Different types of seal rings

The seal ring is a ring-shaped seal with a gap. Place it in the ring groove of the sleeve. The sleeve and the shaft rotate together. The seal ring is pressed against the stationary part by the elasticity of the gap after the gap is compressed. The wall of the inner hole can play a sealing role. Each contact surface needs to be hardened and polished. The sealing ring is made of chromium-containing wear-resistant cast iron and can be used where the sliding speed is less than 100m / s. If the sliding speed is within the range of 60 ~ 80m / s, tin bronze can also be used to make the sealing ring.

According to the different manufacturing methods and materials, the seal ring has a variety of structures such as an integral seal ring (made of the same material), a combined seal ring, surfacing carbide and sprayed ceramic on the surface.

Integral seal ring

This kind of sealing ring is made of the same material, the performance of the material is uniform at all parts of the sealing ring, there is no defect of the combined sealing ring leakage and separation, and there is no possibility of electro chemical corrosion. Most of the soft rings are made of graphite, and various alloy steels, and some alloy cast irons can also be used in the manufacture of hard rings. When these materials are used, they must be supplemented by appropriate heat treatment processes to improve their hardness and wear resistance. The price of such materials is lower, and if used properly, they also have a longer life. In order to further increase the hardness and extend the service life, it can be made of cemented carbide. The commonly used cemented carbide is cobalt-based tungsten carbide, which has good performance but high price. The price of steel-bonded carbide is lower. In order to improve the corrosion resistance in corrosive media, there are nickel-based tungsten carbide, and hastelloy has higher corrosion resistance, but it is expensive. In addition, there are sealing rings made of silicon carbide and other ceramic materials.

Combined sealing ring

Tungsten carbide and other materials have excellent performance, but the price is high and the processing is difficult, which limits its use. In order to solve this contradiction, a combined sealing ring appeared. The sealing ring end surface is made of cemented carbide, and the base body of the sealing ring (called the ring seat) is made of ordinary materials. In order to solve the connection and sealing between the cemented carbide ring and the ring seat, four combined seal rings were produced: hot-fit type, with seal ring type, welding and brazing.

1. Sealing ring with O-ring

This combined seal ring uses a sliding fit of H7 / g8 between the cemented carbide ring and the ring seat. A Teflon or synthetic rubber is placed between the two cylindrical surfaces. In this combined structure, there is no combined stress or deformation of the sealing end face of the combined sealing ring, but the number of parts of the combined sealing ring is increased, and it is necessary to drill holes or grooves in the hard coupling ring that increases the manufacturing difficulty.

2. Function hot seal ring

In order to improve the service temperature of the band-shaped sealing ring, a hot-seal sealing ring appeared. It relies on the interference fit between the carbide ring and the ring seat to transmit torque and achieve sealing, and it is the most widely used sealing ring.

3. Welded combined sealing ring

In order to overcome the defect of loose-fitting sealing ring, welding sealing ring appeared. The cemented carbide used is a sintered alloy material with Cr3C2 as the hard phase and Ni as the bonding phase. Corrosion resistance is better than cemented carbides such as YG6. It has excellent oxidation resistance at high temperatures. There is no change in heating at 1000 ℃ air for 2 hours. However, the thermal conductivity is poor, only 1/3 of YG6, and the coefficient of linear expansion is large, more than double that of YG6, which is 10.2 * 10-8 / ℃ (at 10 ~ 500 ℃). These two points determine that the thermal shock resistance is not as good as YG6.

4. Brazed combined sealing ring

In order to support the excellent performance and rhythm defects of tungsten carbide, a brazed sealing ring has appeared. A groove is formed on the seat, and a low melting point solder is used to weld between the ring and the seat. After the solder melts, the ring and the seat are connected together, and the seal between the two is achieved. The outstanding advantage of this kind of sealing ring is that the cemented carbide overcomes the deformation and loosening of the hot-seal sealing ring.