OPS SCC Workshop R

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OPS - SCC Workshop RD Past and Present

• December 2, 2003

Jerry Rau - Panhandle Energy
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Outline

• Review of past RD accomplishments
• Recent and current SCC RD efforts

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The History

• 1965
• Identified SCC as a possible cause of pipeline
  failures
• 1965 - 1970
• SCC identified as an industry-wide concern, not
  an isolated incident

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Early Research

• 1966 - 1968
• Carbonate/bicarbonate environments existed at
  locations of high-pH SCC
• A carbonate/bicarbonate environment could cause
  SCC of a carbon steel
• 1966 - 1970
• Reproduced high-pH SCC in the laboratory

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Research on the Stress Component

• 1975 - 1983
• Thorough cleaning of the pipe surface to remove
  mill scale prior to coating should significantly
  reduce the probability of high-pH SCC
• 1980 - 1984
• Developed a method to determine the threshold
  stress for SCC in a single test with a single
  (tapered) specimen
• 1973 - 1983
• Discovered that low-frequency, low-amplitude
  stress fluctuations could reduce the threshold
  stress considerably

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Material Issues

• 1970 - 1980
• Showed that there is no direct correlation
  between the grade of pipe (for X46 through X80)
  and its susceptibility to high-pH SCC (1970-1980)
• 1973 - 1981
• Shot peening and grit blasting can significantly
  increase the resistance of a pipe to SCC

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Temperature Issues

• 1968 - 1975
• Demonstrated that lower discharge temperatures
  can have a substantial beneficial effect on
  reducing the probability of a failure due to
  high-pH SCC.
• Results in much lower crack growth rates
• Results in narrower range of environmental
  conditions that will support SCC
• Slower deterioration of coatings

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Mitigation Issues

• 1975 - 1995
• Periodic hydrostatic retesting is an effective
  way to assure the integrity of a pipeline that
  may have stress-corrosion cracks
• 1972 - 2002
• Developed a life-prediction model for high-pH SCC
  that enables a pipeline operator to evaluate the
  significance of cracks that are discovered and
  adequately sized.

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Environmental Issues

• 1977
• Discovered that relatively dilute groundwater
  containing CO2 could cause transgranular
  (near-neutral-pH) SCC
• 1977 - 1987
• Determined that near-neutral-pH SCC occurs only
  in areas where little, if any, cathodic-protection
  current reaches the steel
• 1980-2000
• Determined that stress fluctuations are critical
  with near-neutral-pH SCC as well as with high-pH
  SCC

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Prioritizing Areas to Inspect for SCC

• 1977 - 2002
• Guidelines developed for improving the cost
  effectiveness of hydrostatic retesting, in-line
  inspections, and bellhole inspections.
• Based upon proximity to other SCC locations,
  coating type, geology, soil type, temperature
  history, and pressure history

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Managing SCC

• 1965 - 2000
• A practical way to manage the SCC problem (both
  high-pH and near neutral-pH) for future pipelines
  
• The coating and
• The condition of the pipe surface
• Eg. The use of fusion-bonded epoxy coatings on
  mechanically cleaned surface preparation

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RD Projects in PRCI Materials Committee

• SCC Susceptibility
• SCC Initiation Susceptibility Ranking/Screening
• Review of Stress Corrosion Cracking of Pipelines
  in Contact with Near-Neutral (Low) pH Solutions
• SCC Crack Growth / Re-inspection Intervals
• Growth Model for Assessment after SCC Detection
• SCC Crack Growth - Effects of Operating
  Practices
• Effects of Pressure Fluctuations on Near-Neutral
  SCC Propagation
• SCC Crack Extension and Coalescence Modeling
• Hydrostatic Testing Frequencies for SCC Control
• Field Studies to Support SCC Life Prediction
  Model

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RD Projects in PRCI Materials Committee

• SCC Direct Examination
• Application of Phased Array UT Characterization
  in the Field
• Reliable Diagnosis of SCC During Field
  Inspection
• SCC Engineering Critical Assessment
• SCC Acceptance Criteria
• Model for Assessing Remaining Strength of Line
  Pipe with Co- existent Corrosion and SCC
• SCC Mitigation Repair
• Permanent Field Repair of SCC
• Cyclic Stress/Strain Behavior of Steels for SCC
  Service

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RD Projects in PRCI CI Committee

• Transforming Shallow Cracks to Significant Cracks
• SCC Sample management
• Disbonded Tape - EMAT on MFL
• Prediction of SCC from Field Measurements
• Maps Technology for Stress Measurement
• SCCDA Development Support
• NLH/Barkhausen

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Summary

• Research Continuous From 1965
• Much has Been Learned
• More Still to be Learned