1. The sealing ratio pressure is high. For hard sealed ball valves used in coal water slurry working conditions, due to the use of metal materials as the sealing surface, the required sealing ratio pressure is much higher than that of soft seals. Therefore, it is very important to ensure appropriate sealing ratio pressure in design, improve the shape and position tolerance of parts, and improve surface smoothness requirements.

2. The surface hardness of the sphere is high, and the hardness of coal powder particles is also high. In this working condition, it is required that the surface hardness layer of the sphere has a high hardness when the valve is closed. Otherwise, when the valve is opened, coal powder particles will be embedded on the surface of the sphere, which will damage the surface of the sphere and affect the overall sealing performance of the valve.

3. The bonding strength of the spray welding layer is high, and the flow speed of coal powder in the pipeline is very fast. Therefore, it is required that the sealing surface of the sphere must have high hardness and strength. At the same time, it is also required that the sealing material to be sprayed has high bonding strength with the substrate material, and the substrate material itself has good strength, so that the spray welding layer cannot detach from the surface of the substrate and lose its sealing performance.

4. Self cleaning function, strong adsorption of coal slurry, easy to adhere to the surface of the sphere. During the opening and closing process of the valve, the medium particles are carried between the sealing surfaces of the valve seat and the sphere, damaging the sealing pair between the sphere and the valve seat, thereby affecting the sealing performance of the valve and greatly shortening its service life. The development of a new technology called "scraper valve seat" has a good "self-cleaning" function, ensuring that the sealing pair between the sphere and the valve seat is not damaged.

5. Processing is difficult. Due to the fact that the sealing surface of the hard sealed ball valve used in coal water slurry working conditions is made of ultra hard alloy material, ordinary cutting tools are no longer able to process it. Even if it can be processed, its processing accuracy cannot meet the requirements. At the same time, it is also required that the processing equipment has sufficient strength. Therefore, selecting a suitable cutting tool is very important. In order to ensure that the valve can have excellent sealing performance, the sealing surface of the valve also needs high-precision grinding.