Use of oil-free mechanical pumps with leak detectors

Abstract

With the growing demand for contamination-free leak detectors, the replacement of the oil-sealed mechanical pumps has become an important issue. Despite their higher total ultimate pressure (0.010 Torr), the oil-free pumps retain the pumping speed for helium at pressures less than 1×10−7 Torr. This is sufficient in most applications using a turbomolecular pump as the high vacuum pump. Experimental results obtained with a Contra-Flow leak detector with both mechanical pumps replaced by oil-free pumps are presented. System stability and helium background levels permit leak rate measurements near 2×10−10 atm cc/s.