Abstract: Aiming at the failure of the girth welding in compressor inlet process piping, the analysis approaches such as the macro morphology, chemical composition, mechanical properties, metallographic structure and corrosion products were adopted to explore the failure reasons in combination with corrosive medium and corrosion acceleration test in order to improve the equipment integrity level in the compressor station. The results show that the corrosion rate of the weld is higher than that of the substrate in both gas and liquid phases, and the corrosion rate of the liquid phase is much higher than that of the gas phase. The failure site is located at 6 o 'clock direction at the bottom of the tube, and the failure develops from the inner wall to the outer wall. The external cause of girth welding failure is the welding quality defect, which forms turbulent cavitation zone locally in the weld, and the internal cause is the fluid containing corrosive gases such as CO₂ and H₂S. H₂S is the main corrosion type, and the looseness of corrosion scaling products creates conditions for the formation of block batteries. It is suggested to change the corrosion environment of pipeline by ungrading welding technology, improving welding quality, adding natural gas purification devices and dewatering devices. The results of this study can provide practical reference for failure analysis of the same type of process piping and for improving the management level of equipment integrity.

Key words: compressor station, process piping, girth welding, failure, CO₂, H₂S