Fuzzy Fault Tree Analysis Method Research Articles

Reliability Analysis of Subsea Riser System Based on Fuzzy Fault Tree Analysis Method

Abstract To deal with the complex structure of subsea riser system and the lack of failure statistics and insufficient information during operation, a fuzzy fault tree analysis (FFTA) method is applied to analyse the reliability of the subsea riser system, and a qualitative and quantitative analysis is carried out by establishing a fault tree model of the riser system to obtain the minimum set of cuts and the basic events. The fuzzy importance degree of each fundamental event is determined as well as the failure probability of the headline event of the fuzzy fault tree, “failure of subsea riser system,” using the triangular fuzzy number computation method. Finally, the “average value” method of comprehensive analysis of the fault tree model, the analysis results show that the bottom event riser check valve, riser buoyancy device, riser working medium isolation valve, riser line, riser gas lift device and other components of the failure of the subsea riser system is relatively the weak links, compared with the actual situation, the analysis results in line with the actual engineering situation, these five aspects should be regularly detected and focused on prevention. In conclusion, this research helps to comprehensively analyse the reliability of the riser system and take into account the uncertainty factors, and provides more accurate guidance on the reliability constraints for the localized design and production of subsea riser system.

Failure probability estimation of natural gas pipelines due to hydrogen embrittlement using an improved fuzzy fault tree approach

The estimation of failure probability is challenging in hydrogen embrittlement in steel pipelines due to the complexity of the synergistic effect of multiple factors. The present study proposed a hybrid methodology to estimate the failure probability of steel pipelines due to hydrogen embrittlement. The methodology integrates the fault tree analysis with a fuzzy comprehensive evaluation. Fault tree analysis captures the logical relationships between influencing indicators to develop a new assessment model of hydrogen embrittlement in steel pipelines. An improved fuzzy fault tree analysis method was proposed to process aleatoric and epistemic uncertainties to estimate the probability of each basic event due to the difficulty in obtaining the actual probabilities. The failure probability of blended hydrogen natural gas pipelines was estimated by considering the correlation of events. A case study demonstrated the applicability of the proposed method. Maintenance measures can be implemented according to the evaluation results to ensure pipeline safety.

Fuzzy fault tree analysis method of denitration system in thermal power plant

Fuzzy fault tree analysis method of denitration system in thermal power plant

Fuzzy fault tree analysis method of denitration system in thermal power plants

Fuzzy fault tree analysis method of denitration system in thermal power plants

Risk Analysis of Autonomous Underwater Vehicle Operation in a Polar Environment Based on Fuzzy Fault Tree Analysis

Autonomous underwater vehicles have long been used in marine explorations, and their application in recent polar expeditions is particularly noteworthy. However, the complexity and extreme conditions of the polar environment pose risks to the stable operation of autonomous underwater vehicles. This study adopted the methodology of fuzzy fault tree analysis to deeply analyze the operational risks of autonomous underwater vehicles in polar environments. While traditional fault tree analysis maps the causal relationships and probabilities between basic and intermediate events, fuzzy fault tree analysis models the uncertainty of data and determines the failure probability by integrating expert opinions. This study revealed that polar environment-induced failures play a more substantial role in autonomous underwater vehicle loss in polar regions than inherent system failures. The study identified ‘recovery failure’ and ‘poor communication’ as the major risk factors facing autonomous underwater vehicles in polar environments, exhibiting the highest failure probabilities. Specifically, among various polar environmental factors, ‘large ice concentration’, ‘ice thickness’, and ‘roughness of ice underside’ under ‘bad’ conditions were found to have a significant impact on the autonomous underwater vehicle’s failure probability. The fuzzy fault tree analysis method in this study successfully filled the gap created by the absence of historical data by effectively incorporating expert opinions, enabling a quantitative presentation of the impact of polar environments, which has been previously difficult to convey in qualitative terms.

Quantitative Assessment of Risks Caused by Blowout in Yaran with Fuzzy Fault Tree Analysis

Background: Blowout is one of the most significant accidents in the drilling industry. Because of a shared field with a neighboring country and is located on Hur al-Azim wetland, Yaran Oil Field in the west of Ahwaz city needs special attention in terms of blowout control. 
 Methods: Four main events including kick prevention, kick detection, failure in the blowout preventer, and blowout occurrence have been identified by expert interviews and field studies as top events. Each top event by fault tree method was analyzed and its intermediate and basic causes were identified. The oil field includes 20 wells and one well was selected for the study. In this study, the fuzzy fault tree analysis method was used to assess the failure rate of events leading to a blowout.
 Results: Based on the obtained results, the failure rate in kick prevention has been estimated to be 0.2863, the failure rate in kick detection 0.3878, the failure rate of blowout preventer 0.08443, the failure rate of a blowout from the first path 0.011, and the failure rate of a blowout from the second paths has been estimated to be 0.0286. In the event of kick prevention, hydrostatic pressure reduction with a failure rate of 0.227, in the event of kick detection, the failure rate of change in mud volume and change in current volume were 0.1462 and 0.133 respectively. 
 Conclusion: The results have been used to better understand the blowout and prevention actions and prevent losses due to the blowout.

Risk assessment of mobile crane overturning in Asymmetric Tandem Lifting (ATL) operation based on fuzzy fault tree analysis (FFTA)

Lifting operation, especially Asymmetric Tandem Lift, is one of the essential activities in the construction industry, posing a substantial threat to sustainable management. This study aims to assess the risk of crane overturning in ATL using the fuzzy fault tree analysis method. The risk factors affecting crane overturning were identified and quantified. the required information was collected through literature review, previous incidents data and expert opinions. The weight of experts was determined based on a combination of two methods, including conventional scoring methods and the best-worst fuzzy method. A total of 53 events in four categories of loading technique, weather conditions, ground failure, and organizational factors were determined as the main factors of crane overturning. The probability of the crane overturning was 10.68%. The highest probability of occurrence among 34 minimum cut sets was related to the risks due to failure in the supply of modern equipment and technologies (0.132), failure in load/equipment information provided by the manufacturer (0.125) and failure in instructions and administration (0.110). The proposed method in this study could reduce the ambiguities and uncertainties in identifying and evaluating risk factors. Moreover, presented prevention strategies could enhance the reliability and sustainability of cranes in asymmetric tandem lift operations.

Assessing the life cycle risks of offshore wind turbines with suction bucket foundations

The risk assessment of offshore wind turbines is increasingly significant due to the increase in accidents. However, the life cycle risk assessment of suction bucket foundations is challenging owing to the limited number of installations and lack of relevant data. In this study, an improved fuzzy fault tree analysis method (IFFTA) based on the analytic hierarchy process (AHP) is proposed to evaluate the life cycle risks of offshore wind turbines (OWTs) with suction bucket foundations. First, a fault tree analysis (FTA) model was employed to establish a risk index system for the suction bucket foundation. Then, the fuzzy set theory was performed to obtain the crisp probabilities of basic events, and AHP was adopted to determine the importance weights of basic events. Finally, the risk occurrence probability and risk level of OWTs with suction bucket foundations were determined, and the critical risk factors were identified. A case study demonstrated the applicability of the proposed method. The results show that the risk occurrence probabilities of OWTs with suction bucket foundations in the construction, service, survey and design periods are 3.25e-03, 4.47e-03, and 5.48e-04, respectively, and the corresponding risk levels according to DNV-RP-F107, one of the most authoritative recommended practices in the field of ocean engineering, are high, high, and medium respectively. The proposed method overcomes the limitations of traditional methods and provides some risk reduction measures for engineering references. • Improved fuzzy fault tree analysis is developed for the life cycle risk assessment of offshore wind turbines. • The risk factors of offshore wind turbines with suction bucket foundations are identified. • The critical risk factors are identified, and several risk reduction measures are recommended. • The economic advantages of offshore wind turbines with suction bucket foundations are studied.

Hardware Reliability Analysis of a Coal Mine Gas Monitoring System Based on Fuzzy-FTA

The hardware reliability of a gas monitoring system was investigated using the fuzzy fault tree analysis method. A fault tree was developed considering the hardware failure of the gas monitoring system as a top event. Two minimum path sets were achieved through qualitative analysis using the ascending method. The concept of fuzzy number of the fuzzy set theory was applied to describe the probability of basic event occurrence in the fault tree, and the fuzzy failure probabilities of the middle and top events were calculated using fuzzy AND and OR operators. The results show that the proposed fuzzy fault tree is an effective method of reliability analysis for gas monitoring systems. Results of calculations using this method are more reasonable than those obtained with the conventional fault tree method.

Safety risk assessment in shopping center construction projects using Fuzzy Fault Tree Analysis method

Safety risk management is one of the important techniques to be performed in large construction projects. The purpose of risk management is to identify the origin of the risks, uncertainties, and effects then offer suitable management responses to these risks. In this research, first, the possible accident in construction projects was identified by studying various sources and statistics in Iran. Brainstorm was used to specify the determinant factors in these accidents. Fault tree analysis and fuzzy logic were employed to evaluate these accidents and calculate their probability of occurrence. Next, the significance of each determinant factor in the accident was identified using the improvement index in fault tree analysis. Finally, the determinant factors in the accident were prioritized in terms of significance to provide a proper solution. The mentioned steps were carried out in two commercial building projects located south of Tehran, Iran. The most important safety risks were determined to be the fall of materials from the height with a probability of 92% in project A, and the fall of workers from the height with a probability of 52% in construction project B. Also, the second important risk in both projects was the fall of objects with a probability of 91% of construction project A and 51% for project B. The most important determinant factors were the insufficient skill of the workers in project A (with an improving safety index of 14.4%) and insufficient light and visibility in project B (with an improving safety index of 9%). The use of the Likert scale in the questionnaire instead of the Thurston scale and applying improvement index of fault tree in prioritization may be new compared to other studies.

Risk assessment of ice dams for water diversion projects based on fuzzy fault trees

Ice dams are among the important risks affecting the operational safety and water conveyance efficiency of water diversion projects in northern China. However, no evaluation indicator system for ice dam risk assessment of water diversion projects has been proposed. Therefore, in this paper, based on the formation mechanism of ice dams, the risk assessment indicator system and the possibility calculation model of ice dams were both proposed for water diversion projects based on the fuzzy fault tree analysis method. The ice dam risk fault tree constructed in this study mainly includes three aspects: ice production, ice transport, and ice submergence conditions. Eighteen basic risk indicators were identified, and 72 minimum cut sets were obtained by using the mountain climb method. Eight risk indicators were determined as the key risk indicators for ice dams, including meteorological conditions, narrowed cross section, sluice incident, erroneous scheduling judgment, ice cover influence, flat bed slope, control structures, and ice flow resistance of piers. Then, the canal from the Fenzhuanghe sluice to the Beijumahe sluice of the Middle Route of the South-to-North Water Diversion Project was taken as the research object. Combined with the expert scoring method, the ice dam risk probability of the canal was determined to be 0.2029 × 10−2, which was defined as a level III risk, which is an occasionally occurring risk. The study results can support ice dam risk prevention and canal system operation in winter for water diversion projects.

A hybrid model for human-factor analysis of engine-room fires on ships: HFACS-PV&FFTA

In this study, an analysis of fire-explosion accidents in ship engine rooms was conducted. For analysis, a hybrid method including the Human Factors Analysis and Classification System (HFACS) and fuzzy fault tree analysis (FFTA) was used. Using the HFACS method, the factors in the formation of engine-room fires were classified according to a hierarchical structure. The possible accident scenarios and probabilities were calculated using the FFTA method. In this study, it was observed that fire-explosion accidents were concentrated in ships over 20 years old and that mechanical fatigue affected accident formation. In particular, when the increased hot surfaces due to the operation of a ship's engines while it is in motion are combined with oil/fuel leakage, fire-related accidents become inevitable. Failure to provide proper insulation also triggers the occurrence of accidents. It has been observed that some of such accidents occur because the materials used in maintenance and repair work are not original to the ship. During this study, the causes of accidents were examined to prevent fire-related accidents from occurring in engine rooms, and suggestions were made to prevent similar accidents from happening in the future.

Fuzzy risk prediction of roof fall and rib spalling: based on FFTA-DFCE and risk matrix methods.

The working conditions of underground mining are complex and variable, and roof fall and rib spalling are one of the main types of accidents that can occur. Building an integrated model to evaluate the risk of roof fall and rib spalling is the foundation of mine safety. On the basis of the inherent attributes of event risk, the fuzzy evaluation set and probability of basic events are obtained by using the fuzzy fault tree analysis method based on the sample's fuzzy information. Subsequently, the likelihood of roof fall and rib spalling is determined. Consequence severity data are obtained by using the dynamic fuzzy logic method, and the consequence severity grade of roof fall and rib spalling is evaluated via the dynamic fuzzy comprehensive evaluation method. The event risk level is determined by the risk matrix method. Roof fall and rib spalling in a non-coal mine is analyzed and evaluated by using fuzzy fault tree analysis and dynamic fuzzy comprehensive evaluation. The weak links in the operation of an underground mine are identified by fuzzy fault tree analysis as "mining process, roof management, support and reinforcement." Then, the risk development trend is determined by the dynamic fuzzy comprehensive evaluation method. The risk matrix method is integrated to determine whether the risk level of the mine is "high risk, unacceptable" and expected to deteriorate in the future. The results show the validity and feasibility of the risk analysis and prediction model for roof fall and rib spalling.

A novel ranking function-based triangular intuitionistic fuzzy fault tree analysis method

In reliability field, the probabilities of basic events are often treated as exact values in conventional fault tree analysis. However, for many practical systems, because the concept of events may be ambiguous, the factors affecting the occurrence of events are complex and changeable, so it is difficult to obtain accurate values of the occurrence probability of events. Fuzzy sets can well deal with these situations. Thus this paper will develop a novel fault tree analysis method in the assumption of the values of probability of basic events expressed with triangular intuitionistic fuzzy numbers. First, a new ranking function of triangular intuitionistic numbers is established, which can reflect the behavior factors of the decision maker. Then a novel fault tree analysis method is put forward on the basis of operational laws and the proposed ranking function of triangular intuitionistic numbers. Finally, an example of weapon system “automatic gun” is employed to show that the proposed fault tree analysis method is feasible and effective.

RELIABILITY MODEL AND CRITICAL FACTORS IDENTIFICATION OF CONSTRUCTION SAFETY MANAGEMENT BASED ON SYSTEM THINKING

Safety is a key objective of construction management, but construction safety management is complex due to various types of technical and management factors. If critical factors can be identified and corresponding measurements can be adopted, it will be more direct and effective to improve safety performance. In this paper, by using the system thinking method, construction safety management is considered as a system and decomposed into six subsystems and related management factors. The fuzzy fault tree analysis method was used to build a reliability analysis model and reveal the failure probabilities of factors in the safety organization management subsystem. Through a questionnaire survey conducted in Wuhan, China, the pivotal importance degrees and average occurrence probabilities of basic factors are figured out. On the basis of that, nine critical factors of the safety organization management subsystem are identified and corresponding improvement measurements are proposed. More, a case study of Hangzhou underground railway tunnel collapse accident in 2008 is conducted, which verifies that the framework of construction safety management based on system thinking can be a useful tool for identifying faults or failure reasons of construction safety management.

Assessment of gas and dust explosion in coal mines by means of fuzzy fault tree analysis

During the past decade, coal dust and gas explosions have been the most two serious types of disasters in China, threatening the lives of miners and causing significant losses in terms of national property. In this paper, an evaluation model of coal dust and gas explosions was constructed based on a fuzzy fault tree by taking the Xingli Coal Mine as a research site to identify the risk factors of coal dust and gas explosions. Furthermore, the hazards associated with such explosions were evaluated for this particular coal mine. After completing an on-site investigation, the fuzzy probabilities of basic events were obtained through expert scoring, and these expert opinions were then aggregated as trapezoidal fuzzy numbers to calculate the degrees of importance of all basic events. Finally, these degrees of importance were sorted. According to the resulting order, the basic events with higher probabilities were determined to identify key hazards in the daily safety management of this particular coal mine. Moreover, effective measures for preventing gas and coal dust explosions were derived. The fuzzy fault tree analysis method is of high significance in the analysis of accidental coal mine explosions and provides theoretical guidance for improving the efficiency of coal mine safety management in a scientific and feasible manner.

Risk Assessment of Agricultural Water Conveyance and Delivery Systems by Fuzzy Fault Tree Analysis Method

Improving the efficiency of main Agricultural Water Conveyance and Delivery Systems (AWCDS) has a significant impact on improving water productivity in agriculture. Therefore, risk assessment of mentioned systems is necessary to increase reliability of operational performance. Accordingly, this study for the first time presents a unique framework to assess the adequacy, equity, and efficiency of agricultural water distribution and delivery risk assessment within AWCDS. In this way, the Fault Tree Analysis (FTA) technique is employed for risk assessment of “undesirability of supply and delivery”. The west Dez main irrigation canal in Khuzestan province of Iran was determined as the case study of the research. A set of questionnaires filled up by managers and experts of this irrigation district, the failure probabilities of the basic events are gathered in the form of linguistic terms. Due to the uncertainty in these terms, the system’s risk assessment to determine the failure probability of the top event was performed based on Fuzzy Fault Tree Analysis method (FFTA). The results of the study showed that the failure probability in the fuzzy approach is 0.55 which is roughly 0.15 more than crisp approach. Also, the rating of the basic events based on their contribution to the occurrence of the top event was carried out using importance measures. Five major events were identified with an emphasis on operational and socio-economic issues related to distribution and delivery of water. Comparing the results of risk assessment with the mathematical model reveals that the latter’s failure probability will be less than the system’s FTA due to non-consideration of some important factors.

A collaborative modelling of ship and port interface operations under uncertainty

Fault tree analysis is a known methodology used for analysing engineering systems. The approach is usually conducted using known failure data. Given that most maritime operations are conducted in a challenging and uncertain environment, their failure data are usually unavailable requiring a flexible and yet robust algorithm for the analysis of the systems. This research therefore seeks to analyse hazards of ships during ship and port interface operations as a result of manoeuvring by incorporating fuzzy fault tree analysis method to optimise the performance effectiveness of the system. Fuzzy set theory provides the needed flexibility to represent vague information from the analysis process. The methodology is structured in such a manner that diverse sets of data can be integrated and synthesised for analysing the system. It is envisaged that the proposed method could avail safety specialist with a simple and a step-by-step framework for evaluating maritime hazards in seaport operations in a concise way.

Analysis of Mine Hoist System Monitoring and Fault Diagnosis

This paper is Zhengli Coal JKMD3.5 × 4 (III) E-type floor-type multi-rope friction hoist for the study, in order to enhance the system to improve monitoring and fault diagnosis for the purpose of fuzzy fault tree analysis method as the lift system the method of fault diagnosis on hoist brake system fault tree analysis, the results of the analysis can play a guiding role in the daily repair and maintenance, thereby enhancing the safety and reliability of the hoist.

Risk Identification of Sudden Water Pollution on Fuzzy Fault Tree in Beibu-Gulf Economic Zone

Sudden water pollution incident has the characteristics of instantaneity and uncertainty. Based on the characteristics, fuzzy fault tree analysis method was used to identify the potential risks of water pollution in Beibu-Gulf economic zone, and it also combined with the collected data and analysis results. The research results showed that the abnormal discharge of sewage was the main risk factor of the economic zone; the probability value of water pollution potential risk in this study area ranged from 4.6 percent to17.7 percent,which considered the random uncertainty and fuzzy uncertainty of the causes. This research could be considered as an instruction for future risk management, and it will play a great role in the healthy development of ecological environment.