1. Saudi Aramco
Managing SCC in Gas
Pipelines
Nader Al-Otaibi
Oct 4th, 2011
© Copyright 2011, Saudi Aramco. All rights reserved.

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
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3. QAISUMAH SAFANIYA
JUBAIL
RAS TANURA
QASSIM QATIF
DHAHRAN
AL MADINAH ABQAIQ
KHURAIS
SHEDGUM
RIYADH
YANBU’
‘UTHMANIYAH HAWIYAH
Rabigh HARADH
HAWTAH
SHAYBAH
In Operation
Mothballed
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4. Pipelines Network Description
22050
19300
18000
12500
5500
2500
1000 1500
1940 1950 1970 1980 1990 2002 2009 2014
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5. Pipelines Network Description
<20” 22-46” >46”
Sizes 25% 40% 35%
Crude Gas Product & NGL
Service 35% 36% 29%
<20 Years 20-30 Year >30 Year
Age 44% 33% 23%
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6. What is SCC?
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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
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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
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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)
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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
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11. Contributing Factors
• Role of Stress
– Hoop stress 60% of SMYS
– Secondary loading
– Stress concentration
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12. Contributing Factors
• Role of Temperature
– Distance from compressor
– 40 ᵒC
– Exponentially decrease
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13. How to Predict and Manage SCC?
Demonstrated with a Case Study
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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
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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
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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
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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)
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18. EMAT Technology
• Working Principle:
– SCC detection
– Coating Disbonded
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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. 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. Case Study: Gas Pipeline
• Verification Program
– Refine ILI tools findings and complement inadequacy
– Improve ILI Analysis (learning curve)
• MPI
• Shear Wave UT
• Phased Array
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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*
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23. Case Study: Gas Pipeline
• Verification Program
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24. Case Study: Gas Pipeline
• Verification Program
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25. Case Study: Gas Pipeline
• Failure Analysis
– Sample defect
– Lab Failure Analysis
– Longitudinal Cracks
– High PH
– Inter-granular Cracks
– Carbonate/bi-Carbonate
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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%
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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
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28. To Recap
• What is SCC?
• What contributes to it?
• How to predict SCC?
• How to manage it?
• Case Study
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29. SCC … Don’t Wait for it!
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30. Thank You
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