With the challenges faced by operations in a continuing low oil price environment and the continuing high failure rate of offshore moorings, the value derived from traditional mooring inspection strategies needs to be reassessed. This paper outlines a significantly improved approach to mooring and riser system inspection based on the acquisition of quantitative condition data using low cost/low risk inspection techniques. Specifically, this paper addresses the ability to perform specific, detailed, quantitative inspections using standard inspection tools mobilized to and launched from an offshore facility. By modifying inspection strategies to target specific areas of high risk and known degradation mechanisms, a much-improved understanding of the current condition of the system is gained and appropriate integrity management strategies developed based on the observed and measured rate of component degradation. In addition, the ability to respond rapidly to event-based forms of degradation is significantly improved. This approach will be demonstrated by a case study of the inspection of a known area of risk that is traditionally difficult to inspect and interpret - mooring chain links within a hawse pipe.
High definition imagery of elements within the hawse pipe of an FPSO turret mooring system were acquired and then post processed into highly accurate (±1 mm) 3D chain link data, following which detailed numerical analysis of the remaining link capacity for worn links was performed. Previously acquired diver measured data is compared against 3D scan data and the improvements in the accuracy of the estimate of the remaining strength on the worn links is demonstrated. Based on the understanding of the remaining capacity and rate of degradation, future inspection intervals can be set on an informed basis, such that the rate of volumetric loss can be verified by measurement, thereby confirming the rate of degradation in link capacity. A cost-benefit analysis highlights the improvements in overall lifecycle costs that these quantitative, facility-based, inspection techniques can provide. This paper provides a demonstration of the ability to perform detailed quantitative surveys and utilize the acquired information to assess both current and future condition of safety critical elements. The paper demonstrates improvements in inspection strategy that are consistent with the new approaches to mooring system integrity management that are currently being finalized (e.g. the new API-RP-2MIM).