CH671819A5 - - Google Patents

Description

DESCRIPTION

The invention relates to a welding sleeve according to the preamble of claim 1 and a socket connection with such a welding sleeve at the joint of two pipe sections of a thermally insulated line.

In the case of pipe connections at the joint of two pipe sections of a thermally insulated pipe, in particular an underground pipe, in which the pipe sections consist of a plastic jacket pipe and a medium-carrying inner pipe passing through it with the interposition of foamed thermal insulation, the projecting inner pipe ends are welded to one another at the connection point and the cavity between them and a sleeve, which is supported on the ends of the casing pipes and bridges the joint, to complete the thermal insulation.

It is particularly important to prevent moisture from entering the connection point from the outside through the annular gap between the sleeve and the jacket pipe end enclosed by it, especially in the case of lines laid directly into the ground. Even slight traces of moisture at the connection point can cause damage, but also lead to leakage protection devices responding, even though the medium-carrying pipes show no leak.

In an effort to achieve such a seal, it is, for. B known from DE-A-3 217 820 or CH-A-396 536 to arrange a resistance wire on the inside of the socket ends. The sealing between the jacket pipe and the sleeve is then carried out by directly melting together the material of the sleeve and the jacket pipe ends when the heating wires are heated. In these known methods, however, the play between the sleeve and the casing pipe must not be too great for understandable reasons. Your application is therefore limited to small to medium pipe diameters.

From EP-A-36 963 and EP-A-75 901 it is also known to arrange a closed welding ring with an inserted heating wire between the sleeve and the casing tube. According to EP-A-75 901, a welding ring made of a thermoplastic is pushed onto the jacket tube ends, in which the heating wire development is embedded from a spirally wound resistance wire. According to EP-A-36 963, the welding ring consists of a spiral winding of a resistance wire sheathed with thermoplastic material, the sheath of each turn of the winding being welded to the sheath of the next turn and thus forming a compact sleeve. The winding is firmly connected to the sleeve by partial shrinking, the sleeve having a frozen latent radial residual shrinkage tension which, when heated during the welding process, is intended to eliminate the radial play between the winding and the tubular casing parts and to generate the 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 bridge the sleeve on the casing pipe into its joint in such casing pipes and under the difficult conditions in the open trench.

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To be able to shift the position, the free play between the sleeve or welding ring and the casing tube must be chosen so large that the overlap gap to be sealed is too large for sealing by melting together in the manner described. The above-mentioned irregularity of the outer dimensions of commercially available jacket pipes has hitherto also prevented the known welding rings from being applied to the jacket pipe ends, instead of into the sleeve ends.

Rather, it has been used in such cases so far (e.g. EP-A-30 776) to be able to effect the contact pressure required for the welding process by means of a clamping band or clamping tool, first to split lengthwise, to adjust the circumference, then to fold over the connection point and to weld in the longitudinal direction.

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

The invention has for its object to design a welding sleeve of the type mentioned in such a way that even with extreme deviations from the outside diameter and shape of the inner pipe parts, in particular jacket pipes of thermally insulated lines, with little expenditure of time and work and without special aids can be used in a pipe trench and ensures a reliable and permanent sealing of the welded pipe parts, in particular a seamless welding over the entire circumference of these pipe parts.

According to the invention, this object is achieved by a welding collar with the features specified in the characterizing part of claim 1.

Because the sleeve according to the invention is designed as an open, flexible or flexible ring, it can be easily applied all around on its outer surface to a pipe part. The interdigitated butt ends of the sleeve ensure that any deviations in the outside diameter of the pipe part from the standard are compensated for without creating a gap in the covering of the pipe part with heating wire. This ensures a seamless, flawless welding across the entire circumference of the pipe parts to be welded.

With an embodiment of the welding sleeve according to one of claims 2 or 3, the welding of the overlapping pipe parts is further improved, since during the welding process the heating wire jacket or the band in which the heating wire is embedded enters into a welded connection with the adjacent pipe parts.

The feature of claim 4 eliminates the risk of a short circuit between adjacent or crossing heating wires.

A particularly simple manufacture of a welding collar according to the invention results from an embodiment according to claim 5.

The uses of the welding collar according to the invention for producing pipe connections are diverse.

Particular advantages result from the use of the welding collar according to the invention in the case of a socket connection at the joint of two pipe sections of a heat-insulated pipe, in particular an underground pipe, the pipe sections consisting of a casing pipe made of a thermoplastic and a medium-carrying inner pipe penetrating this with the interposition of a foamed thermal insulation the

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Connection point, the projecting inner pipe ends are welded to one another and the cavity between them and a sleeve, which is supported with its ends on the ends of the casing pipes and bridges the butt joint, is foamed to complete the thermal insulation.

In an effort to achieve a perfect seal of such sleeve connections, it is known (e.g. from DE-A-3 110 503) to seal the ends of the sleeve by means of shrink sleeves seated on both the sleeve ends and the jacket tube. Foaming of the cavity between the sleeve and the inner tube can take place, before or after this seal, through an opening in the sleeve. The disadvantage in the former case is the possibly high foam losses due to the play between the casing pipe and the casing necessary for moving the casing on the casing pipe. If, on the other hand, the cavity is filled with foam after the shrink sleeves have been attached, there is a risk that the gas shrink sleeves may leak locally without being noticed and thus no longer fulfill their task in the event of any excess gas pressure.

When using the welding collar according to the invention in accordance with the characterizing part of claim 6, these and other disadvantages are avoided.

These measures eliminate complex circumferential adjustments and longitudinal welding of the socket pipe. There is also no risk of leaks when using shrink sleeves. The creation of the pipe connection is limited to a few operations that can also be carried out by inexperienced personnel. After welding the inner pipe ends and the leak test, the plastic sleeve pipe is pushed over the joint as already described so that it overlaps the two casing pipe ends. The sleeve is then heated, for example by means of a gas burner or another suitable heat source, and thereby shrunk as a whole. In this case, the socket ends fit tightly around the jacket pipe ends and in particular around the welding sleeves applied to them, which ensures that the sleeve ends merge seamlessly with the jacket pipe ends during the subsequent electrical heating thereof. A constriction occurs between the jacket pipe ends, where the sleeve can shrink a little further during the shrinking process. Then, in a known manner, the cavity closed in this way can be foamed through an opening in the shrunk sleeve and thus the thermal insulation of the line can be completed. Due to the constriction, the sleeve is also in the axial direction, for. B. if the pipe connection is in the sliding area of a district heating pipe, secured against displacements from its position, thereby avoiding excessive stress on the weld.

This is particularly important if, according to one embodiment, in addition to the welding sleeve in the overlap gap between the sleeve and the casing tube, an annular sealing tape, preferably a viscoelastic hot-melt adhesive tape, is arranged.

In contrast to the known methods, the welding collar according to the invention can also be used with larger pipe diameters because the original overlap gap between the sleeve and the casing pipe, which is impossible due to its size, is practically no longer present after the sleeve has shrunk. Even with such a rigid sleeve connection, the constriction of the sleeve between the jacket tube ends offers advantages, because, as already mentioned, because of the fact that

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achieved fixation of the sleeve in the axial direction hardly shear forces can occur at the welded joints.

Exemplary embodiments of the invention are explained in more detail below with reference to the drawing. It shows:

1 shows a plan view of a tube part with a welding collar bent into an open ring according to a first embodiment;

FIG. 2 the welding collar according to FIG. 1 folded 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 aid of the welding sleeve between two pipe sections z. B. an underground district heating pipe, and

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

The welding sleeve 11 shown in detail in FIGS. 1 and 2 consists of meandering loops 13 running parallel to one another, here shown close to each other, made of a flexible or flexible electrically insulated heating wire 14. This heating wire 14 is useful, but not necessarily, as the first insulation applied a layer of heat-resistant paint. The heating wire 14 carries a sheath 16 made of a thermoplastic material of the same specification as that of the pipe parts to be fused 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 stripping of 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 in area 17 by the setback of the loop ends, if, as shown, the band is bent into an open ring around a tubular 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 also achieved in the area of the annular gap in use, even if the sleeve, as shown in FIG. 1, due to tolerances of the pipe part 4, which it encloses cannot be closed completely.

The welding collar illustrated in FIG. 3 differs from this first embodiment according to FIGS. 1 and 2 only in that the heating wire 14 formed into loops 13, with or without additional electrical insulation, is covered by a coating of a heat-resistant lacquer in a flat band 25 made of thermoplastic material of the same specification as that of the sleeve and casing pipe.

The use of the welding sleeve 11 just described according to FIG. 1 or 3 in the production of a socket connection at the joint of two pipe sections of a thermally 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-in plastic rigid foam insulation 5. The tube sections 1 and 2 are, as is known, prefabricated with over the jacket tube 4 and the thermal insulation 5 protruding ends 6 of the inner tube 3 to the construction site and z. B. laid in corresponding trenches dug in the ground. At the abutment 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 z. B. checked for leaks 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 jacket 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 applied 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. Dimensional inaccuracies in 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 onto the casing tube 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 located in the overlap gap, as is the dash-dotted representation of FIG 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 for this purpose to foam this cavity 15 at the point of installation with a rigid foam, usually a polyurethane foam.

Unlike the previously known pipe connections, a pipe section made of plastic is used for the sleeve 8, which is shaped to oversize in the factory, so that the sleeve formed thereby, as indicated by dash-dotted lines in FIGS. 4 and 5, easily on the casing 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 critical 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. B. by means of a gas burner, it shrinks and takes about the position shown at 8 'in a solid line, with their ends 9 overlapping the casing pipe ends tightly around this and around the welding sleeve 11 and a constriction 10 formed between the casing pipe ends, which from now on s

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prevents any axial displacement of the sleeve.

After the described shrinking process, the ends of the heating wires 14 of the two welding sleeves 11 which are led outwards are connected to a programmable current source. As a result of their heating, the parts of the sleeve and the casing tube which are in contact with the sleeves 11 and the plastic sheathing of the wires 14 of the sleeves 11 are fused or welded to one another, as a result of which the ring gap is sealed properly.

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 casing tube, in addition to the welding sleeves in the axial direction, an annular sealing band 24, preferably an elastic one, can be seen between these and the adjacent casing tube end Hot melt adhesive tape are arranged, around which the sleeve 8 is then shrunk. This band 24 can

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also consist of a sealing tape wound around the jacket tube end made of a plastic adhesive combination which allows slight relative displacements between the ends 9 of the shrunk sleeve 8 'and the associated jacket 5 tube ends.

Finally, as a further or alternative safety measure, the pipe connection can be additionally sealed from the outside by shrink-10 hose sleeves 12 which are seated on both the ends 9 of the shrunk and welded sleeve 8 'and on the casing pipe ends, as is the case on the right half 5 is shown.

Thereafter, if this has not already been done beforehand, the thermal insulation of the line 15 can usually be completed by liquidly introducing a reaction mixture through an opening 23 in the shrunk sleeve 8 'which fills the cavity 15 by foaming, as well as all of them remaining open spaces penetrates 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.

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3 sheets of drawings

Claims (8)

671819 PATENT CLAIMS 1.Welding cuff, with resistance heating wires that can be connected to a power source via leads leading to the outside, for producing a pipe connection by welding pipe parts made of thermoplastic synthetic material of the same specification pushed over one another in such a way that, when the cuff arranged in the overlap ring gap between the pipe parts is heated, the cuff that is under pressure against one another overlapping pipe parts can be welded to one another, characterized in that the sleeve (11) is formed as an open, resilient or flexible ring from heating wire loops (13, 14) which run in a meandering manner in the circumferential direction of the ring and are 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) is provided with a sheathing (16) made of a thermoplastic, the meandering loops (13) of the sheathed wire (14) being connected to one another in parallel ( Fig. 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. 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 from the other and protrude tongue-like (21) in the opposite area of the other butt end of the sleeve . 6. socket connection at the joint of two pipe sections of a thermally insulated pipe, in particular an underground pipe, with a welding collar according to one of claims 1 to 5, wherein the pipe sections (1,2) from a casing pipe (4) made of a thermoplastic material and one under There is an intermediate layer of a foamed thermal insulation (5) penetrating medium-carrying inner tube (3) and at the junction the protruding inner tube ends (6) are welded to each other and the cavity (15) between them and one that is supported with its ends on the ends of the jacket tubes and the butt parts bridging sleeve (8) is foamed to complete the thermal insulation, characterized in that a welding sleeve made of a thermoplastic material of the same specification as that of the pipe parts is arranged in the overlap gap between the sleeve (8) and the jacket pipe end underneath, and that the sleeve ( 8) a pipe down cut, which is molded at the factory under heat to allow it to be moved onto the jacket tubes (4) and pushed onto the jacket tube ends, and which in its position bridging the joint has shrunk under the influence of heat to such an extent that its ends (9) over the welding sleeves (11) are pressed against the jacket pipe ends and a constriction (10) is created between the ends of the jacket pipes (4), which prevents axial displacements of the shrunk sleeve (8 ') (Fig. 4.5). 7. Socket connection according to claim 6, characterized in that an annular sealing tape (24), preferably an elastic hot melt adhesive tape, is additionally arranged in the overlap gap between the sleeve (8) and the casing tube. 8. socket connection according to one of claims 6 or 7, 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.