British Gas Plc

Leslie Maine

Kenneth Hicks

Trevor G Stafford

Valerie Margaret Linton

Method and apparatus for lining a pipe with a polymer linear

The invention provides a joint 80 for two steel pipes 50, 52 each containing a liner 54, 56 of polyethylene. The invention also provides an electrofusion fitting for joining the liners 54, 56; a method of making the fitting and a method of making the joint 80. The joint 80 consists of an electrofusion fitting having two frusto-conical outer end surfaces which match similar surfaces on the insides of the end portions of the liners 54, 56. Fusion welded joints are formed at the interfaces between the frusto-conical surfaces. A body of insulating material 66 is received in a central recess in the fitting and protects the fitting from the high temperature of the seam 70 between the steel pipes 50, 52. The frusto-conical surfaces make an angle of 10.degree. or less with the longitudinal axis of the fitting. A support body 14 of metal or of synthetic plastics material contained by the electrofusion fitting ensures that the fitting is adequately supported during electrofusion.

Fitting and pipe joint using the fitting

A method of lining a pipeline 24 intended to carry gas, oil, water, sewage or chemicals in which a cross-linked polymeric liner pipe 10, which has been reduced from its original diameter to a lesser diameter or to a shape of reduced maximum dimension, is pulled through the pipeline 24. The lesser diameter is less than the least inner diameter of the pipeline 24. After the liner pipe 10 has been fully pulled through, the pipe liner 10 is heated by means of a source 60 of visible or infrared radiation forming part of a pig assembly 50 to cause it to revert to the pipeline. The pig assembly or assemblies are stationary at zones 70 where service connections are to be made. Subsequently, the remaining liner pipe 10 is reverted by pulling the source 60 through the liner pipe 10.

Method of lining a pipeline

A die for reducing polyethylene pipe temporarily to enable it to be inserted in a pre-existing metal pipe is made of cast iron and has formations by which the die is splittable into two portions. The formations receive cylindrical bars which are squeezed together by a hydraulic squeeze off machine. Each formation is a U-shaped aperture with a saw cut extending from the base of the U into the ligament beneath the formation. The saw cut acts as a stress raiser. In a modification only one formation is provided. The die is made of grey cast iron or some other brittle material.

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Cramlington, United Kingdom

Leslie Maine