Abstract: This paper introduced the short service life and frequent replacement of mechanical seals of the decompression tower bottom pump of an atmospheric and vacuum distillation unit, as well as the obvious axial displacement detected during startup and shut-down by on-line monitoring. Based on the comprehensive analysis on the running condition of the pump, the paper proposed a specific scheme to improve the pump head structure and sealing type of the pump. This has solved the problem of axial displacement of the pump and frequent seal failures, prolonged the operating cycle of the pump and eliminated the potential safety hazards of high-temperature oil pump during operation.

Key words: decompression tower bottom pump, axial displacement, mechanical seal, fault analysis