Direct Assessment Basics Richard Lopez Office of Pipeline

Direct Assessment Basics Richard Lopez Office of Pipeline Safety Southwest Region

Why Direct Assessment? n Alternative to ILI or Hydro Test When Not Feasible or Practical n Many Gas Transmission Pipelines are “Not Piggable” n The Cost to Make Them Piggable can be Prohibitive (from $1 M to $8 M per mile)

Why Direct Assessment? n ILI or Hydro-testing Could Cause Customer Supply Interruptions Ø LDC Laterals Often Sole Source Supply n Pipeline Safety Improvement Act 2002 – Section 23 Ø TPSSC Equivalency Recommendation

Factors Impeding Piggability n Telescopic Connections n Small Diameter Pipelines n Short Pipelines n Sharp Radius Bends

Factors Impeding Piggability n Less than Full Opening Valves n No Alternate Supply if Pig is “Hung Up” n Low Pressure & Low Flow Conditions n Scheduling and Coordination is an Anti- trust Issue

Features in Common with ILI n Indirect Examinations n Validation/Excavation/Direct Exam n Integrate & Analyze Data n Identify & Address Data Gaps n Identify Remediation Needs n Determine Re-assessment Intervals

Factors Impeding Hydro-Test n Service Interruptions n Sole Source Supplies n Concerns of Causing Pipeline Damage n Dewatering Concerns/Difficult to Dry

Factors Impeding Hydro-Test n Dewatering Concerns/Difficult to Dry n Growth of Sub-critical Defects n Water Availability & Disposal n No Characterization of Future Risk

DA Basics - Overview n Distinct Assessment Process for each Applicable Threat (i. e. , EC, IC, & SCC) n Scope of DA as an IM Assessment is more Limited than either ILI or Hydro

DA Basics - Overview n May be the Assessment Method of Choice (esp. for Non-piggable Lines and Low-Stress Gas Lines that cannot be Hydro Tested) n Involves Integration of Risk Factor Data to Identify Potential Threats

Keys to Successful DA n Expertise, Skill, Experience n Follow NACE Standards Ø Document Justifications for Not Implementing “Should” and “May” Recommendations in the Standards Ø Documents Reasons for Program Decisions and Options Selected

Keys to Successful DA (cont. ) n Data Management Ø Collection, Integration, Analysis Ø Data Quality n Understand Limitations of DA n Provide Detailed Procedures for All Process Steps

Today’s Discussion will Focus on ECDA n NACE RP 0502 has been Issued n ECDA Process is More Mature than ICDA or SCCDA n Overview of NACE RP 0502 Process for ECDA

Limitations of ECDA n ECDA Can Not Deal With: Ø Lines Susceptible to Seam Failure Ø Near-neutral p. H SCC Ø Fatigue Failures in Liquid Lines Ø Internal Corrosion Ø Plastic Pipe Ø Pipe in Shielded Areas

Limitations of ECDA n ECDA has Limited Applicability to: Ø Mechanical Damage (Only to the Degree that Coating is also Damaged)

4 Step ECDA Process of NACE RP 0502 n Pre-assessment n Indirect Assessment n Direct Physical Examination n Post-assessment

Pre-assessment n Process Similar to Risk Assessment n Assemble and Analyze Risk Factor Data

Pre-assessment n Purpose: Ø Determine Whether ECDA Process is Appropriate and Define “ECDA Regions” Ø Select Appropriate Indirect Inspection Tools (e. g. , CIS, DCVG, PCM, C-SCAN) Ø Complementary Primary and Secondary Tools are Required Ø Identify Inspection Expectations

Pre-assessment n Data Collection (Table 1 of NACE Standard) Ø Pipe Related Ø Construction Related Ø Soils/Environmental Ø Corrosion Protection Ø Pipeline Operations

Pre-assessment n ECDA Indirect Insp. Tool Feasibility n Complementary Tools – Evaluate pipe with different technologies (see table 2 of NACE RP 0502)

Pre-assessment n Feasibility Influenced by: Ø Degree of Shielding (Coating type, Terrain) Ø Accessibility (Pavement, Water Crossings, Casings)

Pre-assessment n Establish ECDA feasibility regions Ø Determine which indirect methods are applicable to each region Ø Tools may vary from region to region

Pre-assessment n What is a Region? Ø Segment is a Continuous Length of Pipe Ø Regions are Subsets of One Segment ü Characterized by Common Attributes ü Pipe with Similar Construction and Environmental Characteristics ü Use of Same Indirect Inspection Tools Throughout the Region is Appropriate

Indirect Inspection n Close Interval Survey (CIS) n Direct Current Voltage Gradient (DCVG) n C-Scan n Pipeline Current Mapper (PCM) n Alternating Current Voltage Gradient (ACVG) (PCM with A-Frame)

Indirect Inspection n Pearson n Ultrasonic n Waveform n Soil Resistivity, Pipe Depth

Indirect Inspection n Direct Current Ø Measure Structure Potential Ø Identify Locations of High CP Demand to Small Area

Indirect Inspection n Alternating Current Ø Apply AC signal Ø Determine Amount of Current Drain (i. e. , Grounding) and Location Ø Identify Locations of High AC Current

Indirect Inspection n Types of Direct Current Tools Ø Close Interval Survey (CIS or CIPS) Ø Direct Current Voltage Gradient (DCVG) n Types of Alternating Current Tools Ø Alternating Current Voltage Gradient (ACVG) Ø Pearson Survey Ø AC Attenuation (PCM, EM, C-Scan)

Indirect Inspection n Purpose: Ø Locate Areas Where Coating Damage May Exist Ø Evaluate Whether Corrosion Activity is Present n Apply Primary and Secondary Tools

Indirect Inspection n Timing Such That Conditions are Same n Overlay and Evaluate Data for Clarity, Quality, and Consistency n Distance Correlation Should be Good

Indirect Inspection via CIS n May Detect Large Coating Holidays n Measure Pipe to Soil Potential at Regular Intervals (2. 5 – 5 ft. Desirable) Ø Protection criteria ü -850 m. V polarized potential ü 100 m. V polarization

Indirect Inspection via CIS Ø Secondary Interpretation ü Change in potential profile ü Amount of IR drop (Low or High) Ø ON and OFF Readings are Desirable

Indirect Inspection via DCVG n Measures Voltage Gradient in Soil n CP Current Greatest Where Coating is Damaged

Indirect Inspection via DCVG n Interrupt Rectifier to Determine ∆V Ø One Electrode Ø Two Electrodes ü Parallel or perpendicular to ROW n Coating Holiday Size Indicated by % ∆V n Triangulation Used to Locate Holiday

Indirect Inspection via ACVG n Impose AC current n Measure Gradient Between 2 Electrodes Spaced ~1 m Apart n Gradient Corresponds to Current Flow

Direct Physical Examination n Establish “Priority Categories” from Indirect Inspection n Excavations for Direct Examination

Direct Physical Examination n Purpose: Ø Confirm Presence of Corrosion Activity Ø Determine Need for Repair or Mitigation Ø Evaluate Likely Corrosion Growth Rate Ø Support Adjustments to Excavation Scope Ø Evaluate Need for Other Technology

Direct Physical Examination n Categorize Indications Ø Immediate Action Required Ø Schedule for Action Required Ø Suitable for Monitoring n Excavate and Collect Data Where Corrosion is Most Likely

Direct Physical Examination n Characterize Coating and Corrosion Anomalies n Establish Corrosion Severity for Remaining Strength Analysis n Determine Root Cause

Direct Physical Examination n In-process Evaluation, Re- categorization, Guidelines on Number of Direct Examinations n All “Immediate” Must be Excavated n Prioritize “Scheduled” & “Monitored” n If >20% Wall Loss Found, Examine at Least 1 More (2 More for 1 st ECDA)

Direct Physical Examination n If No Indications Ø At Least 1, and 2 for 1 st ECDA Ø Choose More Corrosive Region

Direct Physical Examination n Dig a Bell Hole n Visual Inspection n Coating Condition n Ultrasonic Testing n Radiography n Soil Chemistry and Resistivity

Direct Physical Examination n Collect Data at Dig Site Ø Pipe to Soil Potentials Ø Soil Resistivity Ø Soil and Water Sampling Ø Under-film p. H Ø Bacteria & SCC Related Data Ø Photographic Documentation

Direct Physical Examination n Characterize Coating and Corrosion Anomalies Ø Coating Condition ü Adhesion, Under Film Liquid, % Bare Ø Corrosion Analysis ü Corrosion Morphology Classification ü Damage Mapping ü MPI Analysis for SCC

Direct Physical Examination n Remaining Strength Analysis Ø ASME B 31 G Ø RSTRENG

Direct Physical Examination n Determine Root Cause Ø For Example ü Low CP ü Interference ü MIC ü Disbonded Coatings ü Construction Practices ü 3 rd Party Damage

Post-Assessment n Evaluates Composite Set of Data and Assessment Results n Sets Re-inspection Intervals n Validates ECDA Process

Post-Assessment n Remaining Life - Maximum Flaw n Maximum Remaining Flaw Size Taken Same as Most Severe that was Found Ø Second Maximum if Unique Ø If No Corrosion Defects, Same as New Ø Other (e. g. , Statistical)

Post-Assessment n Remaining Life Growth Rate n Measured Corrosion Rate Ø Maximum Depth / Burial Time n 16 mpy (80% C. I. for Corrosion Tests) Ø 0. 3 mm/y if at Least 40 m. V CP Demonstrated

Post-Assessment n Linear Polarization Resistance (LPR) Ø Probe or Existing Buried Coupon n Coupon Retrieval n Assess ECDA Effectiveness

Post-Assessment n Perform at Least 1 Extra Dig at Random Location Ø Pipe Condition Should be Better than at Indications n For 1 st ECDA Ø Additional Dig at Low Priority Indication n Company-specific Performance Metrics

ECDA Summary n There is No Panacea for Pipe Integrity Verification n All Tools Have Limitations n External Corrosion Direct Assessment is Based on the Use and Integration of Existing and Emerging Technologies

ECDA Summary n External Corrosion Direct Assessment can be Effective if Properly Applied n Requires Effective Data Collection and Management as well as a Commitment to Validation n Operators Choose Best Tools to Achieve Pipeline Reliability, Safety, and Asset Preservation