At present, the hydraulic seals commonly used in the hydraulic transmission system can be roughly divided into static seals and moving seals according to whether there is relative movement between the sealing joint surfaces. If reciprocating motion occurs between the sealing joint surfaces, the seal used is called reciprocating hydraulic seal (referred to as sliding seal). If a rotary action (also known as a rotary movement) occurs between the sealing joint surfaces, it is called a rotary motion hydraulic seal (referred to as a rotary seal). Therefore, the hydraulic seals commonly used in the hydraulic transmission system can be roughly divided into: gaskets, packing seals, self-sealing compression seals (also known as extrusion seals), self-sealing compact seals (also known as lip seals), combination seals and dust-proof seals in a total of 6 structural forms.
Hydraulic cylinder sealing system
1 Gasket
Wall roofing material production equipment hydraulic transmission system commonly used sealing gaskets are mainly cotton rubber gaskets, rubber sealing gaskets, metal sealing gaskets and metal-non-metallic sealing gaskets, etc., of which the sealing pressure of non-metallic sealing gaskets (strictly speaking, it should be pressure) is low, followed by metal-non-metallic sealing gaskets, and the sealing pressure of metal sealing gaskets is the highest.
2 Packing seals
Packing seals, commonly known as packing, usually refer to hydraulic seals wrapped in shafts or members with square-section fiber ropes and tightly sealed under the action of compression. Usually the frictional resistance of the packing seal is large, the wear is fast, and it is only suitable for the production of sliding seals and low-pressure low-speed rotary seals for low-pressure low-speed hydraulic cylinders with low sealing pressure and small speed. Sliding seals for medium speed medium pressure hydraulic cylinders with high sealing pressure requirements and large speeds have been gradually replaced by lip seals.
3 Extrusion seals
At present, the extruded seals commonly used in the hydraulic transmission system are mainly O-shaped rubber seals (also known as circular sealing rings), square (rectangular) rubber sealing rings [also known as square (rectangular) sealing rings], X-shaped rubber sealing rings (also known as star sealing rings, as shown in Figure 1a) and O-shaped hollow metal sealing rings (also known as circular hollow sealing rings, as shown in Figure 1b), which have the advantages of simple structure, easy design and manufacture, easy installation and disassembly and low cost. Therefore, they are widely used static sealing elements and dynamic sealing elements in hydraulic transmission systems (except for O-shaped hollow metal sealing rings, which can only be used as static seals).
In fact, the sealing effect of the X-shaped rubber sealing ring and the O-shaped rubber sealing ring is basically similar, and the structure of the X-shaped rubber sealing ring is complex and the production cost is high, so the extruded seals used in production practice are almost all O-shaped rubber seals. When used as a sliding seal, the O-shaped rubber seal has a two-way sealing effect, but in order to reduce frictional resistance and avoid the twisting deformation of the O-shaped rubber seal (commonly known as flipping), the O-shaped rubber seal is rarely used alone when it is used for dynamic sealing, and usually needs to be combined with lip seals or other structural seals to improve its sealing performance and service life.
4 Lip seals
At present, the lip seals commonly used in the hydraulic cylinder of wall roofing material production equipment are mainly V-shaped clip fabric rubber seal rings, U-shaped clip fabric rubber seals, Y-shaped rubber seals and YX-shaped rubber seals. Lip seals have the advantages of simple design and manufacture, low price and good sealing performance. However, considering that the sealing lip contact area of the lip seal is small, easy to wear, and its sealing effect is significantly reduced after wear, the sliding seal for high-speed high-pressure hydraulic cylinders with higher working pressure requirements and larger speed has been gradually replaced by combined seals.
5 Combination seals
At present, the commonly used combination seals of hydraulic cylinders in wall roofing material production equipment are mainly composed of ○-shaped rubber seals and rectangular seals, Y-shaped sealing rings and other special shape sealing rings in the extruded seals. Such as: lace sealing ring (O-shaped rubber sealing ring and Y-clamp fabric rubber sealing ring superimposed use, as shown in Figure 2), drum sealing circle [ drum clamp fabric rubber sealing ring and two filled PTFE support rings (commonly known as L-ring) superimposed use, as shown in Figure 3], coaxial sealing circle (such as: grid ring, Stefon, composed of O-shaped rubber sealing ring and filled PTFE sealing ring, as shown in Figure 4 and 5) and slip ring combination sealing circle (such as: composed of O-shaped rubber sealing ring and C-shaped slip ring combination sealing ring , as shown in Figure 6) and so on.
The combination seals give full play to the advantages of the sealing elements, and finally the performance is less frictional resistance, excellent sealing performance, smooth work, long service life, and easy to install, disassemble and repair. Therefore, at present, the hydraulic seals widely used in the hydraulic transmission system of the wall roofing material production equipment such as the hydraulic transmission system are almost all combination seals, such as: radial rings, drum rings, lattice rings, stow rings and slip ring combination seals.
6 Dust seals
Dust-proof seals are seals that prevent and prevent dust particles such as soil, ice and snow and powder dust from the outside world and harmful gases such as rainwater, acid mist, and water vapor from entering the hydraulic transmission system through the relative motion coupling surface. Dust-proof seals for retractable movement exposed parts such as hydraulic cylinder pistons and piston rods are often referred to as dust rings, while dust seals for rotating motion exposed parts such as hydraulic motor rotary shafts are often referred to as oil seals. Dust rings and oil seals are generally made of rubber materials with good elasticity.
Othello dust seal
At present, the commonly used dust rings for hydraulic cylinder pistons and piston rods are A type dust ring, B type dust ring (commonly known as metal skeleton dust ring, the outer circle is a metal skeleton), C type dust ring (also known as double lip dust ring) and TZF type combination dust ring (also known as double lip combination dust ring). Obviously, the C type dust ring (double lip dust ring) has better dustproof performance than the A type and B type dust ring, and the B type dust ring (metal skeleton dust ring) has a longer service life than the A type dust ring. Since the TZF type combination dust ring is composed of an O-shaped rubber sealing ring and a filled PTFE double lip slip ring, it is especially suitable for heavy loads and harsh working conditions.
Oil seal is the abbreviation of lip-shaped dustproof sealing circle for rotating shaft, which can be divided into B type (inner bag skeleton type) oil seal, W type (exposed skeleton type oil seal, Z type (assembly type) oil seal, FB type (with secondary lip inner cover skeleton type) oil seal, FW type (with secondary lip exposed skeleton type) oil seal and FZ type (with secondary lip assembly type) oil seal. Obviously, the dustproof performance of the oil seal with the auxiliary lip type is better than that of the oil seal without the auxiliary lip type, and the dustproof performance of the inner bag skeleton type oil seal and the exposed skeleton type and the assembly type oil seal is basically the same, but its price is cheap, and only under heavy load and particularly harsh working conditions is the dustproof oil seal with the outer lip inner frame type oil seal is selected.
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