Towards a Robust Offshore Bonded Repair Strength Evaluation

Since the early 2000s, the number of Floating Production, Storage and Offloading (FPSO) units is increasing significantly. And so now, half of the fleet is over than 10 years old. As FPSO are mainly installed in tropical areas, with marine environment, high temperature and high humidity, corrosion is a permanent threat. Maintenance of steel structures become a challenge for oil major companies in offshore operation. Indeed, when allowable corrosion limit are reached, plates are to be repaired. However the current “crop and renew” technique implies a number of major issues for owners such as: “hot work”, i.e., welding; temporary structure weakening; necessity to empty, clean and vent oil tanks, leading to a long down time and an expensive solution. “Cold repair”, such as bonded repair, is an obvious solution, due to a short down-time and non-intrusively process. However, currently no standards or rules exist for this kind of repair and engineering faces problems as basic as strength qualification. To address the lack of knowledge on the strength assessment of bonded repair for primary structure, Bureau Veritas Marine & Offshore launched a Joint Industrial Project (JIP) named StrenghBond Offshore with oil companies, shipyards and suppliers. The main objectives of the JIP are to: Assess short term and fatigue strength of typical bonded repairs, Enrich knowledge of adhesive joints strength on typical offshore repairs cases, Enable a better evaluation of the margin between the actual strength of a repair and the design load, Validate the characterisation procedure for strength prediction of bonded assembly, Define a robust strength prediction method, Gather the collected experience in a industrially applicable guideline, Standardise qualification process for offshore composite bonded repairs. The project intends to provide a design approach for bonded reinforcement that is design orientated, accurate and recognized by the offshore industry.