Background Oil field pipelines are a system of sequentially connected elements (pipes, fittings, pipe parts), so the failure of any of them leads to a stop in the transportation of the product and economic losses. When analyzing the places of destruction of welded samples of thermally hardened steels and the value of the relative transverse constriction, it was found that in the range of relative thicknesses of the «soft» layer, when the strength of the welded samples is at the level of thermally hardened base metal , destruction occurs both on the base metal at a distance from the weld, and along the weakened area in the heat-affected zone. At large values, the destruction of welded samples occurs, as a rule, along a weakened area near the weld. A characteristic feature of fracture of welded specimens in a weakened area is a decrease in the relative transverse narrowing as compared to when the fracture occurs in the thermally hardened base metal at a distance from the weld, although, as is known, the value of the relative transverse narrowing for thermally hardened metal is lower than for normalized. Aims and Objectives To develop recommendations on the choice of parameters for the hydraulic testing of the pipeline in the area of 266-505 km in the Tyumen region. Results Based on the results of theoretical and experimental studies, as well as taking into account the basic principles of the fracture mechanics, recommendations have been developed for choosing the parameters of the hydraulic testing regime for an oil pipeline at a section of 266-505 km in the Tyumen region. Crack depths obtained 3.9-4.3 mm correspond to acts of technical failures of the oil pipeline on the site 335-337 km. Conducting scientific research in Russia and abroad to increase the strength, ductility, crack resistance of large-diameter pipes and their welded joints, refinement of methods, design estimates will allow the development of new Building Codes and Regulations, State Standards, update regulatory and technical documentation, significantly reduce financial expenses for accident recovery, reconstruction, overhaul and to ensure the economic and environmental safety of the main and field pipelines of the Russian Federation.