PIPE FOR RELINING UNDERGROUND PIPELINES

Abstract: A pipe for relining underground pipelines, which is of composite type having an annularly rigid corrugated outside wall (10) of polymer material, which is attached to the outside of an inside wall (11) which as such or after heating, maintaining the annular rigidity of the outside wall, can be stretched and/or compressed under bending of the composite pipe.

Description: PIPE FOR RELINING UNDERGROUND PIPELINES The invention relates to a pipe for relining underground pipelines. A method for restoring underground pipelines comprises relining of the pipeline with a pipe which is drawn into the pipeline and is then fixed therein by a hardening material, e.g. cement mortar, being injected between the outside of the relining pipe and the inside of the pipeline. The re'lining pipes which are used at present are relatively stiff and therefore it is in most cases necessary to make a large excavated shaft at one end of the pipeline where the relining pipe is to be inserted into the underground pipeline. Moreover, it may be difficult to draw these relining pipes through the pipeline if there is a restriction, a change of direction, or some other obstacle in the old pipeline. The object of the invention is to provide a relining pipe which can be handled more easily and which facilitates the insertion and reduces the work that has to be done at the site as compared with the use of conventional relining pipes also in case of obstacles in the pipeline. The relining pipe provided according to the invention comprises a pipe of known composite type with an annularly rigid corrugated outside wall of polymer material, which is attached to the outside surface of an inside wall. In known embodiments of this type of pipes, the inside wall is rigid and thus the composite pipe is so stiff that it is not suited for overcoming the drawbacks mentioned above. In order to achieve the object of the invention the pipe has therefore obtained the characteristic features appearing from claim 1. For a better understanding of the invention this will be described in more detail below, reference being made to the accompanying drawings in which FIG. 1 is a half side view and a half axial sectional view of a relining pipe according to one embodiment of the invention, FIG. 2 is a vertical sectional view which illustrates the use of the relining pipe according to FIG. 1, FIG. 3 is a fragmentary axial sectional view of a relining pipe of the invention with another profile of the outside wall of the pipe, FIG. 4 is a fragmentary axial sectional view of the relining pipe of the invention in a second embodiment thereof during bending, FIG. 5 is a fragmentary axial sectional view of the relining pipe of the invention in a third embodiment thereof, conditioned for insertion into a pipeline, and FIG. 6 is a fragmentary axial sectional view of the relining pipe of FIG. 5 after the pipe having been drawn into the pipeline. The relining pipe shown in FIG. 1 is of a known embodiment as far as it comprises a corrugated outside wall 10 and an inside wall 11 having smooth inside and outside surfaces, the inner peaks of the outside wall being attached to the smooth outside surface of the inside wall at 12. The ribs of the corrugated outside wall in this case have a semi-circular shape. The outside wall consists of polyethylene, polypropylene, or PVC as is customary for pipes of the type referred to herein. However, the inside smooth wall 11 of the pipe according to the invention consists of a thermoplastic elastomer which can be worked in an extruder and can be fused to the corrugated outside wall. Suitable materials for the inside wall can be e.σ. EPDM mixed with polyethylene (synthetic rubber), thermoplastic polyolefines, e.g. VISTAFLEX (reg. trademark) and SANTOPRENE (reg. trademark), ethylene vinyl acetate polymers, e.g. ESCORENE (reg. trademark), and mixtures of styrene, ethylene, and butane, e.g. ELEXAR (reg. trademark) and DRYFLEX (reg. trademark). The relining pipe described is finished in a factory and can then be used without any after-treatment for restoration of underground pipelines in the manner illustrated in FIG. 2. In FIG. 2 there is shown an underground pipeline 13 which extends between a manhole 14 and a manhole 15. The figure shows that the relining pipe generally indicated at 16 herein, is inserted into the pipeline from the end thereof which connects to the manhole 14. Since the relining pipe according to the invention can be easily bent at a relatively small radius due to the fact that the inside wall 11 consists of a thermoplastic elastomer so that it can be compressed (wrinkled) at the inner side of the bend and/or can be stretched at the outer side of the bend so as to return to a tensionfree condition when the relining pipe is straightened out, no excavation need be made at the insert end of the pipeline; the relining pipe can easily pass from ground level through the manhole 14 into the pipeline 13 while being bent to the extent necessary. In order to facilitate the passage of the relining pipe into the pipeline a bent insertion funnel 17 is provided at the insert end of the pipeline. The relining pipe is drawn into the pipeline by means of a' rope 18 which extends over a pulley 19 in the manhole 15 and is connected to a hoist 20 located at ground level. Due to the fact that the relining pipe has corrugation ribs of semi-circular shape, the insertion of the relining pipe into the pipeline is facilitated, because in that case the relining pipe more easily can pass existing sharp edges in the pipeline without getting caught by such edges. Moreover, the flexible construction makes it very easy to pass depressions and direction changes in the old pipeline. The insertion is further facilitated by the relining pipe when being stretched e.g. due to the fact that it jams in the pipeline owing to existing great friction forces or for other reasons, diminishes in diameter and therefore more easily can pass restrictions in the pipeline. The corrugated outside wall 10 imparts annular rigidity to the relining pipe, the smooth inside surface of the pipe at the same time being hydraulically advantageous. When the relining pipe has been installed, it is fixed in the position thereof e.g. by injecting a hardening material such as cement mortar between the outside surface of the relining pipe and the inside surface of the pipeline, the corrugated outside surface of the relining pipe providing a good adhesion to 'the relining pipe. However, it is possible to exclude such injection when using the relining pipe., of the invention. If a certain resistance is established against the insertion of the relining pipe, the outside diameter of this pipe will decrease when the pipe is being drawn into the pipeline and then, when the relining pipe is left alone and the stretching thereof ceases, the pipe will return to the original outside diameter which can have such dimension in relation to the inside diameter of the pipeline that the relining pipe presses against the inside surface of the pipeline and accordingly is held fixed therein. The outside wall of the relining pipe described can also have conventional parallelogrammic profile as shown in FIG. 3. In another embodiment of the invention the annularly rigid corrugated outside wall 10 consists of polyethylene, polypropylene, or similar polymer material. The inside wall does not consist of an elastic polymer; it is rigid and consists of a polymer material, e.g. the same material as that of the outside wall but with a lower softening range than that of the outside wall. As seen in axial sectional view, the pipe has the appearance of FIG. 1 or FIG. 3. When this pipe is drawn into an underground pipeline in the manner shown in FIG. 2, the inside wall 11 is heated to. a temperature slightly above the softening range in the initial part of the installation procedure, the outside wall 10 being relatively unaffected by the heating. This can be effected by means of a heat source 21, FIG. 2, which is- centered in the pipe on a slide which is held stationarily such that the pipe when drawn into the underground pipeline as shown in FIG. 2, passes the heat source while the inside wall of the relining pipe is being heated. By such heating the inside wall will be soft and therefore can bulge into the spaces formed by the corrugated outside wall in the manner shown in FIG. 4 at the inner side of the bend formed by the relining pipe. Without this possibility of deformation of the inside wall it would not be possible to bend the composite relining pipe in the manner required in order to draw such pipe into the underground pipeline through a relatively narrow manhole, but when the inside wall has been softened, the relining pipe will be sufficiently flexible for this operation. By the relining pipe being held under tension when it ' has been installed into the pipeline, and the material of the inside wall is allowed to cool, the inside wall will return to the smooth shape thereof according to FIG. 3 as far as the inside wall earlier has been deformed during insertion of the relining pipe. Also in the embodiment according to FIGS. 5 and 6 the corrugated annularly rigid outside wall 10 can consist of polyethylene, polypropylene, or similar polymer material. However, in this case the inside wall 11 consists of cross-linked polyethylene or another cross-linked polymer. When leaving the extruder and the mold chains forming the outside wall, the pipe has the appearance shown in FIG. 3, but when the polyethylene of the inside wall has been cross-linked, corrugated shape is imparted also to this wall as shown in FIG. 5 by heating the inside wall and exposing it to pressure in order that the inside wall shall bulge into the spaces formed by the outside wall. By the inside wall being cooled after corrugation thereof, this wall will have a remaining corrugation such that the composite pipe will be considerably.more flexible than if the inside wall were smooth. Due to this increased flexibility the composite relining pipe can be drawn into an underground pipeline in the manner illustrated in FIG. 2. Thus, the relining pipe can be delivered from the factory in the condition according to FIG. 5, but after the insertion the inside wall will be heated by drawing a heat source 22 supported by a slide which is centered in the pipe, through the pipe as shown in FIG. 6 in order to increase the temperature of the inside wall 11 to such extent that said wall due to the inherent thermal memory of the cross—linked polyethylene returns to the original " smooth shape according to FIG. 3. Also in the embodiment according to FIGS. 5 and 6, the inside wall preferably has a lower softening range than the outside wall in order that said latter wall will stay unaffected by the heating.

Claims: CLAIMS 1. Pipe for relining underground pipelines, which is of composite type with an annularly rigid corrugated outside wall (10) of polymer material, which is attached to the outside surface of an inside wall (11), c h a r a c t e r i z e d in that the inside wall (11) as such or after heating, maintaining the annular rigidity of the outside wall (10), can be stretched and/or compressed when the composite pipe is being bent. 2. Pipe as claimed in claim 1 wherein the inside wall (11) consists of a thermoplastic elastomer so as to be inherently stretchable and compressible. 3. Pipe as claimed in claim 2 wherein the outside wall (10) consists of polyethylene, polypropylene, or PVC and wherein the inside wall (11) consists of a polymer material which can be worked in an extruder and can be attached by fusing to polyethylene or polypropylene. 4. Pipe as claimed in claim 3 wherein the inside wall (11) consists of a thermoplastic polyolefine. 5. Pipe as claimed in claim 3 wherein the inside wall (11) consists of an ethylene vinyl acetate polymer. 6. Pipe as claimed in claim 3 wherein the inside wall (11) consists of a mixture of styrene, ethylene, and butane. 7. Pipe as claimed in claim 3 wherein the inside wall (11) consists of EPDM mixed with polyethylene. 8. Pipe as claimed in claim 1 wherein the inside wall (11) consists of a thermoplastic polymer having a lower softening range than the outside wall (10) to be softened by heating and thus compressed under deformation of the inside wall, maintaining the annular rigidity of the outside wall. 9. Pipe as claimed in claim 1 wherein the inside wall (11) consists of a cross-linked polymer, e.g. polyethylene, and has been corrugated after cross-linking.

Inventors: JOHANSSON THOMAS, OLSSON BJOERN, JOHANSSON, THOMAS, OLSSON, BJOERN
Applicants: UPONOR NV, UPONOR N.V.
Application year: 1987
Main classification: F16L55
IPC codes: B29C53, B29C61, B29C63, B32B1, F16L1, F16L55