The gas flow through Polish pipeline systems have been gradually changing from the east-to-west, to the opposite direction in the last few years. Based on this fact, a requirement to increase the capacity of gas pipelines to transport gas at the pressure of 7.4 MPa has occurred in some Polish regions. This is achieved not only by the construction of new high pressure pipelines but also by integriting of older revalidated pipelines operated in the past at the lower pressure into the pressure level of 7.4 MPa. A concrete example of this comprehensive approach to ensuring the integrity was revalidation of 55 km long gas pipeline DN 400 in south-western Poland. Revalidation included the following basic steps: • cleaning the pipeline • performing of in-line inspection by MFL tool, • material test of samples taken from the original pipeline, • model integrity test of pipe body vessel from a pipe taken from the original pipeline, • design of working procedures for integrity test, • preparation the pipeline for testing, • integrity test performance and drying by super dry air • final report