Abstract: The washing tower feed pump was used for the gas water separation unit in the gasification device of a large coal chemical project and operated stably for nearly one year. A serious production accident of shutdown occurred because of broken shaft when there were no abnormalities appeared in the central control room and on-site inspection records. Entrusted by the owner, our company has carried out disassembly, cleaning, testing and maintenance of this pump. After replacing the pump shaft, mouth ring, shaft sleeve, bushing and other friction pair during this emergency repair, the pump has operated smoothly so far without similar accidents. Since the causes of the accident were unknown, this paper analyzes and troubleshoots the causes from such aspects as rotor strength, material selection, and structural design. It finally found the causes for the accident accepted by both sides. Meanwhile, the paper summarizes the key considerations for the safe and stable operation of the pump.

Key words: multistage pump, broken shaft, cause analysis