Reliability Block Diagram Research Articles

Forecasting Project Duration in the Face of Disruptive Events: A Resource-Based Approach

Disruptive events are the main source of delays in projects. A key task for construction managers is to revise the project schedule plan based on time delays caused by these events. Consequently, project management research has developed various forecasting methods to evaluate the prospective impact of disruptive events on project completion time. This article tackles three shortcomings of the available forecasting methods: (1) the extrapolative and judgmental nature of these methods, (2) the lack of an explicit focus on project resources, and (3) the lack of attention to the disproportionate impact of disruptive events on project resources. The method developed in this study takes into account the detrimental effects of disruptive events on project resources in the case where there is no historical precedence. In this method, project resources are first mapped into reliability block diagrams (RBDs) to develop a stochastic variable that reflects the impact of resource shortages on project activity. A Monte Carlo simulation analysis is performed to simulate the uncertainty in acquiring resources during disruptions. The impact of resource shortages on the completion time of project activity is then quantified by means of the stochastic variable developed in the first step. The proposed method is demonstrated in a real-life construction project. The validation results prove the better performance of the new method in forecasting time delays caused by unexpected events compared to the existing methods. The proposed method assists construction managers in revising project schedule plans and provides benefits in framing and solving problems that arise when disruptions occur.

Optimal Placement of Remote Controlled Switches in Electric Power Distribution Systems with a Meta-heuristic Approach

In the present work the problem of Optimal Placement of remote controlled switches, through the replacement of installed manual switches, in Electric Power Distribution Systems with radial configuration is approached, considering economic, technical, operational and social aspects. The approach used for the identification of strategic points is based on the implementation of meta-heuristic algorithms for optimization with multiple objectives. For the evaluation of each solution, an evaluating function based on the Monte Carlo method is implemented, which estimates the defined indices through the simulation of failures in the network, whose probabilities are obtained using the Reliability Block Diagram method. Three different multi-objective algorithms were implemented and their results compared using the hypervolume metric, having the Generalized Differential Evolution 3 algorithm the best performance.

Application of a SPAR-H based framework to assess human reliability during emergency response drill for man overboard on ships

Emergency preparedness is of paramount importance in successful emergency responses at sea. Therefore, emergency drills are regularly conducted to maintain acceptable levels of emergency preparedness. However, it needs to be considered that emergency drill operations themselves include significant risks, and there is no evidence that these risks are appropriately considered when planning emergency drill operations. Human error is one of the main contributors of accidents during emergency drill procedures. The main question posed is how overall risk, including human errors, during an emergency drill can be correctly evaluated. This paper introduces a new hybrid approach based on the Standardised Plant Analysis Risk Human Reliability Analysis (SPAR-H) method with a fuzzy multiple attributive group decision-making method. The method provides a framework for evaluating specific scenarios associated with human errors and identifies contributors that affect human performance. Estimated human errors are utilised to assess human reliability using a new approach based on a system reliability block diagram. The rescue boat drill procedure for a man overboard is selected to illustrate the method. The findings of this research show each human error probability and its contributing factors per task. As a result, overall reliability of 6.06E-01 was obtained for rescue boat drill operation.

A demand-based framework for resilience assessment of multistate networks under disruptions

Multistate networks composed of many independent components are susceptible to natural disasters and intentional attacks. Resilience is described as the capability of keeping and enhancing the required functionality under disruptions, which is of great importance to design and analyze multistate networks. While the resilience engineering community makes great contributions to resilience assessment, approaches for measuring network performance are limited and the practical demand of users is neglected in multistate networks. This paper proposes a demand-based framework for resilience assessment under disruptions in order to address these issues. After specifying network structure with the help of reliability block diagram, component behavior is modeled as a Markov reward process. Both the probability of staying in a particular state and the cost of recovery actions can be calculated. Furthermore, network performance with multiple levels is quantified using universal generating function. Finally, network resilience is comprehensively evaluated from the perspectives of absorption, adaptation and recovery. Besides assessing overall resilience with the consideration of network demand, the proposed framework conducts quantitative analysis of multistate networks. A case study of the potable water network is used to demonstrate the applicability of the proposed framework.

Availability Optimization of the Mobile Crane Using Approach Reliability Engineering at Oil and Gas Company

Reliability engineering is needed for scheduling maintenance to improve system or equipment performance. The purpose of this paper is to provide recommendations for maintenance schedules based on reliability, availability, and maintainability (RAM) analysis that optimizes the availability of mobile cranes operating in Indonesian oil and gas companies. This paper begins with searching for a critical system using the Pareto principle. The critical system is then made a reliability block diagram to facilitate the analysis. However, before conducting the analysis, it is necessary to know the characteristics of the probability distribution of the data so that the analysis results are accurate and stable. Analysis of reliability, availability, and maintainability (RAM) is then carried out in the probability distribution equation for each system. The analysis results show that the implementation of maintenance at the time of reliability reaches the mean time between failure, and the maximum maintainability time is 240 minutes. The result is an increase in the availability of the lower structure (LS) system by 0.53% (98.78% to 99.31%), electrical and safety equipment (ESE) by 0.19% (99.02% to 99.21%), upper structure (US) was 0.07% (99.32% to 99.39), and overall system availability was 0.07% (99.31% to 99.38%).

Efficiency, safety, and reliability analysis of turbocharging in a large container vessel

AbstractCommercial shipping is currently dominated by mega container vessels. The shipping industry has seen a 10‐fold increase in the size of containers over the last four decades. These vessels are propelled by large marine diesel engines, hereafter referred to as the main engine. The performance of the main engine is determined by its subsystems. An important part of the main engine is the turbocharging system, which contributes to its safety, efficiency, and reliability. In this study, the effectiveness and reliability of the turbocharging system are evaluated. The Australian Maritime College has a Kongsberg Engine Simulator that can produce a variety of malfunctions on a running engine's turbocharging system. Analyzing the results obtained from the simulator determines the efficiency of the turbochargers. The study will provide recommendations for improving the safety of the turbocharging system for better performance to be achieved by the turbochargers, leading to an improvement in the main engine's performance. Last, the reliability of the turbocharging system is evaluated quantitatively using a fault tree analysis and reliability block diagrams. This will enable an optimum maintenance strategy to be established to ensure the safe operation of the vessel.

Enhancing Lifetime of 1U/2U CubeSat Electric Power System With Distributed Architecture and Power-Down Mode

The successful mission of CubeSat require reliable and fault-tolerant electrical power system (EPS) that powers all the other subsystems and payloads. Several studies have shown that EPS failure has been one of the main contributors for the CubeSat mission failure. The main objective of this paper is to enhance the lifetime of CubeSats EPS by proposing a distributed EPS architecture and power-down mode. The distributed architecture consists of independent converters for maximum power point tracking operation of photovoltaic (PV) panels. This is possible by using gallium nitride field-effect transistors to reduce the converter footprint and placing the converters on the back-side of the PV panels. Also, single-inductor based <inline-formula><tex-math notation="LaTeX">$N$</tex-math></inline-formula>-1 redundant converters for generation and load-side are proposed to provide uninterrupted operation during component failures. Thus, the proposed distributed architecture not only improves the reliability but also facilitates placement of redundant converters to achieve the fault-tolerant capability. To further reduce the electrical and thermal stresses on the semiconductor devices and thus, improve the EPS life span, a novel power-down mode is proposed for the power converters. In this mode, semiconductor devices are switched-<small>off</small> whenever the power processed is below the threshold level and/or no-load operation. Reliability block diagrams are illustrated to demonstrate the reliability improvement and calculations shows that the proposed distributed architecture has higher reliability than the conventional EPS architecture. All the proposed concepts are validated using a prototype developed based on the specifications of MYSAT-1, which is an 1U CubeSat launched by Khalifa University.

An Overview of Lifetime Management of Power Electronic Converters

An expected lifetime of converters is of great importance for optimal decision-making in the planning of modern Power Electronic (PE) systems. Hence, the lifetime management of power electronic systems has attracted a lot of attention in academia and industry. This paper is a guideline for managing the lifetime of power converters. Analyzing the different kinds of failures, failure modes and their corresponding mechanisms are investigated in the first section along with the failure data needed as input parameters of the assessment. In the second section, lifetime prediction in two aspects of component-level and system level is discussed and all the possible techniques to achieve them are investigated and compared. All the steps required to predict the lifetime in the component-level including electrothermal modeling, cycle counting, lifetime model, damage accumulation, parameter estimation, and lifetime distribution are described and then system level methods consisting of reliability block diagrams, fault-tree analysis, and Markov chains are examined and compared. The last section contains the roadmap of the lifetime extension including the reliable design and condition monitoring.

RAMI Analysis for PF Power Supply System of ITER

According to the ITER requirement, the availability of the poloidal field (PF) coil power supply system must be 98.3% during the life cycle of ITER. In order to meet this requirement, Reliability, Availability, Maintainability, and Inspectability (RAMI) analysis has been applied for analyzing the availability and reliability of the PF power supply system. First, the function analyses, which are described using the Integration Definition Function–language Ø or IDEFØ model are performed. Second, the failure mode effect and criticality analyses are used to calculate the risk level, present the potential causes and effects, and provide the risk mitigation actions to reduce the risk level for each failure. Third, the reliability block diagram is built to simulate the availability and reliability of the system. RAMI analysis provides a method that can be followed to improve the availability and reliability of the system, and from the results, the design requirement can be satisfied.

Dynamic Reliability Evaluation of Diesel Generator System of One Chinese 1000MWe NPP Considering Temporal Failure Effects

Loss of power supply from the diesel generator system (DGS) after loss of offsite power (LOOP) will pose great threat to the safety of GEN-II pressurized water reactors (PWR). Therefore, it is very desirable to evaluate the DGS’s reliability. The traditional analyzing tools are limited to static approaches neglecting the dynamic sequence failure behaviors, such as reliability block diagram (RBD), static fault tree (SFT). Static reliability modeling techniques are not capable of capturing the dynamic sequence-dependent failure behaviors typically existing in NPP safety systems such as DGS, and thus often overestimate the unreliability of systems. In this paper, motivated to study the effects of sequence failure behaviors, dynamic fault tree (DFT) is applied to evaluate the reliability of the DGS of one Chinese 1000MWe Nuclear Power Plant (NPP), and an integrated two-phased Markov Chain model is also developed, which can be considered as a contribution of this article. Comparative study of DGS reliability between DFT and SFT is carried out. The results indicate that compared with the result derived from the DFT model, the unreliability of DGS calculated by SFT is greatly overestimated by about one to two orders of magnitude. Therefore, DFT has a potential to improve the economy of NPP by relaxing the overestimated unreliability of nuclear power systems.

How to Succeed in Digestive Research

It is amazing how many individual factors potentially determine success or failure of research in digestive disease.1–8 The aim of the present article was to describe these factors and provide an explanatory framework for their interactions. We used the statistical concept of a reliability block diagram to illustrate how some factors function in a serial and others in a parallel fashion. Based on these consideration, we have also tried to provide some practical guidance on how to succeed in a career devoted to digestive research.

PFD analysis of LNG fuel gas supply system for improving combined-cycle power plant safety

In order to determine an unavailability of each safety function subsystem that influences on an overall unavailability of entire protection system for safety analysis and enhancement, a modeling is required. This article presents a safety system modeling to evaluate the detected–undetected failures and repairable behaviors of each safety function subsystem in the studied fuel gas supply system (FGSS), which is utilized in a combined-cycle power plant. The proposed modeling deals with probability of failure on demand (PFD) analysis for calculation of the unavailability of three safety function subsystems, which are gas analytical subsystem (GAS), fuel gas controller subsystem (FGC), and shutdown valve subsystem (SDV). The interested GAS includes two different groups of gas analyzers in 2-out-of-2 (2oo2) voting scheme, when using three gas analyzers in each group in 2-out-of-3 and diagnosis (2oo3D) voting scheme. The interested FGC consists of two controllers in 2oo2 voting scheme, when the structure of each controller is in 1-out-of-1 and diagnosis (1oo1D) voting scheme. The interested SDV consists of two shutdown valves, which are installed in 1-out-of-2 (1oo2) voting scheme. The reliability block diagram is utilized for representative of combination of all three safety function subsystems, and the fault tree is utilized for calculation of PFD unavailability of each safety function subsystem. As the results obtained from the proposed safety function modeling, the influence of three safety function subsystems on the total unavailability of the FGSS is described. In addition, an example of the proposed modeling application to provide two guidelines for effective engineering design and operation is also presented. The first is a guideline to implement an effective human machine interface (HMI) at an operator workstation for real-time monitoring of the studied FGSS in the presence of failures that can be automatically detected by device diagnosis. The latter is a guideline to maintain and troubleshoot the failures that can be revealed by proof test. Based on diagnostic information and proof test results, operation and maintenance savings can be achieved.

Sterilizer Reliability Analysis Using Reliability Block Diagram Based on Failure Identification Through Fault Tree Analysis

A sterilizer is a pressurized steam vessel used to boil palm oil. The condition of the sterilizer at PT .X often emits steam at the door and body of the stew. Throughout 2020, there were 12 critical components that were frequently damaged, such as ball valve, actuator, exhaust valve, packing door, elbow, condensate nozzle, liner, pipe, condensate valve, strainer valve, pipe flange, and packing flange. Fault Tree Analysis is an analysis tool that graphically translates the combinations of errors that cause system failures. Reliability Block Diagram is a diagramming method for showing how reliability components contribute to the success or failure of a complex system. Based on the results of the failure calculation using fault tree analysis, the probability of failure of the horizontal sterilizer component is the ball valve 12.2%, exhaust valve 10.9% actuator 6%, door packing 0.24%, elbow 0.24%, condensate nozzle 4.8%, liner 8.61%, 0.25% pipe, 0.21% condensate valve, 4.4% filter valve, 0.22% pipe flange and 0.27% packing flange. The reliability value of the horizontal sterilizer from the calculation using the reliability block diagram is 85.69% if it operates for 8 hours, 62.93% if it operates for 27 hours, 39.6% if it operates for 54 hours, 13.34% if it operates for 117 hours. o'clock. o'clock. o'clock. hours and 1.81% when operating for 234 hours. To maintain reliability above 60%, the preventive maintenance schedule is: Every 80 hours of operation a door packing inspection is carried out. Every 234 hours of operation, elbow tubing and flanges are checked. Every 300 hours of operation, a pipe inspection is carried out. Every 450 operational hours an inspection is carried out on the ball valve, condensate nozzle, liner, actuator, and exhaust valve. Every 30 hours of operation, valve condensate, filter valves and packing flanges are checked.

Estimate the useful life for a heating, ventilation, and air conditioning system on a high-speed train using failure models

&lt;p class="Abstract"&gt;Heating, ventilation, and air conditioning (HVAC) is a widely used system used to guarantee an acceptable level of occupancy comfort, to maintain good indoor air quality, and to minimize system costs and energy requirements. If failure data coming from company database are not available, then a reliability prediction based on failure rate model and handbook data must be carried out. Performing a reliability prediction provides an awareness of potential equipment degradation during the equipment life cycle. Otherwise, if field data regarding the component failures are available, then classical reliability assessment techniques such as Fault Tree Analysis and Reliability Block Diagram should be carried out. Reliability prediction of mechanical components is a challenging task that must be carefully assessed during the design of a system. For these reasons, this paper deals with the reliability assessment of an HVAC using both failure rate model for mechanical components and field data. The reliability obtained using the field data is compared to the one achieved using the failure rate models in order to assess a model which includes all the mechanical parts. The study highlights how it is fundamental to analyze the reliability of complex system integrating both field data and mathematical model.&lt;/p&gt;

Estimation of the failure flow of a set of passenger car doors

An estimation of the failure flows is a prerequisite for the operation of industrial products. It is based on statistical data about failures that occur within technical items in the process of their operation. In the technical product documentation, this indicator shall be featured in the “Dependability parameter estimation” section. The dependability analysis of rolling stock is still affected by the difficulty of defining the methodology for evaluating this parameter at various system levels. For the purpose of analysing a multicomponent system, a reliability block diagram should be developed, and the possible replacement (redundant) elements should be taken into consideration. Multicomponent systems are often represented through various block diagrams, where, among others, the “m-out-of-n” structure may be used referring to a system with a parallel arrangement of elements that is operable when at least m elements operate. An example of such system is a set of passenger car doors. The manufacturers and customers may have different approaches to calculating technical system dependability. First, the required dependability indicator for the entire train is defined that, in turn, defines the dependability requirements for a car. At the same time, the dependability indicator for a car is determined by the respective values of its components (subsystems, units and parts). However, the nature of the relationship between a car and its components is not always taken into account. At the same time, car manufacturers can and should define in the regulatory documentation (and later supervise in operation) the dependability indicators for a set of doors (components of a car in our case) as a single system. However, the failure criteria of a set of doors are not always defined. This paper examines the method of calculating the failure flow for a set of passenger car doors based on operational data and the failure flow of a single door. Aim. To propose a method for calculating the failure flow of a set of 6 car doors by analysing the possible reliability block diagrams with subsequent transition to transition and state graphs.Conclusions. A number of block diagrams were developed for the purpose of dependability calculation of sets of passenger car doors based on the system failure criterion. The failure flow of a set of car doors was calculated according to the developed block diagrams. It is concluded that the Markovian method of calculating the failure flow is of higher priority than the logic-and-probability approach, since it takes into account the recovery factor. A Markovian method was proposed for calculating the failure flow and recovery time of a set of car doors for the “3-out-of-4” reliability block diagram.

A novel design layout of three disjoint paths multistage interconnection network &amp; its reliability analysis

Purpose The purpose of this paper is to design a efficient layout of Multistage interconnection network which has cost effective solution with high reliability and fault-tolerence capability. For parallel computation, various multistage interconnection networks (MINs) have been discussed hitherto in the literature, however, these networks always required further improvement in reliability and fault-tolerance capability. The fault-tolerance capability of the network can be achieved by increasing the number of disjoint paths as a result the reliability of the interconnection networks is also improved. Design/methodology/approach This proposed design is a modification of gamma interconnection network (GIN) and three disjoint path gamma interconnection network (3-DGIN). It has a total seven number of paths for all tag values which is uniform out of these seven paths, three paths are disjoint paths which increase the fault tolerance capability by two faults. Due to the presence of more paths than the GIN and 3-DGIN, this proposed design is more reliable. Findings In this study, a new design layout of a MIN has been proposed which provides three disjoint paths and uniformity in terms of an equal number of paths for all source-destination (S-D) pairs. The new layout contains fewer nodes as compared to GIN and 3-DGIN. This design provides a symmetrical structure, low cost, better terminal reliability and provides an equal number of paths for all tag values (|S-D|) when compared with existing MINs of this class. Originality/value A new design layout of MINs has been purposed and its two terminal reliability is calculated with the help of the reliability block diagram technique.

Performance analysis of safety instrumented systems against cascading failures during prolonged demands

Cascading failures may occur in many technical systems where the failure of one component triggers successive events. Safety barriers like safety instrumented systems are installed in many industries to prevent failures and failure propagations. However, little attention has been paid to the impacts of safety instrumented systems employed to prevent cascading failures in the literature. This paper proposes a novel method for analyzing how the performance of safety instrumented systems influences the protection against and mitigation of cascading failures. It considers SIS reliability and SIS durability in the mitigation of cascading failures. The method uses recursive aggregations based on the reliability block diagram and is verified with Monte Carlo simulations. The application is illustrated with a practical case study, where the proposed method is found beneficial to identify the criticality of safety instrumented systems in consideration of their locations and performance.

Approach for analysis and modeling of reliability of network connectivity from the perspective of efficiency and its applicability

Reliability analysis and assessment methods can be used at any stage of system or component design, including development, operation, and maintenance. Fault Tree-based models and reliability block diagram RBD (qualitative and quantitative) are typically used to provide reliability and readiness assessments for both the early and later stages of design, where system models are more -improved and have more detailed specifications compared to the models of the early stage of the system. On the other hand, models based on the Markov Chain are mainly used in the later design phase. The aim of the work is to define ways to use methods for modeling reliability, with a subsequent goal for analysis taking into account the effectiveness. An approach for modeling the end-to-end network connectivity with different reservations of the connection lines is considered. The results are illustrated by graphical ratios at different influencing parameters, for different reservation methods. A comparative analysis was made using different reservation methods. The practical applicability of the proposed approach and the performed analysis, incl. for training purposes.

Offloading Data through Unmanned Aerial Vehicles: A Dependability Evaluation

Applications in the Internet of Things (IoT) context continuously generate large amounts of data. The data must be processed and monitored to allow rapid decision making. However, the wireless connection that links such devices to remote servers can lead to data loss. Thus, new forms of a connection must be explored to ensure the system’s availability and reliability as a whole. Unmanned aerial vehicles (UAVs) are becoming increasingly empowered in terms of processing power and autonomy. UAVs can be used as a bridge between IoT devices and remote servers, such as edge or cloud computing. UAVs can collect data from mobile devices and process them, if possible. If there is no processing power in the UAV, the data are sent and processed on servers at the edge or in the cloud. Data offloading throughout UAVs is a reality today, but one with many challenges, mainly due to unavailability constraints. This work proposes stochastic Petri net (SPN) models and reliability block diagrams (RBDs) to evaluate a distributed architecture, with UAVs focusing on the system’s availability and reliability. Among the various existing methodologies, stochastic Petri nets (SPN) provide models that represent complex systems with different characteristics. UAVs are used to route data from IoT devices to the edge or the cloud through a base station. The base station receives data from UAVs and retransmits them to the cloud. The data are processed in the cloud, and the responses are returned to the IoT devices. A sensitivity analysis through Design of Experiments (DoE) showed key points of improvement for the base model, which was enhanced. A numerical analysis indicated the components with the most significant impact on availability. For example, the cloud proved to be a very relevant component for the availability of the architecture. The final results could prove the effectiveness of improving the base model. The present work can help system architects develop distributed architectures with more optimized UAVs and low evaluation costs.

A reliable framework for satellite networks achieving energy requirements

Satellite networks with the advantage of fast transmission and global coverage are treated as significant infrastructures. They can provide a variety of services, especially those concerned real-time requirements, such as voice communication in which information is bound to be delivered within the specified time. In order to facilitate the smooth implementation of these services, operators must take actions to ensure reliable data transfer while considering on-board energy limitation. Moreover, due to the fact that data about random services is processed on satellites and transmitted over links, the uncertainty of data transfer needs to be considered. This paper presents a new framework based on queuing graphical evaluation and review technique (Q-GERT) to address these problems. Firstly, an approach is introduced to describe the transmission process under uncertainty, in order to give an accurate assessment of satellite performance. Secondly, with the help of reliability block diagram, four practical structures are designed for data transfer to guarantee satellite availability and network stability. Finally, a routing protocol considering energy requirements is proposed to enhance both global and local reliability. Case analysis demonstrates that the proposed framework compared with state-of-the-art algorithms achieves high reliability and energy efficiency.