Abstract: In a large ethylene plant, the steam turbine used for the cracking gas compressor has experienced severe coking in thrust bearings du-ring operation and the axial displacement has remained in the alarm range for a long time, which eventually triggered high-high interlock and led to unplanned shutdown. The external manifestation of these issues are all characterized by excessive axial displacement in the compressor. When the axial displacement increases to the high-high interlock value, an unplanned shutdown will occur.The analysis has revealed that rotor axial force imbalance is the root cause of excessive axial displacement. Based on the actual operating conditions of the unit, this study tho-roughly resolved the aforementioned issues by expanding and relocating the balance pipe, as well as conducting domestically transformed thrust bearing modifications. These measures have yielded good results, while also pioneering the localization of critical spare parts for core units and accumulating valuable experience.

Key words: steam turbinelrotorlaxial forcelbalance pipelbearing