Prediction of gas flow in compressible and low permeability porous media

Predicting leak rate through porous compression packing rings is a significant challenge for the design of external sealing of valves. Although few studies have been conducted to predict the leak rate through these seals, there is no comprehensive standard procedure to be used to design and select suitable compression packings for a maximum tolerated leak for a given application. With the ubiquitous use of the yarned packing rings in the sealing of the valves, and the strict regulations on fugitive emissions and the new environment protection laws, quantification of leak rate through yarned stuffing boxes becomes more than necessary and a tightness criteria based design procedure must be developed. In this study a new approach to predict leak rate through compression packing rings has been developed. It is based on Darcy's model to which Klinkenberg's slippage effect is incorporated. The predicted leak rates are compared to those measured experimentally using two different graphite-based packing rings subjected to different compression levels and pressures. A good agreement is found between the predicted and the measured leak rates which illustrates the validity of the developed model.