Design and characterization of refrigerant reference leaks

•New design for R134a permeation leaks developed with leak rates ranging from 1 to 30 g/year−1.•Proposed design fulfills the requirements of EN14624:2012.•MVQ silicone was found to be a suitable membrane and its permeability was measured for R134a.•Twelve leaks were assembled and calibrated; leak rate was controlled by the cap hole diameter.•Leak rate was well predicted assuming a spherical shaped permeation area. Nowadays, leak detection is widely used in many fields such as automotive and refrigeration industries. European Regulation No 517/2014 identifies leak tightness as the key point to decrease the emissions of the refrigerant gases with greenhouse effect. Tightness of systems charged with refrigerant fluids must be controlled periodically by refrigerant gas detectors. According to the Commission Regulation No 1516/2007 these detectors are required to be tested at least once per year with reference leaks, or “calibrated” leaks, to confirm a detection limit of 5 g per year. For this purpose, a technique to built reliable reference leaks made of R134a (1,1,1,2-tetrafluoroethane) is described. These leaks are suitable to fulfill the requirements of EN14624:2012 which defines the procedure to test refrigerant leak detectors. The proposed design takes advantage of the suitable permeability of vinyl methyl silicone rubber (MVQ silicone). The leak rate is adjusted by the size of a hole drilled in the reservoir cap. The described design is suitable to manufacture reference leaks having leak rates from 1 to 30 g per year. The long term stability was found to be within the calibration uncertainty of ±3% and the temperature coefficient of 3.2% per K. [Display omitted]