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Reliability and availability analysis of the ash handling unit of a steam thermal power plant
Abstract
The paper aims at assessing the reliability and availability of a critical ash handling unit of a steam thermal power plant by making a performance analysis and modeling, using probability theory and the Markov Birth-Death process. After drawing a transition diagram, differential equations are generated. After that, steady state probabilities are determined. Certain decision matrices are developed, which provide various availability levels. The behaviour analysis of the reliability module reveals that the availability decreases with increasing failure rates, while operational availability improves with initial increases in repair rates for different subsystems. Based upon various availability values, the performance of each subsystem is analyzed and used to make maintenance decisions for all subsystems.
... These probabilities offer the opportunity to use the Markovian approach for the availability analysis of the power generation process because they are mutually exclusive. In this respect, the Reliability and performance prediction of a small serial solar photovoltaic system for rural consumption using the Gumbel-Hougaard family copula was analyzed by Anas and Yusuf [22]. ...
... As the methodology adopted by Yusuf et al. [21]. Where (1) to (5) are operational, and (6) to (22) are failure states. ...
The prospects for modeling and decision-making regarding maintenance in solar photovoltaic systems are covered in the current research. In reliability theory, redundancy is a technique widely used to improve system availability and reliability. The k-out-of-n : G system as a popular type of redundancy is often encountered in industrial systems. Evaluation of a simulation model that will be created for the solar photovoltaic system will be used to identify these opportunities. We report on simulation of availability and decision-making using a newly constructed model. Four subsystems namely, solar panel, charge controller, batteries and inverter subsystem, make up the solar photovoltaic current system, with two conceivable states: functional and failing. A Markov-based probabilistic simulated model has been created while taking a few presumptions into account. Each subsystem's availability decision matrix is also created to offer several levels of availability. The performance or availability of each solar photovoltaic subsystem is examined in light of this analysis, and maintenance priorities are then established for the current system. Through the schematic diagram of state of the system, availability model is formulated using mnemonic rule and Chapman-Kolmogorov differential difference equations are developed and solved by Runge-Kutta method of order four.
... Dai et al. [2] performed both reliability and availability analyses for some different complex systems. Gupta et al. [3,4] discussed performance modeling using probabilistic approach and developed Markov model for performance evaluation of a system of coal handling of a thermal power plant. Gupta et al. [5] examined soap production system and flexible powder polymer production system in a soap plant. ...
... Gupta et al. [5] examined soap production system and flexible powder polymer production system in a soap plant. Gupta et al. [4] discussed Mathematical formulation for reliability analysis in terms of availability of a critical ash handling system. Kumar [6] have done availability analysis using Markov approach of air circulation system. ...
In the present stimulated business environment, power sector is playing a major role in the economic growth of India. During the last 20 years, the country had been facing a poor supply of energy and this supply–demand gap is increasing continuously. Therefore, it is important for power plants to improve its power generation capacity drastically by reducing the failure rate. In the present paper, to analyze the causes of poor availability, thermal power plant has divided into six different systems and a system comprising waste gases heating system has been considered. With the help of transition diagram, mathematical equations have been used to find out the availability. After analyzing, it was found that the value of availability is very low and boiler tube failure is one of the most critical factors for this low availability of system. The power plants have low availability causing serious concern and need to identify the responsible factors for this low availability. Boiler tube failure is identified as a responsible factor for low availability, and economizer is the zone where maximum failure occurred. From the maintenance history sheet, it was identified that economizer is a critical zone where maximum tube failures occur and the main cause of economizer failure is due to high-velocity flue gas particle, i.e., erosion. To increase the availability and minimize the failures, erosion process must be reduced in economizer tubes which is mainly responsible for economizer failure and then CFD analysis has been done for this purpose. This results in a decrease in the shutdown period of the plant and an increase in the system availability as well as the power of the system.
... Operating power plants efficiency is very important in the economics of power generation. Gupta et al. [32] describes the thermal power plant as a complex engineering system comprised of various systems: coal handling, steam generation, cooling water, steam and water, crushing, condensate, ash handling, power generation and feed water system. Amongst the several utilities, the power generation system constitutes the most essential part of a thermal power plant. ...
... Power generation system, with whatever may be the operational intentions, i.e. continuous or intermittent, is expected to furnish excellent performance. The high performance of such a power generation system can be achieved with a highly reliable power plant and perfect maintenance [32]. According to Arora and Kumar [33], the hot gases evolved (by coal burning) circulate in the boiler drum, conduct heat to the circulating water and finally leave through the boiler chimney. ...
The present research deals with the opportunities for the availability predictive modeling of a thermal plant using the Markov process and probabilistic approach. These opportunities will be identified by evaluation of a power generation system of a thermal power plant. This feasibility study covers two areas: development of a predictive model and evaluation of performance with the help of the developed model. The present system under study consists of four subsystems with three feasible states: full working, reduced capacity working and failed. Failure and repair rates of all subsystems are assumed to be constant. After drawing a transition diagram, differential equations are generated and then a probabilistic predictive model using Markov approach has been developed, considering some assumptions. The availability matrix for each subsystem is also developed, which provides various availability levels for different combinations of failure and repair rates of all subsystems. On the basis of this study, the performance of a power generation system is evaluated. The developed model helps in the comparative evaluation of alternative maintenance strategies.
... The most useful feature of such kind of computational model is that, it can be used for all kinds of fuels and parameters. An optimal design of the turbine system will be obtained which will provide maximum efficiency for any given set of parameters (Indian Cane Power Limited; Gupta et al., 2009;Hosseini et al., 2006;Kumar et al., 1995). Figure 1. ...
... For direct water (DW) and energy consumptions, three main parts are considered: (1) the production line (blast furnace, converter, ladle furnace, casting and rolling sections); (2) raw material processing (coke, agglomeration, pelletising, and lime); and (3) facilities and washing. The electricity required for steel production is assumed to be generated by power plants located in the steel plant, though electricity might be supplied from national grids (Gupta et al., 2009;Singh et al., 2011). Water needed for power plants is treated as a DW consumption as it is supplied from local water resources. ...
The water footprint concept has been widely applied to the agriculture sector; however, little attention has been given to industrial products. In this paper, the concept of water footprint is applied to a large steel plant located in a semi-arid basin in the central part of Iran. The limitations of existing research, including the lack of any advanced approach for assessing the virtual water of personnel's food, working in the plant, and the lack of providing independent data sources, are addressed. An improved water footprint model of steel production is proposed based on the water footprint network methodology and the life cycle assessment framework. Ideas from food ecological footprint are applied to measure the water footprint of personnel's foods. The case of Iran demonstrates that the water footprint of steel production is considerably large compared with other industrial products. The results highlight the relevance of production line technology, energy efficiency measures, and human management on reducing the water footprint of steel products. The paper adds to a growing body of literature on environmentally friendly steel production.
... Mathematical formulation of the model was carried out using mnemonic rule and the differential equations were solved by Runge-Kutta method. Gupta et al. (2009) assessed the reliability and availability of a critical ash handling unit of a steam thermal power plant using the concept of performance modeling and analysis. Mathematical formulation for reliability of ash handling unit of plant has been carried out using probability theory and Markov birth-death process. ...
In the present work, a recently developed advanced optimization algorithm named as teaching–learning-based optimization (TLBO) is used for the parameters optimization of fabric finishing system of a textile industry. Fabric Finishing System has four main subsystems, arranged in hybrid configuration. For performance modeling and analysis of availability, a performance evaluating model of fabric finishing system has been developed with the help of mathematical formulation based on Markov-Birth-Death process using Probabilistic Approach. Then, the overall performance of the concerned system has first analyzed and then, optimized by using teaching–learning-based optimization (TLBO). The results of optimization using the proposed algorithm are validated by comparing with those obtained by using the genetic algorithm (GA) on the same system. Improvement in the results is obtained by the proposed algorithm. The results of effect of variation of the algorithm parameters on fitness values of the objective function are reported. © 2018 Growing Science Ltd. All rights reserved. and 2017 by the authors; licensee Growing Science, Canada.
... Jain et al. utilized Markov model to study the performance of a machining system with warm spares and heterogeneous servers considering switch failure [21]. Gupta et al. employed Markov birth-death process to analyze the performance of ash handling unit of a steam thermal power plant [22]. Kumar et al. developed a stochastic model to analyze the performance of a two-unit cold standby [23]. ...
Systems operating in risky environments strive for guaranteeing the highest possible availability. This paper addresses the effect of redundancy and components' economy of scale on achieving a high level of availability. An availability estimation model for a 3-out-4 cold standby system was developed and compared with 6-out-8 system. The analysis of the two models revealed that at relatively low availability target, using larger economic components results in higher availability. On the other hand, targeting an extremely high availability requires to scarify the components' economy of scale.
... Deepak, Tri and Mahesh [11] undertook reliability and availability evaluation of Sunkoshi Hydro power station Nepal, during the period of FY 2009/10 to FY 2013/14. Gupta, Tewari and Sharma [12] carried out reliability and availability analysis of the ash handling unit of a steam thermal power plant. ...
... Deepak, Tri and Mahesh [11] undertook reliability and availability evaluation of Sunkoshi Hydro power station Nepal, during the period of FY 2009/10 to FY 2013/14. Gupta, Tewari and Sharma [12] carried out reliability and availability analysis of the ash handling unit of a steam thermal power plant. ...
... • Standby subsystems are of the same nature and capacity as that of active subsystems (Gupta, Tewari and Sharma, 2009b). ...
The present paper deals with the opportunities for the modeling of flue gas and air system of a thermal power plant by making the performance evaluation using probabilistic approach. The present system of thermal plant under study consists of four subsystems with three possible states: full working, reduced capacity working and failed. Failure and repair rates for all the subsystems are assumed to be constant. Formulation of the problem is carried out using Markov Birth-Death process using probabilistic approach and a transition diagram represents the operational behavior of the system. Interrelationship among the full working and reduced working has been developed. A probabilistic model has been developed, considering some assumptions. Data in feasible range are selected from a survey of thermal plant and the effect of each subsystem on the system availability is tabulated in the form of availability matrices, which provides various performance/availability levels for different combinations of failure and repair rates of all subsystems. Based upon various availability values obtained in availability matrices and graphs of failure/repair rates of different subsystems, performance and optimum values of failure/repair rates for maximum availability, of each subsystem is analyzed and then maintenance priorities are decided for all subsystems.
... The maintenance of repairable systems has been widely studied by many authors, considering different focus of interest, such as the repair/replacement policy, periodic inspections, degrading, optimization problems, among other topics [2]. Gupta et al. [3] stated that it is necessary to maintain the thermal power plant to provide reliable and uninterrupted electrical supply for long time. In order to obtain regular and economical generation of electrical power, plant should be maintained at sufficiently high availability level corresponding to minimum overall cost. ...
The present paper discusses the development of a performance model of power generation system of a thermal plant for performance evaluation using Markov technique and probabilistic approach. The study covers two areas: development of a predictive model and evaluation of performance with the help of developed model. The present system of thermal plant under study consists of four subsystems with three possible states: full working, reduced capacity working and failed. Failure and repair rates for all the subsystems are assumed to be constant. A transition diagram represents the operational behavior of the system. A probabilistic model has been developed, considering some assumptions. Data in feasible range are selected from a survey of thermal plant and the effect of each subsystem on the system availability is tabulated in the form of availability matrix, which provides various performance/availability levels for different combinations of failure and repair rates of all subsystems. On the basis of this study, performance of power generation system is evaluated.
... 2. A repaired unit is as good as new, performance wise, for a specified duration [15]. 3. Sufficient repair facilities are provided [16]. 4. ...
This paper discusses the stochastic analysis and performance evaluation of condensate system of a thermal plant. These opportunities will be identified by evaluation of a simulation model to be built for the condensate system. The present system under study consists of six subsystems A, B, C, D, E, and F arranged in series with two feasible states: working and failed. After drawing transition diagram, differential equations are generated and then a probabilistic simulated simulation model using Markov approach has been developed considering some assumptions. Performance matrix for each subsystem is also developed, which provide various availability levels. On the basis of this study, performance of each subsystem of condensate system is evaluated and then maintenance decisions are made for subsystems.
Key words: Transition diagram; Markov approach; Performance matrix; Maintenance decisions.
DOI: 10.3329/bjsir.v44i4.4587
Bangladesh J. Sci. Ind. Res. 44(4), 387-398, 2009
... It is necessary to maintain the steam thermal power plant to provide reliable and uninterrupted electrical supply for long time. In order to obtain regular and economical generation of electrical power, plant should be maintained at sufficiently high availability level corresponding to minimum overall cost [1]. ...
The aim of this study is to develop an availability simulation model that can be used for evaluating the performance of coal crushing system of a thermal power plant using probability theory and Markov birth-death process. The present system under study consists of five subsystems with three possible states i.e. full capacity working, reduced capacity working and failed. Failure and repair rates of all subsystems are assumed to be constant. After drawing transition diagram, differential equations have been generated and solved using recursive approach. Then, steady state availability is determined, which is the developed availability simulation model. Besides, some availability matrices are also developed, which provide various performance or availability levels for different combinations of failure and repair rates of all subsystems. Hence, performance of coal crushing system is analyzed and evaluated. The developed model helps the plant management in getting the information about maximum availability of each of the five subsystems with optimum values of failure/repai r rates and in comparative evaluation of alternative maintenance strategies.
... 6. Sufficient repair facilities are available (Srinath [19]). 7. A repaired system is as good as new, performance wise, for a specified duration (Gupta et al. [36]). 8. System failure/repair follows the exponential distribution. ...
The present paper deals with the opportunities for the availability simulation modelling and maintenance decision making in thermal power plant. These opportunities will be identified by evaluation of a simulation model to be built for the steam and water analysis system (SWAS) of a thermal power plant. This feasibility study covers two areas: development of an availability simulation model and decision making with the help of developed model. The present system of thermal plant under study consists of six subsystems with two possible states: working and failed. A probabilistic simulated model using Markov approach has been developed considering some assumptions. Availability decision matrix for each subsystem is also developed, which provide various availability levels. On the basis of this study, performance or availability of each subsystem of SWAS is analyzed and then maintenance priorities are decided for present system.
... Formulation is carried out using the joint probability functions based on the transition diagram (Gupta et al., 2009). The system starts from a particular state at time 't' and reaches another state (failed) or remain in the same state (operative) during the time interval ∆t. ...
The present paper deals with development of a simulation model for the performance evaluation of feed water system of a thermal power plant using Markov Birth-Death process and probabilistic ap-proach. In present paper, the feed water system consists of four subsystems. After drawing transition dia-gram for feed water system, differential equations are developed and then solved recursively using proba-bilistic approach. Then to predict the steady state availability i.e. measure of performance of feed water sys-tem, normalizing conditions are used. Thus availability simulation model has been developed. After that, the availability matrix and plots of failure/repair rates of all subsystems are prepared to decide the availabil-ity trends. Based upon various availability values in the availability matrix, performance of feed water sys-tem has been evaluated. Further the optimum values of failure/repair rates for maximum system availability have also been determined. The finding of this paper might be helpful to the plant management for futuris-tic maintenance decisions.
... The assumptions used in developing the probabilistic model are: (1) Failure/repair rates are constant over time and statistically independent [7,14] . ...
This paper discusses performance evaluation of the steam and water system in a thermal power plant, with the help of developed probabilistic model. The system consists of six subsystems with two possible states: working and failed. Failure and repair rates for each subsystem are taken to be constant. Using a probabilistic approach, the differential equations are generated. After that, steady state probabilities are determined. Besides, availability matrix is also developed, which provide various availability levels. The performance evaluation reveals that availability figure decreases with increasing failure rates, while operational availability improves with initial increase in repair rates for different sub-systems. Based upon various availability values, performance of each subsystem is analyzed and then maintenance decisions are made for all subsystems.
... 3. Service includes repair and/or replacement, as given by Khanduja et al. (2008) and Sufficient repair facilities are available, as given by Srinath (1994). 4. System failure/repair follows the exponential distribution, as stated by Gupta et al. (2009B).and at any given time, the system is either in operating state or in the failed state, as assumed by Gupta et al. Figure 2 Transition diagram of steam generation unit ...
This paper presents the stochastic analysis and performance evaluation of turbo generator system of a thermal plant by making the use of performance evaluation using probabilistic approach. The steam generator system of thermal power plant under the research study consists mainly sub-systems boiler, super heater and reheater arranged in series with two feasible states: working and failed. Failure and repair rates for all the sub-systems are assumed to be constant. Initially transition diagram representing the operational behavior is drawn and then problem formulation is done using Markov approach. Based on the data collection and its analysis for thermal Power Plant, Performance matrix for each subsystem is also developed. Then from these results, availability matrices and graphs of failure and repair rates for maximum availability of each system is analysed and then condition based maintenance decisions are decided.
... repair rates are constant over time and statistically independent, as stated by Gupta et al. (2009).2.At any given time, the system is either in operating state or in the failed state, as assumed byGupta et al. (2009A). ...
The present paper discusses the development of a Markov model for performance evaluation of coal handling unit of a thermal power plant using probabilistic approach. Coal handling unit ensures proper supply of coal for sound functioning of thermal Power Plant. In present paper, the coal handling unit consists of two subsystems with two possible states i.e. working and failed. Failure and repair rates of both subsystems are taken to be constant. After drawing transition diagram, differential equations have been generated. After that, steady state probabilities are determined. Besides, some decision matrices are also developed, which provide various performance levels for different combinations of failure and repair rates of all subsystems. Based upon various performance values obtained in decision matrices and plots of failure rates/ repair rates of various subsystems, performance of each subsystem is analyzed and then maintenance decisions are made for all subsystems. The developed model helps in comparative evaluation of alternative maintenance strategies.
... Standby subsystems are of the same nature and capacity as that of active subsystems (Gupta, Tewari and Sharma, 2009b). ...
The present paper deals with the opportunities for the modeling of flue gas and air system of a thermal power plant by making the performance evaluation using probabilistic approach. The present system of thermal plant under study consists of four subsystems with three possible states: full working, reduced capacity working and failed. Failure and repair rates for all the subsystems are assumed to be constant. Formulation of the problem is carried out using Markov Birth-Death process using probabilistic approach and a transition diagram represents the operational behavior of the system. Interrelationship among the full working and reduced working has been developed. A probabilistic model has been developed, considering some assumptions. Data in feasible range are selected from a survey of thermal plant and the effect of each subsystem on the system availability is tabulated in the form of availability matrices, which provides various performance/availability levels for different combinations of failure and repair rates of all subsystems. Based upon various availability values obtained in availability matrices and graphs of failure/repair rates of different subsystems, performance and optimum values of failure/repair rates for maximum availability, of each subsystem is analyzed and then maintenance priorities are decided for all subsystems.
Systems operating in risky environments as
weapon systems, hospital energy supply systems, and
broadcasting systems strive for guaranteeing the highest
possible availability. As a matter of fact, redundancy is the vital
solution to the problems of poor availability.
The paper presents the explicit expressions for measuring reliability parameter of systems, Graphs were plotted to highlight important results. Results have shown that measures of system effectiveness such MTSF, system availability and profit increases with repair rates and decreases with failure rates.The developed model helps in determining the optimal maintenance strategies which ensure the maximum overall availability of the system. The optimum values of failure and repair rates for each subsystem were given. It is observed that the first subsystem is having the maximum availability with (97%). The optimum values of failure and repair rates for maximum availability level for each subsystem is also shown.
The paper presents the explicit expressions for measuring reliability parameter of systems, Graphs were plotted to highlight important results. Results have shown that measures of system effectiveness such MTSF, system availability and profit increases with repair rates and decreases with failure rates.The developed model helps in determining the optimal maintenance strategies which ensure the maximum overall availability of the system. The optimum values of failure and repair rates for each subsystem were given. It is observed that the first subsystem is having the maximum availability with (97%). The optimum values of failure and repair rates for maximum availability level for each subsystem is also shown.
Cogeneration plants are one of the major power generation sources in this era of industrialization and automation. Bagasse is a by-product generated by the sugar industries on a large scale in India. The cogeneration plants use the bagasse produced by the sugar industries to generate power. Boiler system forms one of the primary components of the cogeneration plant. Designing a virtual model of the boiler system will help to model optimal systems. Simulation of the performance of the boiler system will aid in predictive maintenance as well. In this paper, a virtual model of a boiler system for a bagasse unit is designed in the LabVIEW software package. Such kind of performance analysis aids in better designs of actual models and predictive maintenance, which in turn saves time and reduces unwanted expenditures due to failures.
The present paper deals with the opportunities for the availability predictive modeling of a thermal plant using Markov process and probabilistic approach. These opportunities will be identified by evaluation of a predictive model to be built for the steam generation system of a thermal power plant. This feasibility study covers two areas: development of a predictive model and evaluation of performance with the help of developed model. The present system under study consists of five subsystems with three feasible states: full working, reduced capacity working and failed. After drawing transition diagram, differential equations are generated and then a probabilistic simulated predictive model using Markov approach has been developed considering some assumptions. Availability matrix for each subsystem is also developed, which provide various availability levels. On the basis of this study, performance of each subsystem of steam generation system is evaluated and then maintenance decisions are made for subsystems.
Purpose
The purpose of this paper is to present the technique for evaluating the performance of a condensate system of a coal-based thermal power plant situated in the northern part of India. The data which used for system availability evaluation are not precise and are uncertain and, further, collected from concerned power plant history sheets and from discussion through plant personnel.
Design/methodology/approach
In the proposed model, traditional Markov birth-death process using a probabilistic approach is used to analyze the performance of a complex repairable condensate system of power plant up to a desired degree of accuracy. This approach has been demonstrated by breaking the condensate system into six subsystems arranged in series with two feasible states, namely, working and failed, labeled in a transition diagram and modeled as a Markov process, using Chapman–Kolmogorov equations, which are used for development of a probabilistic stochastic model for availability analysis in a more effecting manner, considering some suitable assumptions.
Findings
This study of analysis of reliability and availability can help in increasing the plant production and performance. The analysis is done with the help of availability matrices, which are developed using different combinations of failures and repair rates of all subsystems. To achieve the goal of maximum power generation, it is required to run the various subsystem of the concerned system of plant, failure free for a long duration. Therefore, the present approach may be a more powerful analysis tool to access the performance of all subsystems of a condensate system in terms of availability level achieved in availability matrices. The results of present study are found to be highly beneficial to the plant management for making maintenance decisions.
Originality/value
The present paper suggests a suitable technique for stochastic modeling and availability evaluation of an industrial system using Markovian approach and drawing a transition diagram to represent the operational behavior of the system. The present methodology includes the advantage of the ability to model and develop a more complex industrial system and helps in improving the performance and handling the uncertainties and possibilities of an industrial system.
The unscheduled outage of thermal power plants following the Great East Japan Earthquake in 2011 greatly degraded the reliability of the power supply. As thermal power plants were a major part of the supply capacity after the disaster, especially under peak load conditions, consumers located both within and outside the severely damaged area had to reduce power usage to meet power consumption targets and avoid major blackouts. Therefore, experts and decision makers should use the records available from such accidents to determine appropriate margins of supply capacity and demand constraint policy during a crisis. Here, we constructed a probability model describing the likelihood of accident occurrence for thermal power plants based on the actual accident and recovery data obtained after the Great East Japan Earthquake. The lognormal and Weibull hazard models fit the observed data well, where the accidents tended to occur for many times at the same power generation unit under heavy-duty conditions. We then applied the developed probability model to Japanese thermal power plants in a bootstrap framework to understand the potential risk of power shortages during such events and to derive policy implications.
The present paper describes the development of an availability simulation model for Coal handling unit of a thermal plant by making the performance analysis using probabiltic approach. In the present paper, the Coal handling unit consists of five subsystems. Assuming constant failure and repair rates for all the subsystems, the mathematical formulation is based on Markov birth-death process. After drawing the transition diagram, differential equations are generated. After that, steady state probabilities are determined. One availability matrix is also developed, which provides various performance/availability levels for different combinations of failure and repair rates of all subsystems. Based upon various availability values obtained in the availability matrix and graphs of failure/repair rates of different subsystems, performance and optimum values of failure/repair rates for maximum availability of each subsystem are analyzed. Subsequently maintenance priorities are decided for all subsystems.
Many authors have developed models on two units' cold standby system, but little or no attention is paid on series-parallel system involving four types of failures. In this study, measures of system effectiveness such as mean time to system failure (MTSF), steady state availability, busy period and profit function were discussed. The system is analyzed using Kolmogorov's forward equations method. The result has shown that MTSF, steady state availability and profit function increases with repair and decreases with failure rate.
Conventional reliability analysis relies on the probability theory and the binary states i.e. success or failed state of a component or system only. This type of reliability analysis amplifies the uncertainty in computation of system reliability. To overcome this problem, the concept of fuzzy reliability has been used in the evaluation of reliability of the system and the binary states i.e. success and failure of a component or system is viewed in a fuzzy way. Mathematical formulation of the fault-tolerant skim milk powder system is carried out using mnemonic rule and the governing Chapman–Kolmogorov differential equations are solved with fourth order Runge–Kutta method. In this paper, the effect of failure rate, repair rate of each subsystem and coverage factor on fuzzy availability of skim milk powder system is analyzed.
This paper discusses the performance analysis of the furnace draft air cycle in a thermal power plant. The furnace draft air cycle in a thermal power plant has three main subsystems. These subsystems are arranged in series and parallel configurations. For the analysis of availability, formulation of the problem is carried out using Markov Birth-Death process based upon probabilistic approach. Failure and repair rates for all the subsystems have been taken from maintenance history sheets of plant. A transition diagram representing interrelationship among the full working, reduced capacity and failed states has been developed. The effect of failure and repair rates of each subsystem on the system availability has been determined. The results are supplied to the management, which will help to improve the overall performance of the thermal power plant concerned.
Purpose
To define availability importance measures in order to calculate the criticality of each component or subsystem from the availability point of view and also to demonstrate the application of such importance measures for achieving optimal resource allocation to arrive at the best possible availability.
Design/methodology/approach
In this study the availability importance measures of a component are defined as a partial derivative of the system availability with respect to the component availability, failure rate, and repair rate. Analyses of these measures for a crushing plant are performed and the results are presented. Furthermore, a methodology aimed at improving the availability of a system using the concept of importance measures is identified and demonstrated by use of a numerical example.
Findings
The availability importance measure of a component/subsystem is an index which shows how far an individual component contributes to the overall system availability. The research study indicates that the availability importance measures could be applied in developing a strategy for availability improvement. The subsystem/component with the largest value of importance measure has the greatest effect on the system availability.
Research limitations/implications
The result of availability improvement strategy is demonstrated using only a hypothetical example.
Practical implications
Using availability importance measures will help managers and engineers to identify weaknesses and indicate modifications which will improve the system availability.
Originality/value
This paper presents the concept of availability importance measure for a component/subsystem. It also introduces some availability importance measures based on failure rate, mean time between failures (MTBF), and repair rate/mean time to repair (MTTR) of a component /subsystem. The concept of importance measures is used to prioritise the components or subsystems for the availability improvement process.
A “Review Integrity of Critical Equipment” (RICE) programme is presented here. The programme has a systematic structure that facilitates the development of strategic maintenance plans for critical pressure vessels. The programme is based on the reliability, availability and maintainability (RAM)` principles and was developed and applied to Sasol's vessels in order to ensure compliance with future statutory requirements. It is believed that the presented programme will be useful for other users than Sasol.The programme consists of a number of stages; systematic data acquisition, assessment of data and proposed principle inspection plan, acceptance of the plan followed by detailed planning, actual inspection and evaluation of results. The inspection plan is supplemented by proactive measures to solve suspected problems. The paper includes a case study of a critical scrubber vessel in order to illustrate how the programme works.
Closed-form expressions are derived for the steady-state availability, mean rate of failure, mean duration of downtime and lower bound reliability of a general system with randomly and independently failing repairable components. Component failures are assumed to be homogeneous Poisson events in time and repair durations are assumed to be exponentially distributed. The results are expressed in terms of the mean rates of failure and mean durations of repair of the individual components. Closed-form expressions are also derived for the rates of change of the various probabilistic system performance measures with respect to the mean rate of failure and the mean duration of repair of each component. These expressions provide a convenient framework for identifying important components within the system and for decision-making aimed at upgrading the system availability or reliability, or reducing the mean duration of system downtime. Example applications to an electrical substation system demonstrate the use of the formulas developed in the paper.
An update for the commonly used conventional advanced reliability and reliability related areas. Emphasis is on the structure of concepts rather than on mathematical rigor and minute details. For practicing safety and maintenance engineers. Contents, abridged: Engineering reliability mathematics. Reliability optimization. Failure data analysis. Life cycle costing. Power equipment reliability.
The paper explores the application of artificial neural networks to model the behaviour of a complex, repairable system. A composite measure of reliability, availability and maintainability parameters has been proposed for measuring the system performance. The artificial neural network has been trained using past data of a helicopter transportation facility. It is used to simulate behaviour of the facility under various constraints. The insights obtained from results of simulation are useful in formulating strategies for optimal operation of the system.
This paper provides general equations for calculating the time-dependent unavailability, the failure intensity and the distribution of the time to the first undesired event for components with tolerable down times. In many systems undesired events occur later than the components fail, and only if repairs are not completed within a grace period. Explicit equations are presented for several repair and maintenance categories, with ageing and renewed failure and repair characteristics. General methods for time-dependent grace periods and considerations for systems analysis are included.
General analytical models are developed to quantify the frequencies and durations of transients involving loss of off-site power or total loss of alternating current. Such transients are often important initiating events in probabilistic safety studies of nuclear power plants. Recursive equations are developed for the frequencies of production loss events when there is one or more standby systems available and a grace period to start a reserve unit. The methodology is illustrated with numerical applications.
This article is based on a previous study made by Bris, Châtelet and Yalaoui [Bris R, Chatelet E, Yalaoui F. New method to minimise the preventive maintenance cost of series–parallel systems. Reliab Eng Syst Saf 2003;82:247–55]. They use genetic algorithm to minimize preventive maintenance cost problem for the series–parallel systems. We propose to improve their results developing a new method based on another technique, the Ant Colony Optimization (ACO). The resolution consists in determining the solution vector of system component inspection periods, TP. Those calculations were applied within the programming tool Matlab. Thus, highly interesting results and improvements of previous studies were obtained.
The paper aims at assessing the availability of a critical pumping system of the Crude Distillation Unit of a refinery with recourse to the Markovian model. Actual field data on failure and the repair times have been collected and analyzed by fitting exponential distribution. Also a simulation model has been developed for assessing the system availability. The availabilities based on both the analytical and the simulation models have been compared. The simulation model has been used for predicting system availability for varying failure and the repair rates. The repair strategies for the increasing failure rate in order to attain the desired availability have also been discussed in the paper.
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