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

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.

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.

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

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

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.

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

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

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

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

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

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

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

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

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

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

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.

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

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

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.

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