Abstract: This paper focuses on the frequent leakage of the mechanical seal of the bottom pump in the atmospheric and vacuum distillation unit of a certain refinery, which led to multiple operational fluctuations of the unit and affected the normal production order of the refineryseriously. Each seal leakage causes direct economic loss of nearly 100,000 yuan and a large amount of residue oil needs to be cooled and emptied for seal replacement. This not only wastes precious resources, but also increases processing costs and environmental pollution risks. To solve the problems, this paper analyzes in depth various reasons affecting the mechanical seal effect. Through elaborate optimization design of the sealing structure and precise adjustment of the sealing auxiliary system, the expected effects were achieved after the new scheme was put into use. This has improved the operational stability and economical efficiency of the unitsignificantly.

Key words: atmospheric and vacuum distillation unit, mechanical seal, spiral seal, pumping ring, auxiliary system