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Introduction of Common Seals
Release time:
2019-07-03 12:30
Source:
Introduction of Common Seals
1.O-ring
1. O-ring sealing mechanism
O-ring is a typical compression seal with self-sealing effect, mainly used for compression sealing. The O-ring is installed between the groove and the sealed surface with a certain amount of compression. The resulting rebound force gives the sealed smooth surface and the bottom surface of the groove initial compression stress, thus playing the role of pre-sealing (if the O-ring has no compression, the O-ring is not in close contact with the sealed surface and the bottom surface of the groove, and the fluid may infiltrate the periphery of the O-ring section and lose any sealing effect).
When internal pressure is applied, the O-ring is pushed to the other side of the groove and squeezed into a D-shape, and the pressure is transmitted to the contact surface. The greater the internal pressure, the greater the O-ring deformation, so that the greater the pressure transmitted to the contact surface, the greater the sealing effect. This effect of automatically enhancing the sealing effect by the fluid pressure is called the self-sealing effect.
O-ring if the compression is too small, the initial contact pressure is very small, the maximum contact pressure will not be too large, the sealing safety factor is very small; If the compression is too large, the O-ring may increase the compression stress relaxation and permanent deformation, but affect the service life of the O-ring, will lead to early loss of elasticity caused by leakage and failure. In addition, for reciprocating motion, the greater the compression, the greater the friction, the greater the loss of power and the wear of the sealing surfaces. Therefore, it is very important to select the appropriate compression amount for various sealing methods.
2, compression calculation of pneumatic dynamic seal compression of 4-15%, the general checking calculation to 9%; The compression of hydraulic dynamic seal is 7-17%, and the general checking calculation is 13%. The compression of static seal is 11-20%, and the general checking calculation is 15%.

2. lip seal 1. Lip seal ring refers to a type of seal ring (e. g. TC oil seal) that makes the pressure surface of the seal ring into a lip shape and has a pressure-enhanced sealing effect. The structural forms are V, U, Y, L, J and various special shapes. In the material is mainly rubber, cloth rubber, leather, PTFE and metal. Lip seals are mainly used for reciprocating seals, some of which can also be used for low-speed rotary seals or static seals.
2. Sealing mechanism The sealing principle of the rubber lip seal ring is to rely on the preload force filled in the sealed cavity, and its lip is close to the surface of the sealed cavity to block the leakage channel and obtain the sealing effect. When the medium pressure is applied, the lip further abuts the sealing cavity surface to enhance the sealing effect of blocking the leakage channel. The lip seal has a more pronounced self-sealing effect than the squeeze seal.
3. Advantages and disadvantages of lip seal
1) Excellent self-sealing effect, whether used for low pressure or high pressure, the sealing efficiency is very high; and the wear has a certain compensation effect, not too fast leakage;
2) Good shape stability and low friction resistance, it is not easy to cause torsion damage during reciprocating motion;
3) In the hydraulic system, it has the special properties of the control fluid film and good lubricity;
4) Suitable for large diameter reciprocating seals;
5) the use of rubber/plastic (nylon, POM, PTFE, etc.) composite structure, can make this kind of sealing ring has a wide range of pressure and long working life.
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