Types and characteristics of hydraulic seals

Types and characteristics of hydraulic seals

Hydraulic seals are the most important and effective means of solving hydraulic and pneumatic system leakage problems. If the system is poorly sealed, there may be an impermissible external leakage. The oil leaking out will pollute the environment; it can also cause 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); In severe cases, the system volumetric efficiency is too low, and even the working pressure does not reach the required value. If the seal is excessive, it can prevent leakage, but it will cause severe wear of the seal part, shorten the service life of the seal, increase the frictional friction resistance in the hydraulic component, and reduce the mechanical efficiency of the system. Therefore, the rational selection and design of sealing devices is very important in the design of hydraulic and pneumatic systems.

First, the requirements of hydraulic seals for sealing devices

1. It should have good sealing performance under working pressure and a certain temperature range, and can automatically improve the sealing performance with the increase of pressure.
2. The friction between the sealing device and the moving part should be small, and the friction coefficient should be stable.
3. Strong anti-corrosion ability, not easy to aging, long working life, good wear resistance, and can be automatically compensated to a certain extent after wear.
4. Simple structure, convenient to use and maintain, and low in price.

Second, the type and characteristics of hydraulic seal sealing device [sealing gasket metal winding gasket metal coated gasket ladle gasket stainless steel gasket copper gasket]

Hydraulic seals can be divided into non-contact seals and contact seals according to their working principle. The former refers to the gap seal and the latter refers to the seal seal.

1. Gap seal Gap seal is sealed by a small gap between the mating surfaces of the moving parts. It is commonly used in the cylindrical mating pair of plungers, pistons or valves. Generally, there are several equidistances on the outer surface of the valve plug. The pressure equalizing groove, its main function is to make the radial pressure distribution uniform, reduce the hydraulic clamping force, and at the same time make the valve core in the hole better in the hole, to reduce the gap to reduce the leakage. The friction is small, and the shortcoming is that it cannot be automatically compensated after wear. It is mainly used between cylindrical surfaces with small diameters, such as between the plunger and the cylinder in the hydraulic pump, and between the spool and the valve hole of the spool valve.

2. O-ring O-ring is generally made of oil-resistant rubber. Its cross section is round. It has good sealing performance. The inner and outer sides and the end face can seal. The structure is compact and the frictional resistance of the moving parts is small. It is easy to manufacture, convenient to assemble and disassemble, low in cost, and high and low pressure can be used, so it is widely used in hydraulic systems. O-ring seal groove, in addition to rectangular, also has V-shaped, dovetail, semi-circular, triangular, etc., in practical applications can refer to the relevant manuals and national standards.

3. Lip seal The lip seal can be divided into Y shape, V shape, U shape, L shape, etc. according to the shape of the cross section. The hydraulic pressure presses the two lips h1 of the seal against the surface of the two parts forming the gap. The sealing function is characterized in that the sealing performance can be automatically adjusted according to the change of the working pressure. The higher the pressure, the tighter the lip is pressed, and the better the sealing property; when the pressure is lowered, the degree of the lip pressing is also reduced. Thereby, frictional resistance and power consumption are reduced, and in addition, the wear of the lip can be automatically compensated, and the sealing performance is not lowered. The lip seal should be installed with its lip opening facing the pressure oil so that the lips are opened and attached to the surface of the machine. [Sealing gasket metal winding gasket metal coated gasket ladle gasket stainless steel gasket copper gasket]

4. Combined sealing device With the increasing application of hydraulic technology, the system has higher and higher requirements for sealing. The common sealing ring alone can not meet the sealing performance, especially the service life and reliability requirements. Therefore, a combined sealing device composed of two or more elements including a seal ring has been researched and developed. The combined sealing device fully utilizes the advantages of the rubber sealing ring and the slip ring (support ring), so it not only works reliably, but also has low friction and stability, and the service life is nearly 100 times higher than that of ordinary rubber sealing, and it is widely used in engineering. .

5. Sealing device for rotary shafts There are many types of sealing devices for rotary shafts. These seals are mainly used as seals for hydraulic pumps, hydraulic motors and extended shafts of rotary hydraulic cylinders to prevent oil from leaking to the outside of the housing.

6. Glue Sealing and Sealing Glue sealing is the application of a sealant to the bonding surface, and the bonding force generated by it glues the two bonding surfaces together. The tape seal is to wind the sealing tape around the thread of the desired seal, so that the sealing material is filled between the thread pairs to form a leakage resistance. (Source: Hebei Innovation Sealing Material Co., Ltd.)

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