ULVAC’s oil diffusion ejector pumps are generally used in industrial processes to provide high pumping speed. They are particularly well-suited for use in metallurgy, plastic coating and chemical manufacturing, where large quantities of gas have to be pumped away as quickly as possible.


  • These pumps have maximum pumping speed at 10-1 Pa level.
  • Stainless steel is used for the pump bodies of Model PBL-02 and PBL-04 in order to minimize outgassing of the pumps, eliminate corrosion and to ensure a long operating lifetime of the pump.
  • The PBL Series are particularly well-suited for the use as an intermediate pump between an oil rotary pump, a mechanical booster pump and oil diffusion pump.
  • The larger capacity pumps (PBL-06 – PBL-20) have the heaters directly immersed in the operating fluid for maximum thermal efficiency.

Working Principle and Structure

The oil diffusion pump consists of a pump body, boiler heater and 3-stage fractionating jet stack assembly. The working fluid (oil) is heated in the boiler, vaporized and streams out of each stage of the stack at high speed. Gases on the high vacuum (inlet) side of the pump are captured in the jet vapor by diffusion,and are carried from upper to the lower jet staged which compresses them in the process. These pumped gasses are then exhausted through the outlet  port to the fore pump. The vapor stream from the jet stack is cooled and condensed on the inner walls of pump body,and returned to the boiler. By repetition of this precess,evacuation is accomplished. The weir plate provided in the boiler permits return and recirculation of the work fluid,allowing the fractional distillation of the fluid to be a continuous process. (High vapor pressure components in the working fluid are evaporated at the outer zone of the pump housing,while low vapor pressure components are evaporated at the inner zone.)



















Dimension & Pumping Curve 

                                        PBL Dimension
                                  Pumping Curve