FIELD SURVEY RESULTS OF A RECENTLY DEVELOPED CATHODIC PROTECTION SURVEY METHODS TO IMPROVE THE ECDA PROCESS

摘要

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:1. External interference by stray currents2. External interference by AC interference3. 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.