Lining existing subterranean pipe - by inserting flexible pipe to blow in steam, inserting folded thermoplastic pipe inside and expanding this into circular cross=section

摘要

A pipe is inserted into a long existing length by a method in which a flexible pipe is introduced into the existing pipe so that at least one end of the insertion is accessible at the one end of the existing pipe, and the insertion is inflated to an at least partially rounded shape. A length of a normally rigid thermoplastic pipe is folded and inserted into the flexible insertion so as to extend along the outermost length of pipe; at least one end of the first and second insertions is closed and a heated pressure agent is admitted so as to pass through both, heat them, and make the second insertion flexible; pressure is then applied internally to the thermoplastic pipe so as to expand it to a rounded section.