e xternal c orrosion d irect a ssessment nace 2005 northern area western conference by gord parker,...
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E xternalC orrosionD irectA ssessment
NACE 2005 Northern Area Western Conferenceby
Gord Parker, C.E.T.Radiodetection Ltd.
Background
(USA) The Pipeline Safety Improvement Act of 2002signed into law on December 17, 2002applies to natural gas transmission (dist. coming)must identify "high consequence areas (HCA)"
conduct risk analyses of these areasperform baseline integrity assessments of each pipeline segmentinspect the entire pipeline system according to a prescribed schedule and using prescribed methods
Other provisions of the law include
(US) The Pipeline Safety Improvement Act of 2002Participation in one-call notification programs Increased penalties “Whistle-blower" protection Qualification programs for employees O.Q. Government mapping of the pipeline systemOther Housekeeping Stuff
BUT…Some pipes have serious limitations to inspection
Not Pigable (small valves/openings, 90° fittings)No redundant loops – had to stay in service
Hence, no hydro-testing either
Best Quote I’ve heard this year…“Congress is a little leery of engineering because
you can’t barter, you can’t negotiate with it.”
Direct Assessment came alongIt seems to have been accepted & implemented fast
There are 3 types of DA (for 3 types of threats)External Corrosion (ECDA)Internal Corrosion (ICDA)Stress Corrosion Cracking (SCCDA)
ECDA is the most mature of them.RPO502 – 2002 is the defining NACE document
ECDA is a 4 Step ProcessPre-assessment
Most important stepIndirect Inspections
Above-ground ToolsDirect Examinations
Verification Digs AND MitigationPost-assessment
Define Reassessment Period (US: 7 yr typ. max)Assess Overall Effectiveness
Important DefinitionsECDA Region – Section(s) of pipeline with similar physical characteristics and history in which the same indirect inspection tools are used
Segment – A portion of pipeline assessed using ECDA. Consists of one or more regions.
HCA – High Consequence Area (higher population density, limited mobility, gathering places, etc.)
General NotesThere is some flexibility to chose suitable processesContinuous Improvement Process
Compare successive applications to gauge effectiveness
Primary Purpose – Preventing future problemsRP0502 is for onshore, buried, ferrous pipelinesStand-alone or compliment other tests (ILI, hydro)Has limitations (like all asses’mts), use appropriatelyUse under the direction of ‘competent persons’
Step 1 – Pre-AssessmentDetermine if ECDA is feasible and applicable
Collect ‘Soft’ Data (both current & historic) Construction, Operating, Maintenance, CP survey, Adjacent
Land Use (and changes to), and more This is a big part – spend the time planning
Define Regions Especially HCA
Select Indirect Tools appropriate for those regions
Include each of these Data ElementsPipe-Related
mat’l, diam.,thickness, year, seam type, coatingConstruction Related
year, route, aerial photos, construction practices, valves, depth of cover, more
Soils/Environmentalsoil, drainage, topography, use, frozen, wet
Corrosion ControlCP system, location, stray current, history, evaluation, coating
Operational Datatemperature, stress, fluctuations, excavations, accidents
Decide which tools are applicableClose-Interval Survey (CIS)AC Voltage GradientDC Voltage GradientPearsonElectromagneticAC Current Attenuation Surveys
Stray Current analysisDifferent regions may require different tools
Step 2 – Indirect InspectionsIdentify and Define the severity of coating faults, other anomalies, and areas where corrosion may beRequires at least two aboveground tools over the entire length of region
Then align & compare the data
More than 2 may be required
Gathering Indirect DataQuite expensiveDo it right the first timePlan for traffic, access, problems, surveyingConduct & Analyze with accp’d Industry PracticesReading spacing must be suitably fineDifferent tool (passes) done close in time as wellPrecise Geographic References (GPS)
Compare ResultsIf indirect tool results vary greatly, reexamine (directly if need be)Compare the results with Pre-Assessment
Step 3 – Direct ExaminationsPurpose: To determine which indirect indications are most severe and collect data to assess corrosionRequires pipe surface exposure & testingAt least one dig is always required
Steps IncludedPrioritization of IndicationsExcavations & Data CollectionMeasurements of Coating Damage & CorrosionRemaining Strength CalculationsRoot Cause AnalysisProcess Evaluation
Prioritization (3)Immediate Action Required
Ongoing corrosion likelyMultiple Severe IndicationsUnresolved Discrepancies from Indirect Exams
Scheduled Action RequiredSevere indications NOT in area of other severe
Suitable for MonitoringInactive or little likelihood of ongoing/prior corrosion
Measurements Used in Direct ExamsPipe-Soil potentialsSoil ResistivityWater & Soil Samples (ph, etc.)Under film liquid phPhotographic DocumentationOther Integrity Data
MIC, SCC, etc..
Coating MeasurementsTypeConditionThicknessAdhesionDegradation (blisters, disbondment, etc.)Corrosion productsMapping and photographic documentation
Mitigation Shall identify and undertake remediation
Aim to mitigate and preclude future problems
Assess Classification CriteriaReclassification & Reprioritization
Indications Encountered – 4 levelsIn each segment….
Immediate – dig allScheduled – dig most severe
If first use of ECDA, must dig 2
Monitored – dig most severe If first use of ECDA, must dig 2
No Indication – one excavation is required To validate Direct tests
Step 4 – Post AssessmentDefine re-assessment intervalsAssess overall effectiveness of ECDA programRemaining life calculationsFeedback & Continuous Improvement
ECDA Success RequiresExpertise, skill, and experience in understanding and implementing the standardDetailed procedures for all stepsDocument all decisions made in processAssessment and integration and analysis of data during all steps of the DA processData ManagementUnderstand what may limit DA effectiveness
CostA properly done ECDA process will have very similar costs to ILI.Don’t expect it to be an order of magnitude cheaper.
