(EXTERNAL CORROSION DIRECT ASSESSMENT (ECDA)
ECDA is a continuous improvement process through successive applications, ECDA should identify and address locations at which corrosion activity has occurred, is occurring, or may occur.
ECDA is a continuous improvement process through successive applications, ECDA should identify and address locations at which corrosion activity has occurred, is occurring, or may occur.
ECDA includes the following four steps:
Step 1: Pre-assessment
Step 2: Indirect Inspection
Step 3: Direct Examination
Step 4: Post- Assessment
In indirect inspection step, at least two complementary indirect inspection tools such as DCVG and CIPS should be selected for all ECDA regions.
Direct Current Voltage Gradient )ِِDCVG(
DCVG is a coating inspection method that works by detecting the voltage gradients generated in the soil by the passage of cathodic protection current to the exposed steel at a fault in the protective coating on a pipeline.
Close Interval Potential Survey )CIPS(
CIPS is the effective method of determining the level of cathodic protection on the underground/ underwater metallic pipelines. A CIPS survey is the measurement of the rectifier ON and instant OFF potentials (IR Free) along a pipeline cathodically protected by an impressed current cathodic protection system.
C-Scan
C-Scan inspection method accesses the state of pipeline’s coating according to attenuation of electric current. Using this method, it is possible to determine the depth, the route, the geographical location of the pipeline, to examine the quality of coating and to detect the defect. In this method the state of coating is categorized into 4 classes according to its quality.
After pre-assessment step, and when the indirect inspection data are taken, indications should be identified and aligned for comparison, then direct examination should be done. After excavations and data collection, the remaining strength should be evaluated. Then, any existing root cause of all significant corrosion activity should be identified. At the Post-Assessment step, remaining life calculations and definition reassessment intervals should be done. Finally ECDA effectiveness should be assessed.