A Simplified Explanation
There is no question that a properly designed, operated and maintained vapor degreaser is the very best and least-expensive cleaning choice for most industrial applications. The concept of a vapor degreaser is really very simple. Diagram 1 illustrates the basic design, which includes four components:
A “boil sump” filled with a nonflammable, fast-drying cleaning fluid heated to its boiling point. It is in this sump that the first and most aggressive cleaning takes place. Some companies use spray-under-immersion and/or ultrasonics to enhance the cleaning results.
The “rinse sump” is exactly that: a sump, identical to the first, but filled with pure solvent. This is used to rinse the parts after their first cleaning.
A “vapor section” above both sumps. This is where the saturated vapors of the boiled solvent collect and condense on refrigeration coils. The condense liquid is then routed thru a water separator and back to the rinse sump.
The “cold barrier” above the vapor section. This is a blanket layer of very cold air that creates a temperature inversion, trapping the hot solvent and the vapors in the machine.
In metal cleaning operations, most companies immerse their parts directly into the rolling solvent in the boil sump for two to five minutes. The purpose of this step is to heat, loosen and remove the vast majority of contamination in this sump. The boil sump also collectors all the contamination and concentrates it within the boil sump.
After cleaning, the system slowly removes the parts from the boil sump, dwelling above the boil sump in the vapor zone for approximately 15-30 seconds to drain the contaminated solvent back into the boil sump. The parts remain under the vapor blanket until the entire cleaning cycle is complete.
In step three the parts are immersed into the rinse sump, with or without ultrasonic energy for two to ten minutes. This delivers the final cleaning.
The final step is to remove the parts from the rinse sump up into the vapor zone until the parts stop dripping. Next, the parts should then be slowly raised to slightly above the cold coils for approximately 30 seconds to allow any entrapped vapor to “flash off” and to allow the vapor blanket “settle down” and return to its “normal” operating level on the primary condensing coils. Finally, the basket is lifted out of the degreaser. The parts come out clean, dry and ready for subsequent processing or packaging.
The proper design, operation and maintenance of a vapor degrease is imperative in order to safely obtain the desired results, in the most economical manner and in an environmentally acceptable way. The vapor degreasing process has proven to be the most consistent and “head-ache” free cleaning process for the manufacturing engineer.
When analyzing a cleaning application, always define the soils first, then select the chemistry that removes those soils, and then lastly select the equipment that uses the chosen fluid properly. Never select the equipment first. While buying equipment can be exhilarating, it can be an expensive “dead end” since not all cleaning chemistries can clean all contaminants and not all equipment can use all cleaning chemistries. There have been numerous instances of people who have unfortunately purchased a vapor degreaser that was not designed to use the most effective chemistry for their cleaning needs.