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Stephen Rowbotham, Quest Integrity: Critical spares: Who needs them and why?

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Stephen Rowbotham, Quest Integrity delivered this presentation at the 2013 Gas Turbines conference. The event is designed as a platform for discussion on the latest technologies & developments in gas …

Stephen Rowbotham, Quest Integrity delivered this presentation at the 2013 Gas Turbines conference. The event is designed as a platform for discussion on the latest technologies & developments in gas power generation. For more information on the annual event, please visit the conference website: http://www.informa.com.au/gasturbinesconference

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  • 1. Critical Spares Who Needs Them and When? Australian Gas Turbines Conference 30th October 2013
  • 2. Agenda • Definition • Strategy • Types of spares • Factors to consider • Equipment / spares management • Determination of criticality • Spare levels • Spares Identification 2
  • 3. Critical Spares Who Needs Them and When? • To answer the first part is easy Everyone who operates a system that has to perform when required will have critical spares • The second half, now that’s the difficult part! 3
  • 4. But First - Definition • All parts of a system can be critical unless redundancy is built into the design • One definition is : “A part that if not available when required results in the loss of production, power generation or endangers peoples lives or seriously damages the environment” 4
  • 5. Two Extreme Maintenance Strategies Conservative Most companies fall somewhere in between Run till it drops 5
  • 6. Strategy Affected by • • • • • • • • Contracts in place Type of equipment Fuels used Maintenance Strategy Skills availability Spares availability Geographic location Age of plant Not static – review ever 2 years 6
  • 7. Types of Maintenance and Repair • Breakdown • Routine • Planned • Preventative • Predictive • Corrective • Design Out/Elimination Maintenance • Total Production Maintenance • Contracted Out Maintenance • Cannibalisation 7
  • 8. Types of Spare Parts Commissioning Spare parts Mean Failure Rate h(t) Operating Spare parts (2 year rolling) Initial Spare parts (1st year) Outage Capital Insurance and Critical Operating Time 8
  • 9. Where do you Start – Original Procurement and Build • Due Diligence • Fleet data • Operating history • Number of similar units in fleet • Availability required • Storage facilities 9
  • 10. Other Factors to Consider • Assessment of the whole system • Identify redundancy • Cost of holding spares – 20 to 40 % of purchase price per year • Maintenance of the spare part • Change of operation 10
  • 11. Equipment /Spares Management • Implement full Reliability-Centered Maintenance (RCM) to high risk components – Covered in standard SAE JA1011, Evaluation Criteria for RCM Processes • Identify all failure modes for each component • Develop detailed monitoring & inspection test plans specific to each component • Identifying equipment risk through reliability based inspection is the first step toward this 11
  • 12. Determination Criticality • Review history of failed components for the individual plant and across the fleet • Review OEM Manuals • Talk to the Plant Engineers • Check PID • Review supply chain • Component availability • Risk assessment for mechanical and electrical systems 12
  • 13. Likelihood Questions • Age of component? • Are there damage processes and what is the likelihood? • Rapid unpredictable failure likely? • How good is the inspection? • How good is the maintenance? • How well is it operated? 13
  • 14. Consequence Questions • Extent of damage to other equipment? • Part availability? • Length of repair time? • Safety hazard to personnel? • Potential loss of production ? • Cost to repair or replace? • Potential damage to environment? 14
  • 15. Total Risk • Total Risk is defined as the likelihood versus consequence • The risk profile can then be generated as a plot of the risk for each piece of equipment or area 15
  • 16. Distribution of Risk for a Frame Unit 16
  • 17. Distribution of Risk for an Aero-derivative Unit 17
  • 18. Likelihood versus Consequences • Frame Unit - GE Frame 9 • Aero-derivative Unit - GE LMS100 18
  • 19. Maintenance / Critical Spares – Reliability – Failure Rates • Assume a constant failure rate • With a constant failure rate the reliability is based on the exponential distribution – ܴ ‫ ݐ‬ൌ exp െλ‫ݐ‬ሻ ሺ • Failure rate (λ) reciprocal is the mean time between failure (MTBF) 1 ‫ ܨܤܶܯ‬ൌ ߣ • The survival probability time is given by using tr ൌ 1/ߣ x ln(1/R(tr )) 19
  • 20. Maintenance Spares – Levels • To determine maximum stock level required is given by = λ +K√λ λ = average consumption/failure rate per year K = a factor depending on service level required • Minimum stock is given by = K√λ • Should be reviewed - approximately every 2 years 20
  • 21. Example Effect of Various MTBF on Spares Service Level/ Reliability 75% 90% 95% 99% K Factor 0.7 1.3 1.7 2.3 MTBF λ +K√ߣ λ +K√ߣ λ +K√ߣ λ +K√ߣ 0.75 month 19 22 23 26 1.5 months 12 13 15 16 2 months 8 10 11 12 3 months 6 7 8 9 1 year 2 3 3 4 10 years 1 1 1 1 100 years 1 1 1 1 21
  • 22. Spare Parts Identification • Depending on the model, year of manufacture and any service bulletins applicable the correct part number may have changed. The OEM spare parts manual details how the system is structured • The OEM manual structure is normally based on flange to flange Gas Turbine Type/Model Section Number Subsection Number TURB9EA2##/BA05A/0512 – 112E1407G016 Unit Number Article Number 22
  • 23. Outside the Gas Turbine/ Balance of Plant • The identification system relays on tag numbers which are referred to on the process line diagrams • Reference then has to be made to the manufacturers operating manual for each component 23
  • 24. Outage Spares – • Planned Maintenance - regular inspection of the combustion and hot gas path parts of the gas turbine Frame Hours Starts Aero Derivative Hours CI 12000 450 2000 -4000 HGP 24000 900-1200 Inspection and Blade wash Major Inspection 48000 2400 Annual Inspection 8000 Hot Section Overhaul 25000 Full Overhaul 50000 24
  • 25. Typical A/B Inspection Consumable Packages • 28 line items • 131 components Qty Description Part # Delivery (weeks) 24 Hexagon Socket Head bolt HTMA200312P0013 16 1 Packet Welding Electrode HZN 403494P0250 6 1 Welding Wire HTCZ401077P0003 9 2 Packet of shims GMD5246056R001 12 2 Gasket GMD0924574P0001 16 25
  • 26. C Inspection Consumable Package • Broken down into six parts : – C inspection package – C inspection bolting package – C inspection compressor spares – C inspection consumables – C inspection MTS consumables – Noble parts assembly material • Total number of line items 708 • Longest lead time 34 weeks 26
  • 27. Critical Spares and Integrity Management Activities Procurement Operation Engineering Inspection Maintenance Organisation Training Competencies Structure People Succession Equipment Integrity Management Processes Policies Standards Record practices Procedures Control Disciplines Involved Everybody 27
  • 28. Main Benefit of Critical Spares Review Cost of unplanned outage or failure Cost of undertaking review and holding necessary parts 28
  • 29. Any Questions? Remember look after your spares! 29