0. John A. Beavers Chairman of NACE TG 273 on SCC DA
SCC Direct Assessment
John A. Beavers
Chairman of NACE TG 273 on SCC DA

1. SCC DA Program
Stress-corrosion-cracking direct assessment (SCCDA) is a structured process that contributes to pipeline company’s efforts to improve safety by reducing the impact of external SCC on pipeline integrity.

2. Scope of NACE SCC DA Recommended Practice
Addresses buried onshore petroleum (natural gas, crude oil, and refined products) pipelines constructed from line-pipe steel.
Addresses the situation where a pipeline company has identified a portion of its pipeline as an area of interest with respect to SCC based upon its risk assessment process and has decided that SCCDA is an appropriate approach for integrity assessment.
Provides flexibility for an operator to tailor the SCCDA process to a specific pipeline situation.

3. SCC DA Program
SCC DA: One component of SCC integrity management program
Other Components
In-Line Inspection
Hydrostatic Testing
Repair and Replacement

4. SCC DA Program
All of the available techniques for SCC integrity management have strengths and weaknesses.
A combined approach is generally most effective.

5. Purposes of SCC DA Program
Determine whether pipeline system is susceptible.
To SCC
To significant SCC
Prioritize system for ILI, hydrostatic testing, or other forms of remediation where significant and extensive SCC is found.

6. NACE SCC DA TASK GROUP Members from pipeline operating companies
Natural Gas and liquids
Members from engineering services companies
Researchers
Representatives from PRCI

7. Components of SCC DA Program
Step 1 (Pre-Assessment)
Evaluation of existing data
Step 2 (Indirect Inspections)
Collection of additional required data
Prioritization of pipeline segments
Site selection

8. Components of SCC DA Program
Step 3 (Direct Examinations)
Field verification of selected sites
Excavation and examination
Step 4 (Post Assessment)
Evaluation and documentation

9. Step 1 (Selection of Susceptible Segments)
High-pH SCC: Follows ASME B318S Appendix A3 for selection of susceptible segments
Age of Pipe (>10 Years)
Operating Stress Level (>60% of SMYS)
Operating Temperature (>100 F)
Distance from Compressor Station (<20 miles)
Coating Type (All but FBE)
Prior history of SCC (service or hydrostatic test failure)
Unless conditions were corrected

10. Step 1 (Selection of Susceptible Segments)
Near Neutral pH SCC: Uses same criteria excluding temperature
Age of Pipe (>10 Years)
Operating Stress Level (>60% of SMYS)
Distance from Compressor Station (<20 miles)
Coating Type (All but FBE)
Prior history of SCC (service or hydrostatic test failure)
Unless conditions were corrected

11. Steps 1 and 2
Prioritize segments and select sites based on probability and consequences
Probability
Coating type, age, stress level, historical information, in-line inspections, terrain models, other operators experience base
Consequences
Proximity to public, product type, pipe diameter and operating pressure

12. Step 3 Field verification of sites selected Conduct field digs
Based on factors used for site selection
Conduct field digs
Examine pipe for SCC
Evaluate SCC if found
Type and severity of cracking
Collect other relevant data
Extent depends on use

13. Post Assessment (Step 4)
Objectives
Determine whether general SCC mitigation is required.
Define reassessment intervals.
Evaluate the effectiveness of the SCCDA approach.

14. Post Assessment (Step 4)
Primary guidance for SCC mitigation is provided in Part A3 of ASME B31.8S.
Each company is responsible for selecting post assessment options.
SCC Mitigation
Definition of reassessment intervals
Evaluation of effectiveness of SCC DA

15. Post Assessment (Step 4)
No SCC Found
Recoat Pipe at disbondments or where coating has been removed
Evaluate re-inspection interval
SCC Found
Repair or replace pipe joint
Engineering critical assessment (ECA) to evaluate risk and identify mitigation methods

16. Post Assessment (Step 4)
Non Significant SCC Found
Engineering critical assessment (ECA) to determine whether cracks should be removed.
Recoat Pipe at disbondments or where coating has been removed.
Evaluate re-inspection interval.

17. Post Assessment (Step 4)
Isolated Significant SCC
Requires Discrete Mitigation
Options for Discrete Mitigation
Repair or removal of the affected pipe length
Hydrostatically test the pipeline segment
In-Line inspection where appropriate tools are available
Engineering critical assessment to evaluate the risk and identify further mitigation methods

18. Post Assessment (Step 4)
Widespread Significant SCC
Requires General Mitigation
Options for General Mitigation
Hydrostatic testing of affected segments
In-Line inspection where appropriate tools are available
Pipe replacement in affected segments
Re-coating of affected segments

19. Summary
SCC DA is one component of an SCC integrity management program.
Other components include in-line Inspection, hydrostatic testing, and repair and replacement.
A combined approach is generally most effective.

20. Summary Four Components of SCC DA Program Step 1 (Pre-Assessment)
Step 2 (Indirect Inspections)
Step 3 (Direct Examinations)
Step 4 (Post Assessment)