Oil Sealed High Vacuum Pump

In this type, the pump is immersed in the sealing fluid (oil) and this is re circulated. The vapors sucked by the pump are exhausted thru the oil resulting in the vapors condensing in the oil and contaminants. Again if the vapors are corrosive then the pump itself will be subject to corrosion and heavy maintenance. To regain the required ultimate vacuum one needs to service the pump and fill in fresh oil which is time consuming and expensive.