Effects of operating parameters on gas transportation of radial lip seals

This paper describes the effects of shaft speed, sump temperature, sump level, and sump pressure on gas transportation of standard plain lip seals. The volume of helium pumped from the air side to the sump side of lip seals, and that leaked from the sump side to the air side, were measured using gas chromatography. Lip seals pump helium and, at the same time, leak it in the opposite direction. The helium pump rate and the leak rate increase with the shaft speed, suggesting that the gas moves through the gap between the lip and the shaft. Helium also moves across lip seals by permeation through the seal material. Therefore, lip seals have two paths for gas movement. Path-1 is the seal material in which helium moves by permeation. Path-2 is a gap between the seal lip and the shaft in which helium is transported by the dynamic effect. The helium pump rate and the leak rate through path-2 do not change with sump level but do increase with sump temperature. The helium pump rate decreases remarkably with sump pressure and is lower than the helium leak rate at a sump pressure higher than 30 kPa.