Thermally insulated pipes with expansion compensation - have outer and inner tubes filled with plastics foam and inner tube distended during setting of foam

摘要

Thermally insulated pipes consisting of an outer pipe and a concentric inner pipe for conveying heated medium is produced by distending the inner pipe before and/or during the foaming of the plastics insulating material of polyurethane between the pipes and holding the inner pipe in the distended state until the foam has set. Pref. the outer pipe is a plastic tube, e.g. polyethylene, or a steel tube coated with a corrosion preventing agent and the inner pipe is a steel tube whose outer periphery may be profiled. Used for conveying heated media over long distances without the use of expansion joints. Pre-stressing inner pipe at site is dispensed with.