High temperature control valve selection

High temperature control valve is the working temperature is greater than 450 ℃ valve. Can be divided into 450 ~ 600 ℃, 600 ~ 700 ℃, 750 ℃ ​​three categories.

What are the main problems usually involved in high temperature control valve?

Severe thermal expansion and contraction problems, so that the guide gap, the valve plate rotation due to expansion of the gap to reduce or even become an interference, and thus stuck. Under high temperature, the creep of the material leads to the decrease of the mechanical properties of the material.

From the hot strength considerations, the valve body and valve parts of the material how to choose?

For the adjustment of the environment above 450 ℃ hair, in the design and selection must take into account the temperature and pressure of the standard room on the mechanical strength of the material, such as boiler feed water system and overheating bypass system under high temperature conditions, the conventional valve body and valve Piece of material is not applicable. Therefore, we must use more durable materials. General materials can use the maximum temperature of about 500 ℃. For more than 538 ℃ occasions. The body is usually made of chrome molybdenum steel. For the highest temperature of about 1035 ℃ occasions, usually selected SUS310S-type stainless steel, and the carbon content of the material must be controlled with 0.04% ~ 0.08% between. For higher temperatures, it is recommended to use lined with non-metallic heat-resistant material (can be used at 1200 ℃ high temperature occasions) or special high temperature, high strength alloys (such as engine combustion chamber with high temperature high-strength alloy, ℃ high temperature occasions.)

From the thermal expansion and contraction considerations, how to adopt measures to prevent leakage from the structure?

Can be used with the valve seat seal welding method to prevent leakage. At temperatures up to 750, the threaded seat creates a leak on the sealing surfaces and threads connected to the body and can erode the threads, posing a risk of the seat being dropped. Encounter this aggregate failure, should consider the seal seat welding, to prevent loosening and loss.