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International Encyclopedia of Robotics: Applications and Automation Volume 3 Complete Document

1988 Edition, January 1, 1988

Complete Document



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Active, Most Current

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ISBN: 9780470172315
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Product Details:

  • Revision: 1988 Edition, January 1, 1988
  • Published Date: January 1988
  • Status: Active, Most Current
  • Document Language: English
  • Published By: John Wiley and Sons (WILEY)
  • Page Count: 748
  • ANSI Approved: No
  • DoD Adopted: No

Description / Abstract:

INTRODUCTION

Reliability engineering, as a separate engineering discipline, originated in the United States during the 1950s. The increasing complexity of military electronic systems generated failure rates that resulted in substantially reduced availability. The problems of diagnosing and repairing the new complex equipment became more and more time consuming and seriously affected the availability. The cost of spares, training, and other logistical support became excessive. In 1952, the U.S. Department of Defense and the electronics industry jointly set up the Advisory Group on Reliability of Electronic Equipment. This was in fact the start of the development of reliability engineering. Much was published on the cost-benefit analysis of improving reliability, to show that effort and resources expended during the early design and test period of equipment led to reductions in in-service costs that exceeded the reliability program expenditure. More and more textbooks on using statistics in reliability estimation were written.

Reliability engineering has become indispensable for the large and sophisticated industries with high potential risks, such as aircraft building, nuclear power generation, and chemical plants. It is obvious that the concepts of reliability and availability have become of vital importance for smaller-scale production equipment. Efficient use of production installations requires economic balancing of reliability improvements against costs of unavailability. Therefore, insight into the effects of failures on production or safety is necessary. As software has recently become more and more important to the industry for management decision support systems and for the control of complex technical systems (eg, AS/RS, FMS, robots), software errors can be extremely serious. For this reason, software reliability has become an interesting topic in reliability engineering. Although the reliability of the manufactured products is, of course, important from the point of view of customer servicing, it will not be discussed here.

In this text, attention will be focused on the interaction between the reliability of equipment and the maintenance program. Reliability is defined as the probability that an item will perform a required function under stated conditions for a stated period of time. Reliability and maintenance considerations are important in each stage of the equipment life, as illustrated in Table 1. In this context, maintenance means more than repairing or replacing failed components [breakdown or corrective maintenance (CM)]. Maintenance also means setting up a preventive maintenance (PM) program in order to reduce the number of breakdowns and to increase the reliability and availability of the system. Finding an efficient program consists of drawing up appropriate checklists for each piece of equipment, choosing the right condition-monitoring equipment, determining the frequency of the PM jobs and the PM/CM ratio, and looking for an optimal scheduling of production and maintenance jobs. The costs that are to be taken into account are, on the one hand, direct costs such as labor and materials (eg, spare parts), and on the other hand, indirect costs such as production losses due to failures of the production equipment. Another aspect of the maintenance policy is the design-out maintenance (DOM). The purpose ofDOM is either to improve the equipment in such a way that the required maintenance decreases or to improve the maintainability of the installations; that is, maintenance jobs become easier and can be done faster than before. In the literature many models taking into account the previous factors may be found. Some other, logistical aspects, such as availability of spare parts or the maintenance crew, are very often overlooked.

This article consists of three sections. Reliability Estimation in Practice reviews some basic concepts and statistical functions frequently used in reliability studies. Next, the available methods for reliability estimation of complex equipment are discussed. Most of these techniques apply to the design stage. In Maintenance of Equipment, a short introduction to maintenance engineering is presented. Attention is focused on the aspects that are relevant in the context of reliability engineering. To start with, some definitions and some elementary statistical analysis of maintenance data useful for reliability calculations are mentioned. Next, the possible influence of some organizational features of the maintenance department on the reliability of the equipment is discussed. Some maintenance models found in the literature are reported. Reliability/Maintenance Models covers examples of replacement models (agebased, block-based) and some extensions of these traditional models.