According to working conditions
, design requirements of cryogenic valves are listed below.
A cryogenic valve
is supposed to work for long periods of time with cryogenic media and under low temperature.
A cryogenic valve
cannot become an main heat source in the cryogenic system because the flow of heat can reduce thermal efficiency. At the same time, if there are too many fluids flowing into the valve, the fluid inside the valve will evaporate rapidly, resulting in the abnormal increase of valve
pressure and potential danger.
Cryogenic media should not have harmful effects on the hand wheel and sealing performance of the cryogenic valves
The components of the cryogenic valve
in direct contact with cryogenic media are supposed to have structures with explosion-proof and fireproof.
Since the components of the cryogenic valve
can't be lubricated, it is necessary to adopt a certain structure for preventing the damage of components.
The materials of the cryogenic valve body
It is necessary to think about the metal material for the cryogenic valve
body. Except the metal material with the face-centered cubic lattice, such as the Austenitic steel, copper and aluminum, general steel gets low-temperature brittleness under low temperature, reducing the strength and operating life of the cryogenic valve
. The first priority of selecting valve
body materials is ensuring the low-temperature resistance of the material. Aluminum is such a kind of material that it does not have the low-temperature brittleness under low temperature. However, since the low hardness of aluminum and aluminum alloy, the aluminum sealing surface has the poor wear resistance and scratch resistance, which limits the applications of the cryogenic valve
. Therefore, aluminum is only used for the small-diameter cryogenic valve
under low pressure.
The working performance of valve
materials under low temperature must be guaranteed, especially the impact strength. In order to prevent breakage, the components inside the cryogenic valve
are necessary to have high impact strength under low temperature by means of suitable materials.
Ni steel with 3.5% Ni is adaptable to the working temperature down to -100℃ while Ni steel with 9% Ni is suitable for the working temperature down to -192℃.
Austenitic stainless steel, Ni, Monel, Hastelloy, titanium alloy, aluminum alloy and bronze are applied to working conditions at operating temperature as low as -273℃.
, here are some other factors worth considering
The minimum operating temperature of cryogenic valves should be considered.
It is necessary to keep the mechanical properties of metal materials under low temperature, especially impact strength, relative elongation and microstructure stability.
Without lubricating oil and under low temperature, the cryogenic valve
is supposed to have great wear resistance.
The cryogenic valve
is supposed to have good corrosion resistance.
It is necessary to consider the welding performance of the valve
material before welding.