Gasunie applies the External Corrosion Direct Assessment (ECDA) methodology to ensure the integrity of its
non-piggable pipelines. To have a structured methodology available, a Pipeline Integrity Management System
(PIMS) is in operation. For the non-piggable pipelines an ECDA management software module has been
developed which is in operation. Within the ECDA process the indirect inspections (surveys) were found to be one
of the critical factors. With the objective to improve the productivity and reliability of the ECDA process as well as
the workability for surveyors, KEMA developed a new survey set. During 2007 and 2008 initial test were carried
out to demonstrate basic principles of improvements. Based on these results, it was decided to spend R&D efforts
on developing a prototype CP survey set that had to be capable of including new survey methods in addition to
existing methods.
From the third quarter of 2008 onwards, this prototype has been applied extensively under realistic practical
conditions in which new methods have been compared with existing methods.
The results of workability for surveyors have improved, as well as the results of the survey methods, particularly in
situations with:
• External interference by stray currents
• External interference by AC interference
• Pipelines with rather large depth of cover.
The productivity of surveys remained dependant on the number of defects and could not be improved
significantly. However, as the survey set produces data which is ideally formatted for the ECDA management
software module, the productivity of the entire process was significantly improved.
KEY WORDS: Close-interval potential survey, close-interval survey, CIPS, CIS, DCVG, external corrosion direct assessment, ECDA, indirect inspection, potential survey, cathodic protection survey, CP