Cryogenic valves require a long neck bonnet because:

(1) The long neck valve cover has the function of protecting the stuffing box, because the sealing of the stuffing box is one of the keys of the low temperature valve. If there is leakage, it will reduce the cooling effect and lead to the gasification of liquefied gas. At low temperature, with the decrease of temperature, the elasticity of packing gradually disappears, and the leak-proof performance decreases. Due to the media leakage, the packing and the valve stem are frozen, which affects the normal operation of the valve stem. At the same time, the pulp packing is scratch due to the movement of the valve stem up and down, causing serious leakage. Therefore, it is necessary to ensure that the temperature of the filler base is above 8℃.

(2) The long neck structure is convenient for winding cold retaining materials to prevent the loss of cold energy.

(3) The long neck structure is convenient for the main parts of the valve to be removed through the valve cover for quick replacement. Since the PROCESS PIPES AND VALVES IN THE COLD section of THE EQUIPMENT ARE often HOUSED in the "cold box", the long-necked valve cover can be extended through the wall of the "cold box". When replacing the low temperature valve main parts, only through the valve cover to remove, without removing the body. The valve body and the pipeline are welded into one, as far as possible to reduce the leakage of the cold box, to ensure the sealing of the valve.

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