Evaluation of mechanical properties of gas pipeline DN 500 after more than 40 years of its operation

Abstract The paper deals with the mechanical properties of steel gas pipeline DN 500 after more than 40 years of operation. Mechanical properties of the pipeline were established by a tensile test at an ambient temperature according to the standard EN ISO 6892-1. The resistance of the pipeline against brittle failure was evaluated by using Charpy impact test according to EN 10045-1. The character of fracture surface after the Charpy test was analysed by using scanning electron microscopy. A high proportion of transcrystalline cleavage was a characteristic feature of fracture surfaces. Mechanical characteristics obtained by static tensile testing were compared with the values obtained from steel manufacturer. Higher elongation was observed in a parallel direction compared to the perpendicular direction to the axis of the pipe. The observed anisotropy of properties was related to the distribution of inclusions in the direction of the deformation of the steel sheets used for the pipeline construction.