The Welch Belt Drive Corrosive Series Vacuum Pump for the pumping of corrosive gases. the Chemstar's large oil resevoir dilutes contaminants. The pump draws clean oil from the top of the oil resevoir, not from the bottom as do direct drive vacuum pumps. Fewer moving parts increase the durability of the Chemstar. Vital parts are corrision resistant. Chemstar pumps rotate at speeds less than 580 RPH compared with over 1700 RPM of direct drive pumps for reduced frictional wear. Nitrogen purge standard - both degassing and cooling the pump oil reduce the corrosion rate in the pump.