Risk reliability-based underwater inspection method for jacket platforms in Indonesia

The purpose of this paper is to carry out the application of risk reliability-based underwater inspection (RReBUI).

The consequence of failure factor is calculated qualitatively in accordance with the risk-based underwater inspection (RBUI) method but the criteria are modified as an adjustment to the addition and combination of production and reliability information of the analyzed platforms. The probability of failure (PoF) is determined quantitatively by calculating the structure reliability index based on collapse failure mechanism in which the uncertainty of wave load is considered. The PoF criteria from the RBUI are re-modified to adjust the criterion with the highest and lowest reliability indexes obtained in RReBUI study. Selection of exposure category of the platform is still the same as the RBUI method.

The models of three offshore jacket platforms located in each of Java Sea and Natuna Sea were used for the RReBUI application. These six models were previously used in the traditional RBUI application. The results of RReBUI analysis indicated that including the environmental characteristics in the risk assessment resulted in more reliable inspection interval plans.

The drawback of RBUI is that it cannot be used for platforms spread over a distance or different areas, as the failure parameters of these platforms cannot be compared. Furthermore, the RBUI method does not consider the environmental characteristics in its risk assessment. Unlike RBUI, the purpose of RReBUI method is to assess the reliability of a platform based on both structural and environment characteristics. Therefore, the RReBUI method determines the risk of every platform quantitatively without having to compare the failure parameters based on expert justification. The application of RReBUI for jacket platforms has never been developed in Indonesia.