It is increasingly necessary to perform risk analysis in marine structures, to ensure system safety, as they are large and complex. In view of the shortcomings of failure mode and effect analysis (FMEA), a modified fuzzy TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) approach is proposed that is based on fuzzy evidence reasoning (FER), and considers the risk factor rating and relative weight. The presented method is used to prioritize the risk of equipment failure modes for the floating production storage and offloading system (FPSO) oil and gas processing system. The subjective weights and objective weights of occurrence (O), severity (S), and detectability (D) have been considered comprehensively. The subjective experience of the experts and the objective information reflected by the O, S, and D ratings are all included in the weights, making the ranking results closer to reality. The results can be scientific references for decision-makers in risk identification.

An innovative methodology is proposed to identify potential risk factors and possible accident escalation consequences, and to determine the evolution of an accident from cause to consequence, thereby to identify the most probable path and discover key risk factors along the path rapidly. Based on the principle of a directed weighted complex network (DWCN), the bow-tie (BT) model, risk entropy and the improved ant colony optimization (IACO) algorithm are integrated into this methodology. First, the qualitative analysis of risk evolution based on the BT model is carried out. The evolution development based on accident suppression can be divided into two stages: accident precursor stage and accident evolution stage. Then, a new method for mapping BT into DWCN is proposed. Lastly, the shortest path analysis of risk evolution based on the IACO algorithm is carried out, fuzzy set theory (FST) is introduced to calculate the failure probability of risk factors, and risk entropy is used to represent the uncertainty of risk propagation. Thus, the IACO algorithm can be used to calculate the shortest path of risk evolution. The proposed method is applied to oil and gas leakages in the FPSO oil and gas processing system. The results show that it is an effective method to identify the shortest evolution path and the most vulnerable risk factors.

To address the challenges in traditional Failure Mode and Effects Analysis (FMEA) related to determining factor weights, identifying risk priority of failure modes, and managing uncertainties in the risk assessment process, this paper proposes an enhanced FMEA risk factor evaluation method. This method integrates incomplete and imprecise expert assessments using a fuzzy multi-criteria compromise ranking technique called the “V1seKriterijumska Optimizacija I Kompromisno Resenje” (VIKOR). By employing Fuzzy Evidence Reasoning (FER), the risk factor ratings are represented using fuzzy belief structures to capture their diversity and uncertainty. Objective weights are adjusted using Shannon entropy to correct subjective weights, and the VIKOR technique is applied to prioritize failure modes based on the principles of minimizing individual regret and maximizing group utility. The improved model is applied to identify key equipment associated with oil and gas leakage risk in the Floating Production Storage and Offloading (FPSO) system. Validity and sensitivity analysis confirm the robustness and reliability of the method, enhancing the accuracy and credibility of the evaluation results.

The problems of the mat supported jack-up platform caused by the storage mat have not been solved perfectly in some aspects such as oil storage and transmission process monitoring. In this paper, the monitoring system of the mat supported jack-up platform is designed and control principles are proposed. The methods to monitor and control some parameters and processes, such as the oil injection and discharge processes, oil liquid level, oil volume and temperature, are presented. Also, locations of temperature sensors in underwater oil tanks are studied. With this knowledge, the system is developed to monitor the working process of the platform in real-time.

To investigate the variation in the diffusion patterns of natural gas leaks in the Floating Production Storage and Offloading (FPSO) system, with the aim of formulating appropriate emergency response strategies and minimizing accident losses, a study was conducted on the gas leak issues of oil and gas processing equipment in the FPSO upper module. A consequence prediction and assessment model was established based on Computational Fluid Dynamics (CFD) methods. Sixteen working conditions and one control working condition were developed to simulate the diffusion characteristics of combustible gas leaks. The simulations provided insights into the gas leakage patterns under different conditions and identified the most hazardous scenario for gas leaks in the FPSO upper module. The results indicate that the density and shape of the equipment within the upper module significantly influence the diffusion outcome. After a leak, high concentrations of combustible gas were observed near the crude oil heat exchanger skid in Industrial Zone II. The effects of individual factors on gas diffusion were significant, and the interactions among multiple factors were complex. Wind speed had a more pronounced effect on longitudinal gas diffusion compared to wind direction and leak aperture, while wind direction significantly influenced lateral gas diffusion. The leak aperture, on the other hand, had a more substantial impact on vertical gas diffusion.

Leakage through the confined annular clearance around a plunger is influenced by groove-induced flow restructuring and liquid-film evolution rather than by clearance size alone. Transient volume of fluid simulations under a constant-density–air approximation, together with visualization experiments, were used to examine the effects of periodic grooves on flow separation, local recirculation, reattachment, liquid-phase redistribution, and axial leakage. Within the adopted numerical framework, the grooves divided the continuous high-speed leakage core into repeated separation–recirculation–reattachment regions, generating local low-velocity zones and promoting liquid accumulation within and between the grooves. Groove profile primarily affected the separated-flow path and spatial organization of recirculation, whereas groove width and depth mainly modified their spatial extent. Among the tested configurations, the inverted right-trapezoidal groove produced the best numerical sealing response, reducing liquid leakage by 23.83% and yielding an axial pressure attenuation of 44.77%. High-speed imaging independently showed earlier liquid-film formation, prolonged visible-film persistence, and delayed development of a through-going leakage path. These results associate leakage suppression with local velocity and phase redistribution, liquid retention, and axial-pressure-gradient redistribution rather than geometric blockage alone. The local numerical fields and inclination-angle ranking are conditional on the constant-density formulation, and their robustness under compressible-gas modeling remains to be established.