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Reliability, Maintainability, and Risk Practical Methods for Engineers 9th Edition by Dr. David J. Smith | PDF Free Download.
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
After three editions, in 1993, Reliability, Maintainability in Perspective became Reliability, Maintainability and Risk.
The 6th edition, in 2001, included my PhD studies into common cause failure and into the correlation between predicted and achieved field reliability.
Once again it is time to update the material as a result of developments in the functional safety area. The techniques that are explained apply to both reliability and safety engineering and are also applied to optimizing maintenance strategies.
The collection of techniques concerned with reliability, availability, maintainability and safety are often referred to as RAMS.
A single defect can easily cost £100 in diagnosis and repair if it is detected early in production, whereas the same defect in the field may well cost £1000 to rectify.
If it transpires that the failure is a design fault then the cost of redesign, documentation and retest may well be in tens or even hundreds of thousands of pounds.
This book emphasizes the importance of using reliability techniques to discover and remove potential failures early in the design cycle.
Compared with such losses, the cost of these activities is easily justified. It is the combination of reliability and maintainability that dictates the proportion of time that any item is available for use or, for that matter, is operating in a safe state.
The key parameters are failure rate and down time, both of which determine the failure costs. As a result, techniques for optimizing maintenance intervals and spares holdings have become popular since they lead to major cost savings. ‘RAMS’ clauses in contracts, and in invitations to tender, are now commonplace.
In defense, telecommunications, oil and gas, and aerospace these requirements have been specified for many years.
More recently the transport, medical and consumer industries have followed suit. Furthermore, recent legislation in the liability and safety areas provides further motivation for this type of assessment.
Much of the activity in this area is the result of European standards and these are described where relevant.
Software tools have been in use for RAMS assessments for many years and only the simplest of calculations are performed manually.
This eighth edition mentions a number of such packages. Not only are computers of use in carrying out reliability analysis but are themselves the subject of concern.
The application of programable devices in control equipment, and in particular safety-related equipment, has widened dramatically since the mid-1980s.
The reliability/quality of the software and the ways in which it could cause failures and hazards is of considerable interest. Chapters 17 and 22 cover this area.
Quantifying the predicted RAMS, although important in pinpointing areas for redesign, does not of itself create more reliable, safer or more easily repaired equipment.
Too often, the author has to discourage efforts to refine the ‘accuracy’ of a reliability prediction when an order of magnitude assessment would have been adequate.
In any engineering discipline the ability to recognize the degree of accuracy required is of the essence.
It happens that RAMS parameters are of wide tolerance and thus judgements must be made on the basis of one- or, at best, two-figure accuracy. Benefit is only obtained from the judgement and subsequent follow-up action, not from refining the calculation.
A feature of the last four editions has been the data ranges in Appendices 3 and 4.
These were current for the fourth edition but the full ‘up-to-date’ database is available in FARADIP. THREE (see last four pages of the book).
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