A radial load, namely radial pressure, is generated in the process of the oil seal lip engaging with the journal. This pressure has a great influence on the wear rate and sealing performance of the oil seal lip. If the radial pressure is too small, the friction force will be greatly reduced. Although the wear of both can be reduced, the sealing performance of the oil seal will be seriously reduced, resulting in oil leakage or serious oil leakage. If the radial pressure is too large, although it is beneficial to enhance the sealing performance of the oil seal lip, the friction force between the two is increased, and it is difficult to form a good oil film on the ring surface in contact with the two. Therefore, the wear of the two will be intensified, and the lip of the oil seal will be damaged in a short service life, causing damage to the journal and oil leakage.
In addition to the radial pressure, the sealing performance of the oil seal is affected by the surface roughness of the journal, the runout of the journal, the linear speed of the rotating surface, the smoothness of the lip, the rubber material and the elastic force of the self tightening spring. In addition, the bearing is short of oil or the oil quality is too dirty and sand and other impurities invade, which will aggravate the lip wear and make it loose contact with the journal, resulting in seal failure of oil seal.
2、 Precautions for oil seal installation
Although the damage and wear of oil seal are related to improper use and maintenance, they mainly come from improper installation. Therefore, the installation of oil seal should be strictly controlled to protect the installation quality of oil seal.
(1) Select qualified oil seal. When selecting oil seal, the products with credibility and quality assurance should be selected. Do not covet cheap, buy no package, no certificate, no manufacturer of fake and shoddy products. The specification and size of the new oil seal shall be consistent with the old oil seal replaced, and its oil seal framework shall be hard and without deformation; the rubber shall be smooth and smooth without cracking, and shall be firmly combined with the framework; the lip shall be of good toughness and free from defects such as damage and crack; the self tightening spring shall be free from distortion and corrosion, and each spring shall be arranged tightly and evenly.
(2) Press the oil seal with special tools as far as possible. When installing the oil seal, it is not allowed to take a simple and crude method. Use a hammer, iron bar and other tools to knock the oil seal into place, and use a special tool to slowly press the oil seal into place. If there is no special tool, you can find a short section of steel pipe, its inner diameter is slightly larger than the diameter of the journal, and its outer diameter is slightly smaller than the outer diameter of the oil seal. Put the steel pipe on the oil seal, and gently and evenly knock the upper ring surface of the steel pipe with a hammer to make the oil seal installed in place. Put the oil seal in the right position during installation, and do not make the oil seal skew during pressing. In order to reduce the pressure resistance of the oil seal, a thin layer of oil can be applied on the cylindrical outer surface of the oil seal.
(3) Before installing the oil seal into the shaft end, a little oil can be applied on the oil seal lip to make the oil seal fit into the shaft end smoothly. At the same time, check the shaft end and journal, no burr, rust and bruise. If yes, use files, oilstones, grinding wheels and other tools for grinding, so as to avoid scratching the oil seal lip. If the oil seal must pass through a section of spline shaft during the installation, in order to avoid the spline edge from damaging the lip, wrap the spline shaft with plastic film, coat the surface with oil, cover the oil seal on the film cylinder, and slowly rotate and push forward, so that the oil seal can smoothly pass through the spline shaft.
(4) During the installation of oil seal, the position and state of self tightening spring should be paid attention to at all times. Since the self tightening spring is subject to vibration, it is easy to fly off or skew, so it is necessary to pay close attention to it. If the elasticity is not enough, it can be solved by cutting the corresponding length, but the connection between the two ends must be guaranteed. The position where the oil seal is installed and the tools used should be kept clean. All the instruments that may contact the oil seal lip and working surface should be smooth and free of burr and sharp angle to prevent the oil seal from being damaged. If necessary, rubber or other flexible materials can be padded on the oil seal surface to protect the oil seal from damage.
(5) The operator should master the technical essentials of correctly installing the oil seal, operate carefully, and never take care of it to prevent improper installation, oil seal deformation and not in place.