FLOWLINE INSULATION SYSTEM

摘要

There is disclosed a method of controlling the heat transfer properties of a sub-sea conduit having inner and outer walls (800, 802) and a gas-permeable space (804) between the walls providing thermal insulation. The method comprises varying the pressure of a gas within the space between values above and below a critical pressure range at which thermal conductivity of the gas exhibits a high rate of change. Gas connections (808, 810) and control valves (812, 814/816) can be designed to permit a range of opening sequences, for example under control of a remotely operated vehicle (ROV).