R and D series high vacuum pumps are used when the final absolute pressure required is very low. These pumps may run continuously connected to closed containers to be emptied but may not run continuously for a long time at atmospheric pressure. The exhaust from these pumps is not filtered, thus, special purifiers are available for fumes.
The operating principle of these pumps is similar to that of the lubricated pumps. However, in this case, the stator is immersed in the lubrication oil which has also the function of sealing the air loss. The pressure levels reached by this type of pump are higher than any other rotary vane pump. These pumps are equipped with a Gas Ballast system to avoid the condensation of the water vapour.
These kind of pumps can be made of a single rotor-stator group and are called Single Stage; or they can be made of two rotor-stator groups connected in series so the first group drain is connected to the second group intake system. The latter are called Double Stage.
