Reliability Engineering
Fred Schenkelberg
fms@fmsreliability.com
RELIABILITY TECHNIQUES TO
IMPROVE PERFORMANCE
Day 2 Session 2
Objectives
• Examining opportunities and reliability
improvement techniques for robust design
– RCM, FMEA, RCA, 6 step and...
FMEA
• Organized risk analysis
– Severity
– Occurrence
– Detection
• Use in Design process
RCA
• Root Cause Analysis
– Determine fundamentals
– Initiating event
– Contributing events
• Use in design process
6 Steps
+1
FRETT
Cause categories
• design errors
• material defects
• fabrication and
processing errors
• assembly and installation
...
Discussion & Questions
Corrective Action
• Plan Do Check Act
process
• Experiments and
measures
• Verify results
• Document results
Plan
Do
Check...
An Example
• Define problem
• Plan response
• Do experiment
• Monitor results
• Implement fix
Monitor Effectiveness
• What do you measure?
• What can you measure?
• Does absence of failure
mean it’s fixed?
– What is ...
Monitoring
• How to determine
monitoring plan?
• Sample size?
• Duration?
• Focus on failure
mechanism
Discussion & Questions
Example
Repair rate over time
• Trend plots
– MCF – cumulative
failures over time
– Inter arrival times
– Reciprocals of inter
arr...
Cumulative failure vs. time (MCF)
• Failure count vs time
• Straight line (roughly)
means steady failure
rate.
• Curve dow...
Inter arrival failure times
• Plot waiting time
between failures
• Trend up –
improvement
• Trend down –
degradation
• Str...
Reciprocal Inter arrival times
• Plot failure rate
estimates since last
failure
• Trend up –
• degradation
• Trend down –
...
Duane Plot
Time Cum MTBF
5 5
40 20
43 14.3
175 43.75
389 77.8
712 118.67
747 106.7
795 99.4
1299 144.3
1478 147.8
Discussion & Questions
Predictions & Forecasts
Risks
• Might just be wrong
• May miss failure
mechanisms due to
masking
• Unable to predict
every...
Predictions & Forecasts
• Empirical models
– Extension of field data
– Extensions of
experiments
– Extensions of vendor
da...
Cautions
• Check assumptions
• Check sensitivity
• Verify models and fits
• Be conservative
The further from reality
the m...
Monitor and Adjust
• All models are wrong,
some are useful
• Continue to refine and
challenge any model
• RCA with focus o...
Discussion & Questions
Summary
• Examining opportunities and
reliability improvement
techniques for robust design
– RCM, FMEA, RCA, 6 step and
FR...
Reliability Maintenance Engineering 2 - 2 Reliability Techniques
Reliability Maintenance Engineering 2 - 2 Reliability Techniques
Reliability Maintenance Engineering 2 - 2 Reliability Techniques
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Reliability Maintenance Engineering 2 - 2 Reliability Techniques

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Reliability Maintenance Engineering Day 2 session 2 Reliability Techniques
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.

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Reliability Maintenance Engineering 2 - 2 Reliability Techniques

  1. 1. Reliability Engineering Fred Schenkelberg fms@fmsreliability.com
  2. 2. RELIABILITY TECHNIQUES TO IMPROVE PERFORMANCE Day 2 Session 2
  3. 3. Objectives • Examining opportunities and reliability improvement techniques for robust design – RCM, FMEA, RCA, 6 step and FRETT • Developing corrective actions and determining effectiveness • Implementing the growth curve technique • Fault and failure forecasting
  4. 4. FMEA • Organized risk analysis – Severity – Occurrence – Detection • Use in Design process
  5. 5. RCA • Root Cause Analysis – Determine fundamentals – Initiating event – Contributing events • Use in design process
  6. 6. 6 Steps +1
  7. 7. FRETT Cause categories • design errors • material defects • fabrication and processing errors • assembly and installation deficiencies • maintenance-related or procedural errors • unintended operating conditions • operator error Failure mode sets • Force • Reactive environment • Temperature • Time
  8. 8. Discussion & Questions
  9. 9. Corrective Action • Plan Do Check Act process • Experiments and measures • Verify results • Document results Plan Do Check Act
  10. 10. An Example • Define problem • Plan response • Do experiment • Monitor results • Implement fix
  11. 11. Monitor Effectiveness • What do you measure? • What can you measure? • Does absence of failure mean it’s fixed? – What is expected failure rate? – What is probability of failure?
  12. 12. Monitoring • How to determine monitoring plan? • Sample size? • Duration? • Focus on failure mechanism
  13. 13. Discussion & Questions
  14. 14. Example
  15. 15. Repair rate over time • Trend plots – MCF – cumulative failures over time – Inter arrival times – Reciprocals of inter arrival times • Duane Plot • Sample Data • 1500 hour test • With each failure RCA and improvements implemented Observed failure times 5, 40, 43, 175, 389, 712, 747, 795, 1299, 1478 hrs
  16. 16. Cumulative failure vs. time (MCF) • Failure count vs time • Straight line (roughly) means steady failure rate. • Curve down – improvement over time • Curve up – increasing problems over time NIST Engineering Statistics Handbook 8.2.2.3
  17. 17. Inter arrival failure times • Plot waiting time between failures • Trend up – improvement • Trend down – degradation • Straight – no change over time
  18. 18. Reciprocal Inter arrival times • Plot failure rate estimates since last failure • Trend up – • degradation • Trend down – improvement • Straight – no change over time
  19. 19. Duane Plot Time Cum MTBF 5 5 40 20 43 14.3 175 43.75 389 77.8 712 118.67 747 106.7 795 99.4 1299 144.3 1478 147.8
  20. 20. Discussion & Questions
  21. 21. Predictions & Forecasts Risks • Might just be wrong • May miss failure mechanisms due to masking • Unable to predict everything Benefits • Awareness of probability of failure • Awareness of what to expect to fail • Maintenance and logistics planning
  22. 22. Predictions & Forecasts • Empirical models – Extension of field data – Extensions of experiments – Extensions of vendor data • First principle models – Difficult to create – Does it apply in this situation
  23. 23. Cautions • Check assumptions • Check sensitivity • Verify models and fits • Be conservative The further from reality the more risk of being wrong exists
  24. 24. Monitor and Adjust • All models are wrong, some are useful • Continue to refine and challenge any model • RCA with focus on failure mechanisms is key to success
  25. 25. Discussion & Questions
  26. 26. Summary • Examining opportunities and reliability improvement techniques for robust design – RCM, FMEA, RCA, 6 step and FRETT • Developing corrective actions and determining effectiveness • Implementing the growth curve technique • Fault and failure forecasting Reliability techniques to improve performance

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