General low temperature emergency cut-off valve, low temperature globe valve, low temperature check valve, LNG special low temperature valve, NG special low temperature valve and so on are used in the long neck valve cover, these valves are mainly used in 300,000 tons of ethylene, liquefied natural gas and other chemical equipment. These chemical products are not only flammable and explosive, but also vaporized when heated, and when vaporized, the volume expands hundreds of times.

The long neck covers on these cryogenic valves provide several special functions:

(1) Protect the function of the low temperature valve packing box, because the sealing of the packing box is one of the key low temperature valve. If the stuffing box leaks, 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 valve cover structure is easy to wrap the cold retaining material to prevent the cold energy loss of the low temperature valve.


(3) The long neck structure of low temperature valve facilitates the quick replacement of the main valve parts through the valve cover removal. Since the process pipes and valves in the cold section of the equipment are often installed in the 'cold box', the long neck valve cover can be extended through the 'cold box' wall. To REPLACE THE VALVE MAIN component, simply remove through the valve cover, 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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