# Determining Factors of Fixed Offshore Platform Inspections in Indonesia
## 2 Conceptual Background
### Fixed Offshore Platform Inspections  
Along the service period of a fixed offshore structure, there exists a possibility of joint failure through fatigue crack propagation despite the presence of various enhancements--such as a thicker can, weld profiling, or other post-weld improvements [26]. In 1991, to assess the severity and recommendations for corrective actions on fixed offshore platforms using the PLAIM (platform lifetime assessment through analysis, inspection, and maintenance), results were obtained regarding the breakdown of structural defects, ranging from severity scores to a series of recommendations for corrective actions using informal and qualitative knowledge as well as expert systems [27]. In addition, research was conducted on developing and applying inspection techniques for fixed and floating platforms and oil rigs. The comparative and sensitivity studies that have been performed show several important trends in their results that can provide valuable information for decision making related to testing planning. This procedure can also explore and compare different testing planning strategies, such as testing methods and acceptance criteria [28]. Optimizing inspection and maintenance intervals can minimize inspection, repair, and downtime costs. Cost optimization applies to fixed offshore platforms. Estimating the optimal time intervals for the inspection and maintenance of structures should consider changes in structure capacity, needs over time, and the damage situation of fixed offshore platforms [10]. The mechanization of inspection plans is essential for creating a consistent quality inspection program. Today's inspection operations face the challenge of maintaining consistent quality from one inspection program to another due to the variability in planning processes between different inspection planning engineers. The proposed inspection planning mechanism based on fuzzy logic helps to minimize variability and improve the quality of inspection programs [29]. Risk-based inspection (RBI) is based on quantifying the risks associated with the failure of an element or system, considering the likelihood and consequences of failure from both a maintenance and safety perspective. The impact of structural impairment can be quantified using mathematical concepts, such as the value of information (VoI) and expert judgment [30]. This method is also used in other studies [22; 23; 24; 25]. The risk-based underwater inspection (RBUI) method is known in Indonesia, but this method cannot be used for platforms distributed over different distances or areas because the failure parameters of these platforms are not comparable [7]. In addition, the RBUI method does not consider environmental characteristics in its risk assessment. There is a new method, namely risk-reliability-based underwater inspection (RReBUI), which quantitatively assesses platform reliability based on structural and environmental characteristics. The concept of reliability has been proposed in many studies as an approach to maintenance planning, and maintenance should be considered when a structure reaches defined limit conditions [30]. However, the application of RReBUI for fixed offshore platforms has never been developed in Indonesia [8]. Semiquantitative or quantitative approaches are also used in risk assessment. Semiquantitative methods are used to provide a local risk assessment of the structural components of platforms whenever possible and required. Quantitative methods incorporate probabilistic fatigue methods to establish inspection plans for selected pipe joints undergoing fatigue and failure that significantly impact entire platform structures [16]. [PERSON] in 2021 [31], stated that a value of information (VoI)-based approach and Bayesian decision optimization can quantify the added value of future inspections and provide optimal or strategic decisions by directing alternative modeling decisions and evaluating expected results, rather than by using strategies that are predetermined.