Managing the Aging of Dynamically Loaded Pipelines

In the Russian Federation, the requirements for managing the aging (service life) of pipelines classified in the designs of nuclear power plant (NPP) units as elements of safety classes 1, 2, and 3 according to the federal regulations and rules are established in NP-096-15. For the dynamically loaded pipelines of nuclear power plants, one of the most “dangerous” loading factors is just vibration loads, as corrosion/erosion wear values are small for the real structures of NPP pipelines owing to the application of corrosion-resistant steels at a limited velocity of fluid flows (according to NP-068-05, the water flow velocity up to 5 m/s, and the steam and gas flow velocity up to 60 m/s). Some problems of managing the aging of dynamically loaded pipelines are considered. A calculation-experimental method of estimating the stress-strain state of a pipeline under vibration is proposed to determine its damageability under cyclic loads. It is recommended to use the values of accumulated and ultimate damage as a pipeline service life characteristic under vibration loading instead of normalized frequencies or amplitudes of vibrations.