If you’ve ever been wearing glasses as you walked into an air-conditioned building on a hot summer day, you already have a good understanding of part of the Vapor Degreaser process works. (For those in colder northern climates, walking outside while wearing glasses on a cold winter day is an even better example)
A vapor degreaser has two tanks (sumps) of solvent inside. One boils the solvent (boil sump) which creates a vapor or mist of the solvent. The second sump (ultrasonic sump) is heated but not to the boiling point and is used as the second cleaning stage. The vapor degreaser also has bands of cooling coils inside just above the level of the sumps. These coils cause the vapor to return to a liquid state and fall back into the sump. The effect is like small “clouds” of the solvent are formed between the top of the sumps and the cooling tubes.
As parts at room temperature are lowered through the cooling area into the vapor, the vapor from the boil sump condenses on the parts just like moisture in the air does on your glasses in the examples above. This condensation contains the solvent that dissolves the oils on your parts, and the beading action creates droplets which run across the surfaces of the parts and fall back into the boil sump. The parts are then moved to the ultrasonic sump which contains heated but non-boiling solvent. This allows the parts to be lowered into the sump so that any blind holes or internal features are also thoroughly exposed to the solvent.
Finally parts are raised into the cooling coil area to allow the solvent to quickly dry and and then raised through a second layer of freeboard coils near the very top of the vapor degreaser that insure complete drying and the recapture of the solvent from the parts.
The below video demonstrates the process: