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This article is all about the knowledge of oil seal!

What is oil seal

The oil seal is a sealing element for sealing the oil for the rotation axis in the mechanical equipment, and the cavity is basically static, so the oil seal is also called the rotating shaft lip -shaped seal ring.

The mechanical friction part is used in the use of oil during mechanical operation to prevent the use of oil sealing to prevent these oil from leaking from the gap between the mechanical, and in addition to oil, it is necessary to prevent leakage of water and chemical solution and the invasion of dust from the outside. Oil seals should also be used.

The sealing state of the oil seal is static sealing from the outer edge of the oil seal and the cavity, while ensuring the reliable positioning between the outer edge of the oil seal between the outer edge of the cavity. The second is the sealing state between the lip and axis of the oil seal. When the shaft rotates, it is a dynamic seal, and when the shaft is static, it is a static seal. The comprehensive effects and interactions of various influencing factors have a great impact on the sealing performance and service life of the oil seal.

The main characteristics of oil seal

The outer oil seal is used to ensure the static seal of the cavity-the outer edge of the rubber with the inner metal skeleton; the outer edge of the exposed metal skeleton needs to be polished and plated with anti-corrosion coating.

The sealing lips equipped with a spring to ensure the dynamic and static sealing reliability of the shaft. After long -term development research, the sealing lip structure of the oil seal is improved to excellent performance, which in turn improves the sealing reliability within a wider load range.

Adding dust -proof lips, or multiple dust -proof lips used under special circumstances can prevent external pollutants and dust invasion.

The role of all parts of oil seal

Oil seals are mainly composed of sealing body, strengthening skeleton, and self -tight screw spring. The sealing body is divided into the bottom, waist, blade, and sealing lips according to different parts. The picture below is: The main names and terminology of the inner bag oil seal with the inner skeleton with the dust -proof lip with a spring and the dust -proof lips are attached.

The metal skeleton is like the reinforcement in the concrete component, which plays an enhanced role and enables the oil seal to maintain the shape and tension. Generally, the inner diameter in the skeleton in a free state is smaller than the axis diameter, which has a certain "over -profile". Therefore, when the oil is encapsulated into the oil seal and the shaft, the pressure of the oil seal blade and the contraction force of the self -tight screw spring can generate a certain radial tight force on the shaft. After a period of operation, the pressure will quickly decrease or even disappear. Therefore, the spring can compensate the oil at any time.

While the outer edge of the oil seal is fixed in the cavity hole, it will prevent the fluid from leaking and invasion between the contact surface of the outer surface of the oil from the outer surface of the oil and the inner surface of the cavity. In addition, the metal skeleton is to maintain the effect of maintaining a cooperative force when the oil seal is fixed in the cavity.

The sealing lip is a flexible elastic body, which is designed to maintain a stable sealing effect under the influence of the vibration of mechanical vibration and the pressure changes of the sealing fluid, and play a role in maintaining the stable contact state of the lip and axis surface. Spring can increase the tightness of the sealing lips to the axis to maintain this pressure. The end of the lips is made into a oblique shape, and the surface of the part is pressed at the end of the end to seal the fluid.

The dust -proof lips are the auxiliary lips that are not connected to the spring, which plays a role in preventing dust invasion.

The main type of oil seal

Various types of oil seal, see: Common oil seal structure type; common NOK standard oil seal type.

Oil sealing mechanism

The sealing mechanism of oil seal involves two factors, one is the seal of the cavity, mainly the positioning of the outer edge of the oil seal (static component) in the cavity; the second is the dynamic sealing of the sealing lip mouth and the rotating shaft surface. This is the oil seal of the oil seal. Most important features. Attachment Figure: The touches of the surface of the lip with the lip of the oil seal and the rotating shaft.

In order to ensure the static seal of the oil seal in the cavity and the stable positioning of the cavity, it is easy to assemble. Generally, the rubber material is covered with metal skeleton, and the reliable and static sealing capacity of the rubber elastic body is integrated with the advantages of the metal skeleton support positioning. The outer edge of the oil seal has a backward angle to facilitate assembly. In addition, the design groove on the outer edge of the oil can increase the adhesion, avoid the risk of reducing and skewing of the oil seal, and increase the reliability of the static sealing of the oil seal with static sealing. Oil seal design of the outer edge as a metal skeleton is applicable to a particularly firm and accurate occasion in the cavity. It should be noted that when the surface of the oil seal is rough, the seal should be coated. Essence

The sealing mechanism of the sealing lip contact area of the oil seal is of great significance to the sealing function of the oil seal. It depends on the design of the sealing lip; the structure of the elastic material; the roughness of the axis surface. The comprehensive role of the radial force of the sealing lips, the angle design of the sealing lip, and the distance design of the distance between the tip of the lip to the center of the spring produce a kind of contact pressure on the asymmetric distribution of the axis: the most stress on the oil side and increased sharply; The air side pressure is attenuated at a small angle. With the coordination of the inner diameter of the over -profit (the inner diameter of the sealing lip is slightly less diameter of the axis under the condition of free and load), the asymmetric distribution of the contact pressure and the circular ring hingling force produced by the rotating shaft The combination leads to the structural characteristics of the sealing lip contact area deformation. This sealing elastic body deformation structure is formed when the oil seal trial operation is formed, which plays a decisive role in the sealing performance (therefore, the oil seal requires a trial running -in period). The impact of the spiral line plus the rotation of the shaft, which causes the pumping effect to the oil side by this deformation structure.

Oil seal raw material

The skeleton and spring of the oil seal are made of metal, and the main part of the sealing lip mouth is rubber. According to the environment, the oil seal can be produced with different rubber to meet the sealing performance and requirements. The most commonly used oil -resistant rubber is chores, and Tidan rubber is one of the most common rubber in oil sealing and O.

It can be said to be the most widely used rubber sealing parts. Made in oil sealing, there are polybione rubber, silicone rubber, fluorine rubber, and polytrafluoroethylene. For the performance of various rubber, please refer to: the types and strengths of the main rubber.

Oil sealing medium

In the occasion used in oil seals, the applied sealing medium is generally mineral lubricating oil, grease and synthetic lubricating oil, and lubricating fat. In addition, DIN51524 hydraulic oils, VDMA24317 and VDMA24320 high -lubricating hydraulic oils used in industrial production can also be sealed. Under special circumstances, it can also be sealed, low -lubricating acids, alkali, and organic solvents.

The oil seal with fluorine rubber is usually corrosion -resistant. High temperature resistance is better than NBR. It is recommended to use PTFE lip lip oil seal under the conditions without lubrication, pure dryness and multi -media. Lubrication ability greatly reduces the wear of lips. A single oil seal should not be seal two different medias. A large amount of chemicals increase the impact on the performance of the oil seal material. The compatibility of the oil seal on the sealing medium should be determined by laboratory tests.

The pollution of the sealing medium may be the sand casting residue left by the cavity casting process; For example, the wear of bronze turbine in the turbine box; or the product produced by the corrosive medium. In order to prevent the negative impact of the pollution of the sealing medium on the sealing characteristics, we must pay attention to keep the cavity clean as much as possible.

The selection of oil seal affects factors

In order to give full play to the function of the oil seal, the most suitable type and material must be selected according to the conditions of use. Here is a brief description of the main influencing factors.

1. Surface line speed of the shaft: Under the same diameter conditions, the oil seal manufactured by different materials to adapt to the speed of rotation lines of the shaft surface is different. The relationship is shown in the figure below. The line speed range used in oil seal is generally less than 15m/s. The surface line speed of the allowable shaft given in the figure below is the reference value. Satisfactory lubrication and good heat dissipation conditions are the decisive factor. Correspondingly lower data is suitable for more harsh conditions.

2. Temperature: Because the sealing lips of the rotating shaft and the sealing lip of the oil seal produce, the temperature of the sealing lip mouth is higher than the temperature in the oil. Generally, the temperature of the lip margin is higher than the temperature of the working medium at 20 ~ 50 ℃. Essence As the speed increases, the temperature at the mouth of the sealing lips has also increased. In addition, the oil seal with dust -proof lips will appear too high than 20 ° C than the oil -free lip. When exceeding the allowable temperature, the working life of the oil seal will be shortened, resulting in premature permanent sclerosis of sealing lips and increasing wear. The working temperature range of the oil seal is related to the materials used in oil seal: the material is -40 ~ 120 ° C when the material is Ding Qing Rubber (NBR), the Yalik rubber (ACM) -30 ~ 180 ° C, the fluorine rubber (FPM) -25 ~ 300 ° C Essence

3. Pressure: Oil seal is mainly used for use without pressure or under micro -pressure conditions, and the maximum work pressure is 0.02 ～ 0.05MPa. When the work pressure exceeds this value, a pressure -resistant oil seal should be used.

4. Dust -proof: In order to prevent pollutants, dust, and humidity enter the sealing cavity from the air side, it is recommended to use oil seal with dust -proof lips. If the pollutants are invaded, it is recommended to use 2 oil seals to install them one after the other in series.

Leakage of oil seal

When it is found that when the oil seal leaks, the part of the leak should be confirmed first. If it is not leaked by the oil seal, sometimes it is mistaken for the leak due to the reasons other than the leaks such as oil and fat. The main reasons for the leakage of oil seal:

1. Because the size tolerance does not comply with the standard specifications, the static seal surface that coordinates the outer edge of the oil seal and the cavity is deformed;

2. The material cracks are caused by the conditions of the working conditions too harsh, especially the cracks on the mouth of the oil seal and sealed blade;

3. Due to the harsh conditions of the working conditions and the incompatibility between the rubber elastic body and the working medium, the hardness of the rubber hardness is increased, or the hardness of the elastic body is too high;

4. The sealing medium causes the rubber to swell and reduce the hardness of the rubber, which makes the oil seal premature aging and wear;

5. Corrosion from the axis to the sealing lip area will leave a permanent faulty hazard to the sealing performance of the sealing system;

6. The lubricant fails and makes the system in dry operation, so that the sealing lips are worn quickly;

7. Comprehensive aging, both rubber elastic body and sealing medium are both aging;

8. "Oil and carbon" dirt is formed at the sealing lip mouth, causing the oily sealing lips to be held up, causing the leakage failure of the sealing system;

9. The sealing lip margin of the oil seal no longer follows the vibration of the axis surface and the beating of the axis;

10. Pollutants from the sealing blade from the sealing blade from the sealing inside and outside the sealing blade.

11. The irregular assembly process causes the contact surface of the shaft to be destroyed and causes the sealing lips prematurely;

12. The sealing blade is damaged during the storage, transportation and assembly process.

When the oil seal is leaked, the different situations should be analyzed, so as to take different measures. The leakage at different stages of oil seal should be divided into:

1. Different water, no humidity on the oil seal;

2. Moisturizing, a humid film that does not affect the sealing function in the sealing blade mouth area, but the moisture membrane has not expanded to the back;

3. Wet, moisture membranes are extended to the back, and water droplets are formed, but it has not dripped continuously;

4. The measuring leak, you can see that there are small liquid flow flows flowing from the back of the oil seal from the outside of the oil seal;

5. Temporary leakage, a short -term failure of the sealing system. For example, it is caused by pollutant particles under the sealing blade.

6. Obvious leakage, temporary leakage leads to sealing lips and dust -proof lips due to excessive lubricating fats between sealing lips and dust -proof lips.

The overflow of oil is manifested as obvious leaks outside the system. In addition, the cause of leakage is analyzed according to the process of running the use of oil seal, such as: early damage of leakage when it is used at the beginning; premature damage to leakage after use; And leak damage at the end of the life of the oil seal design and so on.

Transportation and assembly of oil seal

First, the oil seal is precision component, which affects the performance of the use of improper assembly and custody. Pay attention to oil seal when transportation and storage:

Do not open the original packaging, pay attention to whether the packaging is damaged, try to keep the oil in the original packaging before assembly;

Avoid direct sunlight, do not place near high temperature heat sources, because this will promote the aging of rubber;

The oil seal must not be dispersed at will. Pay attention to dust and soil to ensure that the oil seal is closed or covered;

When transporting and using oil sealing, in order to prevent oil seal deformation and spring falling off, please do not give too much impact;

The oil seal cannot be tied with a fine rope, and it should not be hung on the nail or metal line, which will damage the sealing lip;

Do not seal the oil in a humid place, which will rust the metal parts;

Do not place the sealing parts near TV and producing ozone;

Please do not rub the ends of your lips with your nails or hard objects to prevent damage to the sealing lips;

Second, the assembly of the oil seal, no matter how suitable the design of the oil seal installation and the choice of oil sealing, if the assembly is rough, it cannot give full play to the function of the oil seal reservation.

When the oil seal is installed, the outer surface should be applied to an appropriate lubricant. The mouth of the lip should be applied to the suitable clean lubricant, and the oil seal with dust -proof lips should be filled with the suitable clean lubricant between the main lips. Then, then, then

Turn the ends of the lip of the oil seal towards the side of the sealing medium. Do not assemble the reverse.

When the oil seal is entered into the seat, the dedicated tool should be pushed in to prevent the position from sinking.

The threads, bonds, flowers, etc. of the lip fate of the oil seal should be adopted to prevent lip damage from damage and assemble it with a dedicated tool.

Put the seat holes horizontally and press it evenly. Do not tilt for compulsory advancement.

The size and specifications of oil seal

There are many oil seals, and various countries and manufacturers have their own labeling methods. Despite this, because the oil seal is the standard part, if it is not newly opened by special designs, the size of the oil seal is generally only given inner diameter and outer diameter, and height.

The small D in the figure above indicates the inner diameter of the oil seal, the large D represents the outer diameter of the oil seal, and B represents the height of the oil seal. Example: TC30*40*5, indicating that the inner diameter of TC (lip bag) is 30mm outer diameter with 40mm height of 5mm skeleton oil seal. Sometimes you can follow the standards based on oil sealing with DIN, GB/T9877-88. The inner diameter size range of the oil seal is generally: φ16 ~ 440mm, and the width is often 7-20mm.

Standard of oil seal

Oil seal is a wide range of industrial applications and important parts. In order to promote the rapid development of the oil seal industry, countries have formulated a series of relevant standards. my country's oil seal standards are generally applied to the national standard GB9877.1/2/3-88 series, GB13871-1992 oil seal standards. HG4-692-67 is the oil seal standard proposed by the Ministry of Chemical of my country.

"GB/T9877.1-88" Applicable range: ——The basic structure, skeleton, and spring size series of inner bone-shaped rotating shaft lip-shaped seals specifies this standard.