The use of hydraulic seals has the following properties:
a. Minimal leakage
The hydraulic seal requires minimal leakage, has a good sealing effect, and automatically increases the sealing effect as the pressure of the hydraulic oil increases. Even under high pressure and high temperature and other harsh working conditions, the leakage of the hydraulic seal is not obvious. The increase.
b. Good compatibility
Due to the long-term immersion of the hydraulic seal in the hydraulic oil, it can easily swell, dissolve, or become brittle and harden, thereby losing the sealing effect. Therefore, the hydraulic seal is required to have good compatibility with the hydraulic oil.
c. Small frictional resistance
In order to avoid or reduce the unfavorable phenomena such as low-pressure creepage of hydraulic equipment, hydraulic seals are required to have low static friction resistance and dynamic friction resistance, and their friction coefficient should be very stable.
d. Long service life
Hydraulic seals should have good elasticity, heat resistance, cold resistance, pressure resistance, abrasion resistance, certain physical and mechanical strength, and long service life.
e. Low prices
The hydraulic seals should be easy to manufacture and install, and the corresponding seal grooves can be easily processed and manufactured. The requirements on the processing precision of the seal surface are low, and the low grids are inexpensive.
Hydraulic seal structure and sealing mechanism
Commonly used self-sealing pressure type hydraulic seals are mainly ○-shaped sealing rings, circular sealing rings and square sealing rings, etc. They have the advantages of simple structure, easy manufacturing, low cost, etc. Therefore, they are widely used in hydraulic transmission systems. Dynamic sealing element and static sealing element. Their installation in the seal groove usually produces a 10-25% radial compression deformation and creates a high initial contact stress on the sealing surface, thus preventing leakage of pressure-free liquid.
When the hydraulic cylinder is in operation, the pressure liquid squeezes the self-sealing pressure-type hydraulic seal to further deform it and generate a large pressure with the pressure of the liquid on the sealing surface, strictly speaking, it should be the pressure. Increases and increases the additional contact stress and together with the initial contact stress prevents the leakage of the pressure fluid. However, when the working pressure is greater than 10 MPa, in order to prevent a part of the synthetic rubber self-sealing pressure-type hydraulic seal from being squeezed into the seal gap and cut in the reciprocating motion of the hydraulic cylinder to cause leakage, it is necessary to seal the pressure in the synthetic rubber. A synthetic resin retaining ring, such as a nylon retaining ring, a polyacetal retaining ring, and a filled PTFE retaining ring, is provided on each pressure side of the tight type hydraulic seal.
Since the synthetic rubber self-sealing compaction type hydraulic seal has a large compression deformation during operation, its static friction resistance is particularly large, and is usually more than double its dynamic frictional resistance. Such large static friction resistance in certain low-pressure hydraulic transmission systems is bound to cause undesirable phenomena such as low-pressure crawling and operational difficulties. This is the reason why the self-sealing compact hydraulic seal is used as a small dynamic seal alone.
Hydraulic seal classification
At present, the commonly used hydraulic combination seals for hydraulic cylinders of ceramic machinery are mainly composed of ○ and square seals, U seals, Y seals, YX seals and other special-shaped hydraulic seals. Overlay used to construct.
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