An Empirical Investigation on Seal-Interface Leakage of an Elastomer Face Seal

For the application of seals used in space, a common assumption is that all leakage is attributed to permeation, that is the gas flows through the porous seal material. In this case, leakage across any seal interfaces are assumed negligible. In fact, state-of-the-art gas leak rate prediction methods rely heavily on this assumption. A recent study into the quantification of the seal-interface leakage of elastomer face seals, however, has revealed that this is not the case. As the preliminary study previously presented, with moderate contact pressure the interface leakage components were found to be significant and distinct from zero. The objective of the research presented herein was to further quantify both the elastomer-metal and elastomer-elastomer interface leakages for various contact pressures. To this end, a series of leak rate experiments is presented on a square-ring seal, manufactured from silicone elastomer S0383-70. The unique experimental design affords the ability to quantify both the elastomer-metal interface, as well as an elastomer-elastomer interface. The experiments utilized matched sets of test specimens, each with a common width but different height. The test apparatus contained both a flow fixture capable of quantifying ultra-low leak rates and an electro-mechanical actuated load frame for precision contact pressure control. The leak rate apparatus consisted of stainless steel platens, near-hermetic plumbing, and the required instrumentation. The initial data reduction was accomplished by the mass point leak rate technique; whereas mass was calculated through measurements of gas pressure, temperature, and volume and a regression analysis yielded the leak rate of the seal. A secondary reduction of the leak rates in the unique experimental configuration further distinguished the total leakage into permeation and interface leak components, accomplished through the algebraic solution of the design of experiments guided matrix. Foremost, results confirmed that the interface leakage is non-negligible and distinct from zero, as with previous studies. Furthermore, results suggested that the interface leakage was drastically decreased with modest seal contact pressure.