Mean time between failure (mtbf) A basic measure of reliability for repairable items: the mean number of life units during which all parts of the item perform within their specified limits, during a particular measurement interval under stated conditions.
An important benefit derived from your efforts to collect good field data is that it enables you to break the random trap.
Before discussing methods, you should familiarize yourself with reliability engineering nomenclature.
Providing readers with a solid foundation in key concepts and practices, the book moves on to offer in-depth coverage of software testing as a primary means to ensure software quality; alternatives for quality assurance, including defect prevention, process improvement, inspection, formal verification, fault tolerance, safety.He found that cancer-related deaths yielded.02 front-page news articles per 1,000 deaths, homicide yielded.7 per 1,000 deaths, aids yielded.3 per 1,000 deaths, and aviation-related accidents yielded a whopping 138.2 articles per 1,000 deaths!This data set typically assumes the Gaussian, or normal, distribution.That is the nature of probabilistic reliability projections.Weibull Distribution Originally developed by Wallodi Weibull, a Swedish mathematician, Weibull analysis is easily the most versatile distribution employed by reliability engineers.For redundant items, this is the definition of mission reliability.And, the following probability density function (pdf Where: pdf(t) Probability density function estimate for a period of time, cycles, miles, etc.If your interest in reliability engineering methods is high, I encourage you to pursue professional certification by the American Society for Quality as a reliability engineer (CRE).This equation is somewhat more complicated.For example, if five electric motors operate for a collective total time of 50 years with five functional failures during the period, the failure rate.1 failures per year.The human body is an excellent example of a system that follows the bathtub curve.Following the run-in period, we might introduce monitoring techniques that are targeted at the time-dependent wearout failures that are believed to affect the system, increase monitoring frequency accordingly or schedule hard-time preventive maintenance actions in some cases.
Moreover, we might add monitoring techniques and/or increase our monitoring frequency during the high risk period.
The mtbf for our industrial electric motor example is 10 years, which is the reciprocal of the failure rate for the motors.
The text's approach and style evolved from the author's hands-on experience in the classroom.
Much like the pdf asymptotically approaches zero, the cdf asymptotically approaches one (Figure 4).Incidentally, we would estimate mtbf for electric motors that are rebuilt upon failure.Used properly, quantitative reliability engineering tools and methods enable the plant reliability engineering to more effectively apply the frameworks provided by RCM, RCA, etc., by eliminating some of the guesswork involved with their application otherwise.Identifying failure time dependencies using the versatile Weibull system.It became rapidly apparent to managers of aviation industry companies that crashes are bad for business.Maintenance, preventive All actions performed in an attempt to retain an item in a specified condition by providing systematic inspection, detection and prevention of incipient failures.As a caveat to tie this tool back to excellence mdickies wrestling mpire crack in maintenance and operations excellence, if we were to more effectively control the forcing functions that lead to mechanical failure in bearings, gears, etc., such as lubrication, contamination control, alignment, balance, appropriate operation, etc., more.