Accurate interpretation of in-line inspection data is a necessity for reliable remaining strength estimation and is an invaluable guide for field evaluation of corrosion defects. However, the important relation of interaction rules to the delineation of the length and width of individual corrosion areas has not been discussed in detail despite the many articles written on the topic of rupture pressure estimation derived from in-line inspection data on corrosion indications. There are almost as many interaction rules as there are operators using them. This article will
provide commentary and insight into the various interaction criteria presently being used by operating companies.