1. Direct Assessment Basics
Richard Lopez
Office of Pipeline Safety
Southwest Region

2. Why Direct Assessment?
Alternative to ILI or Hydro Test When Not Feasible or Practical
Many Gas Transmission Pipelines are “Not Piggable”
The Cost to Make Them Piggable can be Prohibitive (from $1M to $8M per mile)
Industry has estimated that to make lines piggable would cost somewhere between $90 to 700 Billion.

3. Why Direct Assessment?
ILI or Hydro-testing Could Cause Customer Supply Interruptions
LDC Laterals Often Sole Source Supply
Pipeline Safety Improvement Act 2002 – Section 23
TPSSC Equivalency Recommendation
Industry has estimated that to make lines piggable would cost somewhere between $90 to 700 Billion.

4. Factors Impeding Piggability
Telescopic Connections
Small Diameter Pipelines
Short Pipelines
Sharp Radius Bends
Not “piggable” involves pipe with varying diameters, short radius bends, reduced opening and pipe restrictions, as well as operating pressures too low to move pigs in a pipeline at controlled speeds, without exceeding MAOP if pigs get stuck and increased pressure is needed to dislodge them.

5. Factors Impeding Piggability
Less than Full Opening Valves
No Alternate Supply if Pig is “Hung Up”
Low Pressure & Low Flow Conditions
Scheduling and Coordination is an Anti-trust Issue
Not “piggable” involves pipe with varying diameters, short radius bends, reduced opening and pipe restrictions, as well as operating pressures too low to move pigs in a pipeline at controlled speeds, without exceeding MAOP if pigs get stuck and increased pressure is needed to dislodge them.

6. Features in Common with ILI
Indirect Examinations
Validation/Excavation/Direct Exam
Integrate & Analyze Data
Identify & Address Data Gaps
Identify Remediation Needs
Determine Re-assessment Intervals
Obtaining as much Information about a pipeline is a key ingredient to the IMP processes. To refine and define the threats to the pipeline, possibly reduce the threat and the uncertainty, often it is desirable and economical to obtain more data about pipeline conditions and characteristics. Operators search their records for all available information and data about a pipeline’s physical characteristics, construction conditions, and its operating history, (corrosion locations, when CP was fists applied, lost, etc, and where any leaks occurred.
Indirect tools use aboveground diagnostic tools to locate and help prioritize indications.
Direct tools excavate at indications and examine pipe to better understand what is happening to the pipeline.
Methods use the results of examinations for total pipeline assessment.
Remediation Needs may involve pipe replacements, pipe repairs, coating reconditioning, etc.
Evaluating and confirming a pipeline’s integrity involves assessing the remaining risks, reordering anomaly and excavation priorities, and implementing preventive and mitigation programs to reduce or eliminate continued threats to the P/L.
Re-inspection intervals involves applying defect growth models to determine safe operating conditions and to determine intervals for inspection and when the pipe must be re-evaluated.

7. Factors Impeding Hydro-Test
Service Interruptions
Sole Source Supplies
Concerns of Causing Pipeline Damage
Dewatering Concerns/Difficult to Dry
Concerns have been stated that hydro testing grows pipe imperfections and cracks, may do more harm to the pipeline than verify a lines’ integrity, and may result in supply interruptions if water is not completely removed after testing, and may even foster internal corrosion.

8. Factors Impeding Hydro-Test
Dewatering Concerns/Difficult to Dry
Growth of Sub-critical Defects
Water Availability & Disposal
No Characterization of Future Risk
Concerns have been stated that hydro testing grows pipe imperfections and cracks, may do more harm to the pipeline than verify a lines’ integrity, and may result in supply interruptions if water is not completely removed after testing, and may even foster internal corrosion.

9. DA Basics - Overview
Distinct Assessment Process for each Applicable Threat (i.e., EC, IC, & SCC)
Scope of DA as an IM Assessment is more Limited than either ILI or Hydro
What is critical for success in using the Direct assessment process is:
Expertise, skill, and experience in understanding and implementing the NACE ECDA, ICDA and SCC Standards.
Processes of gathering, integration and analysis of data both historical to the pipeline and newly obtained data.
Mechanical Damage detection (or third party damage (TPD)) by ECDA will be limited by presence of coating holidays. It is important to understand the limits of any IMP approach, what threats can be expected and what tools are capable of addressing that threat. If a pipeline is expected to contain failure threats other than those that may be discovered by DA tools, such as material defects, cracks at welds, design or construction defects, low toughness levels, gouges covered over, etc, other tools must supplement DA tools to address these.
Stress that assessment and integration and analysis of data during all steps of the DA process is very important.
There are some advantages compared with Hydro and ILI as we’ll see a bit later.

10. DA Basics - Overview
May be the Assessment Method of Choice (esp. for Non-piggable Lines and Low-Stress Gas Lines that cannot be Hydro Tested)
Involves Integration of Risk Factor Data to Identify Potential Threats
What is critical for success in using the Direct assessment process is:
Expertise, skill, and experience in understanding and implementing the NACE ECDA, ICDA and SCC Standards.
Processes of gathering, integration and analysis of data both historical to the pipeline and newly obtained data.
Mechanical Damage detection (or third party damage (TPD)) by ECDA will be limited by presence of coating holidays. It is important to understand the limits of any IMP approach, what threats can be expected and what tools are capable of addressing that threat. If a pipeline is expected to contain failure threats other than those that may be discovered by DA tools, such as material defects, cracks at welds, design or construction defects, low toughness levels, gouges covered over, etc, other tools must supplement DA tools to address these.
Stress that assessment and integration and analysis of data during all steps of the DA process is very important.
There are some advantages compared with Hydro and ILI as we’ll see a bit later.

11. Keys to Successful DA Expertise, Skill, Experience
Follow NACE Standards
Document Justifications for Not Implementing “Should” and “May” Recommendations in the Standards
Documents Reasons for Program Decisions and Options Selected
Take some time here to explain some keys to successfully implementing a DA approach.
What is critical for success in using the Direct assessment process is:
Expertise, skill, and experience in understanding and implementing the NACE ECDA, ICDA and SCC Standards.
Processes of gathering, integration and analysis of data both historical to the pipeline and newly obtained data.
Stress that assessment and integration and analysis of data during all steps of the DA process is very important. The amount of data and the quality of data will be a key to successful application of DA.
Examples of the Types of Data that will be required:
Design and pipe characteristics
Materials of construction
Construction practices
Cathodic protection application history
CP survey data
Repair and maintenance history (including pipe inspection reports)
Locations of 3rd party construction
Locations of components and appurtenances (valves, taps, supports, clamps, sleeves, casings, etc.)
Soil characteristics
Other integrity surveys or tests (ILI runs)

12. Keys to Successful DA (cont.)
Data Management
Collection, Integration, Analysis
Data Quality
Understand Limitations of DA
Provide Detailed Procedures for All Process Steps
Take some time here to explain some keys to successfully implementing a DA approach.
What is critical for success in using the Direct assessment process is:
Expertise, skill, and experience in understanding and implementing the NACE ECDA, ICDA and SCC Standards.
Processes of gathering, integration and analysis of data both historical to the pipeline and newly obtained data.
Stress that assessment and integration and analysis of data during all steps of the DA process is very important. The amount of data and the quality of data will be a key to successful application of DA.
Examples of the Types of Data that will be required:
Design and pipe characteristics
Materials of construction
Construction practices
Cathodic protection application history
CP survey data
Repair and maintenance history (including pipe inspection reports)
Locations of 3rd party construction
Locations of components and appurtenances (valves, taps, supports, clamps, sleeves, casings, etc.)
Soil characteristics
Other integrity surveys or tests (ILI runs)

13. Today’s Discussion will Focus on ECDA
NACE RP0502 has been Issued
ECDA Process is More Mature than ICDA or SCCDA
Overview of NACE RP0502 Process for ECDA
PSIA of 2002 requires OPS to address DA, this OPS NPRM or one in future will reference the standard, and TPSSC recommended that OPS consider DA equivalent to ILI and Hydro.
The NACE Std on ECDA has been issued. So today we will focus on ECDA. It is a more mature and better understood technique. NACE will brief you later today on the status of development of standards for ICDA and SCCDA.
ECDA is a process to find Holidays, breaks in a pipeline’s coating, where corrosion can attack the pipe wall and reduce its safety margin of operation. Mechanical Damage detection (or third party damage (TPD)) by ECDA will be limited by presence of coating holidays. It is important to understand the limits of any IMP approach, what threats can be expected and what tools are capable of addressing that threat. If a pipeline is expected to contain failure threats other than those that may be discovered by DA tools, such as material defects, cracks at welds, design or construction defects, low toughness levels, gouges covered over, etc, other tools must supplement DA tools to address these.

14. Limitations of ECDA ECDA Can Not Deal With:
Lines Susceptible to Seam Failure
Near-neutral pH SCC
Fatigue Failures in Liquid Lines
Internal Corrosion
Plastic Pipe
Pipe in Shielded Areas
The NACE Std on ECDA has been issued. So today we will focus on ECDA. It is a more mature and better understood technique. NACE will brief you later today on the status of development of standards for ICDA and SCCDA.
ECDA is a process to find Holidays, breaks in a pipeline’s coating, where corrosion can attack the pipe wall and reduce its safety margin of operation. Mechanical Damage detection (or third party damage (TPD)) by ECDA will be limited by presence of coating holidays. It is important to understand the limits of any IMP approach, what threats can be expected and what tools are capable of addressing that threat. If a pipeline is expected to contain failure threats other than those that may be discovered by DA tools, such as material defects, cracks at welds, design or construction defects, low toughness levels, gouges covered over, etc, other tools must supplement DA tools to address these.

15. Limitations of ECDA ECDA has Limited Applicability to:
Mechanical Damage (Only to the Degree that Coating is also Damaged)
The NACE Std on ECDA has been issued. So today we will focus on ECDA. It is a more mature and better understood technique. NACE will brief you later today on the status of development of standards for ICDA and SCCDA.
ECDA is a process to find Holidays, breaks in a pipeline’s coating, where corrosion can attack the pipe wall and reduce its safety margin of operation. Mechanical Damage detection (or third party damage (TPD)) by ECDA will be limited by presence of coating holidays. It is important to understand the limits of any IMP approach, what threats can be expected and what tools are capable of addressing that threat. If a pipeline is expected to contain failure threats other than those that may be discovered by DA tools, such as material defects, cracks at welds, design or construction defects, low toughness levels, gouges covered over, etc, other tools must supplement DA tools to address these.

16. 4 Step ECDA Process of NACE RP0502
Pre-assessment
Indirect Assessment
Direct Physical Examination
Post-assessment
Basic concept is similar to ILI (pigging). Technologies can be used as a diagnostic tool to assess pipeline integrity. Defect growth models can be used to determine “safe” operating conditions and to determine re-assessment or inspection frequencies. Direct Assessment diagnostic techniques generate data concerning integrity characteristics.
Throughout each of the process steps, integration of data from inspection tools and historical data and operational data leads to assessments of the overall health of the pipeline system.

17. Pre-assessment Process Similar to Risk Assessment
Assemble and Analyze Risk Factor Data
Pre-Assessment
Data collection
Threat Analysis
ECDA feasibility for pipeline
Indirect inspection tool selection
ECDA region identification

18. Pre-assessment Purpose:
Determine Whether ECDA Process is Appropriate and Define “ECDA Regions”
Select Appropriate Indirect Inspection Tools (e.g., CIS, DCVG, PCM, C-SCAN)
Complementary Primary and Secondary Tools are Required
Identify Inspection Expectations
Pre-Assessment
Data collection
Threat Analysis
ECDA feasibility for pipeline
Indirect inspection tool selection
ECDA region identification

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

20. Pre-assessment ECDA Indirect Insp. Tool Feasibility
Complementary Tools – Evaluate pipe with different technologies (see table 2 of NACE RP0502)

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

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

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

24. Indirect Inspection Close Interval Survey (CIS)
Direct Current Voltage Gradient (DCVG)
C-Scan
Pipeline Current Mapper (PCM)
Alternating Current Voltage Gradient (ACVG) (PCM with A-Frame)
Examples of the kinds of tools that may be used in ECDA.

25. Indirect Inspection Pearson Ultrasonic Waveform
Soil Resistivity, Pipe Depth
Examples of the kinds of tools that may be used in ECDA.

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

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

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

29. Indirect Inspection Purpose: Apply Primary and Secondary Tools
Locate Areas Where Coating Damage May Exist
Evaluate Whether Corrosion Activity is Present
Apply Primary and Secondary Tools
Indirect Examination Objective: Identify coating faults and areas where corrosion activity may have or may be occurring.
The step utilizes a minimum of two complementary indirect techniques or tools.
Also, extremely important to correlate geospatial tool data – locations where readings are being taken, along with documenting surface conditions, other utility facilities at the location of the readings, trench indications, etc, along with operating history data

30. Indirect Inspection Timing Such That Conditions are Same
Overlay and Evaluate Data for Clarity, Quality, and Consistency
Distance Correlation Should be Good
Indirect Examination Objective: Identify coating faults and areas where corrosion activity may have or may be occurring.
The step utilizes a minimum of two complementary indirect techniques or tools.
Also, extremely important to correlate geospatial tool data – locations where readings are being taken, along with documenting surface conditions, other utility facilities at the location of the readings, trench indications, etc, along with operating history data

31. Indirect Inspection via CIS
May Detect Large Coating Holidays
Measure Pipe to Soil Potential at Regular Intervals (2.5 – 5 ft. Desirable)
Protection criteria
-850mV polarized potential
100mV polarization

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

33. Indirect Inspection via DCVG
Measures Voltage Gradient in Soil
CP Current Greatest Where Coating is Damaged
V = I*R
V = I*R

34. Indirect Inspection via DCVG
Interrupt Rectifier to Determine ∆V
One Electrode
Two Electrodes
Parallel or perpendicular to ROW
Coating Holiday Size Indicated by % ∆V
Triangulation Used to Locate Holiday
V = I*R
V = I*R

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

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

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

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

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

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

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

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

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

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

45. Direct Physical Examination
Remaining Strength Analysis
ASME B31G
RSTRENG

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

47. Post-Assessment Evaluates Composite Set of Data and Assessment Results
Sets Re-inspection Intervals
Validates ECDA Process
This step may result in reordering priorities of anomalous conditions,
It may identify continuing excavation needs for further evaluations and more data upon which to base a decision and eliminate uncertainty of as to whether further work is required.
It may identify the need for other assessment technologies I.e. ILI especially if numerous conditions are identified with ECDA tools, too numerous to dig all of them and analyze the pipe at each location.

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

49. Post-Assessment Remaining Life Growth Rate Measured Corrosion Rate
Maximum Depth / Burial Time
16mpy (80% C.I. for Corrosion Tests)
0.3mm/y if at Least 40mV CP Demonstrated

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

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

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

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