Failure analysis of syngas bypass line rupture in an industrial ammonia plant

Abstract

Abstract In the ammonia plant, the transmission pipeline downstream of CO2 removal unit is suffering from severe corrosion problems worldwide. The safe operation of a transmission piping system depends on various factors that influence each other. The present work has been conducted to investigate the causes of rupturing the 10-inch synthesis gas bypass line downstream of CO2 removal unit in the second ammonia plant of Shiraz petrochemical complex (SPC). The line has been used to control the inlet temperature of methanator catalyst bed. The damage resulted in a large explosion, and the plant was unexpectedly shutdown. A detailed investigation was carried out from a metallurgical and process point of view to reveal the factors that play a major role in the failure of bypass line. The process evaluation was focused on operating variables and the detailed metallurgical investigation was based on microstructural assessment, chemical and reduced thickness analysis, micro hardness measurements, and metallography of transmission pipeline. The findings demonstrated that the failure of bypass line was attributed to the synergistic effect of erosion and corrosion, leading to the wall thinning of the upper part of the line from 9.2 to less than 2 mm and its subsequent rupture.