PRESSURE EFFECTS ON SEAL PERFORMANCE

摘要

Standard shaft seals or rotary shaft seals are typically found in low-speed or low-pressure environments. As the speed of the shaft increases, the maximum allowable pressure decreases, and as pressure or speed increases, the design of the seal needs to change to ensure the life of the seal. Standard shaft seals are designed for pressures from 0 to 7 psi. Slightly increasing this pressure could result in forcing more of the air side of the seal lip down onto the shaft. As the shaft turns, there is more lip contact on the shaft, which can cause greater lip wear. A conventional seal design with a single spring-loaded NBR lip and metal case has a useful seal life of 2,000 hours with a shaft speed of 1,000 rpm or less. The resultant seal lip wear is approximately 0.025". If the pressure in this environment is increased to greater than 10 psi, the seal lip wear increases by a factor of at least four, and the resultant seal lip life is reduced to less than 20% of the design limits for standard seals. This is a dramatic decrease in seal life with just a slight increase in pressure.