Improvement of low temperature pressure vessel

Low temperature operation of pressure vessel with decreasing temperature, the container used steel and its weld will change from ductile brittle state, the compression element in tensile stress under the action of stress levels below the yield strength of the material, or less than the allowable stress under the condition of sudden brittle fracture. After this break, no or only minimal local plastic deformation, but no overall yield, imperceptible in daily life, but often a catastrophic accident, and even pose a great threat to the safety in production. Therefore, compared with the non cryogenic pressure vessel, the design, manufacture and inspection of low temperature pressure vessel are more strict.

Low temperature pressure vessel to determine the requirements of low temperature pressure vessel increase, the low temperature pressure vessel cost is much higher than the general pressure vessel, according to the first design condition to determine whether the container belongs to the low temperature pressure vessel. Due to the influence of the environment, the wall temperature of the container is a kind of pressure vessel under the condition of low temperature during the process operation.

Selection of low temperature pressure vessel: the quality of low temperature pressure vessel is first determined by the quality of low temperature steel. Low temperature pressure vessel steel commonly used, steel at low temperature are the main failure form of brittle fracture of steel at a temperature below the transition temperature, there is enough gap defect or sharp and it will lead to brittle fracture under low stress. The impact value of steel at low temperature AKV reflects the plastic deformation ability and the sensitivity to crack propagation at low temperature, that is, low temperature toughness. The first condition, and must ensure that under the premise of adequate low temperature toughness, high strength steel. In order to obtain good low temperature toughness, low temperature pressure vessel steel in smelting method must be used in smelting furnace or open hearth furnace, BOF, and must be killed steel. Non compression element material directly welded by pressure vessel of low temperature pressure vessel material and low temperature pressure vessel, and its low temperature toughness and welded joint performance should be matched with compression element.

For the low temperature pressure vessel design, the material support is particularly important: cryogenic vessel design of temperature is not higher than 70 DEG C, the bearing materials should use the same material as low temperature toughness and compression components; design of temperature is higher than 70 DEG C and lower than the low temperature from-20 DEG container, the bearing material should be selected low temperature toughness is low pressure components a grade of material. On the equipment installed in a very low temperature region, the influence of environmental temperature must be taken into consideration when selecting the bearing material.