High temperature FBE coating disbondment in Multi-Layer PP insulation coatings

摘要

Multi-layer polypropylene (MLPP) insulation coating has been widely used for thermal insulation of subsea pipelines. Where these MLPP systems have used well proven and correctly applied fusion bonded epoxy (FBE), they have generally functioned as intended. However, in recent years with wellhead temperatures 110°C and above, high temperature (HT) FBEs have been used. The performance of these newly formulated HT-FBEs in terms of maintaining adequate adhesion during long term storage and resistance to FBE disbondment before installation is not well understood. The international codes provide some guidance with regards to qualification testing requirements for the FBE layer and the overall MLPP system but do not provide sufficient detail to assure that the FBE anti-corrosion layer will retain its integrity for a prolonged storage period. This paper describes the author's field and laboratory/ full scale testing experience with the MLPP systems over the last 20 years. It offers some insight into the MLPP insulation system and its design, FBE material selection, FBE and MLPP pre-qualification testing protocol and recommended measures to minimise the potential for FBE disbondment during coated pipe storage.