Correlation of Gaseous Mass Leak Rates Through Micro- and Nanoporous Gaskets

The present work deals with the theoretical and experimental studies of gaseous flow through tight gaskets. The paper presents an innovative approach to accurately predict and correlate leak rates of several gases through nanoporous gaskets. The new approach is based on the calculation of the gasket porosity parameters (⁠$D$ and $N$⁠) using a model based on a first order slip flow regime. The model assumes the flow to be continuum but employs a slip boundary condition on the leak path wall. Experimental measured gas flow rates were performed on gaskets with a microscopic flow rate range and isothermal steady conditions. The flow rate is accurately measured using multigas mass spectrometers. The gasket porosity parameters used in the developed leakage rate formula were experimentally obtained for a reference gas (helium) for each stress level. In the presence of the statistical properties of a porous gasket, the leak rates for different gases can be predicted with reasonable accuracy. It was found that the approach that considers the slip flow with the first order combined to the molecular flow covers the prediction of flow rates at the microscopy level and down to $10−8mg/s$ very well. Tightness hardening is the result of the saturation of the gasket combined porosity parameters or the equivalent thickness of the void layer.