In the period immediately following the signing of the Montreal Protocol, virtually every manufacturing facility using solvents for cleaning was faced a critical decision. The three basic options were -
- Discontinue unnecessary cleaning operations altogether.
- Upgrade or replace existing solvent-based cleaning systems to reduce solvent emissions.
- Switch to cleaning using water-based chemistry.
Surprisingly, the first option, eliminating some cleaning operations altogether, was quite feasible in many cases. The first cleaning operations on the chopping block were those known as “in-process” cleaning. The purpose of in-process cleaning is usually to prepare a part for inspection or to prepare it to facilitate the next manufacturing operation. In many cases, a single part was being cleaned as many as 10 to 15 times throughout the manufacturing process. A lot of these cleaning operations were performed by operators who just “swished” the part in an open container of solvent with no provisions to contain vapors whatsoever. Rags wet with solvent were commonly used to wipe down large surfaces. Huge amounts of the “bad actor” freon as well as other fluorinated and non-fluorinated hydrocarbon solvents were being used in this way with no regard for the emissions they created. I remember asking several manufacturing engineers why parts were being cleaned at a certain stage in the manufacturing process and getting the answer, “Because.” There were also cases, although not as many, where even a “final” cleaning could not be logically justified. With greater awareness of the dangers of solvents many of these uses ceased spontaneously.
Many solvent users who felt compelled to continue to use solvent to clean for one reason or another chose to modify their existing equipment to reduce solvent emissions to levels at or below those mandated by the Montreal Protocol. Measures including the addition of “sub-zero” freeboard cooling, controlling the entry and exit speed of parts through the use of automated material handling systems and adding automated covers were prevalent. These measures, although they provided temporary compliance with the provisions of the Protocol had limited life as the provisions of the Protocol were structured to become increasing more stringent over time until the use of at least some solvents was banned completely.
Many forward-looking managers, feeling the banning of all solvents was inevitable, took the daring plunge of eliminating solvent use immediately and completely. Aqueous cleaning was the only real option if cleaning continued to be a necessity. Unfortunately, the existing solvent machines were not well suited (even with extensive conversion) to clean parts using aqueous based chemistry. Solvent systems which typically had 1 or (maybe) 2 tanks just couldn’t be converted to provide the capability to rinse and dry parts after cleaning. As a result, the manufacturers of water based cleaning systems had a virtual “hay day.” On the good side, the need to clean using water also led to the development of many machine and process refinements that, without the Protocol, would not have happened. Cleaning with water just wasn’t as easy as cleaning with solvents in many applications.
For the last 15 to 20 years or so, aqueous cleaning has “owned” the cleaning equipment market. There are, however, some cleaning applications which can be better accomplished and/or more easily accomplished using solvents. In response to this irrepressible need, new solvents have been developed which do not pollute the earth or its atmosphere. Equipment and means of delivering and disposing of solvents is now available that assures solvent containment and either proper disposal or re-cycling. Cleaning using solvents is re-emerging and promises to find application in cases where the economics and benefits of using solvent make sense. Moreover, solvents are returning to the cleaning scene under strict stewardship of a new generation of responsible users who understand not only its benefits but the risks as well. Upcoming blogs will discuss in more detail the changes in solvent cleaning taking place today and in the future.
- FJF -