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.

The information of non-metallic compensator determines its use
The non-metallic contraction joint can compensate the axial, transverse and angular directions, has no thrust, simplified support design, corrosion resistance, high temperature resistance, noise elimination and vibration reduction, and is especially suitable for hot air pipes and soot pipes.
Main data used for non-metallic contraction joints:
Fluorocarbon tape is made of high-quality tetrafluoroethylene, glass fiber cloth, stainless steel wire mesh and other thermal composite materials. It has strong sealing property and can be used under the pressure of 700KPa. The long-term operating temperature is 250 ℃, and the short-term operating temperature can reach 300 ℃.
Tetrafluoro film sealing layer, high temperature resistance and corrosion resistance.
Teflon sealing layer, high temperature resistance, corrosion resistance, good flexibility.
Silicone tape is made of alkali free glass fiber cloth, silicone rubber, stainless steel wire mesh and other thermal composite materials. It has strong sealing ability, pressure bearing ability, high operating temperature, long-term temperature can be used below 200 ℃, operating pressure is 300KPa, short-term 16 hours can accept 250 ℃, and has good temperature resistance. Silicone tape cannot be used in places containing sulfur dioxide smoke and water vapor.
The non-metallic shrink joint literally means that the main body material is composed of fabric or other non-metallic materials.