This post will explain the procedure for removing oil from a turbo pump if the vent valve failed and oil was sucked up into the blades.

Under normal conditions, when an oil rotary vane mechanical backed turbo pump is turned off it should be vented (preferably with dry nitrogen) to prevent the back streaming of oil or oil vapors onto the turbo pump blades. Sometimes the vent valve will fail, or some other mishap can lead to oil being sucked up the roughing line from the mechanical pump into the turbo pump. When this happens, the symptoms are that the pump will not come up to full speed – usually only 50% to 75%. Or, sometimes the pump will come up to full speed (barely) but the pumping efficiency has been greatly reduced.

For Balzers turbo pumps, the procedure is to pull the turbo pump and place it in a beaker of isopropanol up to the bottom of the inlet as shown in the picture below. For other turbo pumps the procedure is probably similar, but you should check the turbo pump manual to be sure. NOTE: This procedure is only for turbo pumps that have a magnetic bearing on the front end.

Turbo pump shown upside down in container – motor is on top.

If you fill the container higher than the inlet shown in the picture above then you will get isopropanol into the motor (not good).  Let the turbo sit in the isopropanol for a few minutes and then move the turbo up and down a little bit to help remove more oil from the blades. Remove the turbo and if the isopropanol is yellow from the oil, discard the isopropanol (in the appropriate container so that it can be disposed of properly) and repeat.

Once the turbo is clean, remove it and place it on some Kim wipes or paper towels and let it dry thoroughly. Note that in the original Balzers procedure that Freon TF was used. Isopropanol has similar degreasing properties and is not nearly as bad for the environment.

As long as you have the turbo pump out, you should check the condition the bottom bearing. Remove the plug and inspect the felt washer or washer assembly. Clean or replace as needed.

Once the turbo pump is dry, it should be good to go.

You can also use isopropanol to clean the rough lines that go from the mechanical pump to the turbo pump.