Fault Tree Research Articles

Analisis Faktor Penyebab Keterlambatan Pelaksanaan Proyek Konstruksi pada CV. X Menggunakan Metode FTA

Delays that are not handled immediately can affect the quality of a company's performance. This research was conducted on a construction project undertaken by CV. X. Where 4 construction projects undertaken by CV. X as of January 2024 experienced delays in completion. For this reason, it is necessary to analyze the factors that cause delays in the project by using the FTA (Fault Tree Analysis) method which aims to find fault trees from various errors that will result in the occurrence of unwanted events. Data collection is done by survey using a questionnaire. The results of the questionnaire were then analyzed using the FTA Method and then determining the combination of these factors with a minimum cut set. Based on the results of the analysis using the FTA Method, there are 6 aspects that are factors causing delays, namely aspects of labor; material / equipment aspects; project implementation management aspects; contract aspects; aspects of work documents; aspects of natural conditions and force majors. With the largest probability value, namely the contract aspect of 0.21; project implementation management aspect of 0.18; material / equipment aspect of 0.15; aspects of natural conditions and force majors of 0.12; aspects of work documents of 0.09; aspects of labor of 0.08.

A method for safety analysis of human-machine systems based on dynamic Bayesian simulation

Accidents in human-machine systems often lead to serious consequences, so safety analysis is very important for such systems. However, the existing approach to safety analysis of human-machine systems lacks clear delineation of the coupling relationships between human and machine, or provide quantitative analysis. To address these issues, this paper proposes a method for safety analysis of human-machine systems, utilizing dynamic Bayesian network (DBN) and dynamic fault tree (DFT). The core of this method is the identification of human-machine coupling relationships, proposing 10 types of logical relationships and presenting corresponding DFT logic. Then, a conversion method from DFT to DBN is designed to avoid combinatorial explosion in complex FTA calculations. Based on the DBN model, simulation is conducted using Gibbs sampling, which offers higher computational efficiency. Additionally, a method for importance analysis is devised to identify critical nodes that impact the system risk. At last, a case study of refueling mission at space launch site is given to illustrate how to apply the method. Through simulation analysis, the safety risks during the refueling mission are quantitatively assessed, while critical nodes are identified. The results indicate that the dynamic Bayesian simulation method is good in information utilization, dynamic representation, and time performance.

ANALISIS PENYEBAB KETIDAKSESUAIAN PADA SAMPEL PENGUJIAN KUALITAS PRODUK CAT TEMBOK MENGGUNAKAN FAULT TREE ANALYSIS DI PT. XYZ

ANALISIS PENYEBAB KETIDAKSESUAIAN PADA SAMPEL PENGUJIAN KUALITAS PRODUK CAT TEMBOK MENGGUNAKAN FAULT TREE ANALYSIS DI PT. XYZ

Study on reliability of control system in deepwater CBHP MPD system

Deepwater managed pressure drilling technology, with unique advantages in dealing with narrow density window, has been widely used in deepwater drilling operations. As the key equipment to realize managed pressure drilling, the control system in constant bottomhole pressure managed pressure drilling system plays an important role in drilling operations. In this study, a new reliability evaluation method based on fault tree analysis and dynamic Bayesian network model has been proposed to analyze the reliability of the control system. First, the structure of the control system in the deepwater managed pressure drilling system was analyzed to set up a fault tree model of the control system. Second, considering the influence of time on the reliability, a dynamic Bayesian network model of the control system was established. Third, the proposed model was partly verified using the verification method based on three axioms. Fourth, in consideration of the repair factor, the reliability and availability of the control system were calculated by using the exponential distribution model of failure time. Finally, the sensitivity of the control system was analyzed, and the mutual information, variance and entropy were calculated to find out weak links in key components of the control system.

ОЦЕНКА ВОЗМОЖНОСТИ ЭСКАЛАЦИИ ПОЖАРА ПРИ ХРАНЕНИИ МОТОРНЫХ ТОПЛИВ В ПОЛИМЕРНЫХ ЭЛАСТИЧНЫХ РЕЗЕРВУАРАХ

Due to the increase in oil production and production of petroleum products, as well as their transportation and storage, the range and sizes of reservoirs are increasing. For this purpose, polymer tanks are widely used at Russian enterprises of the fuel and energy complex, including mobile tank farmsand oil depots for the operational storage of oil and petroleum products. However, the polymer materials from which the tanks are made are flammable, which increases their fire hazard level. An assessment of the possibility of fire escalation has been carried out using the example of an oil depot model for storing motor fuels in polymer elastic tanks. The results 
 of calculating the dangerous factors of a spill fire during depressurization of polymer elastic tanks with gasoline and diesel fuel, as well as a graph of the dependence of the intensity of thermal radiation during the ignition of these tanks, are presented in tabular form, and an event tree is constructed. The parameters characterizing the possible escalation of a fire at a motor fuel storage site under quasi-stationary conditions have been determined.
 A methodology is proposed that allows assessing the possibility of realizing the escalating nature of a fire at facilities for storing and handling motor fuels in polymer elastic tanks, and recommendations are also given to prevent the progressive nature of the development of negative events and reduce damage in case of fire.

ANALYSIS AND IDENTIFICATION OF DAMAGE TO AMC 36-800/MA AN SHAN LATHES USING FAILURE MODE AND EFFECT ANALYSIS AND FAULT TREE ANALYSIS METHODS

Maintenance emerges as a crucial intervention to ensure the sustained reliability of machinery. The AMC 36-800/MA AN SHAN lathe, a piece of equipment subject to extensive operational demands, frequently encounters breakdowns, thereby obstructing the seamless execution of maintenance activities for facilities. This investigation seeks to pinpoint the components responsible for the failures and malfunctions afflicting the lathe above. Employing the methodologies of Failure Mode and Effects Analysis (FMEA) and Fault Tree Analysis (FTA), this study successfully identifies the components at the epicentre of the machine's vulnerabilities. The analysis culminates in delineating critical components by calculating Risk Priority Numbers (RPN), unveiling a pivotal RPN value of 309.57. Moreover, it isolates two components whose failure modes surpass the critical RPN threshold: the Drive Motor and the Fixed Head. The genesis of these failures can be attributed to the escalating operational intensity, elevated engine temperatures, and a maintenance regimen that is both sporadically scheduled and suboptimal. Keywords: Lathe AMC 36-800/Ma AN Shan, Failure mode, FMEA, FTA, RPN

Optimum maintenance units in multi‐indenture systems

AbstractThis paper deals with an optimization problem of determining the maintenance units and age‐based inspection schemes to minimize the expected maintenance cost rate and satisfy a target system availability for multi‐indenture systems that have a modular structure with redundant units. Failures of primary components directly lead to system failures and can therefore be identified and maintained immediately, while failures of redundant components need to be identified by inspections. And the designated maintenance units need to be replaced during maintenance. By constructing the dual structure of the fault tree, we present a failure path enumeration method, based on which the system availability and expected maintenance cost rate models considering maintenance time are derived. For redundant units, two types of inspection policies are considered in our models: one is the corrective maintenance (CM)‐based inspection policy, and the other one is the age‐based inspection (PM) policy, inspections are performed at failures or age h, depending on which occurred earlier. A heuristic algorithm is proposed to find the reasonable maintenance units and inspection intervals simultaneously, and its performance is also compared and analyzed. Several numerical examples are studied to investigate the effect of parameters on optimal solutions.

A new ordering method of basic events in dynamic fault tree for sequential binary decision diagram

AbstractDynamic fault tree (DFT) is a reliable method for modeling complex systems with dynamic characteristics. However, evaluating the reliability of such systems can be complex. The sequential binary decision diagram (SBDD) method simplifies this process by reducing computational complexity. This study investigates factors influencing SBDD size and proposes a new method, the complete priority ordering method, for ordering basic events in SBDDs. Results demonstrate the method's effectiveness in comparison to existing approaches.

A Case Study of Accident Analysis and Prevention for Coal Mining Transportation System Based on FTA-BN-PHA in the Context of Smart Mining Process

In the face of the increasing complexity of risk factors in the coal mining transportation system (CMTS) during the process of intelligent transformation, this study proposes a method for analyzing accidents in CMTS based on fault tree analysis (FTA) combined with Bayesian networks (BN) and preliminary hazard analysis (PHA). Firstly, the fault tree model of CMTS was transformed into a risk Bayesian network, and the inference results of the fault tree and Bayesian network were integrated to identify the key risk factors in the transportation system. Subsequently, based on the preliminary hazard analysis of these key risk factors, corresponding rectification measures and a risk control system construction plan are proposed. Finally, a case study was carried out on the X coal mine as a pilot mine to verify the feasibility of the method. The application of this method effectively identifies and evaluates potential risk factors in CMTS, providing a scientific basis for accident prevention. This research holds significant importance for the safety management and decision making of coal mine enterprises during the process of intelligent transformation and is expected to provide strong support for enhancing the safety and reliability of CMTS.

Study of Insulation Loss in Boiler

Thermal is the main source for power generation in India. The percentage of thermal power generation as compare to other sources is 65%. The main objective of thermal power plant is to fulfill the energy demands of the market and to achieve these demands; plant requires technical availability with the parts reliability and maintenance strategy. This paper deals with the determination of current operating efficiency of Boiler and calculates major losses for Super thermal power plant (India) of 210MW units. Then identify the causes of performance degradation. Also find the major causes of heat losses by Fault Tree Analysis (FTA) and recommends its appropriate strategy to reduce major losses. The aim of performance monitoring is continuous evaluation of degradation i.e. decrease in performance of the steam boiler. These data enable additional information which is helpful in problem identification, improvement of boiler performance and making economic decisions about maintenance schedule.

Design and Fabrication Pneumatic Expandable Vehicle

Thermal is the main source for power generation in India. The percentage of thermal power generation as compare to other sources is 65%. The main objective of thermal power plant is to fulfill the energy demands of the market and to achieve these demands; plant requires technical availability with the parts reliability and maintenance strategy. This paper deals with the determination of current operating efficiency of Boiler and calculates major losses for Super thermal power plant (India) of 210 MW units. Then identify the causes of performance degradation. Also find the major causes of heat losses by Fault Tree Analysis (FTA) and recommends its appropriate strategy to reduce major losses. The aim of performance monitoring is continuous evaluation of degradation i.e. decrease in performance of the steam boiler. These data enable additional information which is helpful in problem identification, improvement of boiler performance and making economic decisions about maintenance schedule.

Assessing wildfire risk to critical infrastructure in central Chile: application to an electrical substation

Background Wildfires have caused significant damage in Chile, with critical infrastructure being vulnerable to extreme wildfires. Aim This work describes a methodology for estimating wildfire risk that was applied to an electrical substation in the wildland–urban interface (WUI) of Valparaíso, Chile. Methods Wildfire risk is defined as the product between the probability of a wildfire reaching infrastructure at the WUI and its consequences or impacts. The former is determined with event trees combined with modelled burn probability. Wildfire consequence is considered as the ignition probability of a proxy fuel within the substation, as a function of the incident heat flux using a probit expression derived from experimental data. The heat flux is estimated using modelled fire intensity and geometry and a corresponding view factor from an assumed solid flame. Key results The probability of normal and extreme fires reaching the WUI is of the order of 10−4 and 10−6 events/year, respectively. Total wildfire risk is of the order of 10−5 to 10−4 events/year Conclusions This methodology offers a comprehensive interpretation of wildfire risk that considers both wildfire likelihood and consequences. Implications The methodology is an interesting tool for quantitatively assessing wildfire risk of critical infrastructure and risk mitigation measures.

Risk assessment of man‐machine systems under safety‐critical multitasking situations

AbstractMultitasking is increasingly common in highly complex and safety‐critical systems, especially under abnormal situations. Mental overload (MOL) may occur and result in forgetting/mistaking tasks uncertainly. Such probabilistic errors could have catastrophic consequences and contribute greatly to the multitasking risk of man‐machine systems. In this paper, to better identify the risks of safety‐critical multitasking situations, MOL mechanism is investigated and a risk analysis method considering MOL is proposed. MOL occurs when the demand for resources estimated by Multiple Resources Model exceeds an operator's ability. Then, the operator's performance degrades, and s/he tends to mistake or abandon parts of tasks. Based on the MOL mechanism, a MOL‐performance dependency (MOL‐PDEP) gate is proposed to incorporate MOL into risk analysis. Its inputs are concurrent tasks, and it triggers the related hazardous human behavior events with certain probabilities if MOL occurs. Through this gate, the dependence among these events and their nondeterministic cause relationships to MOL are added to traditional fault tree (FT), which presents a challenge issue to FT analysis. An implicit method is proposed to analyze the FT with MOL‐PDEP gate and calculate the accident probability. A case study on a helicopter crash accident demonstrates the effectiveness of the proposed method.

Quantifying the impact of risk mitigation measures using SPAR-H and RCM Approaches: Case study based on VVER-1000 systems

Probabilistic Safety Assessment (PSA) provides a systematic and quantitative approach to assess the risk associated with different components and systems within a nuclear power plant. By quantifying the impact of risk mitigation measures, decision-makers can prioritize and implement solutions that have the most significant impact on reducing risk. Fault Tree Analysis (FTA) is employed as a systematic method within PSA, encompassing all modes of failure across equipment and associated support systems, including unavailability due to maintenance (UDM), human errors (HEs), and common cause failures (CCFs). In the present research, the Extra Borating System (EBS) and the Chilled Water Operating Circuit System (CWOCS) of essential loads are modeled in the SAPHIRE code using VVER-1000 design data. Through importance analysis employing the Fussell-Vesley criterion, the most significant basic events for these two systems are identified. Subsequently, the outcomes of the importance analysis are examined using diversity, SPAR-H, and Reliability Centered Maintenance (RCM) techniques. Recommendations such as the enhancement of diversity, increasing staff training, promoting Human Machine Interface (HMI), reduction of maintenance time, and improvement of power supply reliability are proposed for the most crucial basic events. The ensuing impact of these measures on the reliability of the EBS and CWOCS is subsequently assessed. Through a comparison between the new failure probability and the previous, it is determined that improvements in CCFs contribute a 30% effect; HEs have a 14% effect and UDMs have a 5% effect, with a cumulative impact of 35% on the failure probability of the EBS system. Similarly, for the CWOCS system, enhancements in CCFs contribute 20%, UDMs 17%, and improved power supply reliability 19%, with a cumulative impact of 29%.

Development and evaluation of a 2oo3 safety controller in FPGA using fault tree analysis and Markov models

The Safety integrity level (SIL) is a measure of the reliability and availability of a safety instrumented system. SIL determination involves qualitative and quantitative analysis based on international standards such as IEC 61508 and IEC 61511. Several techniques can be used to analyze safety instrumented systems, including reliability block diagrams, fault tree analysis, and Markov models. The aim of this paper is to design and evaluate a pressure control system for a compressed nitrogen tank using a PID controller implemented in a field programmable gate array with 2 out of 3 architecture. This architecture ensures the safety of measurements and command of the system through a voting arrangement. The availability of the system is determined by the redundancy and the one hardware failure tolerance. The quantitative analysis is performed by calculating the probability of failure on demand per hour using Markov models or a relevant probabilistic approach based on fault tree analysis. The Markov model method gives the probability of failure of the system in different states during the system life cycle. The fault tree analysis method determines the probability of failure of the system using its equivalent failure rate. Furthermore, this paper compares the SIL result obtained by each model.

Reliability assessment applied in the design of an industrial substation in the context of Industry 4.0

Incorporating Industry 4.0 concepts into substation automation systems (SASs) enables the achievement of coordinated, fast, and selective protection systems. In this context, this work presents a reliability assessment applied in an industrial substation of a textile company within the framework of Industry 4.0. The Markov chain models both equipment and protection systems, while fault tree analysis allows for analyzing the alternative design scenarios in detail. The TopEvent software version 1.2.3 is used to provide accurate diagnosis using the min-max method. While enhancing selectivity with circuit breakers decreases failure severity, it concurrently increases contingency probability, not necessarily leading to higher reliability. Notably, adopting IEC 61850-based logical selectivity proves more reliable than time coordination, improving the system resilience with load shedding. With support from real-time communication between intelligent electronic devices (IEDs), this approach facilitates reliability improvement, particularly in severe contingencies.

Rainfall interception by urban trees: Event characteristics and tree morphological traits

AbstractThe rapid expansion of impermeable surfaces in cities has a major impact on urban hydrology by reducing rainwater infiltration and increasing runoff rates and peaks. The use of urban trees as stormwater management tools is gaining recognition for their potential to mitigate flood risk and provide additional ecosystem services. We conducted an in‐situ field experiment to measure throughfall on Norway maple (Acer platanoides) and small‐leaved lime (Tilia cordata) to assess the interception capacity of solitary urban trees under different degrees of surface sealing in the city of Freiburg, Germany. We examined the relationships between rainfall characteristics, tree morphological traits, and the interception behaviour, analysing eight trees per species over 76 recorded rainfall events from April to September 2021. Average interception values were higher for small‐leaved lime trees (70.3% ± 6.6%) than for Norway maple (54.8% ± 10.3%) surpassing those in typical forested environments. The average interception loss of all recorded events was 2.6 ± 0.6 mm for Norway maple and 3.7 ± 0.3 mm for small‐leaved lime. For both tree species, significant linear correlations were found between the relative interception and factors such as rainfall depths, the leaf area index (LAI), and the plant area index (PAI) (adj. R2 >0.45). Unlike Norway maple, small‐leaved lime demonstrated significant relationships between several tree morphological parameters and interception (adj. R2 >0.43). The LAI of both species significantly decreased with the increasing degree of surface sealing, which in turn affected interception rates. Our results enhance the understanding of the interception process by solitary trees in urban contexts and enables the parameterization of interception rates using measurable properties. To develop a comprehensive database for modelling parameters and aid urban planners in stormwater management, further field experiments involving various tree species are essential.

Operational Elements Influencing the Occurrence of Unfavorable Incidents in the Railway System.

The article delves into the intricacies of rail transport, addressing the repercussions of adverse events such as delays, incidents, and accidents within the railway system. It explores the impact of disruptions on the day-to-day responsibilities of railway employees, with a primary focus on Station managers. The study employs two distinct approaches: first, an experimental analysis involving traffic management personnel, where factors contributing to failures are examined through a questionnaire survey. Second, a comprehensive perspective is taken by leveraging expert knowledge, combined with Fault Tree Analysis and Event Tree Analysis methodologies. This combination is used to illustrate how alterations in the system, including erroneous decisions, can lead to subsequent undesirable events.

Applying a semi-quantitative risk assessment on petroleum production unit

Applying safety means in the industry, especially in the petroleum industry is very important to maintain the industrial facility. A semi-quantitative risk assessment as Layers of Protection Analysis (LOPA) is used widely to quantify data after qualitative risk analysis as HAZOP using a simpler way than quantitative risk analysis ‘QRA’ as fault tree analysis ‘FTA’. This determines if a new safety integrity function ‘SIF’ is needed. This paper introduces a novel fuzzy logic system to solve the failure of crude oil shipping pumps. Several models are studied to select the most appropriate fuzzy membership functions. Results are compared with results from the LOPA model, which shows the advantages of using the proposed model to reduce the RRF for the potential hazard and achieve a simple and reliable control method.

Event tree-based risk and financial assessment for power plants

Reliability and risk analyses in engineering have seldom been linked to financial analyses despite the significant role that risk assessment plays in the field of finance. Cash flow analyses for power plants typically do not account for contingent and successive events. Hence, the related financial assessments rarely incorporate a quantification of the adverse effects resulting from the combination of subsequent failures that could lead to extreme outcomes. The proposed approach aims to address this gap by employing the event tree method.The novel contribution lies in introducing an event tree-based method that enables a granular evaluation of the financial performance of power plants and can serve as a foundation for the development of a variety of sensitivity and optimization analyses. The method enhances the accuracy of financial performance estimates by specifically targeting the assessment of operation and maintenance costs. The results show the importance of an improved assessment of the expenses related to equipment failures, which are approximately one-third of the revenue and add up to around 380,000 EUR for the lifespan of а photovoltaic plant with an installed capacity of 1 MW.