Reliability Block Diagram Research Articles

Reliability and redundancy allocation analysis applied to a nuclear protection system

Brazil is constructing with national technology two small nuclear reactors for propulsion and for radioisotope production with thermal power levels between 20 and 50 MW. These nuclear reactors fit more in the class of small modular reactors (SMR) than in the class of large nuclear power plants. In this article we apply the design approach of SMRs to propose an architecture of reactor protection systems for the small reactor under construction in the country. To do that the probabilistic analysis of the architecture of a nuclear reactor protection system is evaluated to determine the sensitivity of the components through an Reliability Block Diagram modeling. It was evaluated the modification of the architecture and the addition of redundancies when using components with lower life time than the components usually used for this purpose. The results showed that after one year of operation, the reference RPS system presents a failure probability of 0.17 %. The modified system, with components with lower life time, presents a point reliability value only 0.070 % lower than the reference one, but this difference grows exponentially over time, and in 10 years of operation it can reach values above 95%. Using equipment with lower life time characteristics implies a greater number of redundancies and, additionally, a greater number of maintenance procedures and spare parts. Therefore, this technical feasibility analysis should consider a RAM simulation as well.

Research on Reliability of Grid Connected Photovoltaic Renewable Generation System

Renewable energy sources are increasingly being implemented in power systems to curb global warming and improve generation adequacy. These renewable sources include Hydro, wind, tidal, and solar power systems. Since Pakistan experiences decent solar irradiation throughout the year, the most viable renewable energy option is photovoltaic generation. Before solar systems are implemented, the proposed design is first simulated using design software such as MATLAB-Simulink to correct and adjust parameters to attain the DC voltage and current through the irradiation and environment temperature. Reliability studies and analysis are performed on the simulated systems to ascertain the success and long life before the system components’ failure. In this thesis, the grid-connected PV system’s reliability model established based on the reliability block diagram method using the MIL-HDBK-217F handbook. The handbook provides the methodology of calculating failure rates of specific physical electronics operations. The mean time to failure (MTTF) and Mean time to repair (MTTR) of the system is calculated from the overall system reliability. Photovoltaic power output varies greatly, and it is dependent on solar irradiation and temperature, resulting in intermittent and variable energy production. All of these considerations have a significant effect on the entire system adequacy of the power generation system. This study uses a probabilistic analytical methodology to develop comprehensive reliability models of grid-connected Photovoltaic generation systems.

PM4 SMP model proposed for system reliability criticality assessment and maintainability improvement

This paper gives a practical systematic approach towards the maintenance procedure optimisation of a critical industrial unit in operation, to improve its maintainability. The resolution of the maintainability challenge in the industrial unit (Vibrating screen unit - VSU) was realised by performing a two-phase critical analysis, encompassing criticality and maintainability assessment. The criticality assessment comprised of failure investigation using fault tree analysis (FTA), vulnerability analysis using reliability block diagram (RBD), and failure mode effect and criticality analysis (FMECA). Furthermore, a maintainability assessment was performed on the industrial unit and improvement opportunities were identified. A generic model (PM4 Model) was conceptualised and used to improve the mean time to repair (MTTR) through a well-documented standard maintenance procedure (SMP).

DMB Machine Reliability Analysis Through Failure Mode Effect Analysis and Reliability Block

The production process is carried out continuously, it will result in decreased machine capability. When a component on a machine is damaged resulting in the production process being interrupted, the machine's performance depends on the Reliability of the machine or the component. The DMB machine is a sorting machine at PT Etex Building Performance Indonesia, because it is the main machine in the production process and DMB has a high downtime in 2019. Failure Mode effect And Analysis, aims to determine the machine failure factor. Reliability Block Diagram, to determine machine reliability. The results of research with FMEA are Pneumatic with RPN value 60, Decelerator value RPN 64, Accelerator value RPN 56, Hydraulic Table Safety Lock value RPN 48, Roller value RPN 48 Bearing Lifting value RPN 36, Sensor Transfer Dolly value RPN 48, Motor Transfer Template RPN value 36, the Suction Cup is the component that has the lowest RPN value with a value of 30, from the Reliability Block Diagram (RBD) calculation, the DMB machine reliability opportunity value is obtained including 88.42% of the production process for 23 hours, 42.25% of the process for 161 hours of operation. , and decreased by 2.70% when used for 674 hours of operation. Recommended action is to perform maintenance actions with the type of daily care and weekly maintenance.

A hybrid approach for an oil and gas company as a representative of a high reliability organization

A hybrid method combining various Reliability (Fault Tree Analysis -FTA-, Reliability Block Diagrams -RBD), Multi Criteria Decision Making (Analytic Hierarchy Process -AHP), High Reliability Organisations (HROs) and Learning from Failures (LFF) framework tools, has been applied to a long-established pattern of small to medium chronic failures in a large Oil & Gas organisation. Through the Reliability techniques FTA/RBD, the root causes of the chronic failure pattern were identified, categorised and their interconnections established. The obtained root causes were then used as criteria and with the five principles of mindful organising as alternatives in constructing the AHP model. Finally, an attempt to extract useful generic lessons from the failure causes identified by applying the learning from failure (LFF) principles was made, in order to obtain guidelines for updating existent company routines. Despite a few shortcomings, some inherent to the tools themselves and some related to the method intent, reasonable results were obtained which appear to demonstrate the applicability of the approach. Abbreviations: AHP: analytical hierarchy process; CAPEX: capital expenditure; CBM: condition based maintenance; CTA: crisis tree analysis; CMMS: computerised maintenance management system; DMG: decision making grid; E&P: exploration and production; FTA: fault tree analysis; HRO: high reliability organisation; LFF: learning from failure; MCDM: multi criteria decision making; OPEX: operational expenditure; PSF: performance shaping factors; RACI: responsible accountable consulted informed; RBD: reliability block diagram; RBM: risk based maintenance.

Reliability Modelling and Analysis of the Power Take-Off System of an Oscillating Wave Surge Converter

Wave power is a potential technology for generating sustainable renewable energy. Several types of wave energy converters (WECs) have been proposed for this purpose. WECs operate in a harsh maritime environment that sets strict limitations on how and when the device can be economically and safely reached for maintenance. Thus, to ensure profitable energy generation over the system life cycle, system reliability is a key aspect to be considered in WEC development. In this article, we describe a reliability analysis approach for WEC development, based on the use of reliability block diagram (RBD) modelling. We apply the approach in a case study involving a submerged oscillating wave surge converter device concept that utilizes hydraulics in its power take-off system. In addition to describing the modelling approach, we discuss the data sources that were used for gathering reliability data for the components used in a novel system concept with very limited historical or experimental data available. This includes considerations of the data quality from various sources. As a result, we present examples of applying the RBD modelling approach in the context of WEC development and discuss the applicability of the approach in supporting the development of new technologies.

Reliability Analysis of Networked Control Systems with the Consideration of Operating Frequency

The operating frequency of the networked control system (NCS) determines both its control performance and heat flux density. Considering the significant effect of thermal stress on the reliability of electronics, a quantitative reliability analysis framework is proposed for NCSs with the consideration of its operating frequency. It includes 5 main steps: 1) compute the power consumption of all its electronic components using circuit simulation; 2) obtain the thermal stress of these components by thermal simulation; 3) apply the thermal stress results to assess the reliability of components using the part stress analysis method; 4) calculate the reliability of the modules using reliability block diagrams; and 5) quantify the reliability of the NCS by combining the graph reduction method and other network reliability algorithms together. A double loop networked control system is used as an example to verify the effectiveness of our method.

An Efficient Library for Reliability Block Diagram Evaluation

Reliability Block Diagrams (RBDs) are widely used in reliability engineering to model how the system reliability depends on the reliability of components or subsystems. In this paper, we present librbd, a C library providing a generic, efficient and open-source solution for time-dependent reliability evaluation of RBDs. The library has been developed as a part of a project for reliability evaluation of complex systems through a layered approach, combining different modeling formalisms and solution techniques at different system levels. The library achieves accuracy and efficiency comparable to, and mostly better than, those of other well-established tools, and it is well designed so that it can be easily used by other libraries and tools.

RAMI analysis of the Collective Thomson Scattering system front-end – Part2 – reliability block diagram analysis

ITER is an experimental tokamak nuclear fusion reactor with the goal of achieving afusion energy gain factor of 10. Nuclear fusion presents an extreme environment for materials during operations while requiring continuous uninterrupted operation.The Reliability Block Diagram (RBD) is a graphic methodology for system reliability modelling which is constructed from the reliability-wise relations between different subsystems/components and their respective reliability and maintenance data. In this paper, we construct andanalyse the RBD for the Collective Thomson Scattering (CTS) front-end both in terms of fulfilling its functions and its effects in the ITER tokamak operations. Our RDB analysis results were then used to propose mitigation actions which include design changes and operational procedures to deal with the identified failure modes.Our initial results indicate that the system's mean availability at the end of its lifecycle of 20 years is no greater than 82.55% which was due to low Mean Time Between Failures (MTBF) of a critical system component – theSplit Biased Waveguide (SBWG) – aswell as several thermally loaded components. After mitigation actions, which aimed at controlling the system's exposure to heat loads, the MTBFs increased and the resulting mean availability achieved values over 97%, in conformity with design specifications. Furthermore, considering the CTS failure modes with impact on ITER operations, the expected value for the mean availability is of 99.995%. Therefore, we concluded that these failure modes did not require mitigation actions.In this article, we cover the second half of the RAMI analysis of the CTS diagnostic, the RBD analysis.

An analytical approach for optimization of computer network design considering the integration of the communication and power infrastructures

SummaryNowadays, computer networks are critical to the success of small and large businesses. They connect people, support applications and services, and provide access to the resources that keep the businesses running. Our work proposes analytical models and a methodology for supporting the optimization of the network infrastructure design, considering both technical and business oriented metrics, such as availability, reliability, and total cost. The integration of communication and power infrastructures is supported by this methodology. The dependability (availability/reliability) models were created using the Reliability Block Diagram and Stochastic Petri Net modeling mechanisms following a hierarchical approach. A case study considering the design of a real‐world network infrastructure is presented to illustrate the proposed methodology. The results showed a significant reduction in the design complexity as well as an improvement in the relationship between technical and business aspects.

RAMI analyses for the primary heat transfer systems of breeding blankets and the related balance of plant of DEMO reactor

Two models are currently taken as reference for the breeding blanket (BB) of DEMO, the Helium Cooled Pebble Bed (HCPB) and the Water Cooled Lithium Lead (WCLL). For both the models two Balance of Plant (BOP) configurations are currently investigated. They are all based on four independent primary heat transfer systems (PHTSs). The largest PHTS is devoted to remove the BB thermal power, two PHTSs for the divertor (DIV) and one for the vacuum vessel (VV) heat removals. Both DIV loops and VV loop transfer their thermal power directly to the power conversion system (PCS). The two BOP configurations are investigated to cope with the pulsed operation of the reactor. The first configuration consists of an “indirect coupling” of the BB PHTS to the PCS by an Intermediate Heat Transfer System placed in between them. The second configuration consists in a “direct-coupling” of the BB PHTS to the PCS.Reliability, availability, maintainability and inspectability (RAMI) analyses for the four PHTS and PCS configurations are presented in this paper. The Failure Mode, Effect Analysis (FMEA) and the Reliability Block Diagram (RBD) methodologies have been used to perform the studies. As main result can be highlighted that even the low reliability of the systems to operate without failure and the large number of requests of corrective maintenance, all the systems are in compliance with an operational availability target of 30 %.

RAMI analysis for the ITER In-Vessel Coils System

The ITER project is the largest international collaboration in the scientific field ever set up. It forms the heart of a unique collaborative agreement to build the first experimental nuclear fusion device designed to prove the scientific and technological feasibility of sustained fusion power generation. Among hundreds of systems, the In-Vessel Coils System plays a crucial role in ITER: ensuring and maintaining stable plasma operations. ITER has an ambitious inherent availability target for plasma production. To be able to achieve this objective, the potential technical risk that may affect the machine operation, was assessed by means of RAMI (Reliability, Availability, Maintainability and Inspectability) approach. The RAMI analysis for the IVC system was performed on the system design, following the Staged Approach Configuration adopted by ITER for Construction and Operation phases. A functional breakdown was prepared, resulting in the system being divided into 3 main functions described using the IDEFØ method. A qualitative analysis was performed applying the Failure Modes, Effects and Critical Analysis technique in order to identify the potential effects due to different anomalies of the IVC components. Criticality chart highlights the distribution of the Failure Modes across three risk zones with regard to their probability of occurrence and the impact on the availability. In relation to the operation of the IVC System, the analysis identified 32 risks, none of whom were classified as major. To estimate the reliability and availability of IVC system and to assess the compliance to the requirements, a quantitative analysis was performed using the Reliability Block Diagrams Analysis. The inherent availability of the IVC system during DT phase was calculated over the 20 years of ITER lifetime. The availability of the ITER IVC system results to be compliant with the inherent availability requirement for DT phase.

A Reliability Analysis Framework for Space Modulation Techniques

Space modulation techniques (SMTs) have emerged as a family of multiple-input multiple-output (MIMO) transmitter designs that require a maximum of a single RF-chain. SMTs have been analyzed in the context of cost, power, and error performance in past studies and have shown to exert favorable advantages over traditional implementations such as spatial multiplexing (SMX). However, given future application requirements, analysis of the hardware also in the context of reliability becomes essential. In this work, an SMT hardware reliability analysis framework is devised using two quantitative analysis tools consisting of reliability block diagrams (RBDs) and Markov Chains. In addition, a comparative study using commercial component failure rates is performed to analyze how SMTs compare to each other.

A functional model-based approach for ship systems safety and reliability analysis: Application to a cruise ship lubricating oil system

The lubricating oil systems are essential for ensuring the safe and reliable operation of the cruise ships power plants as demonstrated by recent incidents. The aim of this study is to investigate the safety enhancement of a cruise ship lubricating oil system by employing safety, reliability, availability and diagnosability analyses, which are based on the system functional modelling implemented in the MADe™ software. The safety analysis is implemented by combining a Failure Modes, Effects and Criticality Analysis and the systems functional Fault Tree Analysis. Subsequently, Reliability Block Diagrams are employed to estimate the system reliability and availability metrics. The MADe™ toolbox for determining sensors locations is employed for a more advanced diagnostic system development. A number of design modifications are proposed and the alternative configurations reliability metrics are estimated. The derived results demonstrate that the suction strainer and the lubricating oil pump are the most critical system components. Seven additional sensors are proposed to enhance the original system design. Compared with the original system design, the investigated alternative designs exhibit significantly lower probabilities of failure and higher values of availability.

Aleatory uncertainty quantification of project resources and its application to project scheduling

The extant literature offers little basis for uncertainty analysis of resource acquisition in project management. Within the spirit of reliability theory, the present paper attempts to fill this gap by taking a success-oriented view of acquiring the required resources for completing a project. In this context, the Reliability Block Diagram (RBD) is constructed to quantify the aleatory uncertainty in resource acquisition by taking into account the supply of and demand for every resource, as well as the probability that the resource is available when it is required. Further, this article generates a new schedule sensitivity index that accounts for uncertainty in both time duration and resource acquisition of project activity. This paper compares the effectiveness of the proposed index in evaluating the relative importance of activities in stochastic project networks. The new index proves better performance due to its ability to capture uncertainty in both time duration and resource acquisition of project activity.

Maximum Entropy Approach to Reliability of Multi-Component Systems with Non-Repairable or Repairable Components.

The degradation and recovery processes are multi-scale phenomena in many physical, engineering, biological, and social systems, and determine the aging of the entire system. Therefore, understanding the interplay between the two processes at the component level is the key to evaluate the reliability of the system. Based on the principle of maximum entropy, an approach is proposed to model and infer the processes at the component level, and is applied to repairable and non-repairable systems. By incorporating the reliability block diagram, this approach allows for integrating the information of network connectivity and statistical moments to infer the hazard or recovery rates of the degradation or recovery processes. The overall approach is demonstrated with numerical examples.

The reliability study of Gili Trawangan photovoltaic system using RBD (Reliability Block Diagram) method

In order for Gili Trawangan On-grid photovoltaic (PV) system to be reliable in supplying electricity, it is necessary to know the reliability of the main equipment in the PV system. The aim of this study is to determine the reliability of the main equipment of the on-grid PV system. The methodology is, collecting primary data in the form of disturbance data reports on Gili Trawangan PV system in 2011-2018, compiling the Reliability Block Diagram (RBD) of the PV system and determining the reliability and critical of the PV system equipment using Reliasoft Blocksim software version 11. The On-grid PV systems Reliability Block Diagram consists of 3 sub-systems; Source system, String Combiner System and Power Conditioning System, each of which is composed of main components. RBD simulation results with Reliasoft Blocksim software obtained the results that the reliability of the On-grid PV system is 49% at t=100 hours and 40% at t=300 hours, this condition is still far from the target of PV system reliability of 80%. From the simulation also obtained critical equipment on the On-grid PV system is an AC Inverter and Breaker component, which has a high Reliability Importance (RI) value and with the highest reliability value.

Effects of Failure Severity and Critical Failure Modes on Reliability and Availability

Unexpected failures in process industries lead to production loss and an increase in the cost of maintenance as well. Reliability, Availability, and Maintainability (RAM) analysis is a helpful tool in reducing the number of failures. Also, it helps to increase the mean time between failures by carrying out necessary design modifications with an appropriate improvement in the maintenance schedule. The present study examines the effect of critical failure modes on the reliability of the Effluent Treatment and Injection plant (ETIP) of an oil field. The essential equipment of the plant is identified, which upon failure could result in downtime of the facility. Based on the field data and OREDA database, probable failure rates in each critical mode and mean active repair time are developed with the help of Reliability Block Diagrams (RBD) using the BLOCKSIM™ tool. Using Monte Carlo approach, performance of the system is analyzed in the critical failure modes over the lifetime. It is seen that the reliability of the chosen process plant decreases with time in the critical failure modes while the combined effect of all critical failures on the reliability is about 5%. While criticality of the analysis depends on estimates of failure rates and the repair time of essential equipment, the mean availability of the plant is estimated to be 97.62%.

System level reliability assessment for high power light-emitting diode lamp based on a Bayesian network method

The increased system complexity in electronic products brings challenges in a system level reliability assessment and lifetime estimation. Traditionally, the graph model-based reliability block diagrams (RBD) and fault tree analysis (FTA) have been used to assess the reliability of products and systems. However, these methods are based on deterministic relationships between components that introduce prediction inaccuracy. To fill the gap, a Bayesian Network (BN) method is introduced that considers the intricacies of the high-power light-emitting diode (LED) lamp system and the functional interaction among components for reliability assessment and lifetime prediction. An accelerated degradation test was conducted to analyze the evolution of the degradation and failure of components that influence the system level lifetime and performance of LED lamps. The Gamma process and Weibull distribution are used for component level lifetime prediction. The junction tree algorithm was deployed in the BN structure to estimate the joint probability distributions of the lifetime states. The degradation and prediction results showed that LED modules contribute a major part for lumen degradation of LED lamps followed by drivers and the least effect is from diffuser and reflector. The BN based lifetime estimation results also exhibited an accurate prediction as validated with the Gamma process and such improved reliability assessment outcomes are beneficial to LED manufacturers and customers. Thus, the proposed approach is effective to evaluate and address the long-term reliability assessment concerns of high-reliability LED lamps and fulfill the guarantee of high prediction accuracy in less time and cost-effective manner.

Modeling dynamic scenarios for safety, reliability, availability, and maintainability analysis

Safety analysis uses probability combinatorial models like fault tree and/or event tree. Such methods have static basic events and do not consider complex scenarios of dynamic reliability, leading to conservative results. Reliability, availability, and maintainability (RAM) analysis using reliability block diagram (RBD) experience the same limitations. Continuous Markov chains model dynamic reliability scenarios but suffer from other limitations like states explosion and restriction of exponential life distribution only. Markov Regenerative Stochastic Petri Nets oblige complex mathematical formalism and still subject to state explosions for large systems. In the design of complex systems, distinct teams make safety and RAM analyses, each one adopting tools better fitting their own needs. Teams using different tools turns obscure the detection of problems and their correction is even harder. This work aims to improve design quality, reduce design conservatism, and ensure consistency by proposing a single and powerful tool to perform any probabilistic analysis. The suggested tool is the Stochastic Colored class of Petri Nets, which supplies hierarchical organization, a set of options for life distributions, dynamic reliability scenarios and simple and easy construction for large systems. This work also proposes more quality rules to assure model consistency. Such method for probabilistic analysis may have the effect of shifting systems design from “redundancy, segregation and independency” approach to “maintainability, maintenance and contingency procedures” approach. By modeling complex human and automated interventional scenarios, this method reduces capital costs and keeps safety and availability of systems.