Environmental Cracking in Steels – Detection Using Advanced NDT Mark F. Rosa, Mohammed A. Abufour, Yousef Al-Munif 16/9/2015 © Copyright 2015, Saudi Aramco. All rights reserved.
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Environmental Cracking in
Steels – Detection Using
Advanced NDTMark F. Rosa, Mohammed A. Abufour,
Yousef Al-Munif
16/9/2015
© Copyright 2015, Saudi Aramco. All rights reserved.
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Agenda
1. Environmental Cracking
2. Hydrogen Damage
3. Stress Corrosion Cracking
4. Case Studies
• Compressor Drum
• Hydrocracker
• Pipeline
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Environmental Cracking
• Susceptible equipment
- Pipeline: thousands of km,
estimated 75% buried
• HIC, SwC, blistering, SCC
• HIC-resistant steels,
environment/alloy combinations,
coatings, inhibitors, CP and coatings
• NDT techniques
- VT, PT, MT, RT
- PAUT, AUT, EMAT
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Hydrogen Damage – Blistering, HIC and SwC
• Sour service
• Blistering often first sign, due to
activity of elemental hydrogen
- Surface corrosion reaction
- Laminations, inclusions
- Build-up of H2 partial pressure
• HIC and SwC link blisters
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• Highly localized
• Even mildly corrosive environments
• Harmful ion concentrations may be small and difficult to detect
• Even in absence of applied stress, residual stresses can be sufficient to cause SCC
Stress Corrosion Cracking (SCC)
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• Can occur anywhere
- Even in locations with little or no applied or
residual tensile stress
• Susceptible in all areas of sour environment
• Absence of visible surface deformations and
blistering can lead to a false sense of confidence
Thorough inspection of all locations, not just
particular areas
Challenges and Methods for Detection
27/10/2014
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Challenges and Methods for Detection
• Many small UT elements, each can be
pulsed individually
• Beam swept through object being
examined and data from multiple
beams combined, real-time
• S-scan, combined formats
- A-, B-, C-scan representations
available on some PA models
• Couplant-free; hot, cold, clean or
dry environments
• Generates sound waves within
material by magnetostriction for
ferromagnetic & Lorentz force for
conductive materials
Phased Array EMAT
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Challenges and Methods for Detection
27/10/2014
Copyright note text (8pt)
• Typically for corrosion defects
• A-scan, B-scan and C-scan
Advanced UT
• Capture of elastic waves generated from
stress release within material
• Indicator of active features
• Absolute energy vs signal duration
- Early detection, identification and
monitoring
Acoustic Emission
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• Two year monitoring
• Initially 1.8 mm SwC at depth of 4.2 mm in 8 mm WT
• 5.8 mm depth of HIC/Blistering
HIC Case Study: Compressor Suction Drum
Compressor Suction Drum and Top Head PA ScanLocation
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HIC Case Study: Compressor Suction Drum
27/10/2014
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Hydrogen Blister and HIC Study: Hydrocracker
Planar UT beam spread as a function ofsignal penetration and material thickness
Image processing program developed to enhance scan images and compute percentage of blister areas
Representative AUT scan covering 3000 mm length x 450 mm height, blister area = 14%
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SCC Case Study: Crude Pipeline
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The top left image shows original scan data of circumferential notch;three echo peaks result from this single indication 620 mm away fromtransducer. The top right image shows the same indication from theopposite direction; 770 mm from the transducer with a slower modearriving approximately 200 mm after.
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SCC Case Study: Crude Pipeline
ILI Inspection Data Table with 13 Anomalies
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• PAUT and AUT have shown to be effective
in detecting and quantifying HIC,
hydrogen blistering and subsequent step-
wise cracking
• SCC also detected and confirmed with
EMAT technology implemented in an ILI
tool
Conclusion
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THANK YOU
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