Imperfect Preventive Maintenance Policies With Unpunctual Execution.

Traditional maintenance planning problems usually presume that preventive maintenance (PM) policies will be executed exactly as planned. In reality, however, maintainers often deviate from the intended PM policy, resulting in unpunctual PM executions that may reduce maintenance effectiveness. This article studies two imperfect PM policies with unpunctual executions for infinite and finite planning horizons, respectively. Under the former policy, imperfect PM actions are periodically performed and the system is preventively replaced at the last PM instant. The objective is to determine the optimal number of PM actions and associated PM interval so as to minimize the long-run average cost rate. While the latter policy specifies that a system is subject to periodic PM activities within a finite planning horizon and there is no PM activity at the end of the horizon. The aim is then to identify the optimal number of PM activities to minimize the expected total maintenance cost. We discuss the modeling and optimization of the two unpunctual PM policies, and then explore the impact of unpunctual executions on the optimal PM decisions and corresponding maintenance expenses in an analytical or numerical way. The resulting insights are helpful for practitioners to adjust their PM plans when unpunctual executions are anticipated

A review on maintenance optimization

To this day, continuous developments of technical systems and increasing reliance on equipment have resulted in a growing importance of effective maintenance activities. During the last couple of decades, a substantial amount of research has been carried out on this topic. In this study we review more than two hundred papers on maintenance modeling and optimization that have appeared in the period 2001 to 2018. We begin by describing terms commonly used in the modeling process. Then, in our classification, we first distinguish single-unit and multi-unit systems. Further sub-classification follows, based on the state space of the deterioration process modeled. Other features that we discuss in this review are discrete and continuous condition monitoring, inspection, replacement, repair, and the various types of dependencies that may exist between units within systems. We end with the main developments during the review period and with potential future research directions

Warranty service contracts design for deteriorating products with maintenance duration commitments

With the increasing diversification of customers’ demand and purchasing behaviors, more and more manufacturers have focused their attention on the warranty service contracts design. The maintenance duration of the sold product, which plays an important role in the normal production and operation process of the user, is frequently taken into consideration in warranty contracts. In this study, we design different warranty contracts with various combinations of maintenance duration and availability requirements. The manufacturer commits to compensate for each overdue repair or failing to satisfy the availability target. The customers’ choice behavior is described by the multinomial logit (MNL) model, and customers often form their own minimum acceptable levels (also referred to as reference points) of maintenance duration and availability when making purchasing decisions, which have an impact on the contract choice. The expected warranty servicing profit is maximized to determine the optimal price, maintenance duration and availability. Finally, the proposed warranty contracts are demonstrated by numerical examples. We find that the maintenance duration affects not only the warranty cost but also the customer choice, which further affects the optimal contract pricing and profits

A performance-based warranty for products subject to competing hard and soft failures

This article studies a performance-based warranty for products subject to competing hard and soft failures. The two failure modes are competing in the sense that either one, on a "whichever-comes-first" basis, can cause the product to fail. A performance-based warranty not only covers the repair or replacement of any defect, but also guarantees the minimum performance level throughout the warranty period. In this article, we propose three compensation policies—that is, free replacement, penalty, and full refund, when a product's performance fails to meet the guaranteed level. The expected warranty servicing costs for the three policies are derived, based on the competing risks concept. A warranty design problem is further formulated to simultaneously determine the optimal product price, warranty length, and performance guarantee level so as to maximize the manufacturer's total profit. Numerical studies are conducted to demonstrate and compare the three performance-based compensation policies. It is shown that the full refund policy always leads to the lowest total profit, whereas neither of the other two policies can dominate each other in all scenarios. In particular, the free replacement policy results in a higher total profit than the penalty policy when the replacement cost is low, the penalty cost coefficient is high, and/or the product reliability is high

Considering greenhouse gas emissions in maintenance optimisation

Greenhouse gases (GHG) from human activities are the main contributor to climate change since the mid-20th century. Reducing the release of GHG emissions is becoming a thematic research topic in many research disciplines. In the reliability research community, there are research papers relating to reliability and maintenance for systems in power generation farms such as offshore farms. Nevertheless, there is sparse research that aims to optimise maintenance policies for reducing the GHG emissions from systems such as automotive vehicles or building service systems. To fill up this gap, this paper optimises replacement policies for systems that age and degrade and that produce GHG emissions (i.e., exhaust emissions) including the initial manufacturing GHG emissions produced during the manufacturing stage and the emissions generated during the operational stage. Both the exhaust emissions process and the failure process are considered as functions of two time scales (i.e., age and accumulated usage), respectively. Other factors that may affect the two processes such as ambient temperature and road conditions are depicted as random effects. Under these settings, the decision problem is a nonlinear programming problem subject to several constraints. Replacement policies are then developed. Numerical examples are provided to illustrate the proposed methods

Condition-based maintenance policy for systems with a non-homogeneous degradation process

This paper investigates a condition-based maintenance policy for systems subject to a non-homogeneous degradation process. A nonhomogeneous degradation process occurs as a result of deterioration nature and the environmental effect. In the first step, it develops two maintenance models, which consider the constant inspection interval and non-periodic inspection interval. The paper then optimizes a maintenance policy with monotone preventive replacement thresholds. The optimal maintenance decision is shown as a control-limit policy, where the optimal preventive replacement threshold is monotonically decreasing with system age. An illustrative example is presented to show the effectiveness of the proposed maintenance models. The result indicates that preventive replacement can significantly improve the effectiveness of the maintenance policy and sustain system operation

Business Process Management and the Need for Measurements - including an empirical study about operating figures

Problem: Since business process management (BPM) is a very spacious concept, it is influenced from many other concepts, standards and methods that determine its constancy. Companies are asked to restructure their organisation in order to meet internal and external customer demands. The term quality comes to the fore. Organisations such as ISO and the EFQM try to certify or assess companies in terms of the course of their qualitative business processes but do not provide them with helpful implementation tools. One task will be to look at these approaches in a critical perspective in order to assess them with regard to BPM. Further, a company’s performance has to be assessed not only from a one-dimensional perspective. Hence operating figures have to be derived that cover a multi-dimensional assessment perspective in order to show if they meet internal as well as external customer demands. Thus, another task is to assess existing measurement systems with regard to BPM and to show how companies can control and monitor their business process in a better, more effective way. Purpose: The purpose is seen in a processing and comparison of different management concepts and methods in order to present an embracing picture within the area of BPM. The need for measurements will be emphasized, existing performance measurement systems towards BPM analysed and the concept of process controlling presented. In the end a rather practical guideline for the derivation of operating figures will be conceived to overcome acceptance problems SME might have. Several strategic and organisational related hypotheses in the field of operating figures will be investigated that support this approach. The evaluation takes place on the basis of empirical findings within a study of SME but also with help of existing theories. Methodology: This research is based on a combination of the systems and actors approach supplied with quantitative as well as qualitative data, which is collected in form of a questionnaire and via participation on a workshop within the so-called be.st (benchmarking for sustainability) project. This master thesis is conducted as an abductive study. As a consequence, reliability and validity are provided. Conclusions: References and adaptabilities of existing management approaches and measurement systems are pointed out. The further focus lies in an efficient and effective monitoring of business processes in the sense of BPM. On the hypotheses it is dwelled on, most notably on the re-use of operating figures and the most effective derivation method for operating figures- the top-down approach. The role of the management comes hereby to the fore. Findings of the empirical study are presented as well, in relation to the theory. A practical guideline for the derivation and re-use of operating figures and an embracing picture of BPM, its related areas and investigated companies is conceived in the end

Aplicación del mantenimiento preventivo para mejorar la productividad de máquinas de tejido, en la empresa Textil S.A, Lima 2021

Esta investigación tiene como objetivo principal en diseñar un plan de mejora para el mantenimiento preventivo y mejorar la productividad en las máquinas de tejido de la empresa textil utilizando herramientas MP. Para el estudio y diagnóstico de la empresa se utilizó las siguientes herramientas: el diagrama de Ishikawa y Pareto de las cuales mostraron de las 5 principales causas: El exceso de paradas repetitivas, tiempo excesivo entre paradas, falta de equipos y herramientas de medición, falta de experiencia y la falta de capacitación generando la baja productividad por tal razón se decidió aplicar la herramienta TPM. Como resultados de la aplicación del mantenimiento preventivo salieron satisfactorios que permitieron incrementar su productividad en un 2% quiere decir que en el mes de setiembre y octubre incremento 3202 metros de tela más que en los anteriores meses mencionados. En conclusión, el método empleado mejoró la productividad significativamente en la empresa superando la meta establecid

Comparison of the vocabularies of the Gregg shorthand dictionary and Horn-Peterson's basic vocabulary of business letters

This study is a comparative analysis of the vocabularies of Horn and Peterson's The Basic Vocabulary of Business Letters1 and the Gregg Shorthand Dictionary.2 Both books purport to present a list of words most frequently encountered by stenographers and students of shorthand. The, Basic Vocabulary of Business Letters, published "in answer to repeated requests for data on the words appearing most frequently in business letters,"3 is a frequency list specific to business writing. Although the book carries the copyright date of 1943, the vocabulary was compiled much earlier. The listings constitute a part of the data used in the preparation of the 10,000 words making up the ranked frequency list compiled by Ernest Horn and staff and published in 1926 under the title of A Basic Writing Vocabulary: 10,000 Words Lost Commonly Used in Writing. The introduction to that publication gives credit to Miss Cora Crowder for the contribution of her Master's study at the University of Minnesota concerning words found in business writing. With additional data from supplementary sources, the complete listing represents twenty-six classes of business, as follows 1. Miscellaneous 2. Florists 3. Automobile manufacturers and sales companie