Cleaning – Solvents – The Phoenix Stirs!

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  –

2 comments on “Cleaning – Solvents – The Phoenix Stirs!

  • Jim,
    Thank you for your input! I was not aware that the split in technologies was quite so different in Europe and that Europe may be moving more toward aqueous cleaning while here in the US it appears to be the opposite. In any event, I don’t think we’ll ever see a return to the level of solvent cleaning here in the US that existed before the Protocol. It is beyond question that solvent has a place in the cleaning technology arsenal. It is my observation that there is a growing “maturity” in the process of selecting from and implementing the various candidate cleaning technologies. This is leading to more responsible decisions and has brought cleaning as a technology to a much higher level of sophistication than we have seen in the past. I applaud this move.

  • John,
    Thank you for a very comprehensive summary of the past 20+ years history of solvent vs. aqueous cleaning. It is interesting and probably important to note that this decades long transition unfolded differently in the US and North America than it did in Europe. What you have described is “spot on” (no pun intended) for the US, but Europe took a somewhat different path.

    At the time of the Montreal Protocol solvent based cleaning was already more prevalent in Europe than in the US. The approach in Europe was to technically refine solvent cleaning and to invest in low to zero emmissions solvent handling equipment and zero emissions processing of solvents used in industrial parts cleaning applications. Over time, this has lead to a difference in the approach to cleaning between the two continents.

    Today, my estimate would be that in North America we sit at about 95% aqueous cleaning with the 5% solvent based cleaning growing slowly as you suggest although I do not see where it will exceed 10% of the market going forward. In Europe my estimate would be that today it is 70% aqueous cleaning with the remainder being solvent based cleaning. I do not believe there is much movement in that ratio in Europe today, but it would not be surprising to see the mix of solvent cleaning lessen in the future. We find this split most interesting when we look at the emerging, and fast growth Asia markets.

    In Asia we find a mix of both technologies as they adopt technologies and best practices from both the US and Europe. The mix in Asia is 80% to 85% aqueous and I would anticipate that this will stay at about this range going forward.

    The key here is to apply the “right” technology, whether aqueous or solvent based, to each application. Thank you again for an excellent history.

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