Optimal imperfect preventive maintenance policy for equipment leased during successive periods

In this paper, we consider randomly failing equipment leased several times during their life cycle with a given warranty period. A mathematical model is developed to determine the optimal efficiency levels of preventive maintenance (PM) to be performed on the equipment between successive lease periods, maximising the expected total profit of the lessor over the equipment life cycle. The model considers the expected leasing revenue as well as the equipment acquisition cost and the average PM and repair costs. PM actions allow reducing the age of the equipment to a certain extent with a corresponding cost depending on the PM level adopted. The efficiency of the PM is determinant of the expected revenue during the next lease period. Given a set of K possible PM levels and the number of lease periods n over the equipment life cycle, K^{n?1 PM} strategies are possible. A genetic algorithm is proposed in order to obtain nearly optimal policies in situations where the number of possibilities K^n?1 is very high. Obtained numerical results are discussed. Small- and big-size instances of the problem are considered in the case of a service company in the oil and gas industry specialised in leasing specific equipment such as separators, to oil companies for production activities with a limited duration of several months like well testing or short production tests.     

Due-window assignment and scheduling with general position-dependent processing times involving a deteriorating and compressible maintenance activity

In this paper, we consider common due-window assignment and scheduling problems with general position-dependent processing times involving deteriorating and compressible maintenance activity on a single machine. Two models associated with maintenance activity are examined in this article, in which the maintenance length is assumed to be either time-dependent and compressible or position-dependent and compressible. The objective is to find jointly the location and size of due-window, position of maintenance as well as resource amount allocated to it, and job sequence to minimise a total cost function based on earliness, tardiness, window location, window size and resource cost. We show that the problem considered in each of the two models’ setting can be optimally solved with polynomial time algorithm by reducing to assignment problem. Finally, two examples are provided to illustrate the solution procedures.     

Dependability and performance stochastic modelling of a two-unit repairable production system with preventive maintenance

In this paper, a two-unit multistate repairable production system is considered in which preventive maintenance (PM) is implemented in order to improve its dependability and performance. A general model is provided for the production system using a semi-Markov process, for examining system’s limiting behaviour. Apart from combining redundancy with PM, we introduce scenarios like imperfect and failed maintenance which are usually met in real life production systems. For the proposed model, we calculate the availability, the mean time to failure and the total operational cost and we formulate optimisation problems settled with respect to the system’s inspection times. The main aim of our work is to determine the optimal inspection times and consequently the optimal PM policies to be adopted in order to optimise system’s dependability and performance.     

Criticality Analysis for Maintenance Purposes: A Study for Complex In‐service Engineering Assets

The purpose of this paper is to establish a basis for a criticality analysis, considered here as a prerequisite, a first required step to review the current maintenance programs, of complex in‐service engineering assets. Review is understood as a reality check, a testing of whether the current maintenance activities are well aligned to actual business objectives and needs. This paper describes an efficient and rational working process and a model resulting in a hierarchy of assets, based on risk analysis and cost–benefit principles, which will be ranked according to their importance for the business to meet specific goals. Starting from a multicriteria analysis, the proposed model converts relevant criteria impacting equipment criticality into a single score presenting the criticality level. Although detailed implementation of techniques like Root Cause Failure Analysis and Reliability Centered Maintenance will be recommended for further optimization of the maintenance activities, the reasons why criticality analysis deserves the attention of engineers and maintenance and reliability managers are precisely explained here. A case study is presented to help the reader understand the process and to operationalize the model. Copyright © 2015 John Wiley & Sons, Ltd.     

TE151A液压站在矿井提升机中的应用及维护

介绍了矿井提升机TE151A液压站的组成及工作原理;阐述了TE151A液压站的日常维护及保养方法;针对TE151A液压站常见的故障现象,分析了可能的故障原因,并提出了相应的解决措施。文章对TE151A液压站操作及维护人员有一定的借鉴作用。     

飞机故障预测与健康管理应用模式研究

针对现有飞机维修机制的不足进行了分析,描述了故障预测与健康管理、视情维修和自主后勤的三者之间的关系。提出了三种典型的故障预测与健康管理(PHM)应用模式,在分析比较现有三种模式优劣的基础上,进一步指出PHM的发展趋势。设计了一种飞机故障预测与健康管理(PHM)系统框架,并运用物联网技术完成了对自主保障系统的构建,能够有效提升飞机的自主保障能力。最后论证了故障预测与健康管理和持续采办与全寿命支持(CALS)之间的关系,为装备采购和全寿命支持提供了技术支持和理论依据。     

电信网络运维阶段风险评估方法研究

安全风险评估是电信网运维阶段安全防护的重要内容,为了深入了解全网的安全状态、控制运行过程中的安全风险,需要建立一套有效的风险评估方法。本文对电信网运维阶段风险评估方法进行研究,提出了一套量化的风险计算方法。该方法不仅可以定量分析网络存在的内在脆弱性和面临的外部威胁,而且可对风险高低情况进行梳理,找出网络运行中的薄弱点,提出安全需求,从而为实施合适的安全防范措施、制定有效的风险控制策略提供理论基础。     

拉丝机步进控制器故障探讨

介绍南京拉丝机步进控制器在使用中的故障现象和解决办法,提出日常维护措施。     

校园网网络安全和维护策略

随着网络技术快速发展和网络应用的不断增多,学校网络信息化也呈快速发展。当前的校园网都已提供了教学、科研、信息交流、资源共享、实时在线互动等教学应用功能,因而校园网在学校的教学中起着重要的作用,但网络应用的增多所带来的网络安全问题也在增多,如病毒传播、黑客入侵、木马植入等,那么,如何加强校园网的安全以及在维护中采取何种策略是校园网维护中所面临的主要问题。本文根据校园网的网络特点以及针对校园网存在的安全问题,提出网络安全的维护策略。     

模拟仿真在高职院校计算机组装与维护实训课程中的应用

在当今各高职院校计算机组装与维护实训室的条件下,很难让学生得到全面的实操练习。将模拟仿真技术应用到高职院校的计算机组装与维护课程的实训教学中,可以较好地弥补当前这一问题,很好的改善了教学效果。该文分析了使用仿真软件的目的和意义,并介绍了实用的仿真环境的建立和使用方法。