EFFICIENT ANTICORROSIVE PROTECTION FOR TURBOMOLECULAR PUMPS, THE INVERTED DYNAMIC SEAL ELIMINATES THE PURGE GAS-LINE CONNECTION

The pumping of chlorinated and fluorine gases exposes the magnetic bea rings, the ball bearings and the motor of turbomolecular pumps to corr osion. The current protection systems use a neutral gas flow to exhaus t the corrosive gases from reaching the bearings. The dynamic seal we tested operates upon the Holweck molecular pump basis. A 150 Pa pressu re drop is produced across the bearing chamber. The gas partial pressu re is consequently reduced to 10(-9) Pa. Its efficiency is comparable to a N2 purge of 6 x 10(-2) Pa m3 s-1. The inverted dynamic seal is a simple and reliable built-in anti-corrosive system.