EVALUATION OF POROUS MATERIALS AS MOLECULAR LEAKS,
ARNOLD ENGINEERING DEVELOPMENT CENTER ARNOLD AIR FORCE STATION TENN
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From the experimental results obtained, adsorption effectively makes Knudsens flow theory inadequate for predicting the conductance of a molecular leak. This necessitates calibrating the molecular leak for each gas or vapor that will be used. Of the four types of leaks tested, porous glass and porous stainless steel offer the best possibilities for use as molecular leaks at relatively high pressures 100-760 TORR. A leak fabricated from porous glass exhibits molecular flow up to atmospheric pressure. For a conductance of 0.00001 literssec for N2, the over-all length of the leak is approximately 8 in. with an OD of 1532 in. The leak is easily contaminated and has a great affinity for water vapor and other vapors. It is difficult to mount and easily broken.