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
- 2. RELIABILITY TECHNIQUES TO IMPROVE PERFORMANCE Day 2 Session 2
- 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
- 5. FMEA • Organized risk analysis – Severity – Occurrence – Detection • Use in Design process
- 6. RCA • Root Cause Analysis – Determine fundamentals – Initiating event – Contributing events • Use in design process
- 7. 6 Steps +1
- 8. 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
- 11. Corrective Action • Plan Do Check Act process • Experiments and measures • Verify results • Document results Plan Do Check Act
- 12. An Example • Define problem • Plan response • Do experiment • Monitor results • Implement fix
- 13. 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?
- 14. Monitoring • How to determine monitoring plan? • Sample size? • Duration? • Focus on failure mechanism
- 16. Example
- 17. 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
- 18. 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
- 19. Inter arrival failure times • Plot waiting time between failures • Trend up – improvement • Trend down – degradation • Straight – no change over time
- 20. Reciprocal Inter arrival times • Plot failure rate estimates since last failure • Trend up – • degradation • Trend down – improvement • Straight – no change over time
- 21. 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
- 24. 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
- 25. 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
- 26. Cautions • Check assumptions • Check sensitivity • Verify models and fits • Be conservative The further from reality the more risk of being wrong exists
- 27. 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
- 29. 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
Notas do Editor
- FRETT - There are literally hundreds of examples of a properly structured root-cause failure analysis and upgrade program yielding immediate and measurable payback. Fortunately, such programs are deceptively simple and quickly implemented by anyone who wishes to do so. We call it the FRETT approach because it recognizes that, without exception, the basic agents of machinery component and part failure mechanisms are always force, reactive environment, time or temperature1. These basic failure mechanism agents may combine to hasten component degradation.http://www.plantservices.com/articles/2006/239.html6 steps - http://pdf.usaid.gov/pdf_docs/pnach088.pdf
- Corrective action and effectiveness
- Heinz P. Bloch, P.E., is owner of Process Machinery Consulting (www.heinzbloch.com) in Westminster, Colorado, and the author of numerous articles and books, including “Improving Machinery Reliability” and “Pump Wisdom.” Contact him at heinzpbloch@gmail.com.
- Balance between investment and value
- Examining opportunities and reliability improvement techniques for robust designRCM, FMEA, RCA, 6 step and FRETT
- Balance between investment and value
- Reliability growth
- A straight line means the NHPP applies – the slope is the rate of improvementThe reliability improvement slope for virtually all reliability improvement tests will be between 0.3 and 0.6. The lower end (0.3) describes a minimally effective test - perhaps the cross-functional team is inexperienced or the system has many failure mechanisms that are not well understood. The higher end (0.6) approaches the empirical state of the art for reliability improvement activities.
- Balance between investment and value
- Fault and failure forecasting
- Balance between investment and value