Comparison of measured leak rates and calculation values for sealing packages

Abstract

It is often necessary to calculate a leak rate from the size of leak hole and vice versa for testing of sealing packages such as foods, medicines and dangerous goods. These calculations are actually rather complicated because the characteristics of the gas flow through the leak hole change depending on the pressure, the gas species, the temperature and the diameter d and length l of the leak hole. In this study, the air flow rate through 12 flow channels with the inner diameter of 5–50 μm and the l/d ratio of 0.72–260 were measured by a pressure change method and compared with the predictions of the equations governing laminar, turbulent, compressible and molecular flow, as well as those of a developed combined governing equation (modified Knudsen equation). The modified Knudsen equation provided good agreement within 20% over the entire range of experimental conditions, including the transition region between laminar and compressible flow.