Dryflo Model GDP 250 from Graham Vacuum and Heat Transfer has no working fluids.

Dryflo Model GDP 250 from Graham Vacuum and Heat Transfer incorporates shaft-mounted hook-and-claw rotors that push the gas or gas mixtures through the pumping stages without mechanical compression. The dry vacuum pump has no working fluids and employs chemical-duty mechanical seals, so it can be started while flooded with liquid.

June 2000, RS# 207