The demand to perform structural integrity review and life extension for existing fixed offshore structures is increasing in order to support the changes arising from new technologies for production enhancement, in-service deteriorating conditions and regulatory requirements on ageing structures. An understanding of fitness-for-purpose criteria is required in performing assessments on existing structures. The criteria as described in performance standards will define the status of structures as one of the Safety Critical Elements (SCE) in offshore fixed platforms.

This paper presents an effective and rational approach in assessing the structural integrity and life extension requirements of ageing offshore structures. The pre-defined performance standards are set from the perspective of SIM (Structural Integrity Management) implementation, which are defined in terms of F.A.R.S.I according to UKOOA: Guidelines for the Management of Safety Critical Elements Standard. It stands for Functionality; Availability; Reliability; Survivability; Interactions.

The acceptance criteria is set to meet the SCE goal for operational and accidental or abnormal events. The structure shall be able to support the platform facilities under all identified loading conditions within the allowable stress set for load bearing members. The overall structures shall have a minimum integrity without collapse for the specified minimum survival time related to facility emergency response for design accident events. The structure shall also be able to accommodate the future changes in facility and estimated degradation for life extension requirement.

The SIM as referred to API RP 2SIM is the basis for developing the assessment criteria, which is defined in terms of F.A.R.S.I. It covers the four phases required in SIM, which are Data, Evaluation, Strategy and Program. The quality of SIM implementation by the asset owner on the offshore structures will determine the assessment results and are accordingly verified against the pre-defined acceptance criteria. This process will determine the gaps in SIM implementation and provide recommendations on corrective actions for gap closure.

The requirements of management of change (MOC) in relation to SCEs, role and responsibilities, execution plan, result management and documentation are also covered here. These are normally covered in structural integrity manuals that outline the processes for the conduct of structural integrity programs.

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