The serv ice life of the components and the efficiency of centrifugal-flow compres so r s depends to a great extent on the design of the ro to r impel ler seal. Conventional floating-type contac t f ree seals loaded with elast ic steel springs cannot be used in the blowers on mainline gas ducts at compres so r stations. End whip of the ro tor is experienced in these blowers because of the high rotation speed (n ~8000 rpm), which sets the seal r ing vibrating. A s l i t type face seal backing up the radia l labyr in th seal great ly improves the blower efficiency and reduces the axial force acting on the thrust bearing [1]. However this type of seal also has its shor tcomings. Gas f rom the delivery cavity leaks through the slit into the intake cavity imnorma l operation. Under surge conditions, the ro to r is set vibrating at a high frequency in the axial direction, and its cover disk s t r ikes its end face against the seal ring and wreaks havoc with the latter. After a surge lasting no more than 3-5 sec, the sys tem will still function as a whole, but it will have to be taken off s t r eam in o rder to replace the ring in the mechanical shaft seal. If the ro tor is shifted axially toward the intake site in an accident because of wear on the thrust bearing, the braking torque on the shaft brought about by the frict ion force of the ro to r on the fixed seal r ing will be so formidable that the reduction gear train in the blower power drive will be hopelessly ruined.