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A newly developed model for performing reliability and availability analysis of mechanical devices subject to multiple failure modes is presented. Using this model, reliability analyses of mechanical devices such as brakes, bearings, engines, fans, gears, generators, heat exchangers and pumps are developed. Real life failure rate data for these devices are obtained from various sources and are used in their reliability analyses. Principal failure modes of these devices are identified and expressions for reliability, state probabilities, mean time to failure and variance of time to failure are developed. For known field failure data reliability and state probability plots are shown.

This article presents four newly developed mathematical models representing non‐maintained parallel systems with hardware failures, common‐cause failures and human error. The Markov method was used to develop expressions for parallel system state probabilities, system reliability and mean time to failure (MTTF). System reliability and MTTF plots are shown. These plots clearly show the effect of common‐cause failures and human error on system reliability.

The purpose of this paper is to study reliability, availability, and mean time to failure of a repairable robot‐safety system composed of (n−1) standby robots, a safety unit, and a switch.

Generalized expressions for system state probabilities, system availability, reliability, and mean time to failure are developed when the failure rates of robot and safety unit are constant and the failed system repair times are arbitrarily distributed. Supplementary variable and Markov methods were used to develop these expressions.

This study clearly demonstrates that standby robots and the repair process help to improve system availability.

This study will help maintenance engineers and reliability practitioners to become aware of the combined effect of standby robots and the repair process on the performance of the robot‐safety system. Consequently, they will make better maintenance related decisions in organizations such as automobile manufacturers that use robots quite frequently.

This paper has studied the effects of having redundant robots and the repair facilities on the performance of a robot‐safety system with perfect mechanism to turn on a standby robot. This is one of the first attempts to study the combined effects of all these factors on a robot‐safety system.

This article presents an extensive up‐to‐date list of selective references on quality circles.