An alternative to the alternatives

In early 1995, a program was initiated by the Environmental Protection Agency to investigate new and innovative surface cleaning and degreasing technologies as alternatives to ozone-depleting compounds including 1,1,1- trichloroethane (TCA), methylene chloride, and Freon 113 [1,1,2-trichloro-1,2,2-trifluoroethane, chlorofluorocarbon (CFC)-113]. One promising candidate identified during the investigation was liquid carbon dioxide (LCO₂).  The United States Air Force at the Warner Robins Air Logistics Center (WR-ALC), Robins AFB, GA, was requested to participate in the demonstration and served as the demonstration site.  The WR-ALC uses several surface cleaning processes at the facility during aircraft systems maintenance.  These processes generate a broad range of air, water and solid waste environmental contaminants.  The volume of these wastes could be reduced by the use of LCO₂ cleaning.

LCO₂ is of interest as a potential solvent degreasing substitute largely because of what it is not.  First of all, it is not an ozone-depleting compound (ODC).  Therefore, it does not present a threat to the earth’s ozone layer as found with typical chlorofluorocarbon (CFC) solvents.  It is nonflammable and has low toxicity.  Thus, is does not present a safety hazard when used properly.  Finally, LCO₂ is not expensive when compared to CFCs and equivalent substitutes.  This is important to its viability as an industrial surface cleaning and degreasing solvent.

The objective of the project was to demonstrate the viability and efficiency of the LCO₂ cleaning as an alternative to current cleaning and degreasing technologies.  The study was designed to show that LCO₂ cleaning, when properly integrated into the manufacturing process, could remove various organic and solid contaminants typically removed during vapor degreasing with ozone-depleting solvents.

The LCO₂ process was shown to be equivalent to TCA in performance for cleaning the parts evaluated during this project.  Successful introduction of the LCO₂ process into a facility will require a detailed knowledge of the contaminant to be removed, the desired surface cleanliness level and the configuration of the part.  This knowledge will permit the LCO₂ process to be effectively implemented into a production operation to achieve the required cleanliness level, with an optimal ROI.

Source:
“Demonstration of Liquid CO₂ as an Alternative for Metal Parts Cleaning”, Precision Cleaning, Sept 1996
“Demonstration of Liquid Carbon Dioxide Process for Cleaning Metal Parts”, USEPA Report, November 1996