INSULATED PIPELINES AND METHODS OF CONSTRUCTION AND INSTALLATION THEREOF

摘要

Disclosed is a double walled pipeline assembly, an associated set of parts and a pipeline installation and a method for forming and installing the same. The double walled pipeline assembly consists of an inner pipe section (304) and an outer pipe section (306) having an internal diameter larger than the external diameter of the inner pipe, enabling the inner pipe to be located coaxially within the outer pipe to leave an insulating gap (314) between them. The gap is sealed at both ends by welding to first and second joining pieces (308, 610) which are formed by machining from a thicker section of pipe or cast material. The first joining piece (308) is formed integrally with shoulders (310, 312) for supporting the pipe sections and welded pipeline during laying, so that the machined pieces add little to the cost, while allowing more conventional welds to be used. Alternatively the second end may be sealed by a circumferential lap weld (1318) formed on a thickened portion (1322) of one of the pipes.