Reliability Maintenance Engineering Day 1 session 5 Measuring Reliability Three day live course focused on reliability engineering for maintenance programs. Introductory material and discussion ranging from basic tools and techniques for data analysis to considerations when building or improving a program.

1. Reliability Engineering
Fred Schenkelberg
fms@fmsreliability.com

2. MEASURING RELIABILITY TO
IMPROVE SAFETY AND
AVAILABILITY
Day 1 Session 5

3. Objectives
• Reliability and the bathtub curve
• Calculating PDF plot
• What to do if you don’t have data at failure
mode level
• Measuring reliability of Line Replaceable Units
• Developing the next generation reliability
growth analysis

5. Early Life Failures
Decreasing hazard rate
Typical failure causes
• Manufacturing defect
• Shipping damage
• Installation damage

6. Useful Life
Constant hazard rate
Typical failure causes
• Overstress
• Random events
Note: rarely occurs in real
life – may be useful if
change in hazard rate is
small enough

7. Wear out
Increasing hazard rate
Typical failure causes
• Material wear
• Rust/Oxidation
• Creep/Crack growth
• Embrittlement

8. Discussion & Questions

10. Probability Distribution Plot
• Like a histogram
• Construction notes
• Continuous distributions
• Discrete distributions
f (x)dx = Pr a £ X £ b[ ]a
b
ò
f x( )= Pr X = x[ ]

12. How to use PDF plot
• Probability plots
• How many will survive
• How many will fail

13. Discussion & Questions

15. Data and Level
• Failure mechanism level
• Subunit level (LRU)
• Unit Level
• System level

16. Plots and levels
• CDF with system and
subunit information
• Continuous Distributions
• Discrete Distributions
F x( )= f m( )dm
-¥
¥
ò
F x( )= f i( )
i=0
x
å

17. time
ProbabilityofFailure(logscale)

18. Repairable Equipment
• MCF example
• How to interpret
– Concave
– Convex
– Straight
Time
CumulativeFailures

19. Discussion & Questions

21. Reliability Growth
• CDF reflecting changes
• Look for change in slope
• Look for change in scale

22. time
ProbabilityofFailure(logscale)
or

23. Cumulative Failures over time
• During development or
improvement projects
• Plot total failures over
time (more later with
Duane and related
plots)

24. Discussion & Questions

25. Summary
• Reliability and the bathtub
curve
• Calculating PDF plot
• What to do if you don’t
have data at failure mode
level
• Measuring reliability of
Line Replaceable Units
• Developing the next
generation reliability
growth analysis
Measuring Reliability to improve
Safety and Availability