Abstract: The operation condition of the rich gas compressor in delayed coking unit is directly related to the smooth operation of the whole unit, and the steam turbine is the most important part of the driving unit. This paper analyzed some problems of rich gas compressor in delayed coking unit during the operation period. Combining with the operation parameters, it analyzed the causes of the failure according to the disassembly and inspection situation. Meanwhile, the paper summarized the problems encountered in the start-up process of the unit after maintenance in July 2020 and the situation in operation. It focused on analyzing the phenomenon of the speed control system in the start-up stage of the unit and several large fluctuations of the steam turbine inlet volume in operation. In addition, it also analyzed the problems encountered in the process of starting-up after the overall replacement of the speed control system. After this troubleshooting, it was concluded that the bolt fracture of the governing valve was the direct cause of the decline of the turbine's power capacity, and the indirect cause of the failure was that the pressure bearing parts were not replaced after two consecutive long-term operation. Each overhaul of a large oil refining unit determines whether or not the whole unit could run for a long period of time, so the depth and accuracy of each overhaul of a large unit plays a crucial role.

Key words: delayed coking unit, rich gas compressor, steam turbine, speed regulating device