Previous blogs discussed the demise of solvents after the Montreal Protocol. Today, in the US at least, solvents are coming back prompting the reader to ask, “What Has Changed.” First of all, there was never any real argument that solvents did, and still do, a good job of cleaning in many, many applications! Are there aqueous and other alternatives to cleaning? In many cases, yes. Are they always effective? No. The problem with solvents that lead to their demise was that they were used irresponsibly (albeit unknowingly) for decades. I, for example, although I did not witness it personally, have strong anecdotal evidence that it was not uncommon for solvents (including the dreaded trichlorotrifluorethane), delivered in rail car and tractor trailer quantities, to be pumped through fire hoses to wash down components at several aerospace facilities starting during the 1960’s. Once the solvent had done its cleaning job, it was left to evaporate without concern for confinement or recovery. Nobody knew it might eventually be a contributing cause to the formation of a hole in the ozone layer. Likewise, solvents used in dry cleaning were seldom efficiently recovered. The “fresh” smell of garments coming from the dry cleaner was really the smell of residual solvent still evaporating from the fabric which had been solvent-soaked during the dry cleaning process.
Equipment Change –
Things have truly changed! Open top degreasers and solvent-soaked rags used for wiping, major contributors to solvent pollution as a result of cleaning, are pretty much a thing of the past – at least here in the US. Early attempts to contain, capture and re-use cleaning solvents, although noble, were often less than effective. In spite of major efforts on the part of equipment manufacturers and users to prevent solvent evaporation during the actual cleaning process, both fresh and spent solvents were still handled and transported in ways that did not ultimately prevent evaporation. “Sealed” degreasers were often only “sealed” when they were in active use. As soon as the access door was opened to load or unload parts, there was no longer any seal thereby allowing solvent vapors to spill into the atmosphere. Today, solvents are delivered in sealed containers which are connected directly to cleaning machines using fittings having dual-sided leak proof fittings to assure that no solvent or solvent vapors escape during the transfer process. Today’s solvent cleaning machines themselves are designed in such a way that interlocks, solvent concentration sensors and other means prevent solvent evaporation into the atmosphere. Following use, spent solvents are collected using sealed containers similar to those in which they had been delivered and are transported to facilities where they are either safely incinerated or reclaimed for re-use. Proper monitoring throughout the life of the solvent assures that the above measures are effective.
Solvent Change –
The “bad actor” solvents are no longer manufactured or available. New formulations of “designer solvents” utilize ingredients that have been proven to be much safer from both a human exposure and environmental impact standpoint than those used decades previously. The combination of containment, monitoring and proper disposition of solvents along with the fact that today’s solvents are less likely to have a negative effect even if they do escape provides multiple layers of protection against the irresponsible and potentially unsafe use of solvents.
The Future –
It may be time for manufacturers using aqueous or other cleaning means, but only with considerable effort, to re-visit the possible use of solvents. Most major suppliers of cleaning equipment have solvent alternatives available if you ask them. Suitable equipment and solvents may be costly but could have the potential to be less costly than aqueous cleaning when all factors are considered. It’s worth investigating if you have a case where you think solvent might be a better alternative. You may be able to have your solvent back!
– FJF –