AVS 56th International Symposium & Exhibition
    Vacuum Technology Monday Sessions
       Session VT-MoM

Paper VT-MoM10
Water Vapor Cryopumping: Refrigerant Phaseout Compliance

Monday, November 9, 2009, 11:20 am, Room C1

Session: Vacuum Contamination and Pumping
Presenter: K. Flynn, Brooks Automation Polycold Systems
Authors: K. Flynn, Brooks Automation Polycold Systems
C. Rebecchi, Brooks Automation Polycold Systems
Correspondent: Click to Email
Water vapor cryopumps, which use mixed gas refrigeration technology, rely on mixtures containing four or more refrigerants, each with widely spaced boiling points. Historically, these mixtures contained two or more chlorinated refrigerants such as chlorofluocarbons (CFC’s) or hydrochlorofluorocarbons (HCFC’s). Both classes of compounds contribute to depletion of the stratospheric ozone layer and are subject to legislative action to phase out these compounds. CFC refrigerants were banned in the US and other developed countries in 1995. HCFC refrigerants are currently in use, but are targeted for phase out. Mixed gas refrigerant water vapor cryopumps have relied on HCFC refrigerants, including HCFC R-22 since the early 1990’s when CFC refrigerants were phased out. Although water vapor cryopumps experience much lower leakage rates than commercial refrigeration systems, they are subject to the same laws as all other refrigeration equipment. Effective January 1, 2010, the use of R-22 will be banned on new equipment in the US. R-22 is a key refrigerant in water vapor cryopumps due to its excellent refrigeration capacity and its relatively low freezing point (-160 °C). The phase out of R-22 has required extensive development of alternative refrigerants. It has been accomplished for three important sizes of water vapor cryopumps. The resulting products provide water vapor cryopumping at the same speeds and water vapor partial pressures as the previous mixtures with R-22. This paper reviews the development approach, and compares system and pumping performance for these green products. Experimental data from commercial vacuum systems is presented for the old and new product.