reliability engineering

Software does not wear out but it does fail and most failures are due to specification errors and code errors with only a few errors in copying or use. The only software repair is by reprogramming and adding safety factors is almost impossible. Software reliability improves by finding errors and fixing the errors but estimating the number of errors which canse failures is extremely difficult as many branches of software code may lie dormant and unused until special events occur to make the latent failures obvious. Software failures are not often time related but are more software code page dependent. Software reliability is improved by extensive testing to disclose the failures and then fixing them to repeat the test all over again to validate the fix did not generate more failures and to continue the search of other latent defects.

Configuration control is involved with the management of change by providing traceability of failures back into the design standard. If the design details are not specified, the design will not contain the requirements and thus implementation of the project will be hit or miss for achieving the desired end results beginning with the conceptual design and resulting in the operating facility.

All actions necessary, both technical and administrative, for retaining an item in or restoring it to a specified condition so it can perform a required function. The actions include servicing, repair, modification, overhaul, inspection, reclamation, and restored condition determination.

For reliability successes, loads must always be less than strengths. When loads are greater than strengths, failures occur. The issue is determining the probability of load-strength interference which is a joint probability of when loads exceed strengths. The loads should include expected conditions plus the foolishness of people to violate rules and overload equipment, plus the vagaries of Mother Nature to impose unexpected static and dynamic loads from hurricanes, tornadoes, earth quakes, wild fires, and so forth.

The smartest way to maintain a reliability database is in Weibull format and Weibull databases are available.

Lognormal distributions are continuous life functions that have long tails to the right (display positive skewness) in time or usage. A lognormal distribution plotted on semi-log papers would appear as a normal curve.

Overall equipment effectiveness (OEE) is a manufacturing index to reduce complexity of discrete systems for problem solving and benchmarking.

Reliability-Centered maintenance (RCM) is a systematic planning process used to determine the maintenance requirements for a system. RCM expects the system has an inherent reliability and maintenance requirements are imposed upon the baseline of inherent safety and inherent reliability which can be no better than the worst than designed into the system.

Reliability is the probability that a device, system, or process will perform its prescribed duty without failure for a given time when operated correctly in a specified environment.

The International Electrical Congress (IEC) defines dependability as "Dependability describes the availability performance and its influencing factors: reliability performance, maintainability performance and maintenance support performance." MIL-HDBK-338 defines dependability differently as a measure of the degree to which an item is operable and capable of performing its required function at any (random) time during a specified mission profile, given that the item is available at mission start. (Item state during a mission includes the combined effects of the mission-related system R&M parameters but excludes non-mission time; see availability.) Dependability is related to reliability with the intention that dependability would be a more general concept than the measurable issues of reliability, maintainability, and maintenance.

Reliability block diagram (RBD) models are graphical representations of a calculation methodology for reliability systems.

A tool for measuring the % of time an item or system is in a state of readiness where it is operable and can be committed to use when call upon.