Direct Assessment Basics

Richard LopezRichard Lopez

Office of Pipeline Office of Pipeline SafetySafety

Southwest RegionSouthwest Region

Why Direct Assessment?

Alternative to ILI or Hydro Test When Alternative to ILI or Hydro Test When Not Feasible or PracticalNot Feasible or Practical

Many Gas Transmission Pipelines are Many Gas Transmission Pipelines are “Not Piggable”“Not Piggable”

The Cost to Make Them Piggable can be The Cost to Make Them Piggable can be Prohibitive (from $1M to $8M per mile)Prohibitive (from $1M to $8M per mile)

Why Direct Assessment?

ILI or Hydro-testing Could Cause ILI or Hydro-testing Could Cause Customer Supply Interruptions Customer Supply Interruptions LDC Laterals Often Sole Source SupplyLDC Laterals Often Sole Source Supply

Pipeline Safety Improvement Act 2002 – Pipeline Safety Improvement Act 2002 – Section 23Section 23 TPSSC Equivalency RecommendationTPSSC Equivalency Recommendation

Factors Impeding Piggability

Telescopic ConnectionsTelescopic Connections Small Diameter PipelinesSmall Diameter Pipelines Short PipelinesShort Pipelines Sharp Radius BendsSharp Radius Bends

Factors Impeding Piggability

Less than Full Opening ValvesLess than Full Opening Valves No Alternate Supply if Pig is “Hung Up”No Alternate Supply if Pig is “Hung Up” Low Pressure & Low Flow ConditionsLow Pressure & Low Flow Conditions Scheduling and Coordination is an Anti-Scheduling and Coordination is an Anti-

trust Issuetrust Issue

Features in Common with ILI

Indirect ExaminationsIndirect Examinations Validation/Excavation/Direct ExamValidation/Excavation/Direct Exam Integrate & Analyze DataIntegrate & Analyze Data Identify & Address Data GapsIdentify & Address Data Gaps Identify Remediation NeedsIdentify Remediation Needs Determine Re-assessment IntervalsDetermine Re-assessment Intervals

Factors Impeding Hydro-Test

Service Interruptions Service Interruptions Sole Source SuppliesSole Source Supplies Concerns of Causing Pipeline DamageConcerns of Causing Pipeline Damage Dewatering Concerns/Difficult to DryDewatering Concerns/Difficult to Dry

Factors Impeding Hydro-Test

Dewatering Concerns/Difficult to DryDewatering Concerns/Difficult to Dry Growth of Sub-critical DefectsGrowth of Sub-critical Defects Water Availability & DisposalWater Availability & Disposal No Characterization of Future RiskNo Characterization of Future Risk

DA Basics - Overview

Distinct Assessment Process for each Distinct Assessment Process for each Applicable Threat (i.e., EC, IC, & SCC)Applicable Threat (i.e., EC, IC, & SCC)

Scope of DA as an IM Assessment is Scope of DA as an IM Assessment is more Limited than either ILI or Hydromore Limited than either ILI or Hydro

DA Basics - Overview

May be the Assessment Method of May be the Assessment Method of Choice (esp. for Non-piggable Lines Choice (esp. for Non-piggable Lines and Low-Stress Gas Lines that cannot and Low-Stress Gas Lines that cannot be Hydro Tested)be Hydro Tested)

Involves Integration of Risk Factor Involves Integration of Risk Factor Data to Identify Potential ThreatsData to Identify Potential Threats

Keys to Successful DA

Expertise, Skill, ExperienceExpertise, Skill, Experience Follow NACE StandardsFollow NACE Standards

Document Justifications for Not Document Justifications for Not Implementing “Should” and “May” Implementing “Should” and “May” Recommendations in the Standards Recommendations in the Standards

Documents Reasons for Program Decisions Documents Reasons for Program Decisions and Options Selectedand Options Selected

Keys to Successful DA (cont.)

Data ManagementData Management Collection, Integration, AnalysisCollection, Integration, Analysis Data QualityData Quality

Understand Limitations of DAUnderstand Limitations of DA Provide Detailed Procedures for All Provide Detailed Procedures for All

Process StepsProcess Steps

Today’s Discussion will Focus on ECDA

NACE RP0502 has been IssuedNACE RP0502 has been Issued ECDA Process is More Mature than ICDA ECDA Process is More Mature than ICDA

or SCCDAor SCCDA Overview of NACE RP0502 Process for Overview of NACE RP0502 Process for

ECDAECDA

Limitations of ECDA

ECDA Can Not Deal With:ECDA Can Not Deal With: Lines Susceptible to Seam FailureLines Susceptible to Seam Failure Near-neutral pH SCCNear-neutral pH SCC Fatigue Failures in Liquid LinesFatigue Failures in Liquid Lines Internal CorrosionInternal Corrosion Plastic PipePlastic Pipe Pipe in Shielded AreasPipe in Shielded Areas

Limitations of ECDA

ECDA has Limited Applicability to:ECDA has Limited Applicability to: Mechanical Damage (Only to the Degree Mechanical Damage (Only to the Degree

that Coating is also Damaged)that Coating is also Damaged)

4 Step ECDA Process of NACE RP0502

Pre-assessment Pre-assessment Indirect Assessment Indirect Assessment Direct Physical ExaminationDirect Physical Examination Post-assessmentPost-assessment

Pre-assessment

Process Similar to Risk AssessmentProcess Similar to Risk Assessment Assemble and Analyze Risk Factor Assemble and Analyze Risk Factor

DataData

Pre-assessment

Purpose:Purpose: Determine Whether ECDA Process is Determine Whether ECDA Process is

Appropriate and Define “ECDA Regions”Appropriate and Define “ECDA Regions” Select Appropriate Indirect Inspection Select Appropriate Indirect Inspection

Tools (e.g., CIS, DCVG, PCM, C-SCAN)Tools (e.g., CIS, DCVG, PCM, C-SCAN) Complementary Primary and Secondary Complementary Primary and Secondary

Tools are RequiredTools are Required Identify Inspection ExpectationsIdentify Inspection Expectations

Pre-assessment

Data Collection (Table 1 of NACE Data Collection (Table 1 of NACE Standard)Standard) Pipe RelatedPipe Related Construction RelatedConstruction Related Soils/EnvironmentalSoils/Environmental Corrosion ProtectionCorrosion Protection Pipeline OperationsPipeline Operations

Pre-assessment

ECDA Indirect Insp. Tool FeasibilityECDA Indirect Insp. Tool Feasibility Complementary Tools – Evaluate pipe Complementary Tools – Evaluate pipe

with different technologies (see table with different technologies (see table 2 of NACE RP0502)2 of NACE RP0502)

Pre-assessment

Feasibility Influenced by:Feasibility Influenced by: Degree of Shielding (Coating type, Degree of Shielding (Coating type,

Terrain)Terrain) Accessibility (Pavement, Water Crossings, Accessibility (Pavement, Water Crossings,

Casings)Casings)

Pre-assessment

Establish ECDA feasibility regionsEstablish ECDA feasibility regions Determine which indirect methods are Determine which indirect methods are

applicable to each regionapplicable to each region Tools may vary from region to regionTools may vary from region to region

Pre-assessment What is a Region?What is a Region?

Segment is a Continuous Length of PipeSegment is a Continuous Length of Pipe Regions are Subsets of One SegmentRegions are Subsets of One Segment

Characterized by Common AttributesCharacterized by Common AttributesPipe with Similar Construction and Pipe with Similar Construction and

Environmental CharacteristicsEnvironmental CharacteristicsUse of Same Indirect Inspection Tools Use of Same Indirect Inspection Tools

Throughout the Region is AppropriateThroughout the Region is Appropriate

Indirect Inspection Close Interval Survey (CIS)Close Interval Survey (CIS) Direct Current Voltage Gradient Direct Current Voltage Gradient

(DCVG)(DCVG) C-ScanC-Scan Pipeline Current Mapper (PCM)Pipeline Current Mapper (PCM) Alternating Current Voltage Gradient Alternating Current Voltage Gradient

(ACVG) (PCM with A-Frame)(ACVG) (PCM with A-Frame)

Indirect Inspection PearsonPearson UltrasonicUltrasonic WaveformWaveform Soil Resistivity, Pipe DepthSoil Resistivity, Pipe Depth

Indirect Inspection Direct CurrentDirect Current

Measure Structure PotentialMeasure Structure Potential Identify Locations of High CP Demand to Identify Locations of High CP Demand to

Small AreaSmall Area

Indirect Inspection Alternating CurrentAlternating Current

Apply AC signalApply AC signal Determine Amount of Current Drain (i.e., Determine Amount of Current Drain (i.e.,

Grounding) and LocationGrounding) and Location Identify Locations of High AC CurrentIdentify Locations of High AC Current

Indirect Inspection Types of Direct Current ToolsTypes of Direct Current Tools

Close Interval Survey (CIS or CIPS)Close Interval Survey (CIS or CIPS) Direct Current Voltage Gradient (DCVG)Direct Current Voltage Gradient (DCVG)

Types of Alternating Current ToolsTypes of Alternating Current Tools Alternating Current Voltage Gradient Alternating Current Voltage Gradient

(ACVG)(ACVG) Pearson SurveyPearson Survey AC Attenuation (PCM, EM, C-Scan)AC Attenuation (PCM, EM, C-Scan)

Indirect Inspection Purpose:Purpose:

Locate Areas Where Coating Damage May Locate Areas Where Coating Damage May ExistExist

Evaluate Whether Corrosion Activity is Evaluate Whether Corrosion Activity is PresentPresent

Apply Primary and Secondary ToolsApply Primary and Secondary Tools

Indirect Inspection Timing Such That Conditions are SameTiming Such That Conditions are Same Overlay and Evaluate Data for Clarity, Overlay and Evaluate Data for Clarity,

Quality, and ConsistencyQuality, and Consistency Distance Correlation Should be GoodDistance Correlation Should be Good

Indirect Inspection via CIS May Detect Large Coating HolidaysMay Detect Large Coating Holidays Measure Pipe to Soil Potential at Measure Pipe to Soil Potential at

Regular Intervals (2.5 – 5 ft. Desirable)Regular Intervals (2.5 – 5 ft. Desirable) Protection criteriaProtection criteria

-850mV polarized potential-850mV polarized potential100mV polarization100mV polarization

Indirect Inspection via CIS Secondary InterpretationSecondary Interpretation

Change in potential profileChange in potential profileAmount of IR drop (Low or High)Amount of IR drop (Low or High)

ON and OFF Readings are DesirableON and OFF Readings are Desirable

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

DamagedDamaged

Indirect Inspection via DCVG Interrupt Rectifier to Determine Interrupt Rectifier to Determine ∆∆VV

One ElectrodeOne Electrode Two Electrodes Two Electrodes

Parallel or perpendicular to ROWParallel or perpendicular to ROW

Coating Holiday Size Indicated by % Coating Holiday Size Indicated by % ∆∆VV Triangulation Used to Locate HolidayTriangulation Used to Locate Holiday

Indirect Inspection via ACVG Impose AC currentImpose AC current Measure Gradient Between 2 Measure Gradient Between 2

Electrodes Spaced ~1m ApartElectrodes Spaced ~1m Apart Gradient Corresponds to Current FlowGradient Corresponds to Current Flow

Direct Physical Examination Establish “Priority Categories” from Establish “Priority Categories” from

Indirect InspectionIndirect Inspection Excavations for Direct ExaminationExcavations for Direct Examination

Direct Physical Examination Purpose:Purpose:

Confirm Presence of Corrosion ActivityConfirm Presence of Corrosion Activity Determine Need for Repair or MitigationDetermine Need for Repair or Mitigation Evaluate Likely Corrosion Growth RateEvaluate Likely Corrosion Growth Rate Support Adjustments to Excavation ScopeSupport Adjustments to Excavation Scope Evaluate Need for Other TechnologyEvaluate Need for Other Technology

Direct Physical Examination Categorize IndicationsCategorize Indications

Immediate Action RequiredImmediate Action RequiredSchedule for Action RequiredSchedule for Action RequiredSuitable for MonitoringSuitable for Monitoring

Excavate and Collect Data Where Excavate and Collect Data Where Corrosion is Most LikelyCorrosion is Most Likely

Direct Physical Examination Characterize Coating and Corrosion Characterize Coating and Corrosion

AnomaliesAnomalies Establish Corrosion Severity for Establish Corrosion Severity for

Remaining Strength AnalysisRemaining Strength Analysis Determine Root CauseDetermine Root Cause

Direct Physical Examination In-process Evaluation, Re-In-process Evaluation, Re-

categorization, Guidelines on Number categorization, Guidelines on Number of Direct Examinationsof Direct Examinations

All “Immediate” Must be ExcavatedAll “Immediate” Must be Excavated Prioritize “Scheduled” & “Monitored”Prioritize “Scheduled” & “Monitored” If >20% Wall Loss Found, Examine at If >20% Wall Loss Found, Examine at

Least 1 More (2 More for 1Least 1 More (2 More for 1stst ECDA) ECDA)

Direct Physical Examination If No IndicationsIf No Indications

At Least 1, and 2 for 1At Least 1, and 2 for 1stst ECDA ECDA Choose More Corrosive RegionChoose More Corrosive Region

Direct Physical Examination Dig a Bell HoleDig a Bell Hole Visual InspectionVisual Inspection Coating ConditionCoating Condition Ultrasonic TestingUltrasonic Testing RadiographyRadiography Soil Chemistry and ResistivitySoil Chemistry and Resistivity

Direct Physical Examination Collect Data at Dig SiteCollect Data at Dig Site

Pipe to Soil PotentialsPipe to Soil Potentials Soil ResistivitySoil Resistivity Soil and Water SamplingSoil and Water Sampling Under-film pHUnder-film pH Bacteria & SCC Related DataBacteria & SCC Related Data Photographic DocumentationPhotographic Documentation

Direct Physical Examination Characterize Coating and Characterize Coating and

Corrosion AnomaliesCorrosion Anomalies Coating ConditionCoating Condition

Adhesion, Under Film Liquid, % BareAdhesion, Under Film Liquid, % Bare Corrosion AnalysisCorrosion Analysis

Corrosion Morphology ClassificationCorrosion Morphology ClassificationDamage MappingDamage MappingMPI Analysis for SCCMPI Analysis for SCC

Direct Physical Examination Remaining Strength AnalysisRemaining Strength Analysis

ASME B31GASME B31G RSTRENGRSTRENG

Direct Physical Examination Determine Determine RootRoot Cause Cause

For ExampleFor ExampleLow CPLow CPInterferenceInterferenceMICMICDisbonded CoatingsDisbonded CoatingsConstruction PracticesConstruction Practices33rdrd Party Damage Party Damage

Post-Assessment Evaluates Composite Set of Data and Evaluates Composite Set of Data and

Assessment ResultsAssessment Results Sets Re-inspection IntervalsSets Re-inspection Intervals Validates ECDA ProcessValidates ECDA Process

Post-Assessment Remaining Life - Maximum FlawRemaining Life - Maximum Flaw Maximum Remaining Flaw Size Taken Maximum Remaining Flaw Size Taken

Same as Most Severe that was FoundSame as Most Severe that was Found Second Maximum if UniqueSecond Maximum if Unique If No Corrosion Defects, Same as NewIf No Corrosion Defects, Same as New Other (e.g., Statistical)Other (e.g., Statistical)

Post-Assessment Remaining Life Growth RateRemaining Life Growth Rate Measured Corrosion RateMeasured Corrosion Rate

Maximum Depth / Burial TimeMaximum Depth / Burial Time 16mpy (80% C.I. for Corrosion Tests)16mpy (80% C.I. for Corrosion Tests)

0.3mm/y if at Least 40mV CP 0.3mm/y if at Least 40mV CP DemonstratedDemonstrated

Post-Assessment Linear Polarization Resistance (LPR)Linear Polarization Resistance (LPR)

Probe or Existing Buried CouponProbe or Existing Buried Coupon Coupon RetrievalCoupon Retrieval Assess ECDA EffectivenessAssess ECDA Effectiveness

Post-Assessment Perform at Least 1 Extra Dig at Perform at Least 1 Extra Dig at

Random LocationRandom Location Pipe Condition Should be Better than at Pipe Condition Should be Better than at

IndicationsIndications For 1For 1stst ECDA ECDA

Additional Dig at Low Priority IndicationAdditional Dig at Low Priority Indication Company-specific Performance MetricsCompany-specific Performance Metrics

ECDA Summary There is No Panacea for Pipe Integrity There is No Panacea for Pipe Integrity

VerificationVerification All Tools Have LimitationsAll Tools Have Limitations External Corrosion Direct Assessment External Corrosion Direct Assessment

is Based on the Use and Integration of is Based on the Use and Integration of Existing and Emerging TechnologiesExisting and Emerging Technologies

ECDA Summary External Corrosion Direct Assessment External Corrosion Direct Assessment

can be Effective if Properly Applied can be Effective if Properly Applied Requires Effective Data Collection and Requires Effective Data Collection and

Management as well as a Commitment Management as well as a Commitment to Validationto Validation

Operators Choose Best Tools to Operators Choose Best Tools to Achieve Pipeline Reliability, Safety, Achieve Pipeline Reliability, Safety, and Asset Preservationand Asset Preservation