SCC Direct Assessment

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SCCDirect Assessment

• John A. Beavers
• Chairman of NACE TG 273 on SCC DA

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SCC DA Program

• Stress-corrosion-cracking direct assessment
  (SCCDA) is a structured process that contributes
  to pipeline companys efforts to improve safety
  by reducing the impact of external SCC on
  pipeline integrity.

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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.

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SCC DA Program

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

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SCC DA Program

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

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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.

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NACE SCC DA TASK GROUP

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

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Componentsof 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

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Componentsof SCC DA Program

• Step 3 (Direct Examinations)
• Field verification of selected sites
• Excavation and examination
• Step 4 (Post Assessment)
• Evaluation and documentation

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Step 1 (Selection of Susceptible Segments)

• High-pH SCC Follows ASME B318S Appendix A3 for
  selection of susceptible segments
• Age of Pipe (gt10 Years)
• Operating Stress Level (gt60 of SMYS)
• Operating Temperature (gt100 F)
• Distance from Compressor Station (lt20 miles)
• Coating Type (All but FBE)
• Prior history of SCC (service or hydrostatic test
  failure)
• Unless conditions were corrected

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Step 1 (Selection of Susceptible Segments)

• Near Neutral pH SCC Uses same criteria
  excluding temperature
• Age of Pipe (gt10 Years)
• Operating Stress Level (gt60 of SMYS)
• Distance from Compressor Station (lt20 miles)
• Coating Type (All but FBE)
• Prior history of SCC (service or hydrostatic test
  failure)
• Unless conditions were corrected

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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

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Step 3

• 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

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Post Assessment (Step 4)

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

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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

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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

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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.

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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

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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

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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.

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Summary

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