NO311952B1 - Process for the preparation of a polyolefin pipeline compound and such a pipeline compound - Google Patents

Abstract

A pipe end (13) of a pipe (12) consisting of polyolefin is deformed cold, that is to say at ambient temperature, with the aid of an expanding mandrel. Once the expanding mandrel has been withdrawn, the expanded pipe end (13) and a respectively desired connecting part, or the pipe end (11) of a further pipe (10), are plugged onto one another. The pipe end (13) consisting of polyolefin experiences only a reversible deformation and, as a result of it deforming back to its original shape, forms a firm, gas-tight connection to the connecting part or to the other pipe end (11). <IMAGE>

Description

The invention relates to a method for producing a pipeline connection, as stated in the introduction in claim 1. Furthermore, the invention relates to a pipeline connection as stated in the introduction in resp. requirements 7 and 11.

In a known method and a known pipeline connection of this type from DE-A 3 817 442, the pipeline connection is produced, e.g. using a shrink sleeve that overlaps the connecting parts for two pipes. The shrink sleeve may consist of a thermoelastic material such as netted polyolefin. It is thus connected to the connecting parts so that the cross-linked polyolefin after heating is deformable in a heated state beyond the crystallite melting point, and in this heated state can be pushed onto the connecting parts during expansion. In the same way, the pipe end of a pipe made of mesh polyolefin can also be pushed onto a connecting part, e.g. a piece.

From EP-A-0 102 919, a method for connecting pipes and such a pipe connection is known, where a first pipe end of the net polyolefin is expanded in a cold state, but preferably in a state heated to above the crystallite melting point.

The implementation of these known methods in practice entails certain difficulties because the cross-linked polyolefin must be heated to relatively high temperatures, e.g. above 135°C in the case of netted polyethylene, and only at this temperature has a sufficiently easy deformability. It is therefore necessary to connect the parts in question to each other in such a short time that during this time no cooling occurs below the crystallite melting point.

The purpose of the invention is to provide a method for producing a pipeline connection of the type mentioned above, which allows the production of a safe pipeline connection under normal temperatures, i.e. ambient temperatures, and to provide a pipeline connection which can be produced under ambient conditions and exhibits a safe sealing connection.

According to the invention, this purpose is achieved with regard to the method by means of the characteristic features stated in claim 1.

As far as the pipeline connection is concerned, this purpose is achieved by means of the characteristic features indicated in the respective requirements 7 and 11.

The invention is based on the surprising fact that thermoelastic polyolefins, especially medium-density, high-density or cross-linked polyolefins, also in a cold and partially crystalline state, i.e. in a state not heated beyond the crystallite melting point, have a sufficiently extensive reversible deformability. This means that the polyolefin is deformable by mechanical impact, but strives in the deformed state to return to its original shape. By providing sufficiently large forces, e.g. by means of an expansion mandrel of the usual type for expanding pipes, it is therefore possible to expand pipe ends of polyolefin pipes reversibly. Under the conditions that prevail at ambient temperature, the deformation occurs automatically back to the original state, i.e. to the original pipe width at a relatively low speed, so that the expansion mandrel can be pulled out of the expanded pipe end and the still expanded pipe end can be pushed onto the relevant desired connection part. On the other hand, the speed of the deformation back by itself is so great that no unnecessary waiting times occur.

Compared to other materials, polyolefins have the advantage that expansion, to the extent that it occurs after the connection with the connecting part, does not lead to the formation of stress cracks.

The method according to the invention therefore provides a particularly advantageous opportunity to connect pipes of polyolefin, in particular pipes of medium-density, high-density or mesh polyolefin, with the relevant desired connection part without the use of heat energy. At the same time, a particularly firm and sealing, particularly gas-tight connection is achieved by means of the deformation back by itself of the extended touching end. During this deformation back of itself, the polyolefin possibly adapts to existing surface structures on the connecting part. Such surface structures that increase bond strength are e.g. beads, grooves, grooves or riffles with which the back-deformed polyolefin engages.

In connection with the method described above, it is also possible to further secure the manufactured pipeline connections, if this is necessary. For this, pipe clamps of a known type can be used. However, it is also possible to attach a clamping ring to the pipe end of the polyolefin pipe. This clamping ring can, if it also consists of a reversibly deformable material, be brought onto the pipe end from the beginning. It is also possible to push on a non- or only slightly deformable clamping ring of e.g. metal on the pipe-side end of the pipeline connection after the production of the pipeline connection, e.g. with known hydraulic means.

The invention will be described in more detail below in connection with some design examples and with reference to the drawings, where fig. 1 is a sectional view of a pipeline connection of a connection part and a pipe end tensioned according to the method according to the invention, fig. 2 is a sectional view of a pipeline connection as shown in fig. 1 with a tension ring, fig. 3 is a sectional view of a pipeline connection according to the invention between two pipe ends.

In the sectional drawing in fig. 1 shows a connecting part 1 which e.g. can be a straight piece of pipe, an angle pipe or another connecting piece for connecting two pipes, but can also e.g. be a triple connector like a T-piece. This connecting part 1 is made of a material such as metal, glass, ceramic, plastic or another material selected for the relevant application purpose. At each connection point, the connection part 1 is provided with a surface structure that increases the bond strength. In the embodiment shown, this surface structure is formed by an end part 2 which tapers towards the end. Instead, one or more beads, channels or grooves or also riffles and the like can also be arranged.

The production in fig. 1 shows a pipe 3 of polyolefin, preferably of a medium density or high density, but especially of a mesh polyolefin. The inner diameter of the pipe 3 is smaller than the outer diameter of the connecting part 1 which (as shown) can be essentially equal to the inner diameter of the connecting part 1, so that the design of flow resistances at tapers and deposits on the tapers can be prevented by the medium flowing through the connecting part 1 and the pipe 3. To make the pipe connection, the pipe end 4 is expanded at ambient temperature, e.g. by means of an expansion mandrel of the usual type so much that the inner diameter of the pipe end 4 is at least as large as the outer diameter of the connecting part 1 in the area of the reinforced end part 2. After pushing over the reinforced end part 2, the pipe end 4 of the deformation lies back on its original a lot. As a result, the pipe end 4 adapts to the outer profile of the connecting part 1 as shown. As the pipe end 4 originally has an inner diameter that is smaller than the outer diameter of the connecting part 1, the pipe end 4 rests closely over its length against the end part 2 of the connecting part 1. In this way, a very narrow connection with a large surface is formed at the end between the pipe end 4 and the connecting part 1 Fig. 2 shows a further embodiment of the pipeline connection described above, with corresponding parts having the same reference numbers. In this embodiment, a clamping ring 5 is arranged as an additional safeguard for making a sealing connection between the pipe end 4 and the connecting part 1. This clamping ring 5 preferably consists of the same material as the pipe 3. In the embodiment shown, the pipe as well as the clamping ring 5 consists of the net polyethylene. The inner diameter of the clamping ring 5 is adapted closely to the outer diameter of the pipe 3, and is pushed onto the pipe end 4 before the production of the pipeline connection. During the subsequent expansion process, the clamping ring 5 is temporarily expanded together with the pipe end 4, so that the expanded pipe end 4 together with the attached clamping ring 5 is brought on the end part 2 of the connecting part 1. Subsequent deformation back by itself then leads, in the above-described manner, to the tight connection between the pipe end 4 and the end part 2 of the connecting part 1, as the clamping ring 5 also contracts and thus further presses the pipe end 4 against the end part 2 in the area at the clamping ring 5. Fig. 3 shows a pipeline connection which is formed between two pipe ends. Both pipes can consist of the same or different materials. The pipes are preferably made of mesh polyolefin and serve as conduits for corrosive media. As an example, industrial waste water should be mentioned, but especially also waste water from households or municipal waste water which requires very special corrosion-resistant pipe materials and for which pipes made of polyolefin have in practice proven to be well suited.

In the design example shown, the two pipes have the same outer diameter and inner diameter. However, this is not a condition, as the same pipeline connection can possibly also be made between pipes of different diameters, if the different internal diameters in connection with this do not cause inadmissible flow resistances and deposits. A first tube 10 has a first touching end 11, a second tube 12 has a second touching end 13. It can be seen that the inner diameter of the second touching end 13 is expanded, and this expanded second touching end 13 is pushed onto the first touching end 11 of the first tube 10 .This extension becomes, as in the execution examples above, e.g. carried out with an ordinary expansion mandrel at ambient temperature and is subject to the described deformation back by itself, by means of which the expanded touching end 13 strives to regain its original shape. The narrow installation with a large area between the two pipe ends 11 and 13 also provides here a tight pipeline connection which, due to the corrosion resistance of the material, does not become leaky against the aforementioned waste water even after prolonged use.

As in the embodiment shown in fig. 2, the connection can also be further secured here by means of a clamping ring. However, care must be taken at the same time that under the pressure of such a clamping ring, an unacceptable deformation of the first pipe 11 does not occur, which exhibits a flow resistance for the flowing waste water or provides a basis for deposits from waste water in the area at the connection point. Instead of the clamping ring, a booklet mediator can also be used to further secure the connection point.

Pipes made of mesh polyolefin are therefore also used in waste water technology for this reason, because safe, self-sealing connections between smooth pipes can easily be made in this way. In addition, it appears as a further advantage that the pipes 10 and 11 which are produced as endless pipes can also be laid as endless pipes without the need for angle pipes or other connecting parts to place the pipe end in a desired course. It is therefore only necessary to provide connections between the pipes at the entry and exit locations.

Claims (15)

1. Method for producing a pipeline connection of a pipe end (4) of a pipe (3) of polyolefin and a connection part (1), where the pipe end (4) of polyolefin has an inner diameter smaller than that of the connection part (1 ) outer diameter, and which by means of an expansion mandrel at ambient temperature is expanded to an inner diameter that is larger than the outer diameter of the connecting part (1), and after removing the expansion mandrel, the still expanded pipe end (4) of the pipe (3) and the connecting part (1) are inserted into each other, and are then connected to each other by shrinking, characterized in that the pipe end (4) of polyolefin which was expanded at ambient temperature is firmly and sealingly connected to the connecting part (1) at ambient temperature. 2. Method according to claim 1, characterized in that an end part (2) of the connecting part (1) is provided with a surface structure to increase the engagement surface with the pipe end (4). 3. Method according to claim 1 or 2, characterized in that the connection is additionally secured by a pipe clamp. 4. Method according to claim 1 or 2, characterized in that the connection is secured by a clamping ring (5). 5. Method according to claim 4, characterized in that the clamping ring (5) consists of a material which is expandable at ambient temperature and deforms back by itself, and expands reversibly together with the pipe end (4). 6. Method according to claim 4, characterized in that the clamping ring consists of a non- or only slightly deformable material, and is hydraulically pushed onto the pipe end which surrounds the connecting part after the connection has been made. 7. Pipeline connection of an end part (2) of a connecting part (1) and a pipe end (4) of a pipe (3) of polyolefin, which has an inner diameter smaller than the outer diameter of the end part (20) of the connecting part (1), the pipe's (3) pipe end (4) which is expanded at ambient temperature is crimped onto the end part (2) of the connecting part (1), characterized in that the pipe end (4) of polyolefin is expanded reversibly at ambient temperature, and is fixed when deformed back by itself at ambient temperature and sealingly connected to the end part (2) of the connecting part (1). 8. Pipeline connection according to claim 7, characterized in that the end part (2) of the connection part (I) is provided with a surface structure to increase the engagement surface with the pipe end (4). 9. Pipeline connection according to claim 7 or 8, characterized by a clamping ring (5) placed on the pipe end (4) of a material which is expandable at ambient temperature and deforms back by itself. 10. Pipeline connection according to one of claims 7-9, characterized in that the pipe end (4) is selected from medium density, high density or netted polyolefin. 11. Pipeline connection of a first pipe end (11) of a first pipe (10) and a second pipe end (13) of a second pipe (12) of polyolefin, having an inner diameter smaller than the outer diameter of the first pipe end (11) , where the first touching end (11) which is expanded at ambient temperature is crimped onto the second touching end (13), characterized in that the first touching end (11) of polyolefin is reversibly expanded at ambient temperature and connected firmly and sealingly to the second touching end (13 ) by deforming back on itself at ambient temperature. 12. Pipeline connection according to claim 11, characterized in that the first pipe end (II) of the first pipe (10) is provided with a surface structure to increase the engagement surface with the second pipe end (13). 13. Pipeline connection according to claim 11 or 12, characterized in that the connection is secured by a clamping ring. 14. Pipeline connection according to claim 13, characterized in that the clamping ring consists of a material which is expandable at ambient temperature and deforms back by itself. 15. Pipeline connection according to one of the claims 11 - 14, characterized in that the first and second pipes (10, 12) are selected from medium density, high density or mesh polyolefin.