Stress Corrosion Cracking�Overview & Introduction

Stress Corrosion Cracking�Overview & Introduction

1. Stress Corrosion Cracking
Overview & Introduction
David Johnson
December 2, 2003

2. 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

3. Requirements for SCC
Environment
StressMetallurgy

4. SCC Characteristics
Factor High pH Neutral pH
Location CS discharges
Wet-dry soils
Aggressive soil
Anywhere
Wet-dry soils
Aggressive soil
Temperature Exponential
temperature
impact
Little apparent
effect

5. SCC Characteristics
Factor High pH Neutral pH
Electrolyte Carbonate-
bicarbonate
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

6. SCC near Seam Weld

7. Metallography of SCC

8. ASME Causes of Gas Transmission Incidents
0.0 2.0 4.0 6.0 8.0 10.012.014.0
Vandalism
Stress Corrosion Cracking
Malfunction
Prev. Damgd Pipe
Mfr
Constr/Instal
Other Failures
Unknown
Incorrect Operation
Misc
Natural Forces
Internal Corrosion
External Corrosion
Third Party Damage
Non-Pipe
Pipe
Summary of Incident Causes

9. 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

10. Why Today’s Interest?
•Other, higher significance threats also
being addressed

11. Other Threats (B31.8S)
•External Corrosion
•Internal Corrosion
•Manufacturing Defects
•Welding & Fabrication Defects
•Equipment Failure
•Third Party / Mechanical Damage
•Incorrect Operations
•Weather & Outside Force

12. External & Internal Corrosion
•CP systems
•Gas quality standards and monitoring
•Relatively mature ILI capability
•Correlated to hydro-test capability
•Rapidly maturing DA capabilities

13. Manufacturing & Construction
•Specifications - materials & construction
•Advances in materials technology
•Mill inspections
•Construction inspections
•Proof testing

14. Third Party Damage
•Dig Safety
•Common Ground Alliance
•One Call enforcement
•Enhanced public awareness

15. Incorrect Operation
•Operator Qualification programs
•Qualification of controllers
•OQ-2
•B31Q

16. Equipment Failure
•Gaskets, Seals, Valves, Pumps, etc.
•Generally not pipe
•Generally confined
•Specifications, testing, maintenance

17. Weather & Outside Forces
•Design & Construction
•Forecasting
•Monitoring
•Better understanding of material
responses

18. 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

19. Today’s Workshop
•Share available information
•Understand application of current
management techniques
•Update on R&D
•Future Needs
–Technology development
–Regulatory approach

20. 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

21. 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

22. Research & Development
•Multi-faceted approach
•Environmental factors
•Surface preparation & coatings
•CP system operation
•Operational factors
•Material behavior
•Detection & sizing

23. Regulatory Response
•Determining reasonable response
•Setting investigation protocols
•Communication needs

24. Upcoming Panels
•Operator Experience with Finding and
Managing SCC
1.TransCanada
2.Enbridge
3.Kinder Morgan
4.Duke
5.Williams
6.Colonial

25. Upcoming Panels
•R & D
–What’s been done
–Current work
–Future needs
–PRCI
–ILIA
–NACE

26. Upcoming Panels
•Regulators
–Concerns & Needs
–NEB
–EUB
–MNOPS
–USDOT-OPS

27. [email protected]
[email protected]
Contacts