How to design and select materials for high temperature valves?

In general information, valves with a valve operating temperature t>450°C are called high-temperature valves. There is no unified standard for the classification of high-temperature valves for high-temperature valves. In the "High-temperature grades and main materials of high-temperature valves" published by Le Jing 》In the article, the high temperature grade is divided into five grades based on decades of experience in producing high temperature valves. That is, the valve working temperature t>425~550℃ is the PI grade, the working temperature t>550~650℃ is the PII grade, and the working temperature t >650~730℃ is PIII grade, working temperature t>730~816℃ is PIV grade, working temperature t>816℃ is PV grade. Among them, PI~PIV valves mainly rely on the selection of suitable materials to ensure their performance, PV In addition to the selection of materials, the more important thing for the grade valve is the use of special design methods, such as lining heat insulation linings or taking cooling measures. As described in the article "Ultra-Ultra High Temperature Pneumatic Angle Globe Valve" by Yang Rongshui, Huang Meilin and other authors, The ultra-ultra-high temperature pneumatic angle globe valve is equipped with 5 sets of cooling structures to ensure the normal operation of the valve when the temperature of the working medium is 2000 ℃.

2. Commonly used high temperature valve types
High-temperature valves include high-temperature gate valves, high-temperature globe valves, high-temperature check valves, high-temperature ball valves, high-temperature butterfly valves, high-temperature needle valves, high-temperature throttle valves, high-temperature relief valves, etc. Among them, gate valves, globe valves, and check valves are more commonly used. , Ball valves and butterfly valves.

3. The design points of high temperature valve
When designing high-temperature valves, pay special attention to the impact of thermal expansion, thermal alternation and mechanical properties of materials. Due to the thermal expansion coefficient of the material, the difference in the thermal load on the parts, etc., even if the valve seat and valve core that are heated almost at the same time expand at high temperatures The performance such as quantity is also different; in order to effectively reduce the sticking or scratches caused by the temperature between the parts, it is necessary to increase the working gap between the valve parts. The increase in the gap should be based on the thermal expansion coefficient of the material, the stress and the actual use temperature. To determine. High temperature thermal alternation will cause the connection between the valve seat and the guide sleeve to become loose, and aggravate the fatigue and aging of the valve parts. Corresponding measures should be taken in the design according to the specific conditions, such as the use of elastic valve seats in the sealing structure. High temperature will affect the mechanical properties of the material. The strength, hardness, plasticity, elastic modulus and Possibility of the material at different temperatures will also be different. The influence of these factors on the performance of the valve should be fully considered when designing.
www.hengjiafirefighting.com