Hydraulic seal sealing device

Hydraulic Seals are important and effective means to solve the leakage problem of hydraulic and pneumatic systems. If the system is poorly sealed, there may be impermissible leakage, and the leaked oil will pollute the environment; It may also cause air and dust to enter the system, affecting the working performance of the system and the stability of the movement of the actuator (such as crawling); In case of serious leakage, the volume efficiency of the system is too low, or even the working pressure cannot reach the required value. If the Sealing is excessive, although it can prevent leakage, it will cause severe wear of the sealing part, shorten the service life of the Seal, increase the movement friction resistance in the hydraulic components, and reduce the mechanical efficiency of the system. Therefore, it is very important to reasonably select and design the sealing device in the design of hydraulic and pneumatic systems.

1. Types and characteristics of hydraulic seals

According to its working principle, hydraulic seals can be divided into non-contact seals and contact seals. The former mainly refers to clearance seal, while the latter refers to seal element seal.

1. Gap seal Gap seal is sealed by the tiny gap between the mating surfaces of relative moving parts. It is commonly used in the cylindrical mating pairs of plungers, pistons or valves. Generally, there are several pressure equalizing grooves with equal distance on the outer surface of the valve core. Its main function is to make the radial pressure evenly distributed, reduce the hydraulic clamping force, and make the valve core neutral in the hole, To reduce leakage by reducing clearance This seal has the advantage of small friction, but the disadvantage is that it cannot be automatically compensated after wear. It is mainly used between cylindrical surfaces with smaller diameters, such as between the plunger and the cylinder block in the hydraulic pump, and between the spool and the valve hole.

2. O-Ring O-ring is generally made of oil resistant rubber, its cross section is round, it has good sealing performance, both internal and external sides and end faces can play a sealing role, the structure is compact, the friction resistance of moving parts is small, manufacturing is easy, assembly and disassembly is convenient, cost is low, and both high and low pressure can be used, so it is widely used in hydraulic systems.

In addition to rectangle, there are also V-shaped, dovetail shaped, semicircle, triangle and other installation grooves for O-ring. In practical application, refer to relevant manuals and national standards.

3. With the increasingly extensive application of hydraulic technology, the system has higher and higher requirements for sealing. Ordinary sealing rings can no longer meet the sealing performance, especially the requirements of service life and reliability, when used alone. Therefore, a combined sealing device consisting of more than two components including sealing rings has been researched and developed.

Because the combined sealing device gives full play to the advantages of rubber Sealing ring and slip ring (support ring), it not only works reliably, but also has low and stable friction, and its service life is nearly 100 times longer than that of ordinary rubber seals. It is increasingly widely used in engineering.

4. Sealing device of rotary shaft There are many types of sealing devices of rotary shaft. This sealing ring is mainly used as the seal of the extension shaft of hydraulic pump, hydraulic motor and rotary hydraulic cylinder to prevent oil leakage outside the housing.

5. Glue sealing and sealing with sealant are to apply sealant on the joint surface, and the adhesive force generated by it will glue the two joint surfaces together. The tape sealing is to wrap the sealing tape on the thread to be sealed, so as to fill the sealing material between the thread pairs, forming the leakage resistance.

6. Lip seal ring The lip seal ring can be divided into Y-shaped, V-shaped, U-shaped, L-shaped, etc. according to the shape of the section. The hydraulic pressure presses the two lip edges h1 of the seal ring against the surfaces of the two parts that form a gap. This sealing function is characterized by automatically adjusting the sealing performance with the change of working pressure. The higher the pressure is, the tighter the lips are pressed, and the better the sealing performance is; When the pressure decreases, the compression degree of the lip also decreases, thus reducing the friction resistance and power consumption. In addition, it can automatically compensate the wear of the lip and keep the sealing performance unchanged. When installing the lip seal ring, make the opening of its lip face the pressure oil, make the two lips open and stick to the surface of the machine parts respectively.

2. Requirements of hydraulic seals on sealing devices

1. It shall have good sealing performance within the working pressure and a certain temperature range, and the sealing performance can be improved automatically with the increase of pressure.

2. The friction between the sealing device and the moving parts shall be small and the friction coefficient shall be stable.

3. It has strong corrosion resistance, is not easy to age, has long service life, good wear resistance, and can automatically compensate for wear to a certain extent.

4. Simple structure, convenient use and maintenance, and low price.