The Influence of Long Operation on Fatigue Strength of Pipe Steel

The paper presents the results of fatigue tests of specimens cut from 630-mm-diameter 018GS2 steel pipes from the "Druzhba" oil pipeline prior to and after a long period of operation. We have found that the fatigue strength of the base and weld metal decreased upon long operation by 14.9% and 9.5%, respectively. Analysis has demonstrated that in the course of operation of linear sections of oil pipelines the material properties of the inner pipe surface deteriorate steadily and substantially, and it is this deterioration which constrains the operating reliability of the pipeline.