Improving Mooring Integrity through Standardized Inspection Practices – A DeepStar® 19403 Project

In-service inspection is a critical element in confirming the integrity of permanent floating production unit mooring systems. Over the unit's operating life, which will typically span 20 years or more, these inspections provide the majority of the condition information on the mooring components and overall system. This information enables operators to proactively address mooring issues caused by degradation mechanisms or deviations in mooring line tensions that could reduce the system capacity and potentially result in premature failure. However, detailed guidance on inspection intervals, and in particular inspection scope, is limited for permanent mooring systems. To address this identified industry need, the DeepStar® technology consortium initiated Project 19403, "Improving Mooring Integrity through Standardized Inspection and Fit-For-Service Assessment" to develop best inspection practice guidance for permanent mooring systems [1]. This paper describes the content and benefits of this new mooring inspection guidance document developed as part of the DeepStar® 19403 project [1] with the support of subject matter experts from major operator companies, Class societies and mooring consultancies. The paper will describe how this new guidance compliments and expands current industry Recommended Practice (RP) guidance. Key aspects related to in-service survey intervals, component inspection work scopes and inspection methods will be discussed as well as the execution planning of in-service mooring inspections. To facilitate inspection work, the predominate deterioration mechanisms are introduced which are corrosion, wear and fatigue. Other types of deteriorations are also summarized. Default in-service survey intervals (frequencies) and component inspections are recommended. In-service inspection methods are reviewed, from General Visual Inspection (GVI) and Close Visual Inspection (CVI) to advanced Non-Destructive Testing (NDT). Guidance on assessing the residual capacity of a damaged or flawed mooring component, known as fitness-for-service, is also covered within the new mooring inspection guidance.