Abstract: The number of domestic RDS units is increasing. And the high-pressure feed pump is developing toward high temperature, high pressure and large flow, requirements for mechanical seals are becoming more stringent. Investigation results of the high-pressure feed pump seal in domestic RDS units show that the average service life of the seals is less than one year and some even fail within two months. Leakage of high temperature residual oil is extremely dangerous. In recent years, high-pressure feed pump seal of some new residue hydrotreating units has been designed as PLAN54, but many problems have been found in the early application process. Without experience for reference, the seal combination scheme is applied innovatively after constant exploring and improving. And the service life of the improved mechanical seal is prolonged to 790 days now from a few days at the very beginning. This paper makes a fault analysis on the PLAN54 seal used in certain domestic RDS unit and presents effective method for improvement.

Key words: residue hydrodesulphurization/RDS, high pressure feed pump, PLAN54, seal, fault, innovative application