Stress Corrosion Cracking Overview & Introduction David Johnson December 2, 2003 SCC History • Not a recent phenomenon • Not exclusive to pipelines • Not confined to underground environment • Not geographically limited • Ammonia cracking of cartridge brass • Chloride cracking of stainless steel Requirements for SCC Environment Metallurgy Stress SCC Characteristics Factor Location High pH CS discharges Wet-dry soils Aggressive soil Temperature Exponential temperature impact Neutral pH Anywhere Wet-dry soils Aggressive soil Little apparent effect SCC Characteristics Factor High pH Neutral pH Electrolyte Carbonatebicarbonate pH > 9.3 Dilute bicarbonate 5.5 < pH <7.5 Higher CO2 Potential -600 to –750 mV Free potential Cracks Intergranular Narrow Not corroded Transgranular Wider May be corroded SCC near Seam Weld Metallography of SCC Summary of Incident Causes ASME Causes of Gas Transmission Incidents Third Party Damage External Corrosion Internal Corrosion Natural Forces Misc Incorrect Operation Unknown Non-Pipe Other Failures Pipe Constr/Instal Mfr Prev. Damgd Pipe Malfunction Stress Corrosion Cracking Vandalism 0.0 2.0 4.0 6.0 8.0 10.0 Avg Annl Incidents, 85-01 12.0 14.0 Summary of Significance • Natural gas transmission(1985-2002) – 15 of 1415 total reported incidents • Liquid transmission (PPTS) – 5 of 472 in database • NEB (Canada) (1992-2002) – 3 of 23 – None since 1995 • Overall - about 1% of incidents Why Today’s Interest? • Other, higher significance threats also being addressed Other Threats (B31.8S) • • • • • • • • External Corrosion Internal Corrosion Manufacturing Defects Welding & Fabrication Defects Equipment Failure Third Party / Mechanical Damage Incorrect Operations Weather & Outside Force External & Internal Corrosion • • • • • CP systems Gas quality standards and monitoring Relatively mature ILI capability Correlated to hydro-test capability Rapidly maturing DA capabilities Manufacturing & Construction • • • • • Specifications - materials & construction Advances in materials technology Mill inspections Construction inspections Proof testing Third Party Damage • • • • Dig Safety Common Ground Alliance One Call enforcement Enhanced public awareness Incorrect Operation • • • • Operator Qualification programs Qualification of controllers OQ-2 B31Q Equipment Failure • • • • Gaskets, Seals, Valves, Pumps, etc. Generally not pipe Generally confined Specifications, testing, maintenance Weather & Outside Forces • • • • Design & Construction Forecasting Monitoring Better understanding of material responses Why Today’s Interest? • Other, higher significance threats also being addressed • Less apparent understanding • Small, but widespread, occurrence • Methods of addressing not as mature – Inspection, characterization, assessment, management Today’s Workshop • Share available information • Understand application of current management techniques • Update on R&D • Future Needs – Technology development – Regulatory approach Managing SCC • Operators have found & managed SCC • Tools as prescribed in PLSIA of 2002 – In-Line Inspection – Hydrostatic Testing – Direct Assessment – Other • All have specific capabilities & limitations • Gas - Liquid Pipeline Differences Major Challenges • Finding SCC – Shallow cracks initially – May not be visible to unaided eye • • • • • Gas - Liquid technology differences Service disruptions Water disposal Assessing what is found Mitigation and Management Research & Development • • • • • • • Multi-faceted approach Environmental factors Surface preparation & coatings CP system operation Operational factors Material behavior Detection & sizing Regulatory Response • Determining reasonable response • Setting investigation protocols • Communication needs Upcoming Panels • Operator Experience with Finding and Managing SCC 1. 2. 3. 4. 5. 6. TransCanada Enbridge Kinder Morgan Duke Williams Colonial Upcoming Panels • R&D – What’s been done – Current work – Future needs – PRCI – ILIA – NACE Upcoming Panels • Regulators – Concerns & Needs – NEB – EUB – MNOPS – USDOT-OPS Contacts [email protected] [email protected]