensure you Compensation for any deviations in the pipe part outside knife from the norm without leaving a gap in the Coating of the pipe part with heating wire is created. In order to  is a complete and perfect welding over the secured the entire scope of the pipe parts to be welded.

With a formation of the welding sleeve according to one of claims 2 or 3, the welding of the overlap donate pipe parts even better because of the welding process the heating wire jacket or the band in which the Heating wire is embedded with a welded joint the adjacent pipe parts.

The danger of the feature of claim 4 of a short circuit between neighboring or cross excluded the heating wires.

A particularly simple manufacture of a Welding sleeve according to the invention results in an education according to claim 5.

The possible uses of the sweat according to the invention cuffs for making pipe connections are a lot wrinkled.

Particular advantages result from the invention proposed use of the inventive Welding sleeve for making a socket connection at the joint of two pipe sections of a thermally insulated Line, in particular an underground line, wherein the pipe sections from a jacket pipe from a thermoplas  tables plastic and this one with a liner a medium penetrating a foamed thermal insulation the inner tube and the at the junction protruding inner tube ends are welded together and the cavity between them and one to deal with theirs Support the ends on the ends of the casing pipes and the Joint bridging sleeve to complete thermal insulation is foamed.

In an effort to ensure a perfect seal of such sleeve joints it is possible to achieve ties (e.g. from DE-A-31 10 503) known the ends of the sleeve through both on the sleeve ends as well as shrink sleeves sitting on the casing tube to seal. Foaming the cavity between the sleeve and the inner tube can, before or after this seal, through an opening in the sleeve. Disadvantageous are in the former case the possibly high foam loss of material because of the displacement of the sleeve on the casing pipe necessary play between the casing pipe and sleeve. On the other hand, the cavity becomes after attachment the shrink sleeves are foamed, there is a risk that any gas overpressure that arises the shrink sleeves leak locally unnoticed can and therefore no longer fulfill their task.

When using the welding collar according to the invention according to the characterizing part of claim 7 these and other disadvantages avoided.  

These measures result in costly changes in scope and longitudinal welds of the socket pipe. Also the Risk of leaks when using Schrumpfman cuffs no longer apply. The creation of the pipe joint be is limited to a few, even by inexperienced staff feasible operations. After welding the Inner tube ends and the leak test is the art fabric sleeve pipe as described above over the joint pushed so that it overlaps the two casing tube ends. The sleeve is then heated, for example by means of a gas burner or other suitable heat source and shrunk as a whole. Here lie down the sleeve ends closely around the casing tube ends and in particular around the welding cuffs attached to them, whereby in the subsequent electrical heating of the same an all-round seamless fusion of the socket ends the jacket pipe ends is guaranteed. Between the coat pipe ends, where the sleeve is still free during the shrinking process can shrink a little further, a constriction occurs. Then in a known manner through an opening in the shrunk sleeve which is completed in this way Foam cavity and thus the insulation of the pipe to be completed. Because of the constriction Sleeve additionally in the axial direction, e.g. if the Pipe connection in the sliding area of a district heating pipe secured against displacement from its position, thereby avoiding excessive stress on the weld becomes.  

This is particularly important if, according to an execution shape, in addition to the welding sleeve in the overlap gap between the sleeve and the casing pipe, another ring-shaped Sealing tape, preferably a viscoelastic hot hot melt adhesive tape is arranged.

Unlike the known methods, the invention is appropriate use of the welding collar even with larger ones Pipe diameters possible because of the original one make such a welding process impossible due to its size de Overlap gap between sleeve and casing pipe the shrinking of the sleeve practically no longer exists is. Even with such a rigid socket connection offers the constriction of the sleeve between the casing pipe ends Advantages because, as already mentioned, because of the achievements ten fixing of the sleeve in the axial direction hardly shear forces can occur at the welded joints.

Embodiments of the invention are as follows explained in more detail with reference to the drawing. It shows:

Figure 1 is a plan view of a tubular member having an open ring to a curved welding sleeve according to a first embodiment.

FIG. 2 the welding collar according to FIG. 1 folds over by 90 °;

FIG. 3 shows a plan view corresponding to that of FIG. 1 to illustrate another embodiment of the cuff according to the invention;

Fig. 4 shows a longitudinal section through a connection made with the help of the welding sleeve two Rohrab sections, for example, an underground district heating line, and

Fig. 5 is a longitudinal section corresponding to that of FIG. 4 to illustrate additional sealing processing elements.

The Schweissman shown in Figs. 1 and 2 in detail cuff 11 is made meander-shaped mutually parallel, close together shown here loops 13 of a flexible or pliable electrically insulated heater wire fourteenth On this heating wire 14 is appropriate, but not necessarily, a layer of a heat-resistant varnish applied as the first insulation. The heating wire 14 carries a sheath 16 made of a thermoplastic plastic of the same specification as that of the pipe parts to be melted together by the welding sleeve. The ends of the heating wire 14 , as can be seen in FIG. 1, are led away vertically from the loops 13 in order to be able to connect the welding sleeve to a programmable current source (not shown). The strip preformed in this way is rolled flat to facilitate wiping off the oxide layer before use. At the same time, the individual loops 13 can be connected to one another by lightly melting.

As can also be seen from FIGS. 1 and 2, the loops 13 are laid in such a way that in a partial region 17 of the end face 19 of the band formed in this way some loops end set back in relation to the adjacent loops. In the partial area of the opposite end face 20 of the band corresponding to the area 17 , the ends of the loops protrude from those of the adjacent loops 13 and form a tongue 21 . This tongue 21 now engages like a comb in the recess formed by the displacement of the loop ends in the region 17 when, as shown, the band is bent into an open ring around a pipe part 4 , the loops 13 then running in the circumferential direction of this ring.

Due to the compact arrangement of the heating wire loops and the comb-like intermeshing of the butt ends of the welding sleeve, a high specific heating power is achieved in use in the area of the annular gap, even if the sleeve, as shown in FIG. 1, due to tolerances of the Pipe part 4 , which encloses it can not be closed completely.

From this first embodiment according to FIGS. 1 and 2 in the embodiment illustrated in Fig. 3 Schweissman separates cuff only in that the shaped into loops 13 heating wire 14, flat with or without additional electrical insulation by a coating of a heat-resistant coating in a Band 25 made of thermoplastic material of the same specification as that of the sleeve and casing pipe is embedded.

The use of the welding sleeve 11 just described according to FIG. 1 or 3 in the manufacture of a socket connection at the joint of two pipe sections of a heat-insulated line, in particular an underground district heating line, will now be described below with reference to FIG. 4.

The two pipe sections 1 and 2 each consist of a medium-carrying inner pipe 3 , which passes through a jacket pipe 4 made of plastic with space. The space between the tubes 3 and 4 is filled seamlessly and homogeneously by a foamed plastic rigid foam insulation 5 . The pipe sections 1 and 2 are, as is known, prefabricated with the jacket pipe 4 and the thermal insulation 5 projecting ends 6 of the inner pipe 3 placed on the construction site and there, for example, laid in corresponding trenches excavated in the ground. At the joint of two pipe sections to be joined together, the projecting ends 6 of the two inner pipes 3 are first connected to one another by a weld seam 7 and the weld is checked for leaks, for example by a water pressure test.

A sleeve 8 is then pushed over the joint. This sleeve 8 is already pushed onto one end of the casing 4 of a pipe section 1 or 2 before the inner pipes 3 are connected to one another. After the inner tube connection 7 has been created and checked, a welding sleeve 11, as can be seen in FIGS . 1 to 3, is firmly attached and fixed to each jacket tube end. Here, a welding collar 11 is selected, the number of loops 13 of which is adapted to the outside diameter of the tubular casing 4 , in order to ensure the necessary heat for the welding process described later. Dimensioning inaccuracies of the outer diameter of the jacket tube end can be easily compensated for, as can deviations in the shape of the jacket tube from a circular cylinder. Then the sleeve 8 is moved so far on the casing pipe 4 of the other pipe section that the overlap of the sleeve 8 and the casing pipe end is approximately the same for both pipe sections 1 and 2 and the two welding sleeves 11 are in the overlap gap as is the dash-dotted representation of the Sleeve 8 in Fig. 4 shows. The remaining annular cavity 15 between the sleeve 8 and the inner tubes 3 is also to be filled with insulation material to complete the thermal insulation. It is known that this cavity 15 at the installation site with a rigid foam, usually a polyurethane foam.

In contrast to the previously known pipe connections, a pipe section made of plastic is used for the sleeve 8 , which is shaped to oversize at the factory, so that the sleeve formed thereby, as indicated by dashed lines in FIGS . 4 and 5, is easily placed on the jacket pipes 4 and can be moved over the welding sleeves 11 , even if the two tube axes should form a small kink. According to a technique known for shrink sleeves and the like, the sleeve 8 is shaped under heat, but below the crystallite point of the pipe material, with subsequent quenching of the shaped pipe section. If a sleeve 8 shaped in this way, in the position shown in broken lines in the drawing, in which it bridges the joint and overlaps the ends of the casing tubes 4 and the two welding sleeves 11 , is heated again, for example by means of a gas burner, shrinks and takes approximately the position shown at 8 'in a drawn line, their ends overlapping the jacket pipe ends 9 tightly around this and around the welding sleeve 11 and between the jacket pipe ends a constriction 10 is formed which prevents any axial displacement of the sleeve from now on.

After the described shrinking process, the outwardly directed ends of the heating wires 14 of the two welding sleeves 11 are connected to a programmable current source. Due to their heating, the parts of the sleeve and jacket tube adjacent to the sleeves 11 and the plastic sheathing of the wires 14 of the sleeves 11 are fused or welded to one another, which results in a perfect sealing of the annular gap.

In some special applications, it may also be desirable to provide additional seals, as illustrated in the left or right part of FIG. 5. For example, as shown on the left-hand side of FIG. 5, before the sleeve 8 shrinks, in the overlap gap between the sleeve and the jacket tube, in addition to the welding sleeves in the axial direction, an annular sealing band 24 , preferably an elastic one, seen between these and the adjacent jacket tube end permanent hot melt adhesive tape are arranged, around which the sleeve 8 is then shrunk. This tape 24 may also consist of a sealing tape wound around the end of the jacket tube made of a plastic adhesive combination, which allows slight relative displacements between the ends 9 of the shrunk sleeve 8 'and the associated jacket tube ends.

Finally, as a further or alternative safety measure, the pipe connection can be additionally sealed from the outside by both the ends 9 of the shrunk and welded sleeve 8 'and the shrink sleeve sleeves 12 seated on the casing pipe ends, as shown on the right half of FIG. 5 is shown.

Then, if this has not already been done beforehand, the thermal insulation of the line can be completed in a conventional manner by introducing a reaction mixture liquid through an opening 23 in the shrunk sleeve 8 ', which fills the cavity 15 by foaming, and penetrates into all remaining open spaces and normally forms a solid bond with the sleeve, the inner pipe ends and the end faces of the thermal insulation of the pipe sections 1 and 2 .

Claims (9)

1.Welding sleeve for producing a tube connection by welding tube parts made of thermoplastic plastic of the same specification, which are pushed one above the other, this sleeve being arranged in the overlap ring gap between the tube parts and having resistance heating wires which can be connected to a power source via lines which lead to the outside and which, when heated, are under pressure against one another welding overlapping tube parts to one another, characterized in that the sleeve ( 11 ) is formed as an open, flexible or flexible ring made of meandering heating wire loops ( 13 , 14 ) running parallel to one another in the circumferential direction of the ring and alternately offset at the butt ends of the sleeve are and mesh like a comb. 2. Welding sleeve according to claim 1, characterized in that the heating wire ( 14 ) with a sheath ( 16 ) made of a thermoplastic material is the same specification as that of the pipe parts to be welded, the meandering loops ( 13 ) of the sheathed wire ( 14 ) are connected to one another in parallel to one another ( FIGS. 1, 2). 3. welding sleeve according to claim 1, characterized in that the heating wire loops ( 13 ) are embedded in a flat band made of a thermoplastic material of the same specification as that of the pipe parts to be welded. 4. Welding sleeve according to one of claims 1 to 3, characterized in that a heat-resistant lacquer layer is applied between the casing ( 16 ) and heating wire ( 14 ) for additional electrical insulation. 5. Welding sleeve according to one of claims 1 to 4, characterized in that the loops ( 13 ) in a partial area ( 17 ) of one butt end of the sleeve end set back relative to the other and in the opposite area of the other butt end of the sleeve te tongue-like ( 21 ) protrude. 6. welding collar according to one of claims 1 to 5, characterized in that the number of loops on the cuff diameter is matched. 7. Use of the welding sleeve according to one of claims 1 to 6, for producing a socket connection at the joint of two pipe sections of a thermally insulated pipe, in particular an underground pipe, the pipe sections ( 1 , 2 ) from a jacket pipe ( 4 ) made of a thermoplastic Plastic and this with the interposition of a foamed insulation ( 5 ) penetrating medium-carrying inner tube ( 3 ) and at the junction the above inner tubes ( 6 ) are welded together and the cavity ( 15 ) between them and one, with their ends on the ends of the casing pipes supporting and bridging the joint ( 8 ) is foamed to complete the thermal insulation, characterized in that depending on the overlap gap between the socket ( 8 ) and the jacket pipe end underneath, a welding sleeve (is arranged and that the socket ( 8 ) is a pipe section, the factory under Wä rme, its displacement on the casing pipes ( 4 ) and its pushing onto the casing pipe ends is made possible inner dimension, and which in its position bridging the butt joint is shrunk under the influence of heat to such an extent that its ends ( 9 ) cuff over the welding man ( 11 ) are pressed onto the jacket pipe ends and a constriction ( 10 ) is formed between the ends of the jacket pipes, which prevents axial displacements of the shrunk sleeve ( 8 '). 8. Use according to claim 7, characterized in that in addition in the overlap gap between the sleeve ( 8 ) and the casing tube an annular sealing tape, preferably an elastic hot melt adhesive tape is arranged. 9. Use according to one of claims 7 or 8, characterized in that the pipe connection is additionally sealed from the outside by shrink sleeve sleeves ( 12 ) seated on both the ends of the sleeve and on the casing pipe.