Abstract: A method for producing temporarily deformed pipe liners from a continuously extruded thermoplastic round pipe, or thermoplastic round pipe extruded in segments of 20 to 50 feet in length and butt-fused together to obtain a pipe liner segment of a length greater than the conduit to be lined; annealing the pipe liner before deformation in a stress release chamber to relieve stresses induced in the extrusion process; collapsing the pipe liner to a flattened shape by means of internal vacuum and subsequently bending deformable portions of the flattened shape toward a back-up portion thereof, and without elongation, maintaining diameter and wall thickness; applying a sealant material on the outer pipe liner surface to seal the gap between the pipe liner and conduit.

Abstract: Apparatus for inserting a generally U-shaped liner into a pipe and reforming the U-shaped liner into a generally cylindrical cross-section to line the pipe includes winches for pulling the U-shaped liner through the pipe, pigs for cleaning the pipe, manifolds to connection at opposite ends of the pipe and wedge-shaped expansion members for initially mechanically reforming the ends of the liner projecting from the pipe. The wedge-shaped members include bores for communicating fluid at elevated temperature and pressure within the liner for setting the liner in generally cylindrical configuration against the pipe wall. A flaring tool is used to flare the opposite ends of the liner.

Abstract: Method is provided for lining a pipe wherein a thermoplastic liner is initially formed in a cylindrical shape with a diameter slightly larger than the internal diameter of the pipe. The liner is temporarily deformed at an elevated temperature to a different cross-section, preferably U-shaped, to reduce it overall cross-sectional dimension to facilitate insertion into the pipe to be lined. Once inserted, the pipe liner is re-heated and pressurized so that the shape memory characteristics of the thermoplastic material causes the liner to return to its original cylindrical shape. Pressure within the liner is increased in two stages to cause the liner to conform to the interior surface of the pipe. An expansion pig may also be employed to ensure even more exact conformance. After expansion, ends of the liner which extend beyond the pipe are flared into engagement with the pipe flanges.