(1) Lip damage
The skeleton oil seal will lead to high temperature carbonization and wear failure of rubber after long time use. The abrasive wear of the seal caused by the continuous high-speed and high-temperature sliding contact between the shaft and the oil seal. The circumference speed of the shaft is also a key factor affecting the sealing effect, the greater the contact pressure between the lip of the oil seal and the surface of the shaft, the higher the relative motion speed, the faster the temperature rise caused by friction, the higher the temperature, so that the lip wear, burn, crack, resulting in the seal failure of the oil seal, shorten the service life of the oil seal.
(2) Shaft wear
Due to the long-term use of the reducer, the wear of the shaft seal is excessive, and some serious cases even appear V-shaped grooves. Once the grooves are formed, the interference between the oil seal lip diameter and the shaft diameter becomes smaller, resulting in the contact pressure between the oil seal lip and the shaft falling, and the oil film is easy to seep from the groove mark, eliminating the sealing effect of the skeleton oil seal. At the same time, the surface roughness of the shaft has a great influence on the performance and service life of the oil seal. The roughness is too low, and the oil is easily extruded from the sealing contact surface, so that the oil film becomes thin, resulting in lip heating. The roughness is too high, the shaft is easy to scratch the lip after high-speed rotation, so that the sealing surface becomes hairy, the friction torque increases, and the lip is quickly worn and caused by leakage.
(3) The influence of eccentricity
Eccentricity means that the inner circle of the oil seal lip is different from the center of the shaft surface. It causes uneven contact between the oil seal lip and the shaft, so the radial compression force of the oil seal on the shaft is uneven, the heat is uneven, and the wear of the lip is uneven, making the oil seal easy to leak and damage. There are many reasons for eccentricity:
(1) Shaft surface eccentricity during machining or eccentricity caused in bearing parts after installation;
② The inner diameter and outer circle of the oil seal lip are different;
(3) The installation hole (shell) of the oil seal is different from the axis.
(4) The effect of metamorphic oil
The deteriorated oil contains a large number of small particles, most of which are oxides, harder than metal, although the particle size is only 0.1~ 3μm, but it is easy to suspend in the oil, and circulate with the oil in the box, once the oil reaches the oil seal lip, it will aggravate the wear of the oil seal lip and shaft.