SEYYED ALI Mirnezhad; Parham Azimi; Ahmad Yousefi Hanoomarvar
Abstract
In the present study, the redundancy allocation problem (RAP) of series-parallel system has been investigated to maximize the system's availability. To achieve the research objective, budget, weight and volume constraints, and the maximum and minimum number of elements assigned to each subsystem have ...
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In the present study, the redundancy allocation problem (RAP) of series-parallel system has been investigated to maximize the system's availability. To achieve the research objective, budget, weight and volume constraints, and the maximum and minimum number of elements assigned to each subsystem have been considered. The main innovation of this research is to consider the failure and repair rates of components with non-exponential distribution function in the process of optimization. Taking into account failure and repair rate via non-exponential distribution function makes it impossible to calculate accessibility using mathematical relations. Therefore, the present study has used simulation method to calculate system availability. Since the simulation has no optimization capability On the other hand, in the redundancy allocation problem, it is necessary to evaluate the system availability recurrently in order to find the optimal solution. Further, due to the high degree of difficulty of developed mathematical function, the genetic metaheuristic algorithm was used to solve it. Finally, the efficiency of the genetic algorithm was measured against particle swarm algorithm and simulated annealing algorithm. To compare fairly, the parameters affecting the algorithms are adjusted using the Taguchi method and the algorithms are in their best practice. The computational results prove the high ability of the genetic algorithm in optimizing the concerned problem.
Arman Sajedinejad; Meysam Lotfi
Abstract
In this paper, a non-periodic preventive maintenance scheduling optimization model for multi-component systems is provided based on the maximum availability of system components. In addition to providing the required level of system reliability and satisfy other system constraints (maintenance activities ...
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In this paper, a non-periodic preventive maintenance scheduling optimization model for multi-component systems is provided based on the maximum availability of system components. In addition to providing the required level of system reliability and satisfy other system constraints (maintenance activities and available resources), total costs (direct and indirect) associated with minimal maintenance and, if necessary, one of the maintenance activities include in inspected and serviced simple, preventive repair and preventive replacement for each component, is proposed. Each of these activities uses various sources and regarding the position of the repairing component, effects differently on the reliability of the system. The costs considered include in direct costs (simple service, repair and replacement) as well as indirect costs (out of order and random failures). Since the proposed model has a complex structure, in order to solve the problem, the Genetic Algorithm (G.A) has been used and the results is presented. In the end, performance and use of this model, for a 10-part series - parallel is presented in the form of a case study.
Seyed Alireza Mir Mohammad Sadeghi*,; Mahdi Moghan; Mahdi Keshavarz; Mehrnoosh Keshavarz; Fatemeh Khaje Nori
Abstract
Subway network extension, growing expansion an inherent management complexities, made it necessary to use scientific approach, modern technology and global experiences about maintenance. Many equipments and trains of subway network, consist of repairable items which consume considerable human and financial ...
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Subway network extension, growing expansion an inherent management complexities, made it necessary to use scientific approach, modern technology and global experiences about maintenance. Many equipments and trains of subway network, consist of repairable items which consume considerable human and financial resources of the organization. This paper aims to measure the efficiency and rank ventilation system of Tehran's DC trains and it's subsystems using three-stage relational data envelopment analysis model. About the importance of Tehran’s subway ventilation system, we can say that for 8 months of the year, ventilation system after driving engines which support the movement of trains, gets most important attention of operation management. In this paper with defining ventilation system as decision-making units, we use it to evaluate the system performance and ultimately for maintenance strategy, including an estimate of the maintenance workshop capacity, spare parts and requiring labor. Due to various errors such as human errors, machinery errors, limitations of field data analysis and etc, in this paper fuzzy logic is used to overcome the uncertainly in data. Also, reliability, availability and maintainability analysis, which are most important indicators in the maintenance field, have been used to determine the ventilation system inputs and outputs
Reza Alikhani; Mahmoud Saremi
Abstract
The scheduling of preventive maintenance and replacement is one of the crucial issues in the literature of system reliability and maintenance engineering. The importance of this issue is more evident in series system in which by stopping a component the whole system will stop. However, the quest of the ...
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The scheduling of preventive maintenance and replacement is one of the crucial issues in the literature of system reliability and maintenance engineering. The importance of this issue is more evident in series system in which by stopping a component the whole system will stop. However, the quest of the efficient periodicity maintenance for all of component of a system which has antagonistic objectives is not a trivial task. The aim of this paper is to presenting scheduling model of preventive maintenance and replacement for series system by variable and not predetertmined periods and also by applying inflation in the model. The model is designed based on fuzzy multi-objective and integer non-linear programming. Also the proposed model is solved for a case study with numerical example and furthermore, analysis of various senarios, the effects of inflation on the model will be considered. The results show that applying inflation in the model changes not only scheduling for replacement and maintenance, but also affects the effective age of components
Mehran Khalaj; Amir Hossine Khalaj; Jalal Talebi
Abstract
Manufacturing systems are always facing different kinds of risk such as failure and interruption risk. Performance risk analysis of manufacturing systems cause errors happening in the prediction of parameters and will also result in wrong decisions where the real and appropriate data is not available. ...
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Manufacturing systems are always facing different kinds of risk such as failure and interruption risk. Performance risk analysis of manufacturing systems cause errors happening in the prediction of parameters and will also result in wrong decisions where the real and appropriate data is not available. In uncertainty condition there is no appropriate data for decision making and in the specific mode of uncertainty the decision maker faces with a lack of information. Risk is a state of uncertainty that the available information from background of system is incomplete. Risks in manufacturing systems are directly related with failure to achieve the reliability of machines. So in this paper the records and the relationship between risk and reliability have been studied, then a model is proposed using Dumpster-Shafer theory to maximize the reliability according to the existing risk. Since the exact calculation of reliability for complex systems and processes is extremely difficult and complicated when the correct data of failure is not available, newly proposed model uses Dumpster-Shafer theory that enjoys all the available data for decision making instead of using the purely qualitative methods. Using this method results in obtain the risk ranges for equipment and machinery. These ranges are drawn in a risk analysis matrix according to the relationship between risk and reliability of machinery and the changes have been determined in order to meet the lower risk. All the proposed methods are examined using the data of a manufacturing company, the concentration of evaluating the reliability is on using the Probability theory in which the failure time is predicted by determining type of component failure distribution while the research provides change in attitude for applying the simultaneous use of possibility and probability theory
Ali Khatami Firouzabadi; Ali Khoramrooz
Volume 4, Issue 12 , March 2006, , Pages 45-71
Abstract
Experiments have shown the most important factor in leakage of gas pressure stations are taps. Gas leakage in industrial environment has hazardous effects.so, there is important to consider the same factors in these environments. To recognize these factors, it is necessary to represent the importance ...
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Experiments have shown the most important factor in leakage of gas pressure stations are taps. Gas leakage in industrial environment has hazardous effects.so, there is important to consider the same factors in these environments. To recognize these factors, it is necessary to represent the importance of avoiding these events by risk evaluation methods. Fault tree analysis is a method which can recognize the fault points in a system and it is able to obtain the probability of these events. To analyze the problem, fault tree of each region in the gas station is drawn. Then the data of these regions (including the probability of failure parts) are entered to FTA software. The outputs of software can be used to analyze the system. The outputs show that the most part of leakage caused by refnenet gas region which turbines are activated. Finally, some procedures are suggested for preventive of leakage in gas stations.
aliasghar tanha
