Vapor Degreasing: Basic Concepts

Design Concepts

Vapor degreasers are a well-proven technology that will deliver fast, reliable and consistent cleaning at the very lowest cost-per-part-cleaned. A vapor degreaser is simply a special type of still. In the simplest form, the degreaser simply boils a solvent in the boil sump, creating vapors. The vapors rise out of the boil sump but are stopped when the vapors reach the condensing coils. The vapors are condensed back into liquid form and returned to the rinse sump to be re-used. The rinse sump gradually overflows and replenishes the boil sump, which is where the heaviest cleaning is performed and where the contamination becomes concentrated.

The schematic on the right illustrates the basic flow of the system.Simplified schematic of basic vapor degreasing system

It's important to note that "boiling" does not imply a lot of heat. Most vapor degreaser fluids boil at very modest temperatures, usually about 40°C-65°C (100°F-165°F). Low to temperatures boost worker safety and keep energy costs down. In fact, many modern vapor degreasers are so energy-efficient they operate on 25 amps or less.

There are many variations and improvements on this very simple process, such as adding ultrasonics and spray wands, but all of those enhancements are merely upgrades to these basic three steps. It's fast, simple, reliable and safe cleaning.

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Details of Vapor Degreaser Design

 

 

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

Location "A" is the boil sump; notice the heating coils tucked underneath the back of the sump.

This cutaway view of a Branson vapor degreaser shows the major components of the system. All vapor degreasers operate in the same basic fashion.

"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. The size of this region is called the freeboard. A freeboard greater than 1.25 is recommended.

 

Photo Gallery of Vapor Degreaser Operations

These photos help to explain the operating process of a vapor degreaser... mouse-over each photo for details.

 

This is a typical vapor degreaser, made by Tiyoda in Rhode Island. Some metal parts have been placed into a basket and are being lowered into the degreaser. The bubbles in the cleaning fluid are from the ultrasonics agitating the solvent. The boil sump is on the left and the rinse sump is on the right.
In an operating degreaser, a layer of invisible solvent vapors fill the lower portion of the machine. Since the solvent vapors are heavier than air, this balloon is actually sitting on top of the vapors. Some solvent has condensed on the balloon and is dripping back into the sump. If you look closely just to the left of the balloon, there is a gray line on the steel side of the tank. This is the top of the vapor layer. Here's a different view of the vapor layer. Notice the balloon floating and solvent dripping. This is only possible because the solvent vapors are low-temperature vapors, usually around 40°C (100°F). If these were water vapors, the steam would be so hot as to melt the balloon.
Here's a close-up on the primary condensing coils. The vapors rise inside the machine until they reach these coils. A barrier of cold air sits at this level and stops the vapors from leaving the machine. Notice the solvent condensing on the coils and dripping into the collection tray which runs around the sides of the degreaser. The water separator is an important part of any larger degreaser. In this case, water and solvent has condensed on the cooling coils. That mixture flows into the water separator. There the heavier solvent is returned into the machine, but the water is trapped in the separator and ultimately purged out of the system. No moving parts or electricity are used in this process; it simply relies on the fact that the water and the cleaning fluid will not mix, and the fluid is heavier than the water. It's very simple.

 

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Vapor Degreaser Configurations

Vapor degreasing – especially when MicroCare solvents are selected – delivers the highest quality of cleaning in the shortest possible time, with the least risk of damage to the components.

Vapor degreasers come in all sizes, from small benchtop models containing four liters (one gallon) to massive machines holding 15,000 liters (4,000 gallons). There also 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.

For more details, see General Vapor Degreaser Costs, below.

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. Engineers are encouraged to download the spreadsheet and plug the company-specific parameters into it.

In short, wherever there are demanding specifications or challenging environmental issues, the MicroCare solvents in a vapor degreaser are an ideal choice.

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Using a Vapor Degreaser

Using a vapor degreaser is simple, and the process usually is semi-automated which makes it even easier:

  1. Place the products to be cleaned in a basket. The photo shows a typical load being prepared for cleaning.
  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 cleaned. The invisible solvent vapors flow around the parts and dissolves oils, greases and fluxes. Eventually, the solvent drips off of the parts, taking the contamination with it, and falls back into the boil sump.
  3. Slowly lower the basket into the boil sump. Here the warm solvent further cleans the parts.
  4. After a few minutes, raise the basket and transfer the basket slowly into the rinse sump. Apply ultrasonics if needed.
  5. Slowly remove the parts from the rinse sump. Hold the for a minute parts in the vapors while any last droplets of solvent evaporate off the parts.
  6. Remove the parts from the system. They will be clean, dry and relatively cool, ready for the next manufacturing process.

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