Patent ID: 6051088
Filing Date: 2000-04-18
Classification: B29C,B29K,F16L

Abstract:
A method of lining an outer pipe with a lining pipe of plastics material comprising providing a precursor lining pipe,said precursor lining pipe being produced by a procedure comprising forming 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,inserting said precursor lining pipe into said outer pipe, providing fluid 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.