by Doug Warner,
Marketing Manager
Advanced Cleaning Systems
Dow Environmental
Midland, Michigan
An aqueous cleaning system, if designed and operated properly, can prove to be an excellent alternative to a solvent vapor degreaser and provide cost and environmental advantages. However, there are a variety of variables that must be understood. Attempting to switch without an adequate grasp of the complexities, can be as risky as sailing the Atlantic without understanding the dynamics of weather, current and wind.
Consider the many factors that can influence the performance of water-based systems: bath temperature, process time, chemistry concentration, mechanical action, the condition of the water supply and washwater contamination. Examining the way a typical aqueous system operates gives an appreciation of the intricacies involved in the conversion process.
Aqueous cleaning systems typically consist of three basic stages: a wash stage, a rinse stage and a drying stage, and there may be multiple stages for each. Cascading rinse baths, for example, help control "drag out" from the wash stage and keep the rinse bath (and the cleaned parts) clean. (see flow diagram.) Water flows in the opposite direction of the movement of cleaned parts.
There are numerous variables in each stage. In the wash stage, cleaning solution may be diluted with water in a ratio from 1:10 to 1:50, depending on the type of chemistry, types and level of soils, desired level of clean and supply water characteristics. The rinse stage may contain a water treatment system to screen contaminants and extend bath life. Drying can be accomplished by simple draining, high velocity air knife, hot forced air, vacuum drying, or some combination of these, and liquid drying agents can aid the drying of blind holes and small internal areas. Each variable can impact capital or operating costs.
Complicating the aqueous conversion process further are the many oils, waxes and lubricants in the manufacturing process. That's why developing a cleaning specification -- by defining what soils and particulates are present and how clean parts must be -- is the first step in the conversion process.
Certain types of machine oils and greases are more difficult to remove than others, and a change on one piece of equipment could wreak havoc on the cleaning system downstream. However, many modern cleaning systems include a separator so heavier oils can, in fact, be recycled or even reused. Some machine oils and lubricants are being reformulated as greener or easier to clean. Yet if they do not perform their primary function as well, the cutting tool suffers.
Balancing Act
While traditional vapor degreasers rely primarily on solvent action
to remove contaminants, aqueous systems depend on the right balance
of chemistry and mechanical action. Achieving this balance is key
to designing the optimum aqueous cleaning process between the thousands
of aqueous cleaners available and the different mechanical actions
that can be designed into the equipment, Advanced Cleaning Systems,
a business unit of Dow Environmental, has estimated that there are
more than a million different combinations that could be explored.
The choice of aqueous equipment also introduces many variables. Equipment can range from small basin washers to fully automated, multi-stage units up to 100 ft. long. Prices can range from $15,000 to more than $8,090,000. Some of the many factors that can influence equipment costs are:
Manufacturers sometimes make the mistake of choosing the equipment and then trying to figure out what chemistry will work best. Still others, particularly larger companies, attempt to formulate the chemistry and then search for the equipment. In either case, it's unlikely the manufacturer will achieve the optimum cleaning level. If a manufacturer overshoots the cleaning process, capital and operating costs will be excessive; if they undershoot, they jeopardize manufacturing throughput. The answer is to explore both in combination. This can be accomplished effectively with the help of an outside cleaning expert that can assess the task, narrow the options and find the optimum formula.
Unfortunately, many manufacturers do not realize the complexity of converting to an aqueous system until time and resources are wasted and they are adrift in problems. Selecting an inadequate system can cause manufacturing (and management) headaches for years to come. The key to converting is to find the right balance between equipment and chemistry and make the right choice the first time.