Vapor degreasing process immersion

The conventional metal cleaning processes have been vapor degreasing, solvent immersion cleaning and cold cleaning. The solvents commonly used in these processes. 

Turco Product Division, Purex Corporation. When combined with vapor degreasing and alkaline cleaning, this process offers very high-strength bonds on titanium. Plasa Jell is also a proprietary chemical marketed by Semco Division, Products Research and Chemical Corp. This formulation is available either as a thixotropic paste suitable for brush application or as an immersion solution for tank treatment. 

The appellation "vapor degreasing" is/was technically incorrect, and it has fostered confusion. While the cleaning process does degreasing work, and the solvent is present in the vapor phase, the soils aren t mainly removed by solvent in the vapor phase. They are removed, mainly, by immersion and solution in liquid solvent at its normal boiling point. 

But there is a "free" step in this process. It is ofvapor contact. This occurs because the parts fixtured in the basket are (probably) at ambient temperature prior to entry into the vapor degreaser. That means they are colder than the solvent in the vapor zone above the immersion sumps (see Figure 1.4). So solvent vapor condenses upon these part surfaces upon entry to this vapor zone - providing a pre-cleaning rinse. This is shown in Figure 1.17 and described in Chapter 1.6. 

A second reason enclosed machines are built is to conduct unique processes which could not otherwise be practiced under ambient atmospheric conditions. Not all cleaning processes are vapor degreasing with solvents at their normal boiling points, or immersion cold cleaning. 

They are called cosolvent processes because more than one solvent is used to clean parts in the same application (Chapter 3.f). Some of these processes are chameleons in that they appear externally to be conducted in conventional vapor degreasers — having a two-sump immersion cleaning apparatus and an attached distillation column. 

Vapor cleaners (degreasers) operate by putting a cold part in the hot vapor above a liquid solvent or rinse material contained in a sump. The liquid condenses on the surface and flows off into the sump. Since contaminants generally have vapor pressures less than the solvent, the vapor stays relatively clean. The cleaning action only occurs during the condensation process. When the part reaches a temperature at which the vapor does not condense, the part should be removed. Parts should never be immersed in the sump fluid. Common solvents used in vapor degreasers are TCA, TCE, and PERC. Azeotropes are mixtures of solvents that have the same composition in the vapor as in the fluid. Vapor dryers often use alcohol. 

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