Reliability, Maintainability and Risk

Practical Methods for Engineers

David J. Smith

• Publisher: Butterworth-Heinemann
• Year: 2017
• eBook ISBN: 9780081020227
• Edition: 9
• Topic: Business
• Subtopic: Insurance
• Index: Business

Reliability, Maintainability and Risk: Practical Methods for Engineers, Ninth Edition, has taught reliability and safety engineers techniques to minimize process design, operation defects, and failures for 35 years. For beginners, the book provides tactics on how to avoid pitfalls in this complex and wide field. For experts in the field, well-described, realistic, and illustrative examples and case studies add new insight and assistance. The author uses his 40 years of experience to create a comprehensive and detailed guide to the field, also providing an excellent description of reliability and risk computation concepts. The book is organized into five parts. Part One covers reliability parameters and costs traces the history of reliability and safety technology, presenting a cost-effective approach to quality, reliability, and safety. Part Two deals with the interpretation of failure rates, while Part Three focuses on the prediction of reliability and risk. Part Four discusses design and assurance techniques, review and testing techniques, reliability growth modeling, field data collection and feedback, predicting and demonstrating repair times, quantified reliability maintenance, and systematic failures, while Part 5 deals with legal, management and safety issues, such as project management, product liability, and safety legislation. - Additional chapter on helicopter and aviation safety record - Coverage of models for partial valve stroke test, fault tree logic and quantification difficulties - More detail on use of tools such as FMEDA and programming standards like MISRA

Part 1

Understanding Reliability Parameters and Costs

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

Chapter 1

The History of Reliability and Safety Technology

Abstract

This chapter provides a historical background to the subject, introduces the difference between hazardous and non-hazardous failures, emphasises the difference between predicted and achieved reliability and between quantitative and qualitative assessment. It touches on the main defences against failure. The design life cycle is introduced and the contractual and legal reasons for interest are explained.

Keywords

reliability

hazardous failure

prediction

safety-integrity

RAMS

life-cycle

Safety and Reliability engineering did not develop as a unified discipline, but grew as a result of integrating a number of activities such as hazard identification, failure rate data collection, reliability modeling (i.e. prediction), previously the province of various diverse branches of engineering.

Since no human activity can ever enjoy zero risk, and no piece of equipment can have a zero rate of failure, safety technology has emerged to optimize risk. One attempts to balance the risk of a given activity against its benefits and seeks to assess the need for further risk reduction depending upon the cost.

Similarly, reliability engineering, beginning in the design phase, attempts to select the design compromise which balances the cost of reducing failure rates against the value of the enhanced performance.

The term reliability is usually applied to failures which have a financial penalty and safety to those where the failure is hazardous. The term Reliability Technology (in the author’s view) covers both scenarios. 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), has arisen as a natural consequence of analyzing failures. This has long been a central feature of development. The ‘test and correct’ principle was practiced long before the development of formal procedures for data collection and analysis for the reason that failure is usually self-evident and thus leads, inevitably, to design modifications.

The design of safety-related systems (for example, railway signalling, plant shut-down systems etc) has evolved partly in response to the emergence of new technologies but largely as a result of lessons learnt from past 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, as mentioned above, all engineered products will exhibit some degree of reliability growth 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 by over-design. The need for quantified reliability assessment during the design and development phase was not therefore identified. Therefore empirical failure rates of engineered components were not needed, as they are now, to support prediction techniques and consequently there was little incentive for the formal collection of failure data.

Another factor is that, until well into the 20th 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 highly dependent on the craftsman/manufacturer and less determined by the ‘combination’ of component reliabilities.

Nevertheless, mass production of standard mechanical parts has been the case for over a hundred years. Under these circumstances defective items can be readily identified, by inspection and test, during the manufacturing process, and it is possible to control reliability by quality-control procedures.

The advent of the electronic age, accelerated by the Second World War, led to the need for more complex mass-produced component parts with a higher degree of variability in the parameters and dimensions involved. The experience of poor field reliability of military equipment throughout the 1940s and 1950s focused attention on the need for more formal methods of reliability engineering. This gave rise to the collection of failure information from both the field and from the interpretation of test data. Failure rate data banks were created in the mid-1960s as a result of work at such organizations as UKAEA (UK Atomic Energy Authority) and RRE (Royal Radar Establishme...

Table of contents

• Cover
• Title page
• Table of Contents
• Copyright
• Preface
• Acknowledgements
• Part 1: Understanding Reliability Parameters and Costs
• Part 2: Interpreting Failure Rates
• Part 3: Predicting Reliability and Risk
• Part 4: Achieving Reliability and Maintainability
• Part 5: Legal, Management and Safety Considerations
• Appendix 1: Glossary
• Appendix 2: Percentage Points of the Chi-Square Distribution
• Appendix 3: Microelectronic Failure Rates
• Appendix 4: General Failure Rates
• Appendix 5: Failure Mode Percentages
• Appendix 6: Human Error Probabilities
• Appendix 7: Fatality Rates
• Appendix 8: Answers to Exercises
• Appendix 9: Bibliography
• Appendix 10: Scoring Criteria for BETAPLUS Common Cause Model
• Appendix 11: Example of HAZOP
• Appendix 12: HAZID Checklist
• Appendix 13: Markov Analysis of Redundant Systems
• Appendix 14: Calculating the GDF
• Index
• Technis