OPS - SCC Workshop R&D Past and Present December 2, 2003 Jerry Rau - Panhandle Energy

Outline 1. Review of past R&D accomplishments 2. Recent and current SCC R&D efforts

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

Early Research  Carbonate/bicarbonate environments existed at locations of high-pH SCC  A carbonate/bicarbonate environment could cause SCC of a carbon steel  Reproduced high-pH SCC in the laboratory

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

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

Temperature Issues  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

Mitigation Issues  Periodic hydrostatic retesting is an effective way to assure the integrity of a pipeline that may have stress-corrosion cracks  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.

Environmental Issues 1977  Discovered that relatively dilute groundwater containing CO 2 could cause transgranular (near-neutral-pH) SCC  Determined that near-neutral-pH SCC occurs only in areas where little, if any, cathodic-protection current reaches the steel  Determined that stress fluctuations are critical with near- neutral-pH SCC as well as with high-pH SCC

Prioritizing Areas to Inspect for SCC  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

Managing SCC  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

R&D 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

R&D 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

R&D Projects in PRCI C&I 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

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