ABSTRACT
“The reliability of an item is the probability that it will adequately perform its specified purpose for a specified period of time under specified environmental conditions”. Both on-stream time and mean-time-between-failures depend on the conjunction of individual event probabilities. For many cases and many measures of reliability, the composite event probability can be calculated from simple rules. System reliability is often improved by having several spare items in parallel and ready to replace a working item that fails. The probability of some events can depend on whether previous events have occurred. The probability of occurrence of an event is one of the common measures of reliability. One important objective in process design and manufacturing is the optimization of process economics, through choices of equipment type, sizing, and redundancy, while designing a process or production line to meet a desired annual capacity or reliability criteria.
