4s-1 McGraw-Hill Ryerson Operations Management, 2 nd Canadian Edition, by Stevenson & Hojati Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Reliability

4s-2 McGraw-Hill Ryerson Operations Management, 2 nd Canadian Edition, by Stevenson & Hojati Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Reliability Chapter 4 Supplement Reliability

4s-3 McGraw-Hill Ryerson Operations Management, 2 nd Canadian Edition, by Stevenson & Hojati Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Reliability Reliability : The ability of a product, part, or system to perform its intended function under a prescribed set of conditions Failure : Situation in which a product, part, or system does not perform as intended Normal operating conditions: The set of conditions under which an item’s reliability is specified

4s-4 McGraw-Hill Ryerson Operations Management, 2 nd Canadian Edition, by Stevenson & Hojati Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Reliability Probability that the product or system will: – Function when activated – Function for a given length of time Independent events Redundancy Reliability is a Probability

4s-5 McGraw-Hill Ryerson Operations Management, 2 nd Canadian Edition, by Stevenson & Hojati Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Reliability Example S-1: Reliability Determine the reliability of the system shown

4s-6 McGraw-Hill Ryerson Operations Management, 2 nd Canadian Edition, by Stevenson & Hojati Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Reliability Example S-1 Solution The system can be reduced to a series of three components (1-.90) (1-.95).98 x.99 x.996 =.966

4s-7 McGraw-Hill Ryerson Operations Management, 2 nd Canadian Edition, by Stevenson & Hojati Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Reliability Failure Rate Few (random) failures Infant mortality Failures due to wear-out Time, T Figure 4S-1

4s-8 McGraw-Hill Ryerson Operations Management, 2 nd Canadian Edition, by Stevenson & Hojati Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Reliability Exponential Distribution Reliability = e -T/MTBF 1- e -T/MTBF TTime Figure 4S-2

4s-9 McGraw-Hill Ryerson Operations Management, 2 nd Canadian Edition, by Stevenson & Hojati Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Reliability Normal Distribution Reliability 0z Figure 4S-3

4s-10 McGraw-Hill Ryerson Operations Management, 2 nd Canadian Edition, by Stevenson & Hojati Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Reliability Availability The fraction of time a piece of equipment is expected to be available for operation MTBF = mean time between failures MTR = mean time to repair

4s-11 McGraw-Hill Ryerson Operations Management, 2 nd Canadian Edition, by Stevenson & Hojati Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Reliability Improving Reliability Component design Production/assembly techniques Testing Redundancy/backups Preventive maintenance procedures User education System design