The majority of these are related to air conditioning hoses. Although the performance of different hoses varies considerably when they are tested with R-1234yf instead of R-134a, the good news was that many of these hoses can and will meet the established acceptance criteria. Many of them are now approved by manufacturers and in use in vehicles with R-1234yf. Apart from this, it is also necessary to investigate whether hoses are compatible with R-1234yf and PAG or POE oils, because not all R-134a hoses are suitable for use in R-1234yf systems.
Solid rubber hose
: for many years, all-rubber hoses were used as suction lines to solve noise problems in R-134a systems. Although they are still a viable option for R-1234yf suction lines, the permeation rate of R-1234yf for all-rubber hoses is considerably higher than that of R-134a. While the permeation rate of R-1234yf may amount to twice the rate of R-134a for the hoses of some manufacturers, the permeation rates for all-rubber hoses do not achieve these high values for all suppliers. This increased permeation leads to losses in the SAE J2727 emission credits, and an increase in the refrigerant charge may have to be taken into consideration in order to keep up the necessary refrigerant quantities over the entire service life of the vehicle.
:hoses with an inner barrier layer have also been used for many years in R-134a systems. These hoses are still a good option for R-1234yf systems. In light of this, the tests have uncovered a possible weakness in this design. As it is primarily the nylon layer that holds the refrigerant in check, damage to this layer may become a problem. If the nylon coating material is exposed to a combination of R-1234yf and PAG oil and a low quantity of water, some nylon materials may be seriously damaged. Here too, very good hoses are available for use with R-1234yf with acceptable compatibility results. For suppliers, it is important to be able to demonstrate an acceptable performance for material compatibility.
: like the aforementioned hoses, barrier hoses were also primarily used for R-134a systems. They are also still an excellent option for R-1234yf systems. Even though not all rubber materials are the same and some rubber compounds pose a possible risk when R-1234yf is used, the rubber inner layer can protect the nylon from damage. As R-1234yf is an olefin, it may polymerize in the presence of certain conditions. During the material evaluations, there were cases in which the contact of rubber hose materials with combinations of R-1234yf and compressor oil led to a polymerization of the coolant. For this reason, rubber materials with certain polymerization initiators, including peroxides, should be avoided. At present, there are acceptably functioning R-134a hoses that have been identified as questionable for use with R-1234yf because their peroxide cross-linking system has verifiably caused a polymerization of the coolant.
The standard SAE J2064 for hose lines has recently been divided into a standard for hoses (SAE J3062) and a standard for hose lines (SAE J2064). Only hoses that satisfy SAE J3062 may be used in lines to achieve certification pursuant to SAE J2064. The SAE Interior Climate Control Component Committee is currently working on a proposal to integrate the test requirements for material compatibility into the hose standard SAE J3062. The acceptance criteria will confirm that the effects of R-1234yf and oil on hose material are acceptable. Within the framework of the acceptance criteria, a proposal confirming that hose materials can come into contact with R-1234yf under the operating conditions of air conditioning units without the coolant polymerizing is also being discussed.
The ContiTech portfolio includes the appropriate solutions for R-1234yf systems, and the suitability of the hoses and lines is already verified. ContiTech is currently in the process of having them officially certified in accordance with SAE J3062 or SAE J2064.