Lining a pipe

Details Lining a pipe Lining a pipe

1999-04-16

2000-04-18

Sells, James

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

156287, 156294, 264267, B32B 3126

Patent

active

060510889

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a method of lining an outer pipe with a lining pipe of plastics material.
2. Discussion of the Background
It is known to line cast iron and steel pipes, for example gas distribution mains, with polyethylene lining pipe pulled through the outer pipe. The lining pipe may have a reduced diameter by pulling the lining pipe through a die immediately before it enters the outer pipe. Thereafter the lining pipe resiles back to its original size to closely line the outer pipe. The reduced diameter of the lining pipe may not be much less than the internal diameter of the outer pipe and thus internal obstructions in the outer pipe, for example joints and service pipe sockets, have to be removed to allow the lining pipe to slip through the outer pipe.


SUMMARY OF THE INVENTION

An object of the invention is to provide a method of lining an outer pipe with plastics material which can be a relatively close fit against an inner face of the outer pipe and which method does not necessarily require internal projections or obstructions within the outer pipe to be removed prior to lining, and can allow the outer pipe to be lined at relatively tight bends therein.
According to the invention a method of lining an outer pipe with a lining pipe of plastics material comprises providing a precursor lining pipe, an initial pipe of plastics material having a first external diameter and deforming the initial pipe to reduce its first external diameter to a second external diameter which is smaller than said first external diameter whereby the precursor lining pipe has said second external diameter and the plastics material forming the precursor lining pipe is memory plastics material having a memory of said first external diameter so that if the memory plastics material is subsequently melted by the application of heat thereto and the molten plastics material is suitably supported the precursor lining pipe will expand in accordance with its memory to increase the external diameter of the lining pipe automatically to a value substantially equal to said first external diameter, fuel burner means inside the precursor lining pipe and applying sufficient heat to the plastics material derived from burning the fuel using the burner means to melt the memory plastics material so that the external diameter of the lining pipe expands automatically in accordance with said memory to a value substantially equal to or at least more closely approaching an internal diameter of the outer pipe than the value of said second external diameter and simultaneously supporting the molten plastics material forming the expanding and expanded lining pipe by gas pressure inside the lining pipe, said gas pressure being created at least in part by gaseous products of combustion emitted from the burner means, and on said molten plastics material cooling to a self-supporting state the lining pipe remaining in an expanded state relative to said second external diameter.
The plastics material may be a cross-linked polyethylene.
The first external diameter of the initial pipe may be substantially equal to the internal diameter of the outer pipe. In order that the precursor lining pipe can be easily passed through the outer pipe, and avoid the need for removal of internal projections or obstructions from the outer pipe, and fit round bends, the external diameter of the precursor lining pipe can be appropriately less than the internal diameter of the outer pipe.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example, with reference to the accompanying drawings in which:
FIG. 1 is a diagramatic representation, partly in section, of apparatus used to carry out the invention, shown with a precursor lining pipe in place within an outer pipe and burner means ready to be drawn through the precursor lining pipe;
FIG. 2 shows the apparatus in FIG. 1 during the course of moving the burner means giving off heat to expand the precursor lining pipe to form a li

REFERENCES:
patent: 4738742 (1988-04-01), Shishkin et al.
patent: 5368669 (1994-11-01), Maine et al.

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