Principle and Selection Scheme of Framework Oil Seal

Skeleton oil seals are an important component of mechanical seals and are a typical representation of oil seals. Generally, when we talk about oil seals, we are referring to skeleton oil seals. Skeleton oil seals are widely used in various mechanical equipment to prevent the leakage of lubricating oil or other liquid mediums. This article will provide a detailed introduction to the structure, working principle, selection, and usage precautions of skeleton oil seals to help better understand and apply this important sealing component.

Structure of Skeleton Oil Seals

Skeleton oil seals mainly consist of three parts: the skeleton, the sealing lip, and the elastic material. The skeleton is the supporting structure of the oil seal, usually made of metal or plastic materials. The sealing lip is the main sealing part of the oil seal, usually made of rubber or polytetrafluoroethylene (PTFE). The elastic material is used to make the sealing lip fit better with the shaft surface to achieve better sealing effect. Typically, the inner diameter of the skeleton oil seal is slightly smaller than the shaft diameter, having a certain amount of "interference fit" to ensure the sealing performance of the skeleton oil seal.

Working Principle of Skeleton Oil Seals

The working principle of skeleton oil seals is mainly based on the principles of axial compression and radial expansion. When the skeleton oil seal is installed on the shaft, due to the elastic material's force, the sealing lip will be axially compressed, thereby tightly adhering to the shaft surface. When the shaft rotates, due to the action of centrifugal force, the sealing lip will undergo radial expansion, further enhancing the sealing effect.

Under the action of the skeleton oil seal, the stiffness of the oil film forms a crescent-shaped boundary at the oil film's contact end with air, preventing the leakage of the working medium, thereby achieving the sealing of the rotating shaft.

The sealing capability 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 to the oil seal and the shaft; if there's no oil film between the sealing lip and the shaft, it may cause heating and wear. Therefore, during installation, it's necessary to apply some oil to the sealing ring and ensure that the skeleton oil seal is perpendicular to the shaft centerline. If not perpendicular, the oil seal's sealing lip may scrub the lubricating oil off the shaft and cause excessive wear to the sealing lip. When in operation, a slight leakage of lubricant from inside the housing is ideal to form an oil film at the sealing surface.

The general function of the skeleton oil seal is to isolate the lubricated parts of the driving components from the output components, preventing lubricant leakage. It is usually used for rotating shafts, functioning as a rotary shaft lip seal. The skeleton acts similarly to rebar in concrete, providing reinforcement and helping the oil seal maintain shape and tension. There are inner and outer exposed skeleton oil seals. skeleton oil seals are made of high-quality nitrile rubber and steel plates, ensuring stable quality and long service life.

Selecting Skeleton Oil Seals

When selecting skeleton oil seals, consider the following factors:

Shaft diameter and speed

Choose the appropriate model and specification of skeleton oil seal according to the shaft diameter and speed.

Working environment

Select suitable skeleton oil seal material and structure according to the working environment, such as high temperature, low temperature, corrosive medium, etc.

Sealing requirements

Choose appropriate skeleton oil seal structure and sealing lip material according to sealing requirements.

Cost-effectiveness

Select cost-effective skeleton oil seals while meeting usage requirements.

Precautions for Using Skeleton Oil Seals

To use oil seals rationally, pay attention to the following points:

• Due to design and structure reasons, high-speed shafts should use high-speed oil seals, and low-speed shafts should use low-speed oil seals. Do not use low-speed oil seals for high-speed shafts or vice versa.

  
  

• Under high temperature conditions, select polypropylene or silicone, fluorine, and fluoro-silicone rubber. Try to lower the oil temperature in the tank. Under low temperature conditions, select cold-resistant rubber.

  
  

• Generally, oil seals have poor pressure resistance. Under high-pressure conditions, oil seals will deform. Use pressure-resistant support rings or reinforced pressure-resistant oil seals under such conditions.

  
  

• If the oil seal and shaft are overly eccentric during assembly, sealing performance will deteriorate, especially at high shaft speeds. Use "W" shaped cross-section oil seals if eccentricity is excessive.

  
  

• The surface smoothness of the shaft directly affects the oil seal's service life; the higher the shaft smoothness, the longer the oil seal will last.

  
  

• Ensure there is a certain amount of lubricant at the oil seal lip.

  
  

• Pay special attention to preventing dust from entering the oil seal.

  
  

In summary, skeleton oil seals are an important component of mechanical seals and play a crucial role in various mechanical equipment. During use, select appropriate models and specifications and adhere to related operational procedures to avoid accidents that could damage the skeleton oil seal, thereby ensuring the normal operation and longevity of mechanical equipment.