Seals shall primarily withstand operating pressures, temperatures and speeds and offer compatibility with given fluids. Moreover they shall feature good wear resistance properties. In order to ensure long service life. therefore they shall offer elasticity, compression strength wear resistance, hardness and chemical compatibility with fluids.
The velocity is affected by various factors, such as the roughness of metal surface, the co-axially of moving parts, temperature and working pressure. These external factors act on the sealing material and determine the maximum moving speed of the seal.
Speed in the range between 0.03 to 0.3 m/s, normally, do not affect the sealing system efficiency. In case of very low speeds, however, the poor hydrodynamic pressure is unable to maintain constant the thickness of the oil gap that forms between sealing lips and sliding surface. It tends to break and reform continuously and the resulting friction cause s “jerky” motion (stick-slip), leading to sealing wearing. On the contrary, at too high speeds the hydrodynamic pressure tends to ” pull” the sealing lip away from the contact surface. In this area the temperature increase. While the fluid viscosity decreases, resulting in leakages.
Post time: Aug-27-2019