# Presentation: 700148

## 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.

## 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.

- To SCC
- To significant SCC
- Prioritize system for ILI, hydrostatic testing, or other forms of remediation where significant and extensive SCC is found.

- Purposes of SCC DA Program

## Members from pipeline operating companies 
Natural Gas and liquids 
Members from engineering services companies
Researchers
Representatives from PRCI

- Natural Gas and liquids
- Members from engineering services companies
- Researchers
- Representatives from PRCI

- NACE SCC DA TASK GROUP

## Step 1 (Pre-Assessment)
Evaluation of existing data

Step 2 (Indirect Inspections)
Collection of additional required data
Prioritization of pipeline segments
Site selection

- Evaluation of existing data
- Step 2 (Indirect Inspections)
- Collection of additional required data
- Prioritization of pipeline segments
- Site selection

- Componentsof  SCC  DA  Program

## 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

## 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

- 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

- Steps 1 and 2

## Field verification of sites selected
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

- 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

- Step 3

## Objectives
Determine whether general SCC mitigation is required.
Define reassessment intervals.
Evaluate the effectiveness of the SCCDA approach.

- Determine whether general SCC mitigation is required.
- Define reassessment intervals.
- Evaluate the effectiveness of the SCCDA approach.

- Post  Assessment  (Step 4)

## 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)