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SUMMARY
Shtoyko I. P. Methods for residual lifetime assessment of gas and oil pipelines
taking into account their corrosion-hydrogen degradation. – The manuscript.
The dissertation for competition of the scientific degree as a candidate of
engineering sciences by 01.02.04 speciality – Mechanics of deformable solid. – Karpenko
Physico-Mechanical Institute of the National Academy of Sciences of Ukraine, Lviv,
2018.
The work is dedicated to the development of models and methods for determining
the pipes residual lifetime of the oil and gas pipelines, under the influence of stress and
physico-chemical factors, namely, a non-stationary operating loading mode, hydraulic
attacks, and hydrogenation effect from the natural gas, the simultaneous action of
hydrogenation and corrosion, in-service steel pipes degradation. Thus, based on the
energetic approach, the calculation model for determining the gas pipeline residual
lifetime under cyclic change of natural gas pressure and hydrogenation influence was
developed. Using this calculation model, the residual lifetime for X60 steel gas pipeline
under cyclic loading and hydrogenation from natural gas was calculated.
Using the finite element method, a distribution of hydrogen concentration in the
wall of the gas pipelines and their welding joint, as well as in a compact specimen, was
found. These data were used in constructing the mathematic model for determining the
kinetics and the period of fatigue crack growth in a ring welding joint from steel X70 of
the gas pipeline under hydrogenation and cyclic change of the natural gas pressure, under
the corrosion potential and under cathodic protection.
The methods of the residual lifetime determining of oil pipelines with internal and
external cracks under hydraulic shocks, laminar and turbulent oil flows were developed.
The methods of the residual lifetime determining of the gas and oil pipelines steel
during their in-service degradation, under simultaneous action of constant loads and a
corrosive-hydrogenating environment were developed. The crack initiation after a certain

service time was considered, up to the essential degradation level. The pipeline steel
degradation during their operation was shown to reduce the residual lifetime essentially.
Keywords: pipes of gas and oil pipelines, calculation methods for the residual
lifetime assessment, corrosion-hydrogen degradation, energy approach, hydrogen
concentration, hydrogen embrittlement, stress corrosion cracking.