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Similar to relaibility engineering slides for reference
Similar to relaibility engineering slides for reference (20)
relaibility engineering slides for reference
- 1. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 1
Chapter 13
Reliability
- 2. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 2
Reliability
• Generally defined as the ability of a product
to perform as expected over time
• Formally defined as the probability that a
product, piece of equipment, or system
performs its intended function for a stated
period of time under specified operating
conditions
- 3. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 3
Maintainability
• The probability that a system or product
can be retained in, or one that has failed
can be restored to, operating condition in
a specified amount of time.
- 4. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 4
Types of Failures
• Functional failure – failure that occurs
at the start of product life due to
manufacturing or material detects
• Reliability failure – failure after some
period of use
- 5. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 5
Types of Reliability
• Inherent reliability – predicted by
product design
• Achieved reliability – observed during
use
- 6. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 6
Reliability Measurement
• Failure rate (l) – number of failures
per unit time
• Alternative measures
– Mean time to failure
– Mean time between failures
- 8. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM
MEAN TIME TO FAILURE
MTBF is a key reliability metric for systems that can be repaired or that
can be restored. MTTF is the expected time to failure of a system. Non-
repairable systems can fail only once, hence for non-repairable items,
MTTF is equivalent to its mean of its failure time distribution. Repairable
system can fail several times, while non-repairable can fail only once.
MTTR MTTR
Point where
a new part
is installed
A B
Time to repair
MTTF
Point where
the new part
will fail again
Total time it
will take for
the part to fail
x x
MTBF
Point where the
1st failure occurs
Point where the
2nd failure occurs
HENCE : MTBF = MTTR + MTTF
- 9. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 9
Cumulative Failure Rate Curve
- 10. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 10
Failure Rate Curve
“Infant
mortality
period”
- 12. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 12
Average Failure Rate
- 13. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 13
Reliability Function
• Probability density function of failures
f(t) = le-lt for t > 0
• Probability of failure from (0, T)
F(t) = 1 – e-lT
• Reliability function
R(T) = 1 – F(T) = e-lT
- 14. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 14
Series Systems
RS = R1 R2 ... Rn
1 2 n
- 15. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 15
Parallel Systems
RS = 1 - (1 - R1) (1 - R2)... (1 - Rn)
1
2
n
- 16. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 16
Series-Parallel Systems
• Convert to equivalent series system
A B
C
C
D
RA RB RC
RD
RC
A B C’ D
RA RB RD
RC’ = 1 – (1-RC)(1-RC)
- 17. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 17
Reliability Engineering
• Standardization
• Redundancy
• Physics of failure
• Reliability testing
• Burn-in
• Failure mode and effects analysis
• Fault tree analysis
- 20. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 20
Reliability Management
• Define customer performance requirements
• Determine important economic factors and
relationship with reliability requirements
• Define the environment and conditions of product
use
• Select components, designs, and vendors that meet
reliability and cost criteria
• Determine reliability requirements for machines
and equipment
• Analyze field reliability for improvement
- 21. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 21
Configuration Management
1. Establish approved baseline
configurations (designs)
2. Maintain control over all changes in the
baseline programs (change control)
3. Provide traceability of baselines and
changes (configuration accounting)
- 22. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 22
Maintainability
• Maintainability is the totality of design
factors that allows maintenance to be
accomplished easily
• Preventive maintenance reduces the risk
of failure
• Corrective maintenance is the response to
failures
- 23. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 23
Design Issues
• Access of parts for repair
• Modular construction and
standardization
• Diagnostic repair procedures and
expert systems
- 24. THE MANAGEMENT AND CONTROL OF QUALITY, 5e, © 2002 South-Western/Thomson LearningTM 24
Availability
• Operational availability
• Inherent availability
MDT
MTBM
MTBF
AO
MTTR
MTBF
MTBF
AO
MTBM = mean time between
maintenance
MTD = mean down time
MTBF = mean time between
failures
MTTR = mean time to repair
