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Typical belt-driven Mobile Air-Conditioning (MAC) compressors require durable seals between a rotating driveshaft and stationary casing in addition to casing and hose connection O-ring seals. This paper explores the experiential and theoretical relationships of HFC134a seal design and materials and also suggests possible improvements. Testing revealed that shaft and O-ring permeation comprised a large part of the total leak rate of HFC134a MAC compressors during static-state leak-rate measurements. Furthermore, testing and Taguchi statistical analysis methods clarified equations concerning permeation area, distance and leak rate. Resulting design and material improvements reduced compressor HFC134a Leak Flow Rates (LFR) by approximately fifty percent.

Several field problems are anticipated with HFC-134a systems. To be evaluated and clarified are the impacts upon: compressors and systems of chlorine based solvents left in the system from flushing or parts cleaning; mixing in CFC-12; mixing the new lubricants with mineral oil; the effects of certain lubricants and HFC-134a's high hygroscopicity and others. The whole industry should share information and endeavor to maintain the reliability of the new systems from a service engineering standpoint. STARTING IN 1991 the ozone safe HFC-134a refrigerant is expected to replace the conventional CFC-12 in car air conditioning systems and in model years 1994-1995 the major portion of the market will be the new systems. The components/elements and parts used in the new air conditioning systems will embody different designs with new materials which are now considered to be compatible with the new refrigerant-lubricant mixtures.

Certain important factors must be considered when the current refrigerant for automotive air conditioning systems, (A/C), is changed from CFC12 to the ozone safe HFC134a. This paper will focus on lubricant compatibility by presenting a screening process which will cover: a screening table of essential physical properties general information on types of available lubricants tests of chemical stability lubricity compatibility with elastomers methods for testing compressor durability service engineering