Improving the bending behaviour of mechanically-lined rigid pipe

A method of making mechanically-lined rigid pipe, comprising:

• inserting an end plug into an end portion of an outer pipe to seal an open end of the outer pipe, the outer pipe surrounding a liner sleeve;
• in a primary radial expansion, expanding the outer pipe by plastically expanding the liner sleeve against an inner surface of the outer pipe, under a lining pressure applied internally to the liner sleeve while the end plug shields the liner sleeve within the end portion of the outer pipe from plastic expansion under the lining pressure;
• relieving the lining pressure to permit elastic radial contraction of the outer pipe around the plastically-expanded liner sleeve, that contraction making a mechanical bond between the outer pipe and the liner sleeve at a body portion of the outer pipe inboard of the end portion that contains the end plug;
• removing the end plug from the end portion of the outer pipe;
• placing an external annular backing ring around the end portion of the outer pipe;
• and
• subsequently, performing a secondary radial expansion of the end portion of the outer pipe by local plastic expansion of the liner sleeve within the end portion of the outer pipe against the inner surface of the end portion of the outer pipe, under a fixing pressure applied internally to the liner sleeve within the end portion of the outer pipe, wherein the fixing pressure is greater than the lining pressure.