How Does a Vapor Degreaser Work?

In truth, degreasers actually are pretty simple. They use a simple thermomechanical process -- boiling and condensing -- in conjunction with special low-boiling solvents to clean quickly, easily and inexpensively. The benefits of a vapor degreaser are listed below.

• Bromothane Solvents Are Engineered for Vapor Degreasers •

• Versatile: Vapor degreasers and their special solvents can easily get into and around parts which are extremely small or have extremely tight clearances.

• Speedy: Vapor degreasers have very short cleaning cycles, so even a modest batch machine can usually outperform an in-line water cleaning system costing two or three times the price.

• No Entrapment: Because the solvents evaporate so quickly, the vapors are easily removed from complex shapes, deep holes, blind vias and other designs where slow-drying solvents could be trapped. This keeps costs down and quality up.

• No Spots: Water often leaves unacceptable water spots which vapor degreasers never leave, making them perfect for cleaning optics and other super-critical applications.

• Broad Compatibility: Solvents and vapor degreasers are highly suitable for use with most components because there are no high pressure sprays, the temperatures are low and the cleaning cycles brief.

• Highly Effective: Vapor degreasers and their solvents can easily clean almost every type of contamination, up to and including heavy greases, oils and even waxes.

• Superior Environmentally: The whole concept of a vapor degreaser is to contain and recycle the cleaning chemistry, which is as good as you can get environmentally. In addition, and proportional to their size, vapor degreasers use tiny amounts of electricity, no water, and concentrates the waste to minimize disposal issues. So vapor degreasers are very gentle on the environment.

• Low Costs: Vapor degreasers are very inexpensive to use. A modern degreaser can limit solvent consumption to pennies or dollars per day.

• The Vapor Degreaser Design Is Simple and Energy Efficient •

A vapor degreaser is simply a special type of still. In the simplest form, the degreaser simply boils a solvent into vapors and vapors. The vapors try to rise out of the machine but are trapped by a layer of refrigeration which is called the cold trap. The vapors are condensed back into liquid form and returned to the cleaning machine to be re-used. Figure 51.1 illustrates the basic flow of the system.

Figure 51.1: Simple Vapor Degreasing System

Click here to download a much bigger version of this graphic, suitable for printing, using in presentations or mounting on your wall next to your Britney Spears poster.

As the schematic shows, there always is fresh solvent in the rinse sump. As more freshly-distilled solvent is returned from the cooling coils back into the system, it always is returned to the rinse sump. This gradually overflows and replenishes the boil sump, which is where the heaviest cleaning is performed and where the contamination becomes concentrated.

It's important to note that "boiling" does not imply a lot of heat. Most Bromothane™ solvents boil at very modest temperatures, usually about 65°C/165°F. Low to moderate temperatures are a nice boost for worker safety, and it also keep energy costs down. In fact, many modern vapor degreasers operate on 25 amps or less.

As you might expect, there are dozens of variations and improvements on this very simple process, such as adding ultrasonics, but all of those enhancements are merely upgrades to these basic three steps. It's fast, simple, fool-proof, and safe cleaning design.

Let's take a closer look at the actual design of a real system. Figure 51.2 shows a cutaway diagram of a typical vapor degreaser system.

Figure 51.2: Cutaway Diagram of
Typical Vapor Degreasing System

Location "A" is the boil sump; notice the heating coils tucked underneath the back of the sump. "B" is the rinse sump, separated from the boil sump by a simple aluminum or steel divider. The saturated solvent vapors sit above and across the two solvent sumps. That's where the cleaning occurs.

Location "C" is a water separator -- since the degreaser is constantly chilling vapors, it collects water out of the air. This water needs to be removed for fast, spot-free cleaning.

Location "D" and "F" highlight the two layers of cooling coils. Using two layers of chilling enhances the ability of the machine to trap and hold the solvent vapors. While these make the system slightly more complex and expensive, a two-layer chilling system pays for itself quickly in reduced solvent losses.

Location "E" is roughly where the saturated solvent vapors are chilled and recondenses; it is the invisible cold trap.

Just as a matter of background, a modest sized system of this degree of complexity would have a retail price of about US$25,000.

• Using a Vapor Degreaser •

There are only a few steps to using a vapor degreaser:

1. Place the products to be cleaned in a basket. Figure 51.3 shows a typical load being prepared for cleaning.

Figure 51.3: Loading into the Machine

2. Slowly insert the basket of parts into saturated solvent vapors above the boil sump for the first few moments of cleaning. This causes the vapors to condense on the (relatively) cool parts being cleaning. The solvents wraps around the parts, goes into and out of the tightest spaces, and dissolves oils, greases and fluxes as it slowly raises the temperature of the part to an equilibrium with the temperature of the vapors. Eventually, the solvent drips off of the parts and falls back into the boil sump.

Figure 51.4: Solvent Condensing on Electronic Circuit

3. Remove the parts from the vapor bath and they are clean, dry and relatively cool, ready for the next manufacturing process.

There are many additional features and accessories which are available from the various equipment manufacturers. Savvy engineers will review their options to insure they get the machine which will provide optimal performance at the lowest total cost per part cleaned.

MicroCare has prepared an Excel spreadsheet which allows engineers to estimate their cleaning costs on a per-part basis. This is by far the most precise way to summarize all of the capital and operating expenses of any cleaning system. We urge you to download the spreadsheet and plug your data into it: you'll be amazed how expensive water cleaners can be, and how very affordable Bromothane™ is.

Vapor degreasing -- especially when you use Bromothane™ solvents -- delivers the highest quality of cleaning in the shortest possible time, with the least risk of damage to the components. In short, wherever there are demanding specifications or challenging environmental issues, the Bromothane™ solvents in a vapor degreaser are the ideal choice. These are great replacements for ozone-depleting solvents such as 1,1,1-trichloroethane, HCFC-141b and HCFC-225, as well as high-global-warming solvents such as perfluorocarbons (PFCs).

Updated: Jan 15, 2004
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