Reliability, Maintainability and Risk

Practical Methods for Engineers including Reliability Centred Maintenance and Safety-Related Systems

David J. Smith

• Publisher: Butterworth-Heinemann
• Year: 2005
• ISBN:
  9780080458939
• Edition: 7
• Topic: Business
• Subtopic: Operations
• Index: Business

For over 30 years, Reliability, Maintainability and Risk has been recognised as a leading text for reliability and maintenance professionals. Now in its seventh edition, the book has been updated to remain the first choice for professional engineers and students. The seventh edition incorporates new material on important topics including software failure, the latest safety legislation and standards, product liability, integrity of safety-related systems, as well as delivering an up-to-date review of the latest approaches to reliability modelling, including cutsec ranking. It is also supported by new detailed case studies on reliability and risk in practice.*The leading reliability reference for over 30 years
*Covers all key aspects of reliability and maintenance management in an accessible way with minimal mathematics - ideal for hands-on applications
*Four new chapters covering software failure, safety legislation, safety systems and new case studies on reliability and risk in practice

Part One

Understanding Reliability Parameters and Costs

Outline

Chapter 1: The history of reliability and safety technology

Chapter 2: Understanding terms and jargon

Chapter 3: A cost-effective approach to quality, reliability and safety

1

The history of reliability and safety technology

Publisher Summary

Because no human activity can enjoy zero risk, and no equipment can enjoy a zero rate of failure, there has grown a safety technology for optimizing risk. Although safety/Reliability engineering has not developed as a unified discipline, it has grown out of the integration of a number of activities which were previously the province of the engineer. The design of safety-related systems has evolved partly in response to the emergence of new technologies but largely as a result of lessons learnt from failures. The application of technology to hazardous areas requires the formal application of this feedback principle in order to maximize the rate of reliability improvement. Nevertheless, all engineered products will exhibit some degree of reliability growth, as mentioned above, even without formal improvement programs. Reliability engineering, beginning in the design phase, seeks to select the design compromise that balances the cost of failure reduction against the value of the enhancement.

Safety/Reliability engineering has not developed as a unified discipline, but has grown out of the integration of a number of activities which were previously the province of the engineer.

Since no human activity can enjoy zero risk, and no equipment a zero rate of failure, there has grown a safety technology for optimizing risk. This attempts to balance the risk against the benefits of the activities and the costs of further risk reduction.

Similarly, reliability engineering, beginning in the design phase, seeks to select the design compromise which balances the cost of failure reduction against the value of the enhancement.

The abbreviation RAMS is frequently used for ease of reference to reliability, availability, maintainability and safety-integrity.

1.1 FAILURE DATA

Throughout the history of engineering, reliability improvement (also called reliability growth) arising as a natural consequence of the analysis of failure has long been a central feature of development. This ‘test and correct’ principle had been practised long before the development of formal procedures for data collection and analysis because failure is usually self-evident and thus leads inevitably to design modifications.

The design of safety-related systems (for example, railway signalling) has evolved partly in response to the emergence of new technologies but largely as a result of lessons learnt from failures. The application of technology to hazardous areas requires the formal application of this feedback principle in order to maximize the rate of reliability improvement. Nevertheless, all engineered products will exhibit some degree of reliability growth, as mentioned above, even without formal improvement programmes.

Nineteenth- and early twentieth-century designs were less severely constrained by the cost and schedule pressures of today. Thus, in many cases, high levels of reliability were achieved as a result of over-design. The need for quantified reliability assessment techniques during design and development was not therefore identified. Therefore failure rates of engineered components were not required, as they are now, for use in prediction techniques and consequently there was little incentive for the formal collection of failure data.

Another factor is that, until well into this century, component parts were individually fabricated in a ‘craft’ environment. Mass production and the attendant need for component standardization did not apply and the concept of a valid repeatable component failure rate could not exist. The reliability of each product was, therefore, highly dependent on the craftsman/manufacturer and less determined by the ‘combination’ of part reliabilities.

Nevertheless, mass pro...