Nader Al Otaibi - Managing SCC in Gas Pipelines

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Nader Al Otaibi - Managing SCC in Gas Pipelines

  1. 1. Saudi AramcoManaging SCC in Gas Pipelines Nader Al-Otaibi Oct 4th, 2011 © Copyright 2011, Saudi Aramco. All rights reserved.
  2. 2. Managing SCC in Gas Pipelines Contents• Saudi Aramco Pipelines Network• Part I: What is SCC?• Part II: How to Predict and Manage SCC? – Assessment Techniques – Technology: EMAT Program – Revalidation – Case Study• Conclusion 2
  3. 3. QAISUMAH SAFANIYA JUBAIL RAS TANURA QASSIM QATIF DHAHRAN AL MADINAH ABQAIQ KHURAIS SHEDGUM RIYADHYANBU’ ‘UTHMANIYAH HAWIYAH Rabigh HARADH HAWTAH SHAYBAH In Operation Mothballed 3
  4. 4. Pipelines Network Description 22050 19300 18000 12500 5500 25001000 15001940 1950 1970 1980 1990 2002 2009 2014 4
  5. 5. Pipelines Network Description <20” 22-46” >46”Sizes 25% 40% 35% Crude Gas Product & NGLService 35% 36% 29% <20 Years 20-30 Year >30 Year Age 44% 33% 23% 5
  6. 6. What is SCC? 6
  7. 7. SCC: what is it?• SCC: Stress Corrosion Cracking – Environment – Susceptible Material – Stress• Typical: Older Pipelines!• SCC Characteristics and Types: – No significant metal loss – Perpendicular to T.S.s – Inter or trans-granular – High PH vs. Near-Neutral 7
  8. 8. SCC Mechanism• Active Path dissolution • Hydrogen Embrittlement – Accelerated localized – H2 dissolves in all materials Corrosion: crack tip between atoms – Material bulk Passive – H2 weaken material – Inter-granular – H2 attack High tensile stresses areas, notches and stress raisers – Active path: Grain boundary – H2 makes cleavage easier – Stress helps open crack tip 8
  9. 9. SCC Types• High PH SCC • Near Neutral (Low) PH SCC – Carbonate/bi-Carbonate – Many species at reduced concentrations – PH: 9.5-10 – PH: 6.4 (near neutral) – Active path dissolution – Hydrogen embrittlement – Inter-granular – Trans-granular – Sensitive to temperature (40 ᵒC) 9
  10. 10. Contributing Factors• Environment – Soil Condition • Wet soil • High salinity and water table (Subkha) – Coating Conditions • Tape wrap and Coal-tar coating • No SCC in FBE coated pipelines 10
  11. 11. Contributing Factors• Role of Stress – Hoop stress 60% of SMYS – Secondary loading – Stress concentration 11
  12. 12. Contributing Factors• Role of Temperature – Distance from compressor – 40 ᵒC – Exponentially decrease 12
  13. 13. How to Predict and Manage SCC? Demonstrated with a Case Study 13
  14. 14. SCC Management Program• SCC Management Program – Pipe Segment Susceptibility to SCC • Identify segments • Investigate for SCC – Classification of Severity • Plan and implement mitigation • Re-assessment interval – Manage SCC Failure • Plan and implement mitigation • Safe operating pressure 14
  15. 15. Assessment Techniques• SCC Models – Pipe Excavation Program • Coating removal • Visual inspection • NDT – Historical trends – Effort vs. Accuracy• In-Line Inspection – Specialized tool – Sufficiently reliable – Recommended if coupled with verification digs 15
  16. 16. Assessment Techniques• Hydro-test Program – Fail critical and near-critical SCC • Lower consequence – Blunt non-mature SCC • Might plastically deform crack tip which might accelerate failure! – Requires Criteria Lower Consequence – Un-failed SCC • Advantage to ILI – Varying cost • Very high if summed to pipeline outage cost 16
  17. 17. EMAT Technology• Need Drives Technologies … – Aramco runs a Master Sales Gas Network that supports growing gas local demand – Reliable supply  no interruption – Aramco search of technology to revalidate pipelines integrity with respect to SCC • Difficulties of hydro test • ILI: EMAT (Electro-Magnet Acoustic Transducers) 17
  18. 18. EMAT Technology• Working Principle: – SCC detection – Coating Disbonded 18
  19. 19. SCC Revalidation Criteria• ILI Optimization Criteria• Category A pipelines – Pipelines History of Stress Corrosion Cracking• Category B pipelines – Similar Pipelines Environment (soil condition)• Category C pipelines – ASME B31.8S — MANAGING SYSTEM INTEGRITY OF GAS PIPELINES – ANSI/NACE Standard RP0204 — Stress Corrosion Cracking (SCC) Direct Assessment Methodology
  20. 20. ASME B31.8S HCA Definition• Identifying SCC Susceptible Areas (ASME B31.8S) – Operating stress > 60% SMYS – Operating temperature > 100°F (for high pH SCC) – Distance from compressor ≤ 20 miles (≤ 32 km) – Pipeline age ≥ 10 years old – Coating is other than FBE
  21. 21. Case Study: Gas Pipeline• Verification Program – Refine ILI tools findings and complement inadequacy – Improve ILI Analysis (learning curve) • MPI • Shear Wave UT • Phased Array 21
  22. 22. Case Study: Gas Pipeline 40” Gas Pipeline (three segments) Built: 1971 (south to North) API 5L Gr. X52/60, Tape-Wrap Coated Section III, inspected : August 28, 2010 Summary: 4 (verified) SCC locations* Section II, inspected: July 14, 2010 Summary: 3 (verified) SCC locations* Section I, inspected March 14, 2010 Summary: 8 (verified) SCC locations* 22
  23. 23. Case Study: Gas Pipeline• Verification Program 23
  24. 24. Case Study: Gas Pipeline• Verification Program 24
  25. 25. Case Study: Gas Pipeline• Failure Analysis – Sample defect – Lab Failure Analysis – Longitudinal Cracks – High PH – Inter-granular Cracks – Carbonate/bi-Carbonate 25
  26. 26. Case Study: Gas Pipeline• Action Plan Crack classification Type of repair These cracks shall be replaced. If the replacement pipe Open or leaking cracks >60% cannot be found, then the sleeve installation option can be worked out, provided that the crack arrestor is used. Cracks with a depth ranging from 20% to 60% Or These should be repaired by installing a repair sleeve. Colonies with more than three linear parallel cracks Cracks with a depth ranging The cracks should be removed by grinding. The maximum from 10% to 20% length of cracks shall not exceed 24”. Cracks with a depth less than The cracks should be removed by grinding 10% 26
  27. 27. Tackling the Contributing Factors !• New Coating Technologies – Success of existing technologies • Visco-Elastic; good track record within Saudi Aramco – Realized Potential of some coating technologies • Under Approval 27
  28. 28. To Recap• What is SCC?• What contributes to it?• How to predict SCC?• How to manage it?• Case Study 28
  29. 29. SCC … Don’t Wait for it! 29
  30. 30. Thank You 30

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