Refurbishment of steel tubular pipes using composite materials

Abstract This paper describes a glass fibre based composite repair system for steel tubular pipes that can cope with internal and external corrosion, as well as mechanical damage. The original objective, to develop a rehabilitation technique for pressures up to 40 bar, has been achieved and significantly higher pressures seem viable. The most critical parameter for tubes subject to internal corrosion, was identified as the ability of a bonded repair system to resist the formation of pressurised blisters. It is shown that, for bonded repairs, the key parameter determining blistering resistance is the fracture toughness of the metal/composite interface in the presence of pressurised fluid. The effective value of this parameter was found to be lower than might be expected on the basis of published fracture toughness values of laminates. This was attributed to the presence of pressurised water at the metal/composite interface. A fracture mechanics based criterion is proposed to enable the performance of repair systems to be assessed and compared. To address different repair scenarios, especially for higher pressures and when surface preparation may be difficult, a novel version of the rehabilitation system has been developed, which does not depend on achieving a bond at the metal/composite interface.