Vapor Degreasing: Past, Present and Future

Other than aqueous, one of the oldest methods of cleaning manufactured parts for the removal of any contaminants that will interfere with further finishing is degreasing with organic solvents. This process is generally called vapor degreasing, even though vapor-only cleaning is the most elemental level of that genre. An early expert in the degreasing industry, Robert O. “Lefty” Grunditz, used to begin presentations with the statement that vapor degreasing was a misnomer. He said that vapor never cleaned anything until the warm vapor condensed on the cooler part and had dissolved and flushed the soil away. When the part temperature has reached equilibrium with the solvent vapor temperature, all cleaning ceases until some other action takes place. A good example of that process is a demonstration of the way that rain develops. Holding a cool plate over a steam kettle produced condensation when the steam contacted the plate and rain happened.

The type of parts to be cleaned and the procedures to do so have changed drastically over the years. There are many new people in various industries who may not be aware of this evolution and may be able to better understand some of their present cleaning problems and their solutions by learning the history of vapor degreasing. An education about the origins may clarify the “best practices” nature of solvent cleaning as it is today.

Early Beginnings

The earliest industrial cleaners used water and soap to clean manufactured parts. A Chicago-based company, G.S. Blakeslee & Company, manufactured industrial dishwashers and food processing equipment and sold one of its dishwashers to the manager of the cafeteria at the Ford Motor Co. The story is that Henry Ford himself saw this and asked if they could build a machine like it to clean engine blocks. That was 1912, and the first industrial parts washer became the benchmark for automated industrial cleaning. The machine built at this time is the predecessor of today’s aqueous cleaners, which have had their own evolution into modern designs. The industry grew steadily for 20 years and new processes and designs were developed.

In the 1930s, this same company entered a new phase of the cleaning business by purchasing basic vapor degreasing patents from Germany. These machines would be used with a new organic solvent, trichloroethylene. Engineering advances for the “new” method of cleaning parts developed quickly. When light weight parts with heavy soil were cleaned in vapor alone, contaminant was left behind. Pumps with hoses and spray wands were added to straight vapor degreasers to improve cleaning. The low pressure spray would provide impingement to flush away soil and allow more vapor action to occur. This feature
was further improved by collecting distilled solvent in a storage tank, and spraying with purer material. As the process grew in popularity, various problems, which had to be addressed, became evident. Continuous use, heating and cooling, water as moisture on cooling coils and the contaminants themselves, were causing the solvents to break down into corrosive components. These components were dangerous to the workers and the equipment. The chemical industry responded by developing additives known as stabilizers, which acted to neutralize the unwanted components. Now, large volumes of work could be processed in a smaller machine that used less energy and resulted in dry parts which then went on to further finishing such as painting, storage or final assembly.

The Best Available Technology

As this revolution in industrial production procedures gained notice, many other manufacturers were drawn to solvent cleaning as a solution for their finishing problems. This presented entirely new challenges to degreaser manufacturers and the result is the large variety of styles and configurations of machines that are in use today. The best available technology used in modern degreasers evolved from many areas of manufacturing requirements that look for high-volume production in an environmentally stable work place. The pressure of competition, also dictates an efficient, costeffective process that means a bottom line of lowest cost per part cleaned. For small and medium size manufacturers, the advanced design of a standard open top degreaser answers the need. These machines will produce volumes of clean parts and take up less floor space with lower energy costs—more than any other method. And the results are the same load after load. Determining which style of machine and the best solvent to use is the biggest part of the decision to use this technology. The manufacturer’s representatives and engineers are available to ease that burden. A plant manager will need to have parts evaluated as to the kind of contaminant involved and the best solvent to remove it. Consideration must be given to the possible side effects the solvent may have on the components. After these factors are resolved, the form of the cleaning process comes into play. Vapor cleaning alone may be the answer, but more than likely, other steps will be necessary. Some of those would be immersion in the boiling liquid, followed by a second immersion in cooler, cleaner liquid. The last step would be a distillate spray then a pure vapor rinse to facilitate the part leaving the degreaser clean and dry. The only other mechanical tool to be added to this “open top” scenario is ultrasonic agitation. Devices called transducers are added to the bottom of the clean rinse tank. These produce high frequency sound waves that cause microscopic bubbles called cavitation to grow all throughout the liquid where they implode on the parts during milliseconds of high pressure and temperature. This produces a scrubbing action that cleans in hard to reach areas and aids in removing particulate soil.

Controls and Regulations

To further increase productivity and efficiency, more enhancements to the base concept have been developed. Equipment manufacturers respond to OSHA regulations to protect workers, and EPA regulations to protect the environment in any number of the following ways. Material handling has been automated to provide reproducible results by removing the human element in the equation. Faster cycle times also result from this. Machines are enclosed to eliminate drafts and make them adaptable to continuous material handling through programmable hoists or even monorail transport through various manufacturing departments, cleaning and final finishing. Other controls and improvements relate to the solvent. Not only do the regulations dictate conservation from safety and environmental considerations, but also from the economic point of view. Today, solvent costs are proportionally much higher. Additionally, solvents that become hazardous waste bring more high cost to the bottom line. Several advances address those issues. Early degreasers controlled vapor loss with cooling coils or water jackets. Plant tap water, cooling towers,
wells, lagoons and other sources were circulated to control the vapor line. The efficiency of this method was directly proportional to the temperature of the cooling source. The higher the temperature of the vapor meant more tolerance to poor water supply. The introduction of chilled water to the picture greatly improved efficiency. In the 1960s, refrigeration cooling was a major leap forward in fume control and also introduced a level of portability to the machines. Provided that they were not too large, they could be mounted on casters and moved between various cleaning stations. Low temperature refrigeration designed to work below freezing and specifically below zero was introduced in the freeboard area. This is the area above the vapor zone where warm vapor tends to migrate from the machine. The proven theory is that the colder or denser the air in that space, the less solvent migration will take place.

Solvent Evolution

Abrief look at the solvent evolution may be helpful here. Trichloroethylene was the first extensively used chemical in the early years. Perchlorethylene and methylene chloride followed. Then lower boiling precision solvents such as chlorofluorocarbons and the trichlor substitute trichloroethane held center stage until environmental regulations changed the picture again. Now the number and variety of chemicals vying for attention is enormous. A review of past issues of magazines which lists them all will amaze you (“Drop-In Alternatives to Trichloroethylene,” Process Cleaning Magazine, September/ October 2006). But the bottom line is this. The old standby vapor degreaser can still be used with any of those that are non-flammable and compatible with materials of construction. A simple adjustment to controls will put you back in business.

At this point, it should be mentioned that while the standard solvent degreaser covered here is very widely used, there are other solvents using technologies in the marketplace as well. Some of these include “airless” systems, which incorporate vacuum technology and totally closed packages. The level of cost for this type of system and the production capacity compared to the basic degreaser is very different and will be left for some future article to explore.

Vapor Degreasing Still Alive

The 1960s brought forth the sages with predictions that, “Vapor degreasing will soon be a thing of the past.” The reality, however, is that by adapting to everchanging requirements, types of cleaning problems and strict regulations, vapor degreasing is still alive. Another maxim from Bob Grunditz was “When the going gets tough, the tough get going.” Rather than choosing to become extinct, this industry continues to have a future and will do whatever it takes to survive. Part of that survival relies on the manufacturers of the solvents used, which go hand-inhand with the technology. As long as there is a demonstrated need, we will continue to see new and better ways to get the job done.


Frank Salamone has been in the solvent cleaning industry for more than 40 years and is currently a consultant for Chicago, IL-based Enviro Tech International, manufacturer of EnSolv, the stabilized nPropyl Bromide degreasing solvent, and Baron Blakeslee Vapor Degreasers. Frank may be reached at (708) 343-6641.