Joint Research Centre review concludes no serious risk in use of R1234yf MAC refrigerant under normal and foreseeable conditions
7 March 2014
A scientific review of research regarding the safety aspects of the use of refrigerant R1234yf in Mobile Air Conditioning (MAC) systems, published by the European Commission, concludes that there is no evidence of a serious risk in the use of this refrigerant in MAC systems under normal and foreseeable conditions of use.
The review, carried out by Europe’s Joint Research Centre, provided an in-depth analysis of testing and a subsequent report on the refrigerant’s safety by KBA (Kraftfahrt Bundesamt, the German authority responsible for market surveillance and product safety for road vehicles) in order to ascertain whether the results stemming from the tests were well founded and supported by a rigorous and scientific methodology.
Europe has banned the use of the refrigerant R134a in new vehicles because of its high global warming potential (GWP). Automotive manufacturers decided in 2009 to use the low-GWP refrigerant R1234yf, developed by DuPont and Honeywell (earlier post), as the technical solution to comply with the targets.
However, in 2012, internal testing by Daimler indicated a safety problem in the use of R1234yf under certain conditions; Daimler ultimately opted not to use R1234yf, and is seeking an alternate solution. The automaker is currently testing R744 (CO2). (Earlier post.)
In response to Daimler’s concerns, KBA launched a series of vehicle tests at three different levels, considering levels 1 and 2 for their assessment of possible risks within the scope of the statutory tasks as product safety authority, and level 3 tests as general risk appraisal.
Testing was in three steps:
Pre-test on highway to determine the maximum temperature of the vehicles Tmax, measured at the exhaust manifold or turbocharger by driving at the vehicles’ maximum speed (about 180 to 190 km/h).
Crash test under “warm and wet”—but not hot—conditions. The purpose of the crash tests was to generate real damages in the air conditioning system for the release of refrigerant in the later test levels 1-3.
Refrigerant release tests at 3 different levels, with engine target temperatures set to Tmax-50°C, except for one test at level 3.
Under level 1 testing, the leakages were those observed after the crash test. Under level 2 testing, additional leakages were introduced in the air conditioning systems in those positions where damages without leakage were already observed after the crash test. Under level 3 testing, further leakage modifications and configurations in the refrigerant release setup were introduced to verify if the worst case was met before under level 1 and level 2 testing.
Testing at levels 1 and 2 found refrigerant release but no refrigerant ignitions and no hydrogen fluoride (HF) release above 1 ppm. Testing at level 3 found elevated HF concentrations under the hood. In one of the test cars, the released refrigerant R1234yf ignited, combined with higher measured values of HF in the engine compartment (3300, 5400 ppm). This happened in two out of three identical tests that were carried out.
Under level 3 the comparative test with refrigerant R134a did not result in ignition; HF concentrations under hood were at about 3 ppm.
The KBA report concluded after level 1 and level 2 testing that its results did not provide sufficient supporting evidence of a serious risk—within the meaning of the Product Safety Act (ProdSG)—with the vehicle types tested.
The JRC shared that conclusion; level 1 and level 2 testing showed no ignition of refrigerant R1234yf and no release of hydrogen fluoride (HF) despite the very high temperatures in the engine compartment. Consequently the results as such with the vehicles tested under the conditions as described for level 1 and level 2 testing provided no evidence of a serious risk.
KBA did not take refrigerant release tests under level 3 into account as relevant input, as it was outside the scope of the statutory tasks as product safety authority. Put differently, KBA concluded that while level 1 and level 2 tests were realistic and appropriate for consideration respect to the product safety regulations, the level 3 tests could not be associated with the necessary concrete probability of occurrence, but served as a general appraisal of the risk.
Level 3 test temperatures were very high, approaching almost always the maximum temperature measured during the motorway high speed pre-test, and exceeding once that maximum temperature by +30 °C. These tests were carried out to understand if ignition might occur under higher engine temperatures that might be achieved with future vehicle technologies and future engine designs.
This approach taken by the KBA is supported by the JRC because it reflects JRC’s understanding of Article 2(b) of the General Product Safety Directive 2001/95/EC in which is stated “… ‘safe product’ shall mean any product which, under normal or reasonably foreseeable conditions of use (…) does not present any risk or only the minimum risks compatible with the product’s use…”.
Therefore drawing of conclusions from level 3 tests, further than the ones already drawn from level 1 and level 2 tests regarding the safe operation of the refrigerant R1234yf in MAC systems, is not appropriate, considering the definition of “safe product” in the General Product Safety Directive 2001/95/EC.
… In summary: Each of the different single test conditions combined under level 3 testing reflect a situation which occurrence can’t be excluded. The combined probability of occurrence for the combination of several single conditions into one scenario was not determined. Compared to the scenarios for the realistic level 1 and level 2 testing, the probability of level 3 scenarios must be assumed to be far lower, and not reflecting “normal or reasonably foreseeable conditions of use” under which the General Product Safety Directive 2001/95/EC applies.—JRC report
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