Managing And Storage Of External Corrosion Direct Assessment Data

External corrosion direct assessment (ECDA) involves a large of amount of data resulting from the associated indirect inspections and direct examinations. It also requires data to even begin with pre-assessment activities.

This article covers the data storage and management considerations of all four ECDA stages as well as enterprise data storage considerations as outlined in the following sections.

ECDA Stage 1
ECDA Stage 1 is pre-assessment data gathering. Prior to gathering data for the pre-assessment stage, establish your criteria for determining ECDA regions (if you don’t already have it captured in internal documentation or work instructions). Then access the amount and condition of data that is available to you as required by your criteria. If your assignment of indirect inspection methods relies on data in addition to ECDA regions, then you should also consider it in this stage. Your ECDA region determination may look something like Table 1.

The ECDA region criteria implies that you should evaluate the condition and availability of surface type as well as the proximity of power lines, railroads and third-party pipelines.

You may also decide to gather data such as soil class, soil resistivity, leak history and CP effectiveness to determine an initial external corrosion rate and likelihood of active external corrosion. If this data is not utilized to determine ECDA regions, it may be better to account for it after ECDA region determination as initial external corrosion rate and likelihood of active external corrosion are attributes of determined ECDA regions.

It is ideal if you can leverage an up-to-date database (perhaps a centrally maintained pipeline GIS) for Stage 1 data gathering, but you may be forced to locate the data from various sources and pull it into one location for your analysis. If some of the required data is not available, you may have to adjust your ECDA region criteria to meet what data you have available.

When collecting Stage 1 data, the most efficient way is to store each data type independently and use “dynamic segmentation” upon analysis. This allows you to minimize the adjustment of segments as you compile the data. Figure 1 explains the dynamic segmentation process.

Figure 1: Dynamic Segmentation Example.

If dynamic segmentation is not an option as part of your analysis, you should still try to store each data type independently and manually segment that data as the last step of the Stage 1 data gathering process.

Once you have your ECDA regions determined, it should be a fairly easy step to assign indirect inspection methods. More challenging is the determination of initial external corrosion rate and likelihood of active external corrosion. To do this, you should already have your logic established for determining these values. Your logic should account for using the worst-case values (in the instance that you have both soil class and soil resistivity data for determining initial external corrosion rates for example). At this point, you can “overlay” the data you have available such as soil class, soil resistivity, leak history and CP effectiveness and for each ECDA region, determine the values.