Application of Combine Harvester Framework Oil Seal

The oil seal on the combine is a small spare part that looks inconspicuous but plays a vital role in the operation of the whole machine. Oil seal is the customary name of general seals, simply the lubricating oil seal. When selecting an oil seal, we should pay attention not only to its quality but also to its model.

The classification of oil seals

Oil seals can be divided into various forms and different names according to sealing function, characteristics, structure type, working state, and sealing mechanism. Oil seals are classified according to the linear speed of shaft rotation.

Oil seals can be divided into low-speed oil seals (less than 6m/s) and high-speed oil seals (more than 6m/s). According to the pressure that the oil seal can withstand, it can be classified into normal pressure oil seal and pressure resistant oil seal (greater than 0.05Mpa).

According to the structure and sealing principle of oil seal, it can be divided into standard oil seal and power return oil seal. In addition, according to the material classification of oil seal components, it can be divided into skeleton oil seals and non-skeleton oil seals; There are spring-type oil seals and non-spring-type oil seals.

Oil Seal

  • Labyrinth oil seal: The clearance between the labyrinth oil seal and the shaft shall not be too large or too small. If the clearance is too small, the shaft will be easily worn. If the clearance is too large, the shaft will leak oil. Since the seal is fixed on the housing and is relatively fixed to the shaft, it cannot adapt to and compensate for the floating of the shaft. The shaft vibration will wear the oil seal clearance more and more, eventually leading to oil leakage.
  • Rubber framework type oil seal: The rubber framework type oil seal is wrapped by the metal framework with rubber. In order to effectively float with the same axis on the inner side of the sealing surface, a spring is specially added. Although it overcomes the disadvantage that the labyrinth seal cannot float with the shaft, it will wear the shaft and will wear itself, which will lead to oil leakage after reaching a certain extent.
  • Felt oil seal: Felt oil seal processes a “V” groove on the bearing cover and uses its own elasticity to act on the shaft for sealing. However, it is easy to inhale small particles to make the felt lose its elasticity and cannot compensate for the vibration of the shaft, leading to failure and oil leakage.

According to the characteristics of the combine, the framework oil seal is often used by the combine. The framework oil seal is a typical representative of the oil seal. Generally speaking, the oil seal refers to the framework oil seal. The role of the oil seal is generally to isolate the parts that need lubrication in the transmission parts from the output parts, so as not to let the lubricating oil leak. The skeleton is just like the steel bar in the concrete component, which plays a role in strengthening and maintaining the shape and tension of the oil seal.

Structure of framework oil seal

The framework oil seal structure comprises three parts: the oil seal body, reinforcing framework, and self-tightening spiral spring. Different parts, the sealing body can be divided into the bottom, waist frame oil seal structure, cutting edge, and sealing lip. Generally, the internal diameter of the framework oil seal in the free state is smaller than the shaft diameter, that is, it has a certain “interference”.

Therefore, when the oil seal is placed on the oil seal seat and shaft, the pressure of the oil seal blade and the contraction force of the self-tightening coil spring will produce a certain radial tightening force on the shaft. After a period of operation, the pressure will rapidly reduce or even disappear. Therefore, the self-tightening force of the oil seal can be compensated at any time by adding the spring.

Structure of framework oil seal

Sealing principle: Because there is an oil film controlled by the oil seal blade between the oil seal and the shaft, this oil film has the characteristics of fluid lubrication.

Under the action of the skeleton oil seal, the rigidity of the oil film just makes the oil film and the air contact end form a crescent surface, preventing the leakage of the working medium, thus realizing the seal of the rotating shaft. The sealing ability of the oil seal depends on the thickness of the oil film on the sealing surface. If the thickness is too large, the oil seal will leak; If the thickness is too small, dry friction may occur, causing wear of the oil seal and shaft; There is no oil film between the sealing lip and the shaft, which is easy to cause heating and wear.

Therefore, during installation, some oil must be applied to the seal ring, and the framework oil seal must be perpendicular to the shaft centerline. If it is not vertical, the sealing lip of the oil seal will drain the lubricating oil from the shaft, which will also cause excessive wear of the sealing lip. During operation, the lubricant in the housing slightly seeps out to achieve the ideal condition of forming an oil film at the sealing surface.

Top points when using oil seals properly

using oil seals

  1. Shaft speed Due to design and structure reasons, high-speed oil seals should be used for high-speed shafts and low-speed oil seals should be used for low-speed shafts. Low-speed oil seals should not be used for high-speed shafts, and vice versa.
  2.  When the ambient temperature is high, polypropylene ester or silicon, fluorine, or silicon fluorine rubber shall be selected. Try to reduce the oil temperature in the oil tank. Cold-resistant rubber shall be selected when the service temperature is too low.
  3. The oil seal with ordinary pressure has poor pressure-bearing capacity. The oil seal will deform when the pressure is too high. In case of excessive pressure, a pressure-bearing ring or reinforced pressure seal shall be used.
  4.  The degree of eccentricity of the oil seal on the installation is too large when it is fitted with the shaft, so its sealing performance will become worse, especially when the shaft speed is high. If the eccentricity is too large, the oil seal with the “W” section can be used.
  5.  The surface finish of the shaft directly affects the service life of the oil seal, that is, if the shaft has a high finish, the service life of the oil seal will be long.
  6.  Note that there should be a certain amount of lubricating oil at the lip of the oil seal.
  7. Pay special attention to prevent dust from immersing into the oil seal.

These are the applications of skeleton oil seals on the combine. If you want to know more, please contact us, and we will provide you with professional services.

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