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Vapor degreasing is an industrial process that uses solvent vapors to wash oils and other contaminants off of metal and plastic parts that will be used in manufacturing. It is especially effective for cleaning small parts and those containing deep recesses that are difficult to reach by hand. The process can be configured in a variety of ways to produce the desired level of cleanliness and to minimize adverse air quality impacts that might be caused by escaping solvent vapors.
At its simplest, vapor degreasing is performed in an open-top tank containing a vat of boiling solvent at the bottom. Parts to be cleaned are lowered into the tank just low enough to be enveloped by the rising vapors. The cleansing process takes place in this so-called vapor zone. When the hot vapors touch the relatively cooler inner and outer surfaces of the parts they condense to a liquid and dissolve any oils, lubricants, waxes or similar contaminants they encounter. The contaminant-laden solvent then drips off the parts under force of gravity and falls back into the boiling vat.
The oils, lubricants, and other contaminants that enter the vat will not dirty the vapors, because the solvents boil at lower temperatures than oils. The vat temperature must be maintained just high enough to vaporize the solvents but not so high as to also vaporize the oils. This is key to the success of the vapor degreasing process.
The upper walls of an open-top degreasing tank typically include a cooling system called a cold trap. Its purpose to cool and condense any vapors that approach the open top of the tank and could escape to the surrounding environment. In practice, cold traps are generally not completely successful at preventing vapor escape. Lost vapors reduce system efficiency and pose a threat to environmental air quality and worker health. That’s why enclosed vapor degreasing systems are often preferred to open-top systems.
An enclosed, or closed-loop vapor degreaser, has an airtight chamber in which degreasing occurs. The parts to be cleaned are first placed in the chamber, and then, vapors are piped into the chamber. Contaminant-laden solvent falls to the bottom of the chamber and is piped away. Once parts cleaning is completed, the incoming vapor source is cut off. Fans are used to blow any remaining vapors out of the chamber and into a cooling system to condense them for reuse. Carbon filters capture any stray vapors lingering in the chamber.
There are many configurations for vapor degreasing processes. Some systems feature a spray wand that can be operated by hand to direct solvent into hard-to-reach areas of complex parts. Liquid immersion degreasing involves dipping parts into liquid solvent, typically to loosen up stubborn oil deposits. This is typically a pretreatment process done prior to conventional vapor degreasing. Modern immersion degreasers use ultrasonic technology to blast the parts with microscopic bubbles that help scour away oils and other contaminants.