Internal Corrosion Direct Assessment (ICDA)
MATCOR has performed ICDA evaluations of numerous pipelines in accordance with NACE Standard SP0206-2006 Dry Gas Internal Corrosion Direct Assessment (DG-ICDA.) The basis behind ICDA is that detailed examination of locations along a pipeline where an electrolyte such as water would first accumulate provides information about the remaining length of pipe. The primary goal of the approach is to determine if internal corrosion is likely or unlikely to exist in a chosen length of pipe. Locations most likely to accumulate electrolyte are predicted using the results of pipeline multi-phase flow modeling. If the locations along a length of pipe most likely to accumulate electrolyte have not corroded, then other locations less likely to accumulate electrolyte may be considered free from corrosion and not require further examination. The method is applicable for gas transmission lines that normally carry dry gas but may suffer from short term upsets of wet gas or liquid water.
The ICDA process is a four step approach as follows:
The Pre-assessment phase involves collecting historical and operational data regarding the pipeline to assure that the ICDA methodology is appropriate for the particular pipeline, plan the collection of field data during the indirect inspection phase and to collect the necessary operational data to properly perform multi-phase modeling.
Utilizing sub-meter accurate GPS and a pipeline current mapping (PCM) tool to collect accurate depth of cover data, a pipeline elevation profile is created from data collected along the operator's pipeline. This data, in conjunction with the multi-phase flow modeling calculations determined by our liquid hold-up software allows for critical inclination angle locations to be identified as potential water hold-up locations.
Based on the model results developed in the indirect inspection, multiple excavations can be performed to allow for direct physical examination of the presdicted hold up points. Ultrasonic thickness testing of the excavated pipeline is performed to evaluate whether or not internal corrosion is a present threat at these hold-up locations.
During this step, MATCOR provides a detailed report outlining the results and assessing the effectiveness of the ICDA process and recommending reassessment intervals.