WHAT IS A VACUUM VAPOR DEGREASER ? 

Many of us recall how straightforward it was to place a component into the vapor zone of an open-top vapor degreaser for cleaning, returning after a few minutes to retrieve a sanitized part. The effectiveness of cleaning in these early open-top vapor degreasers (OTVD) was due to the vapor zone containing pure, uncontaminated solvent vapor. However, these systems had limitations, such as safety concerns and high operational costs. Modern equivalents, like Vacuum Vapor Degreasers (VVD), utilize the same vapor cleaning principle but enhance performance and safety. The critical innovation in VVD technology is the removal of atmospheric air from the process chamber, enabling rapid condensation of pure solvent vapor directly onto the substrate surface. This rapid condensation often manifests as a spray, as the absence of air allows substantial vapor flux to contact the part surface unimpeded. As the part approaches the vapor temperature, the condensation rate decreases in both OTVD and VVD systems. Nonetheless, in a VVD, the absence of air eliminates disruptions caused by trapped or slow-condensing air pockets, ensuring that even complex geometries, blind holes, or tight spaces are thoroughly cleansed. This results in uniform solvent contact across all surfaces previously occupied by air, yielding a more comprehensive cleaning process.

Effective vapor cleaning in an OTVD system critically depends on precise control of the operating temperature, which is governed by the solvent’s Normal Boiling Point (NBP). Solvents with higher boiling points necessitate increased thermal energy input and result in extended drying durations. Elevated operating temperatures pose a risk of damaging sensitive components. Conversely, an NBP that is too low results in insufficient vapor condensation on surface areas. A variable vapor vapor degreasing (VVD) system can surpass the temperature constraints inherent in an OVTD, owing to its ability to operate across a range of temperatures.

(See also: Vacuum Vapor Degreasing Efficiency).

There are numerous devices marketed as Vacuum Vapor Degreasers (VVD), but it is crucial to emphasize the significance of VAPOR generation. The presence of a vacuum alone does not classify a unit as a VVD. A common misclassification arises from the so-called “modified alcohol” units, which operate as soak systems. The normal boiling point (NBP) of these modified alcohol solvents exceeds 160°C (320°F). At 100°C, these units fail to generate the necessary vapor pressure for effective vapor degreasing, as illustrated by the vapor pressure curve. These systems submerge components in the solvent and frequently employ agitation methods—such as ultrasonic energy—to enhance cleaning efficacy. However, solvents with high NBP values exhibit poor cavitation characteristics, thereby diminishing ultrasonic effectiveness relative to the investment. Since this process is immersion-based, multiple cycles may be required to achieve comprehensive, film-free cleaning. It is important to note that solvent vapors produced are inherently pure and uncontaminated.

High NBP (Normal Boiling Point) substances pose challenges in drying and solvent distillation processes. The vacuum pump plays a crucial role in facilitating drying and distillation in both VVD (Vapor Vacuum Distillation) systems and the so-called “modified alcohol” configurations. Elevated NBP levels lead to reduced vacuum efficiency, resulting in slower distillation rates and often incomplete drying cycles. Insufficient drying can cause spotting anomalies. To expedite drying, external heated air is frequently introduced, which necessitates the use of costly activated carbon filters to comply with air quality standards set by regulatory bodies such as the European Union, California’s South Coast Air Quality Management District (SCAQMD), and several US states. These carbon filters generate additional waste streams. Prolonged distillation times diminish the availability of pristine solvent, potentially impacting process throughput and cleaning efficacy. In contrast, a properly designed Vapor Vacuum Distillation (VVD) system does not exhibit these limitations.