Optimizing the performance of a repairable system under a maintenance and repair contract

In this article a number of maintenance models for finite horizons are reviewed. These methods have not been applied as frequently as their infinite horizon counterparts, and yet are very much applicable to systems under maintenance and repair contracts. The emphasis in this paper is on repairable systems under maintenance and repair contracts, where the decision has to be made whether and when to repair or replace the system. Based on a case study, a new finite horizon model will be constructed and new approaches to analyze and improve repair/replacement decisions under a finite horizon introduced. Finally, the meaning of ‘risk’ and ‘criticality’ in the context of maintenance contracts will be discussed and quantified. Copyright © 2007 John Wiley & Sons, Ltd.     

电子设备回收网络决策模型研究

为了便于电子企业在开展电子设备回收业务前定量决策回收网络的规模,在分析现有回收过程特点和决策模型的基础上,提出了四阶段电子设备回收过程模型,并以此为基础,构建了相应的回收网络决策模型.该模型以最低费用为目标构建目标函数,重点考虑物料平衡以及废弃率和翻新率.该模型包含了网络的五项运输费用,七项新建回收中心或外协费用,以及三项政府资助费用,二十二项限制条件.最后通过一个实际算例验证了其有效性.     

Systematic approach for the gap analysis of business processes

Process benchmarking and business process re-engineering (BPR) have become two main methodologies used to implement business process improvement and have attracted much attention in a current fast-changing environment. Leveraging best practice has become the important factor of process benchmarking and BPR. Accurate knowledge of the gaps between best practice processes and a company's business processes is essential for the redesign of business processes. This paper proposes a systematic enterprise model comparison approach to assist a project team in business process gap analysis (BPGA). A three-phased framework including business process modelling, object semantic analysis phase and process gap analysis phase was developed. An approach of applying the concepts of semantic similarity analysis to find the semantic-related objects in different processes was also proposed. In addition, a set of process path patterns and an alternative process path analysis method was developed to facilitate the processed data and process logic gap analysis between two processes. With the proposed BPGA approach, project teams will understand and redesign their processes more effectively.     

Integrated reliability analysis system (IRAS)

This paper will introduce a computer aided reliability analysis system, IRAS, which is a Unix-based software package. It provides the following features: a model builder, failure mode effect and criticality analysis (FMECA), fault tree synthesis and analysis (FTA) and real time fault location (RTFL). 1. The model builder allows the creation of reliability models for production systems, which are able to reflect the initiation and propagation of serious deviations outside the production and performance tolerances. The modelling procedure allows hierarchical modelling. 2. The failure mode effect and criticality analysis (FMECA) option uses the causal trees and cause-consequence diagrams that are created automatically from the IRAS model data base. The trees can be analysed by the user and the basic events can be grouped according to their criticality, probability and severity. 3. The fault tree analysis and synthesis (FTA) option enables the graphical analysis of fault trees. The generated tree can be trimmed automatically or by the user. It is also possible to extract the minimal cut-set from the complete tree. 4. RTFL enables the fast detection of the most probable fault locations in the system, during the continuous measuring of sensors of the production system and comparing the signals with the expected values of the stored operational vector. It alarms the user in case of serious deviations, thus reducing the out of work stage of the system by making quicker and more efficient reaction of the maintenance facility operators. The failure searching time reduction results in lower maintenance cost.     

UO2芯块运输容器核临界安全分析

目的 在开展二氧化铀（UO₂）芯块运输容器设计时,应进行临界安全分析,优化容器设计,并通过得出的临界安全指数（CSI）限定可运输货包的数量,确保在任何可信的运输情景下的核临界安全。方法 文中采用蒙特卡罗软件SuperMC对符合要求的国际临界安全手册中6类49个基准实验案例进行建模计算,获得本案例的次临界上限值,再基于运输容器经受正常运输条件与运输事故条件试验的结果,计算得出正常运输条件与运输事故条件下的单货包与货包阵列的最大中子增殖系数keff值。结果 该案例的次临界限值（USL）为0.91974;UO₂芯块运输容器在正常运输条件与运输事故条件下单货包的最大keff值分别为0.286 08,无限阵列货包的最大keff值为0.798 34。结论 UO₂芯块运输容器在正常运输条件与运输事故条件下的最大keff值均小于0.919 74,临界安全指数为0,容器设计临界安全性能可确保可运输安全。     

Considerations in the use of optimal preventive maintenance policies

Designing products which require maintenance always involves compromises between reliability and maintainability. Both scheduled and preventive maintenance (PM) should be considered in the design phases of a product so that the design can include features to ease the maintenance task. In addition, many design decisions based on Failure Modes and Effects Criticality Analysis (FMECA), Pareto criticality rankings, etc., could and should be strongly influenced by the potential for using preventive maintenance. A component that has a major negative impact on system reliability (because of its life distribution) could become much less consequential if appropriate PM policies are implemented. This paper describes the use of an easy-to-implement analysis procedure to assist a designer or systems analyst in making the reliability/maintainability tradeoff.     

A Failure Mode Effect and Criticality Analysis of Conventional Milling Machine Using Fuzzy Logic: Case Study of RCM

The purpose of this paper is to select the appropriate maintenance strategies for each failure mode of functionally significant item of conventional milling machine. In order to describe the criticality analysis of conventional milling machine, this paper presents a study on reliability‐centered maintenance with fuzzy logic and its comparison with conventional method. On the basis of fuzzy logic, failure mode and effect analysis is introduced integrating with fuzzy linguistic scale method. After that, weighted Euclidean distance formula and centroid defuzzification is used for calculating risk priority number. The results indicate that based on risk priority number, value criticality ranking was decided, and appropriate maintenance strategies were suggested for each failure mode. It also reflects that a more accurate ranking can be performed by the application of fuzzy logic using linguistic rule to failure mode and effect analysis. Copyright © 2016 John Wiley & Sons, Ltd.     

A Fuzzy Cognitive Maps Tool for Developing a RBI&M Model

A proper maintenance plan is directly related to the definition of critical indexes for ensuring a high level of safety and high level in service quality for all equipments in the plants. The traditional approach, according to risk‐based inspection and maintenance (RBI&M), requires that each parameter considered in the definition of critical indexes shall be divided into intervals in order to assign it a score. By the elaboration of these scores, the critical indexes are calculated. However, what are the rules that allow the company the definition of the range and the assignment of the relative score? Are these rules subjective or objectives? Literature in the field highlights that these decisions are often carried out by maintenance managers. In order to overcome this approach, in this paper, a method based on Fuzzy Cognitive Maps (FCMs) is presented. FCMs have been used for structuring and supporting decisional processes. The criticality of equipments is described in terms of concepts affecting its functioning. No ranges or scores are defined, but only structural and functional features are considered in order to define a criticality index. The resulting fuzzy model can be used to analyse, simulate, test the influence of concepts and predict the behaviour of the system. The RBI&M model, proposed in this work, has been analysed through a case study of an Italian refinery Copyright © 2014 John Wiley & Sons, Ltd.     

Analysis of on-line maintenance strategies for -out-of- standby safety systems

The objective of this paper is to compare the performance of three on-line test and maintenance strategies (corrective maintenance, preventive maintenance and predictive maintenance) for standby k-out-of-n safety systems. Each channel of the k-out-of-n system is modelled by an age-dependent unavailability model to reflect the effect of maintenance on the aging process. The system unavailability, the probability of spurious operation and the overall cost under the above maintenance strategies are analyzed and compared to obtain the optimal maintenance strategy. Sensitivity analyses are performed to reveal the effect of different model parameters on the system performance. A standby safety system in Canadian Deuterium–Uranium (CANDU) Nuclear Power Plants (NPPs), the Shutdown System Number One (SDS1), is used to illustrate the proposed analysis and the procedure. It is concluded that maintenance should neither be performed too frequently nor too rarely. When the system deteriorates very slowly, the corrective maintenance is more preferable than the preventive and predictive maintenance. When the failure rate of the system is high, the preventive maintenance results in the best system performance.     

Analysis of investments in autonomous maintenance activities

In this paper, we model the situation where operator maintenance activities improve the failure process of equipment. We analyze the business decision to reduce both the mean and variance of the production cycle time and the overall inventory level through an investment in planned autonomous maintenance. We answer: (i) when do optimal autonomous maintenance decisions most improve inventory levels?; and (ii) how do capacity restrictions, equipment characteristics the maintenance response function, and product characteristics impact the autonomous maintenance investment decision? Extensive numerical analyses are performed to develop an approximation to the optimal response for both inventory and autonomous maintenance investments over a wide range of problem parameters. Our solutions provide guidelines on how much time should be invested in autonomous maintenance activities and describe when companies can most benefit from autonomous maintenance programs that increase equipment reliability. We determine the investment in autonomous maintenance activities as a function of available capacity, equipment reliability and demand characteristics.     

From Drafting to Modern Design Representation: The Evolution of Engineering Design Graphics

This paper briefly reviews the evolution of Engineering Design Graphics (EDG) from ancient times to the modern era. It reports on recent research concerning educational aspects of design representation and its transition from the immediate past dominated by engineering drawings to the current state based on solid geometric modeling. This research resulted in a current EDG curriculum model which is presented here in some detail. On-going trends in design representation are indicated which suggest that in the near future a designer will create a single computer-based product model to be used for all aspects of design, analysis, production, and maintenance. To keep abreast with these advances in design representation, curricular changes in Engineering Design Graphics are proposed which will foster implementation of Computer-Aided Design and Manufacturing (CAD/CAM) programs of the near future.     

A maintenance driven scheduling cockpit for integrated production and maintenance operation schedule

The production and maintenance functions have objectives that are often in contrast and it is essential for management to ensure that their activities are carried out synergistically, to ensure the maximum efficiency of the production plant as well as the minimization of management costs. The current evolution of ICT technologies and maintenance strategies in the industrial field is making possible a greater integration between production and maintenance. This work addresses this challenge by combining the knowledge of the data collected from physical assets for predictive maintenance management with the possibility of dynamic simulate the future behaviour of the manufacturing system through a digital twin for optimal management of maintenance interventions. The paper, indeed, presents a supporting digital cockpit for production and maintenance integrated scheduling. The tool proposes an innovative approach to manage health data from machines being in any production system and provides support to compare the information about their remaining useful life (RUL) with the respective production schedule. The maintenance driven scheduling cockpit (MDSC) offers, indeed, a supporting decision tool for the maintenance strategy to be implemented that can help production and maintenance managers in the optimal scheduling of preventive maintenance interventions based on RUL estimation. The simulation is performed by varying the production schedule with the maintenance tasks involvement; opportune decisions are taken evaluating the total costs related to the simulated strategy and the impact on the production schedule.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00380-z     

A fuzzy knowledge based method for maintenance planning in a power system

The inspection planning in electric power industry is used to assess the safety and reliability of system components and to increase the ability of failure situation identification before it actually occurs. It reflects the implications of the available information on the operational and maintenance history of the system. The output is a ranked list of components, with the most critical ones at the top, which indicates the selection of the components to be inspected.In this paper, we demonstrate the use of a fuzzy relational database model for manipulating the data required for the criticality component ranking in thermal power systems inspection planning, incorporating criteria concerning aspects of safety and reliability, economy, variable operational conditions and environmental impacts. Often, qualitative thresholds and linguistic terms are used for the component criticality analysis. Fuzzy linguistic terms for criteria definitions along with fuzzy inference mechanisms allow the exploitation of the operators' expertise.The proposed database model ensures the representation and handling of the aforementioned fuzzy information and additionally offers to the user the functionality for specifying the precision degree by which the conditions involved in a query are satisfied.In order to illustrate the behavior of the model, a case study is given using real inspection data.     

Resources assignment model in maintenance activities scheduling

This paper proposes an analytical model for resources assignment in the context of maintenance activities scheduling. It takes into account the human as well as material resources availability constraints. It allows the decision maker to consider not only the preventive maintenance activities but also the potential failures which may occur during the scheduling horizon. Opportunistic maintenance may be considered as an option to improve the occupational rate mainly for maintenance operators. Additional constraints such as the completion time of some specific maintenance activities and the earliest starting works on a given machine may easily be considered in the model. Recall that the main purpose of this paper is to suggest an improved model for resources assignment to be implemented into a planning and scheduling module in CMMS software. The proposed model generates a feasible plan and makes sensitivity analysis possible in order to take into account the material and human resources fluctuations. A numerical example has been treated in order to illustrate the modelling process and to validate the coherence of the model. An attempt is made to develop a generic model which must be flexible and user friendly. Authors are investigating many other extensions of this work to fulfil some specific needs for the company which develops CMMS software. For the illustrative example presented in this paper, the explicit form of the mathematical model is provided in the Appendix of the paper.     

Spreadsheet modeling of optimal maintenance schedule for components in wear-out phase

This paper addresses a method for determining the optimum maintenance schedule for components in the wear-out phase. The interval between maintenance for the components is optimized by minimizing the total cost. This consists of maintenance cost, operational cost, downtime cost and penalty cost. A decision to replace a component must also be taken when a component cannot attain the minimum reliability and availability index requirement. Premium solver platform, a spreadsheet-modeling tool, is utilized to model the optimization problem. Constraints, which are the considerations to be fulfilled, become the director of this process. A minimum and a maximum value are set on each constraint so as to give the working area of the optimization process. The optimization process investigates n-equally spaced maintenance at an interval of Tr. The increase in operational and maintenance costs due to the deterioration of the components is taken into account. This paper also performs a case study and sensitivity analysis on a liquid ring primer of a ship's bilge system.     

Time-based replacement policies for a fault tolerant system subject to degradation and two types of shocks

A single component nonrepairable system suffering from both an internal stochastic degradation process and external random shocks is investigated in this paper. More specifically, the Wiener process with a positive drift coefficient is introduced to describe the gradual deterioration and the arrival number of external shocks is counted with a nonhomogeneous Poisson process (NHPP). Meanwhile, fault tolerant design is incorporated into the stochastically deterioration system so as to protect it from shock failures to some extent and is consummately addressed via a generalized m − δ shock model. From the actual engineering point of view, external shocks are typically classified into two distinct categories in this current research, that is, a minor shock (Type I shock) increasing the damage load on current degradation level and a traumatic shock (Type II shock) resulting in system catastrophic failure immediately. The closed-form expression of system survival function is derived analytically and is viewed as the generalization of existing reliability function for systems subject to dependent and competing failure processes. Based on which, two time-based maintenance (TBM) policies including an age replacement model and a block replacement model are scheduled, where the expected long-run cost rate (ELRCR) in each model is, respectively, optimized to seek the optimal replacement interval. In the illustrative example part, a subsea blowout preventer (BOP) control system is arranged to validate the theoretical results numerically. To compare which policy is more profitable under different conditions, the relative gain on optimal maintenance cost rate of the two TBM policies is presented.     

Adaptive sequential predictive maintenance policy with nonperiodic inspection for hard failures

This paper proposes a novel adaptive maintenance policy for degrading systems subject to hard failure. Compared with traditional condition-based maintenance policies, the proposed predictive maintenance policy makes maintenance decisions adaptively based on model prognostic results. The prognostic model is continuously updated based on newly inspected data. The inspection times and preventive maintenance activities are scheduled online in a sequential manner based on the most current prediction of system reliability. A computationally efficient optimization scheme is proposed for obtaining optimal maintenance parameters. The proposed policy is demonstrated and its performance is evaluated through extensive simulations.     

维修管理模式对制造企业质量控制影响的实证研究

可靠的设备预防维修水平和卓越的产品质量保证能力是保障产品过程质量的关键,现有多数研究集中在质量管理模式与企业绩效的关系分析。在对过程质量控制、设备维修管理评述的基础上,探讨了设备维修管理模式与维修绩效及过程质量控制绩效间的关系。以国内制造企业的连续生产方式为研究对象,运用结构方程模型剖析了RCM、TPM、设备采购管理与和设备维修绩效、过程质量控制绩效的路径关系,发现基础维修管理活动对维修绩效有间接影响,RCM、TPM对设备维修绩效有显著影响,路径系数分别为0.346、0.717,设备维修绩效对过程质量控制绩效的影响显著,路径系数为0922。证明制造企业为提升产品质量,需要完善其设备预防维修系统。     

A genetic algorithm approach for production scheduling with mould maintenance consideration

The traditional approach for maintenance scheduling concerns single-resource (machine) maintenance during production which may not be sufficient to improve production system reliability as a whole. Besides, in the literature many researchers schedule maintenance activities periodically with fixed maintenance duration. However, in a real manufacturing system maintenance activities can be executed earlier and the maintenance duration will become shorter since less time and effort are required. A practical example is that in a plastic production system, the proportion of machine-related downtime is even lower than mould-related downtime. The planned production operations are usually interrupted seriously because of the mismatch among the maintenance periods between injection machine and mould. In this connection, this paper proposes to jointly schedule production and maintenance tasks of multi-resources in order to improve production system reliability by reducing the mismatch among various processes. To integrate machine and mould maintenance tasks in production, this paper attempts to model the production scheduling with mould scheduling (PS-MS) problem with time-dependent deteriorating maintenance schemes. The objective of this paper is to propose a genetic algorithm approach to schedule maintenance tasks jointly with production jobs for the PS-MS problem, so as to minimise the makespan of production jobs.     

DFSME: design for sustainable manufacturing enterprises (an economic viewpoint)

Design for sustainable manufacturing enterprise (DFSME) is considered to be a new ideologue regarding survival of manufacturing enterprise and it can also be considered as one of the most important solutions to deal with the existing global financial crisis. The DFSME is a systemic approach that simultaneously determines the aspects of sustainability and how they can be aggregated taking into consideration the globalisation issues. The problem addressed in this paper is how to present the concepts of sustainability to guide manufacturing enterprises analysts and designers with the most effective aspects for analysing sustainability. These aspects are: international issues; contemporary issues; innovative products; reconfigurable manufacturing systems; manufacturing strategies; business models; flexible organisation management; manufacturing strategies and performance measurements. Based on these aspects, the sustainable model will be analysed and presented through covering all aspects of sustainable manufacturing enterprise and the sustainability assessment will be measured. The ultimate goal of this paper is to consider the needs of manufacturing enterprise throughout most of the world to be sustainable as well as to be globalised enterprises. This analysis shows that the DFSME is a very large task and should be taken into consideration as one aspect of the next industrial revolution.