Question: Must historical operating conditions be considered, or only current operating conditions, when using ICDA?
Answer: Historical conditions must be considered. The ICDA process is designed to identify areas where internal corrosion may have occurred, largely due to the fact that an electrolyte is/was present. Direct examinations are then conducted in those areas to determine whether internal corrosion has, in fact, occurred. The fact that an electrolyte is not present under current operating conditions may not mean that internal corrosion does not exist if electrolytes were introduced under previous operating conditions. For at least the first application of ICDA, then, considering historical conditions could be important. Of course, other information that confirms a lack of internal corrosion in areas where electrolyte could have been present historically (e.g., in-line inspection results, results of pipe replacement/examination) could alleviate the need to consider historical conditions. Operators should assure that there has been an opportunity to detect internal corrosion that may have occurred in the past, or should look for it during their initial ICDA.