(1) Selection of materials for the valve body and internal parts
For control valves used in conditions above 450℃, the highest temperature of general materials can be about 500℃. For the temperature above 538℃, chromium-molybdenum steel is usually used for valve bodies. SUS310S stainless steel is usually used when the highest temperature is about 1035℃ and the carbon content of the material must be controlled between 0.04% and 0.08%. For higher temperatures, it is recommended to use non-metallic lining and heat-resistant materials, which can withstand high temperatures of 1200℃. Or special high-temperature resistant and high-strength alloys can be used. For example, the alloys can be used in the engine combustor with the temperature of 1000℃.
(2) Temperature resistance of packing
The standard PTFE packing can only be used in places below 200℃. If it needs to be used for medium and high temperature, the extended bonnet must be used to prevent the packing from being affected by extremely high temperature. However, the longer and thinner valve stem has poor strength at high temperature and is prone to bending. Therefore, flexible graphite packing with excellent temperature resistance (up to 600℃) should be used at high temperature, and the height of the extended bonnet can be greatly reduced. At the same time, the overall strength of the valve is improved by means of "the rotary valve+the thick valve stem", thus solving the above problem better.
(3) Selection of sealing methods
It is difficult to achieve high cutting performance at high temperature, and many conventional sealing methods with high performance are not desirable (e.g. O-rings, PTFE materials, elastic metal materials). Within 500℃, special composite graphite valve seat can be adopted. When it is over 500℃, only metal-to-metal hard sealing can be adopted (butterfly valve structure is generally adopted).
For control valves used in conditions above 450℃, the highest temperature of general materials can be about 500℃. For the temperature above 538℃, chromium-molybdenum steel is usually used for valve bodies. SUS310S stainless steel is usually used when the highest temperature is about 1035℃ and the carbon content of the material must be controlled between 0.04% and 0.08%. For higher temperatures, it is recommended to use non-metallic lining and heat-resistant materials, which can withstand high temperatures of 1200℃. Or special high-temperature resistant and high-strength alloys can be used. For example, the alloys can be used in the engine combustor with the temperature of 1000℃.
(2) Temperature resistance of packing
The standard PTFE packing can only be used in places below 200℃. If it needs to be used for medium and high temperature, the extended bonnet must be used to prevent the packing from being affected by extremely high temperature. However, the longer and thinner valve stem has poor strength at high temperature and is prone to bending. Therefore, flexible graphite packing with excellent temperature resistance (up to 600℃) should be used at high temperature, and the height of the extended bonnet can be greatly reduced. At the same time, the overall strength of the valve is improved by means of "the rotary valve+the thick valve stem", thus solving the above problem better.
(3) Selection of sealing methods
It is difficult to achieve high cutting performance at high temperature, and many conventional sealing methods with high performance are not desirable (e.g. O-rings, PTFE materials, elastic metal materials). Within 500℃, special composite graphite valve seat can be adopted. When it is over 500℃, only metal-to-metal hard sealing can be adopted (butterfly valve structure is generally adopted).
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