2 Overview and trend of relevant technologies at home and abroad
2.1 Introduction to the use of high-end valves in the power plant The high-end valves used in the thermal system of the power plant work in a high-temperature and high-pressure parameter environment, which requires high reliability for the automatic control of high-end valves. As the research and manufacturing of high-end valves in China is still in the technical breakthrough stage, the high-end valves used in China currently mainly rely on foreign imports, and the import quota of high-end valves of domestic power plants alone each year exceeds 10 billion yuan. Therefore, it is of great significance for China's equipment manufacturing industry to introduce, digest and absorb the technology of world famous valves. Among them, the small high-temperature and high-pressure metal seat pneumatic ball valve should be the first to realize localization. This project can not only bring considerable economic benefits for power plant energy conservation, but also have huge promotion space in the power industry.
2.2 Development of supersonic thermal spraying technology Thermal spraying methods can be divided into combustion method and electrothermal method. Combustion method includes flame spraying and explosive spraying; Electric heating method includes arc spraying and plasma spraying. Now there have been supersonic flame spraying, supersonic plasma spraying, laser spraying, reactive thermal spraying, cold spraying and other processes.
(l) Supersonic flame spraying. The High Velocity Oxygen Fuel (HVOF) method mainly uses a high-pressure water-cooled reaction chamber and a slender injection pipe to send fuel (kerosene, acetylene, propylene and hydrogen) and oxygen into the reaction chamber for combustion, generating a high-pressure flame, which is compressed by the injection pipe and accelerates the injection. The sprayed powder can be delivered axially with high pressure or from the side of the injection pipe. The other method is to inject fuel (kerosene, acetylene, propylene and hydrogen) and oxygen through high pressure, burn them outside the nozzle, shoot the sprayed powder axially into the flame from inside the nozzle with high pressure gas, then compress and accelerate the combustion flame through the compressed gas in the air hood outside the nozzle, and spray the molten powder to the substrate. This method is characterized by high jet velocity, lower flame flow temperature than explosive spraying, and is suitable for carbide coating. The highest density of the coating obtained by supersonic flame spraying can reach 99.9% of the theoretical density, and the strength can reach more than 70MPa; In addition, there are few impurities in the coating, and the residual stress of the coating is small. In some cases, the designed residual stress can be obtained. Therefore, thicker coatings can be sprayed, and the spraying efficiency is high. But it also has the disadvantages of high fuel consumption and high cost.

What is the abnormal condition of stainless steel hose when it is screwed into the connector?
What is the abnormal condition of stainless steel pneumatic butterfly valve when it is screwed into the joint?
Answer: For the stainless steel pneumatic butterfly valve cut by the customer, it is recommended to remove the burrs at both ends first, otherwise the burrs will prevent the hose from screwing into the connector, and the hose will be too large during rotation. The correct method is to remove the burr on both ends of the hose, and use a wire cutter to clamp one end of the hose and rotate the hose in reverse direction to reduce the outer diameter of the hose.