tailieunhanh - Lecture Operations management: Chapter 4S - William J. Stevenson

Lecture Operations management - Chapter 4S: Reliability. After completing this unit, you should be able to: Define reliability, perform simple reliability computations, explain the term availability and perform simple calculations. | Reliability Supplement 4 Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 1 You should be able to: LO Define reliability LO Perform simple reliability computations LO Explain the term availability and perform simple calculations Learning Objectives Reliability Reliability The ability of a product, part, or system to perform its intended function under a prescribed set of conditions Reliability is expressed as a probability: The probability that the product or system will function when activated The probability that the product or system will function for a given length of time LO Finding the probability under the assumption that the system consists of a number of independent components Requires the use of probabilities for independent events Independent event Events whose occurrence or non-occurrence do not influence one another Reliability – When Activated LO . | Reliability Supplement 4 Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 1 You should be able to: LO Define reliability LO Perform simple reliability computations LO Explain the term availability and perform simple calculations Learning Objectives Reliability Reliability The ability of a product, part, or system to perform its intended function under a prescribed set of conditions Reliability is expressed as a probability: The probability that the product or system will function when activated The probability that the product or system will function for a given length of time LO Finding the probability under the assumption that the system consists of a number of independent components Requires the use of probabilities for independent events Independent event Events whose occurrence or non-occurrence do not influence one another Reliability – When Activated LO Rule 1 If two or more events are independent and success is defined as the probability that all of the events occur, then the probability of success is equal to the product of the probabilities of the events Reliability – When Activated (contd.) LO A machine has two buttons. In order for the machine to function, both buttons must work. One button has a probability of working of .95, and the second button has a probability of working of .88. Example – Rule 1 Button 2 .88 Button 1 .95 LO Though individual system components may have high reliabilities, the system’s reliability may be considerably lower because all components that are in series must function One way to enhance reliability is to utilize redundancy Redundancy The use of backup components to increase reliability Reliability – When Activated (contd.) LO Rule 2 If two events are independent and success is defined as the probability that at least one of the events will occur, the probability of success is equal