The section of Y-shaped seal ring is Y-shaped, which is a typical lip seal ring. It is widely used in reciprocating sealing devices, and its service life is higher than that of O-ring. The applicable working pressure of Y-type sealing ring is not more than 40MPa, and the working temperature is - 30 ~ 80 ℃.
1. Y-ring classification
Y-shaped seal ring can be divided into wide Y-shaped seal ring, narrow Y-shaped seal ring and YX type seal ring according to the length width ratio of the section. The pressure resistance of Y-shaped seal ring with wide section is slightly less than that of narrow Y-shaped seal ring, which can only be used in the working environment with P < 20MPa, while narrow Y-shaped seal ring can be used in the situation with working pressure P < 32Mpa.
According to whether the height of the two lips is consistent, the Y-shaped seal ring can be divided into unequal height lip Y-shaped seal ring for shaft, unequal height lip Y-shaped seal ring for hole and equal height lip Y-shaped seal ring for shaft hole. Y-shaped sealing rings are made of different materials. They can also be divided into nitrile rubber Y-shaped sealing rings, fluororubber Y-shaped sealing rings, polyurethane rubber Y-shaped sealing rings, etc.
Working speed range: 0.01 ~ 0.6m/s when made of butadiene rubber; When it is made of fluororubber, it is 0.05 ~ 0.3m/s; When polyurethane rubber is used, it is 0.01 ~ LM / s. The sealing performance, service life and working pressure limit of Y-shaped sealing ring under different retaining rings are all made of polyurethane rubber.
2. Sealing principle
The Y-shaped sealing ring is attached to the coupling surface of the sealing pair by its open lip. When there is no internal pressure, only a small contact pressure is generated due to the deformation of the lip tip. In the case of sealing, there is a normal pressure equal to the medium pressure at each point in contact with the sealing medium, so the bottom of the lip ring will be compressed axially, the lip will be compressed circumferentially, the contact with the sealing surface will be widened, and the contact stress will increase at the same time. When the internal pressure rises again, the distribution form and size of the contact pressure will further change, and the lip fits more closely with the sealing surface, so the sealing performance is better, which is the "self sealing effect" of the Y-ring. Due to this self sealing effect, a Y-ring can effectively seal the high pressure of 32Mpa.
The effective sealing pressure of pressure enabled seal is equal to the sum of pre pressure and fluid pressure. The Y-shaped seal ring effectively acts the fluid pressure on the seal through the action of the lip, and its pre pressure can be reduced to a very small value. The higher the fluid pressure is, the smaller the effectiveness of pre pressure is. In high-pressure occasions, the role of pre pressure can be ignored. At this time, it is advantageous to reduce the sealing friction, because the sealing friction is directly proportional to the sealing contact pressure. Therefore, the friction of Y-shaped seal ring is less than that of extrusion seal while ensuring sealing.
The Y-shaped seal ring is mainly used for reciprocating sealing. According to its working principle, when the Y-shaped ring is installed, the lip must face the side with high pressure to play a role, so the Y-shaped seal ring can only work in one direction.
When the coupling moves relatively at the working speed, a layer of sealing oil film is formed between the sealing lip and the sliding surface. The existence of oil film can improve the friction conditions of the sealing ring and reduce the wear; Oil film plays a sealing role in pneumatic seal. In the reciprocating motion of hydraulic components, the oil film thickness is different when the moving parts extend and retract, and this oil film thickness difference product will cause leakage. Therefore, when the Y-ring works normally, a very small amount of leakage occurs. When the reciprocating speed is large, the leakage is large. This is because when the reciprocating speed is large, the reciprocating times become very frequent, and the hydrodynamic action of the oil film increases the thickness of the oil film, forming the rapid accumulation of the oil film. When the viscosity of the working oil increases, the oil film thickness increases, and the leakage caused by the reciprocating speed also increases. However, because the viscosity of hydraulic oil decreases with the increase of temperature, when the hydraulic equipment is started at low temperature, the leakage at the beginning of movement is large. With the increase of temperature caused by various losses during movement, the leakage will gradually decrease.
The leakage of the piston in the reciprocating stroke is different. When the internal pressure is low, the leakage in the extraction stroke increases with the increase of internal pressure; In the press in stroke, it decreases with the increase of internal pressure. When the internal pressure is large enough (about more than 7.5Mpa), the leakage will no longer change with the internal pressure.
When the internal pressure P1 of Y-shaped seal ring is low, the friction increases with the increase of internal pressure. When the internal pressure is large enough, the friction does not change much. If the lubrication is good, there is even a downward trend. The starting friction test results of Y-ring abroad show that the starting friction has little relationship with parking time, which is the biggest difference from O-ring.
This is very advantageous for intermittent machinery. At the same time, when the internal pressure is low, the starting friction increases with the increase of internal pressure. When the internal pressure exceeds 5MPa, the starting friction will have nothing to do with the internal pressure. Therefore, for high-pressure intermittent machinery, there will be no problem of excessive starting friction. After the sealing lip is worn, due to the action of medium pressure, the lip has a certain automatic compensation ability.
3. Characteristics of Y-ring
1) Reliable sealing performance;
2) Small friction resistance and stable movement;
3) Good pressure resistance and wide application range;
4) Simple structure and moderate price;
5) Easy installation.
