Os princípios básicos dos selos de esqueleto: o que você precisa saber

The Basics of Skeleton Seals: What You Need to Know

A skeleton seal is a typical representative of oil seals, often called simply an oil seal.

The function of an oil seal is generally to isolate the parts that need lubrication in the drive components from the output components, to prevent leakage of lubricating oil.

The skeleton is like the reinforcement of the concrete components, it plays a reinforcing role and allows the oil seal to maintain its shape and tension.

The structure of an oil seal skeleton consists of three parts: the oil seal body, the reinforcing skeleton and the self-tightening spiral spring.

The Basics of Skeleton Oil Seals What You Need to Know

The seal body is divided into different parts such as bottom, waist, blade edge and sealing lip according to different positions. Normally, in the free state, the internal diameter of the seal skeleton is smaller than the diameter of the shaft, that is, it presents a certain “interference”.

Therefore, after installing the oil seal on the oil seal seat and shaft, the pressure of the oil seal blade edge and the contraction force of the self-tightening spiral spring exert a certain radial force on the shaft.

After a period of operation, this pressure will quickly decrease or even disappear. Therefore, the spring can compensate for the self-tightening force of the oil seal at any time.

Sealing principle: Due to the oil film controlled by the sealing edge between the oil seal and the shaft, this film has fluid lubrication characteristics. Under the action of the oil seal skeleton, the rigidity of the oil film forms a growing surface at the air contact end, preventing the leakage of the working medium and thus achieving the sealing of the rotating shaft. The sealing ability of the oil seal depends on the thickness of the oil film on the seal surface.

If the thickness is too large, the seal will leak; if it is too small, dry friction may occur, causing wear on the seal and shaft. If there is no oil film between the sealing lip and the shaft, it can easily cause overheating and wear.

Therefore, during installation, oil must be applied to the seal ring, while ensuring that the oil seal skeleton is perpendicular to the shaft. If it is not perpendicular, the oil seal sealing lip will drain the lubricating oil from the shaft, also leading to excessive wear of the sealing lip.

During operation, a small amount of lubricant leaks from the inside of the housing to achieve an ideal state of oil film formation on the sealing surface.

The general function of the skeleton oil seal is to isolate the components that require lubrication from the output components in the transmission parts, so as not to allow the lubricating oil to leak. It is commonly used for rotary shafts and is a type of rotary shaft lip seal.

The skeleton is like the rebar of concrete components, playing a reinforcing role and allowing the oil seal to maintain its shape and tension. There are internal and external exposed skeleton retainers. Skeleton seals are made of high quality nitrile rubber and steel plates. They are of stable quality and have a long service life.

When using oil seals correctly, the following points must be considered:

1) Due to design and structural reasons, high-speed shafts must use high-speed oil seals, while low-speed shafts must use low-speed oil seals. It is not advisable to use low speed oil seals on high speed shafts and vice versa.

2) In high temperature environments, polyurethane, silicone, fluorine or fluorosilicone rubber should be chosen. Efforts must be made to reduce the temperature of the oil in the tank. In extremely low temperature conditions, cold-resistant rubber must be used.

3) Regular oil seals have poor pressure-bearing capacity and may deform under excessive pressure. Under such conditions, pressure-resistant support rings or reinforced pressure-resistant oil seals must be used.

4) If the eccentricity during the installation of the oil seal and shaft pairing is too large, the sealing quality will deteriorate, especially at high shaft speeds. If the eccentricity is excessive, an oil seal with a “W” shaped cross section can be used.

5) The smoothness of the shaft surface directly affects the service life of the oil seal. The smoother the shaft, the longer the life of the oil seal.

6) It is important to ensure that there is a sufficient amount of lubricating oil on the edge of the oil seal.

7) Special attention must be paid to prevent dust from infiltrating the oil seal.

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