1. 4s-1Reliability William J. Stevenson Operations Management 8 th edition

2. 4s-2Reliability CHAPTER 4s Reliability McGraw-Hill/Irwin Operations Management, Eighth Edition, by William J. Stevenson Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

3. 4s-3ReliabilityReliability  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

4. 4s-4Reliability  Probability that the product or system will:  Function when activated  Function for a given length of time  Independent events  Events whose occurrence or nonoccurrence do not influence each other  Redundancy  The use of backup components to increase reliability Reliability is a Probability

5. 4s-5Reliability Rule 1.90.80 Lamp 1Lamp 2.90 x.80 =.72

6. 4s-6Reliability Rule 2.90.80.90 + (1-.90)*.80 =.98 Lamp 1 Lamp 2 (backup)

7. 4s-7Reliability Rule 3.90.80.70 1-[(1-.90)*(1-.80)*(1-.70)] =.994 1 – P(all fail) Lamp 1 Lamp 2 (backup for Lamp1) Lamp 3 (backup for Lamp 2)

8. 4s-8Reliability Example S-1 Reliability Determine the reliability of the system shown.98.90.92.95

9. 4s-9Reliability Example S-1 Solution The system can be reduced to a series of three components.98.90+.90(1-.90).95+.92(1-.95).98 x.99 x.996 =.966

10. 4s-10Reliability Failure Rate Figure 4S.1 Few (random) failures Infant mortality Failures due to wear-out Time, T Failure Rate

11. 4s-11Reliability Exponential Distribution Reliability = e -T/MTBF 1- e -T/MTBF TTime Figure 4S.2

12. 4s-12Reliability Normal Distribution Reliability 0z Figure 4S.3

13. 4s-13ReliabilityAvailability  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

14. 4s-14Reliability Improving Reliability  Component design  Production/assembly techniques  Testing  Redundancy/backups  Preventive maintenance procedures  User education  System design

15. 4s-15Reliability Additional PowerPoint slides contributed by Geoff Willis, University of Central Oklahoma. 4s CHAPTER

16. 4s-16ReliabilityReliability  Probability  Failure  Normal operating conditions (remember Taguchi)  Redundancy