chap 4s reliability
DESCRIPTION
BA187TRANSCRIPT
4s-1
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Reliability
Chapter 4 Supplement
Reliability
4s-2
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Reliability
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-3
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 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-4
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Reliability
Example 1: Reliability
Determine the reliability of the system shown
.98 .90
.90 .92
.95
4s-5
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Reliability
Example 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
4s-6
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Reliability
Failure Rate
Few (random) failuresInfantmortality
Failures dueto wear-out
Time, T
Figure 4S-1
4s-7
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Reliability
Exponential Distribution
Reliability = e -T/MTBF
1- e -T/MTBF
T Time
Figure 4S-2
4s-8
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Reliability
Normal Distribution
Reliability
0 z
Figure 4S-3
4s-9
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 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
AvailabilityMTBF
MTBF MTR
MTBF = mean time between failuresMTR = mean time to repair
4s-10
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 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