External Corrosion Direct Assessment (ECDA)
We cross-check pipeline data with above-ground surveys to locate where external corrosion may exist, and verify it at the critical points.
What it is
External Corrosion Direct Assessment (ECDA) is a four-step process to assess and reduce the impact of external corrosion on a buried pipeline. It not only locates existing defects: it also points out where they may form. It is the usual option when the pipeline cannot be inspected internally with an in-line inspection (ILI) tool.
When it is needed
- When the pipeline does not allow ILI.
- Within an integrity program, to assess the external corrosion threat.
- To prioritize excavations and repairs with field data.
How we do it
Pre-assessment: we gather data on the pipe, the coating, the cathodic protection system and the history. With that we verify that ECDA is applicable, divide the route into ECDA regions and select the indirect inspection techniques.
Indirect inspection: we survey from the surface with at least two complementary techniques, such as Close Interval Survey (CIS) and Direct Current Voltage Gradient (DCVG). We classify each indication by severity and define the excavation urgency.
Direct examination: we excavate at the priority points, inspect the coating and the pipe, measure the corrosion we find, and record the soil and the potential at pipe depth.
Post-assessment: with the data from all steps we define the interval until the next assessment, verify the effectiveness of the process and issue the recommendations.
Equipment
Specific equipment for each indirect inspection technique defined in the pre-assessment.
Deliverables
- Pre-assessment report with the ECDA regions.
- Indirect inspection results: profiles, list of indications and severity.
- Excavation prioritization.
- Direct examination sheets with photographic record.
- Final report in PDF, with conclusions and recommendations.
- Georeferenced KMZ file.
Standards
NACE SP0502 – NACE SP0207 – NACE SP0169
Where we apply it
Pipelines – Industrial plants – Service stations and fuel depots