The main pipelines, like many engineering structures, are subject to high operational safety standards. The safety of their operation is supervised by various institutions from the operator, including supervisors such as the Office of Technical Inspection. Safe operation requires knowledge of their technical condition and trends. One of the important sources of information on the condition of pipelines is their periodic inspection carried out with so-called smart pigs. As a result of the inspection, the operator expects the following questions to be answered: what is the condition of the pipeline examined; where and what metal losses are occurring in its construction; what are the hazards causing these damages for the safety of the pipeline operation; what is the rate of increase in the size of metal losses in the pipeline wall. This article presents technical solutions and methodology to answer the above questions.