Hydraulic seals Type and characteristics of sealing devices

Hydraulic seals are an important and effective means to solve the leakage problem of hydraulic and pneumatic systems. If the system is poorly sealed, there may be an impermissible external leakage, and the leaking oil will pollute the environment; It may also allow air and dust to enter the system, affecting the working performance of the system and the smoothness of the movement of the actuator (such as crawling); When the leakage is serious, the volumetric efficiency of the system is too low, and even the working pressure cannot reach the required value. If the seal is excessive, although it can prevent leakage, it will cause severe wear of the seal part, shorten the service life of the seal, increase the friction resistance in the hydraulic components, and reduce the mechanical efficiency of the system. Therefore, the rational selection and design of sealing device is very important in the design of hydraulic and pneumatic systems.
Hydraulic seals requirements for sealing devices
1, in the working pressure and a certain temperature range, should have a good sealing performance, and with the increase of pressure can automatically improve the sealing performance.
2. The friction between the sealing device and the moving part should be small, and the friction coefficient should be stable.
3. Strong corrosion resistance, not easy to age, long working life, good wear resistance, and can be automatically compensated after wear to a certain extent.
4. Simple structure, easy to use, easy to maintain, low price.
Hydraulic seals Type and characteristics of sealing devices
Hydraulic seals can be divided into non-contact seals and contact seals according to their working principle. The former mainly refers to the gap seal, the latter refers to the seal seal.
1. Clearance seal Clearance seal is sealed by the small gap between the mating surface of the relative moving parts, often used in the cylindrical mating pair of the plunger, piston or valve, generally in the outer surface of the valve spool there are several equal distance pressure grooves, its main role is to make the radial pressure distribution uniform, reduce the hydraulic clamping force, while making the valve spool in the hole neutral good, The advantage of this seal is that the friction is small, the disadvantage is that it can not be automatically compensated after wear, mainly used between small diameter cylinders, such as between the plunger and the cylinder block in the hydraulic pump, the spool of the spool and the valve hole.
2. O-ring O-ring is generally made of oil-resistant rubber, its cross-section is circular, it has good sealing performance, inside and outside and end face can play a sealing role, compact structure, small friction resistance of moving parts, easy to manufacture, convenient assembly and disassembly, low cost, and high and low pressure can be used, so it is widely used in hydraulic system.
The installation groove of O-ring, in addition to rectangle, also has V shape, dovetail shape, semicircle, triangle, etc., the actual application can refer to the relevant manual and national standards.
3. Lip seal ring According to the shape of the section can be divided into Y shape, V shape, U shape, L shape and so on. The hydraulic pressure will press the two lip edges of the seal h1 towards the surface of the two parts that form a gap. The sealing function is characterized by the automatic adjustment of the sealing performance with the change of the working pressure, the higher the pressure, the tighter the lip is pressed, the better the sealing; When the pressure is reduced, the lip compression degree is also reduced, thus reducing friction resistance and power consumption, in addition, it can automatically compensate for lip wear and keep the sealing performance. When the lip seal ring is installed, the lip opening should face the pressure oil, so that the two lips are open and tightly attached to the surface of the machine.
4. Combined sealing device With the increasingly extensive application of hydraulic technology, the system has higher and higher requirements for sealing, ordinary sealing ring alone can not well meet the sealing performance, especially the service life and reliability requirements, therefore, research and development of the combined sealing device composed of more than two components including the sealing ring.
Because the combined sealing device gives full play to the advantages of rubber sealing ring and slip ring (support ring), it is not only reliable, low friction and stable, but also the service life is nearly a hundred times higher than that of ordinary rubber seal, and it is increasingly widely used in engineering.
5. Sealing device of rotary shaft There are many types of sealing device of rotary shaft. This sealing ring is mainly used as the sealing of the extended shaft of hydraulic pump, hydraulic motor and rotary hydraulic cylinder to prevent oil leakage to the outside of the housing.
6. Rubber sealing and sealing with sealant is to apply the sealant on the bonding surface, and the adhesive force generated by it will glue the two bonding surfaces together. Tape sealing is to wrap the tape around the thread required to seal, so as to fill the sealing material between the thread pairs to form leakage resistance.