The questions and answers about the oil seal

July 12, 2018
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1. What is an oil seal?
A: The oil seal is the customary name for general seals. As the name suggests: oil seals are mechanical components used to seal oil. From the sealing function, characteristics, structure, working state, sealing mechanism of the oil seal, it can be divided into various forms and different names. Conventionally, a general rotary shaft lip seal is called an oil seal; a static seal and a reciprocating seal are called seals.
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2. What are the functions of the oil seal?
Answer: Preventing oil leakage in the bearing housing is the most basic function of the oil seal. In addition, a good oil seal should also prevent external pollutants (dust, water vapor) from entering and reduce bearing wear. Therefore, the oil seal is also called a bearing protector.

3. What is the sealing principle of the oil seal?
A: There is a thin layer of adhesive film between the oil seal lip and the shaft contact surface. The presence of this oil film, on the one hand, acts to seal the fluid medium and on the other hand acts as a lubricant between the lip and the shaft. However, during the use of the oil seal, due to the action of the oil seal lip, the difference between the shaft surface and the rotation condition and the fluid seal property, and the interaction and mutual cooperation conditions of the three are often changed, the oil seal is often in the dynamic state. Fluid lubrication, boundary lubrication and dry friction 3 secondary lubrication states alternately coexist, mainly fluid lubrication. Therefore, it is possible to achieve a good seal by ensuring the thickness of the oil film in a suitable range.
The skeleton oil seal oil seal, that is, the seal of the lubricating oil. It is commonly used in bearings of various machinery, especially in rolling bearing parts. Its function is to isolate the oil chamber from the outside world and seal the oil inside to prevent dust. The oil seal differs from other lip seals in that it has a lip with a greater resilience, the seal contact surface is narrow (about 0.5 mm) and the contact stress distribution pattern is sharp. Typical structure of oil seal and schematic diagram of lip contact stress. The cross-sectional shape of the oil seal and the tightening spring make the lip have a good follow-up compensation to the shaft. Therefore, the oil seal can obtain a better sealing fruit with a smaller lip radial force. The oil seal has the following advantages compared with other sealing devices:

The structure is simple and easy to manufacture. Simple oil seals can be molded at one time, and even the most complex oil seals are not complicated. The metal skeleton oil seal can also form the oil seal required by metal and rubber only by stamping, gluing, inlaying, molding and the like. light weight, less consumables. Each oil seal is a combination of thin-walled metal parts and rubber parts, and the material consumption is extremely small, so each oil seal is light in weight.

③The oil seal is installed in a small position, has a small axial dimension, is easy to process, and makes the machine compact. ④ good sealing performance and long service life. It has certain adaptability to the vibration of the machine and the eccentricity of the spindle. ⑤ easy to disassemble and easy to repair .⑥ Itis cheap. The disadvantage of the oil seal is that it cannot withstand high pressure, so it can only be used as a seal for bearing oil. The working range of the oil seal is as follows: working pressure ~0.3MPa sealing surface speed low speed type <4m / s, high speed type 4 ~ 15m / s working temperature -60 ~ 150 °C (related to rubber type) for medium oil, water and weak corrosion The design life of the liquid is 500-2000h.
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4. What are the factors that affect the seal of the oil seal?
Answer: 1). The effect of rubber varieties on oil seal performance; 2) Lubricating oil; 3) Lubricating oil additives; 4). Effect of metamorphic oil; 5) Influence of shaft surface roughness; 6). ;7). The effect of rotor vibration; 8). The effect of eccentricity; 9). The effect of temperature.

5. What types of oil seals are there?
A: The traditional oil seal is divided into a lip seal, a magnetic oil seal, a labyrinth oil seal, etc. according to the sealing principle. Due to the convenient installation and high efficiency, the split oil seal is the main trend of oil seal development in the future.

6. Is the shaft seal and oil seal the same product?
Answer: The shaft seal is the seal between the rotating pump shaft and the fixed pump body. It is usually referred to as mechanical seal or packing. The oil seal is mainly used to prevent bearing oil leakage and prevent external dust, moisture, impurities and so on. Foreign technical data is also known as bearing protector.

7. What is the skeleton oil seal?
A: The skeleton oil seal generally consists of three parts: oil seal body, reinforcing skeleton and self-tightening spring. Generally, the skeleton oil seal in the free state has a smaller inner diameter than the shaft diameter and has a certain "interference". Therefore, when the oil is encapsulated into the seal chamber and the shaft, the pressure of the lip and the contraction force of the spring are The shaft produces a certain radial tightening force that will rapidly decrease to disappear over time. Therefore, the spring can compensate the tightness of the oil seal at any time.

8. What is a floating oil seal?
Answer: The floating oil seal is a mechanical seal. It is composed of a pair of floating end face sealing rings (referred to as floating seal rings) and a pair of rubber rings. Half rotates with the rotating parts, and half is relatively static. The end faces that are in close contact with each other are called sealing faces, also called bright bands.

9. What is a double split oil seal?
Answer: The double-split oil seal is an international patent product of Aizhi Group, a well-known sealing industry enterprise in China. It is a product specially developed for major and difficult to disassemble equipment. The double split oil seal has a double split structure of inner and outer rings, 55' and 05 minute design, double locking structure design and convenient installation.
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10. The relationship between oil seal and dust seal
A: The oil seal, that is, the seal of the lubricating oil. It is commonly used in bearings of various machinery, especially in rolling bearing parts. Its function is to isolate the oil chamber from the outside world, seal the oil inside and seal the dust to the outside. The oil seal can be used as a dust seal. However, special dust seals are often used when dust is severe or to protect other seals. Dust-proof and sealing materials, hydraulic machinery, multi-purpose rubber, pneumatic machinery, multi-purpose felt, aircraft and cold-working cylinders use metal in order to deal with the external ice of the piston rod. The chemical department also uses metal to prevent the stick on the piston rod. Dust seals are important to protect critical hydraulic equipment. Infiltration into the dust not only wears the seal, but also greatly wears the guide sleeve and the piston rod.
In addition, impurities entering the hydraulic medium can also affect the operation of the valve and pump.