SAE initiated the latest CRP after Daimler raised questions about the refrigerant's flammability. SAE said the CRP's latest evaluation was expanded based on Daimler's concerns, but that "the CRP has found that the refrigerant is highly unlikely to ignite and that ignition requires extremely idealized conditions."
"The SAE CRP team of OEMs has also identified that the refrigerant release testing completed by Daimler was unrealistic by creating the extremely idealized conditions for ignition while ignoring actual real world collision scenarios," the SAE said in its announcement. "These conditions include specific combinations of temperature, amount and distribution of refrigerant, along with velocity, turbulence, and atomization, which are highly improbable to simultaneously occur in real-world collisions."
By comparison, the CRP said its safety evaluation of the refrigerant used, "universally accepted engineering methods, including analysis of recent OEM testing from actual vehicle crash data, on-vehicle simulations, laboratory simulations, bench tests, and over 100 engine compartment refrigerant releases."
The CRP said it is continuing to review use of the refrigerant. "The CRP continues to populate the fault trees to insure completeness of the risk assessment through pragmatic and factual input based on the latest and most accurate data available," the CRP said. "Fault tree analysis as conducted by the CRP is the most appropriate approach for evaluating risks of new alternative refrigerants. This approach has been recommended and employed by numerous public and private organizations including the U.S. Environmental Protection Agency, the U.S. Department of Energy, the International Electrotechnical Commission, the European Union Joint Research Centre and the United Kingdom Health and Safety Executive."The latest CRP included European, North American, and Asian automakers, including Chrysler/Fiat, Ford, General Motors, Honda, Hyundai, Jaguar Land Rover, Mazda, PSA, Renault and Toyota. HFO-1234yf is being adopted by automakers in part to meet the European Union's MAC Directive, which aims to reduce the greenhouse gas emissions of air-conditioning systems in passenger cars and light commercial vehicles. The directive requires that refrigerants in all new type vehicles sold in Europe after Jan. 1, 2013, have a global-warming potential (GWP) below 150 and that all cars sold after 2017 meet the lower GWP requirement. SAE International, formerly known as the Society of Automotive Engineers, is an independent, global association of more than 133,000 engineers and related technical experts in the aerospace, automotive and commercial-vehicle industries.