Diffusion pumps boil the oil fluid and then direct the hot oil vapor at very high speeds outwards and downwards through cone-shaped jets. Gas molecules entering the top of the pump are drawn in the vapor stream and redirected to the lower areas of the pump. As they reach the lower part of the pump body gas molecules are pumped away through the pump’s exhaust port and into to the mechanical backing pump. When the hot vapor comes in contact with the cold pump body it changes back to a liquid and drains into the boiler to recirculate through the pump again. With the help of a baffle in the exhaust area of the pump, any remaining oil vapor is condensed back inside the diffusion pump.
“Oil diffusion pumps have been the workhorse in high-vacuum pumping for many decades and remain the standard for industrial applications like brazing/soldering, E-Beam welding, and large-area coating. Their investment costs are relatively low, and they can provide pumping speeds of up to 50.000 l/s. In this blog, we will explain the working principles of oil diffusion pumps, including how to apply and control them in vacuum systems, the typical dos and don’ts, and provide several application examples.”
Source: Vacuum Science World