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Reliability & Maintainability Engineering An Introduction

Reliability & Maintainability Engineering An Introduction. Robert Brown ITS Web Applications Development & Academic Integration Worcester Polytechnic Institute. Reliability / Maintainability * -ability.

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Reliability & Maintainability Engineering An Introduction

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  1. Reliability & Maintainability EngineeringAn Introduction Robert Brown ITS Web Applications Development & Academic Integration Worcester Polytechnic Institute

  2. Reliability / Maintainability*-ability • Reliability – Probability that a device will operate within specifications for the specified duration • Maintainability – Amount of resources required to remove faults • Diagnose-ability – The ability to locate faults • Repair-ability – The ability to remove faults Availability Probability that a device is operationally ready

  3. Why is it important?Reliability & Maintainability Engineering • Mission Success - The product operates for the duration of the mission • Customer Satisfaction – Perceived product quality • Brand loyalty, customer loyalty • Competitive Products – Market requirements • Safety • Support Legal & Contractual Requirements • Reduce Cost of Ownership • Reduce Product Cost – Warranty reserve cost • Reduce Service Cost – Service delivery cost

  4. Bathtub CurveFailure Rate Over Time l Failure Rate Time Infancy Steady State Wearout

  5. Bathtub CurveFailure Rate Over Time l Failure Rate Time Infancy Steady State Wearout Workmanship Contamination Quality Control

  6. Bathtub CurveFailure Rate Over Time l Failure Rate Time Infancy Steady State Wearout Workmanship Contamination Quality Control Random Failures Overload Improper Usage

  7. Bathtub CurveFailure Rate Over Time l Failure Rate Time Infancy Steady State Wearout Workmanship Contamination Quality Control Random Failures Overload Improper Usage Thermal Fatigue Oxidation Cracking-Shrinking Friction Wear

  8. Bathtub CurveFailure Rate Over Time Service Period Warranty Period l Failure Rate Time Infancy Steady State Wearout Workmanship Contamination Quality Control Random Failures Overload Improper Usage Thermal Fatigue Oxidation Cracking-Shrinking Friction Wear

  9. Product Life Cycle ActivitiesReliability & Maintainability Design Develop Deploy Manage • Identify market requirements • Design for reliability • Failure analysis • Reliability predictions • Reliability testing • Maintainability testing • Develop service strategy • Fault insertion • Ongoing Reliability Testing • Engineering changes ECO • Field changes FCO • Maintenance releases • End of product life planning • End of service life planning • Logistics strategy

  10. ReliabilityDeveloping reliable products • Develop products specs • Understand market requirements • Stability – mechanical / electrical • Design for operating environment • Design for anticipated load, duty cycle • Cooling • Reliable materials • Reliability prediction program • Modeling, Continuous Improvement • Redundancy - Remove critical paths

  11. 0.8 0.9 0.8 0.9 Series and ParallelPredicting System Reliability Series Parallel System requires device “A”AND device “B” to operate System requires device “A”OR device “B” to operate RS = R1 * R2 * Rn RS = 1 – ( 1 - R1 ) * ( 1 – RN ) A B RS = 0.8 * 0.9 = 0.72 RS = 1 – (1 - 0.8) * (1 - 0.9) RS = 0.98

  12. 0.8 0.98 0.9 0.8 0.8 Complex ConfigurationPredicting System Reliability System includes series and parallel device configuration B RS = 1 – ( 1 - R1 ) * ( 1 – RN ) RBC = 1 – (1 - 0.8) * (1 - 0.9) RBC = 0.98 A C RS = R1 * R2 * Rn RS = RA * RBC RS = 0.8 * 0.98 = 0.78 A BC

  13. Reliability MetricsReliability is specified and measured in several ways

  14. Calculating System MTBFExample: System with 3 components Component Component l Duty Cycle Failure Rate l CPU 30 100 % 30 Power Supply 20 100 % 20 USB 20 20 % 4 Total 54 1 1,000,000 MTBF = = = 18,518 hrs l 54 Note: l per 1 million Hours

  15. Maintainability • MTTR – Mean Time To Repair • Measured in hours • Major activities • Diagnoses • Repair • Focus on labor and materials Time required to remove faults

  16. Diagnose-abilityDeveloping diagnose-able products • User and service documentation, tools and training • Status indicators, error messages and logs. • Preserved state indicators accessed by repair depot. • Test points • Environmental measurements • Expert and non-expert end users tools • Flow Charts, Fault Trees, Symptom-Solution Database, Knowledge Base, Diagnostics • Remote and On-Site diagnosis • Service / Diagnostic / Maintenance Processor • Product labeling and revision management Quickly and Correctly Locate the Fault

  17. Repair-abilityDeveloping repair-able products • Service strategy: Repair or replace? • Remote and On-site repair? • Firmware, software, micro-code • Limit specialized tools • Eliminate manual adjustments • Hot-Swap • Larger, functionally dense sub-assemblies • Physical layout • Easy to replace maintenance & less reliable components • Minimal disruption to replace a component Remove the Fault Quick - Effective - Efficient

  18. EconomicsReliability & Maintainability Population (units) 20,000 Reliability MTBF Hr 10,000 Repair cost $ 25.00 Duty Cycle12/24 Day = 50% 50 % Operating Hours (12*365*20000) 87,600,000 Repair Calls(87600000/MTBF) 8,760 Annual Service Cost (Calls*Cost) $ 219,000 Savings

  19. EconomicsReliability & Maintainability Population (units) 20,000 20,000 Reliability MTBF Hr 10,000 15,000 Repair cost $ 25.00 $ 25.00 Duty Cycle12/24 Day = 50% 50 % 50 % Operating Hours (12*365*20000) 87,600,000 87,600,000 Repair Calls(87600000/MTBF) 8,760 5,840 Annual Service Cost (Calls*Cost) $ 219,000 $ 146,000 Savings $ 73,000

  20. EconomicsReliability & Maintainability Population (units) 20,000 20,000 20,000 Reliability MTBF Hr 10,000 15,000 10,000 Repair cost $ 25.00 $ 25.00 $ 12.50 Duty Cycle12/24 Day = 50% 50 % 50 % 50 % Operating Hours (12*365*20000) 87,600,000 87,600,000 87,600,000 Repair Calls(87600000/MTBF) 8,760 5,840 8,760 Annual Service Cost (Calls*Cost) $ 219,000 $ 146,000 $ 109,500 Savings $ 73,000 $ 109,500

  21. EconomicsReliability & Maintainability Population (units) 20,000 20,000 20,000 20,000 Reliability MTBF Hr 10,000 15,000 10,000 15,000 Repair cost $ 25.00 $ 25.00 $ 12.50 $ 12.50 Duty Cycle12/24 Day = 50% 50 % 50 % 50 % 50 % Operating Hours (12*365*20000) 87,600,000 87,600,000 87,600,000 87,600,000 Repair Calls(87600000/MTBF) 8,760 5,840 8,760 5,840 Annual Service Cost (Calls*Cost) $ 219,000 $ 146,000 $ 109,500 $ 73,000 Savings $ 73,000 $ 109,500 $ 146,000

  22. Resources • Applied Reliability by Dave Trindade • IEEE Reliability Society • Society for Automotive Engineers (SAE) Reliability, Maintainability, Supportability Division • Reliability and Maintainability Symposium • MILL Handbook 217

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