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Reasons for using long-neck valve caps in low-temperature valves – purely personal opinion. Valves designed for medium temperatures ranging from -40°C to -196°C are known as low-temperature valves, and such valves generally use long-neck valve caps. Low-temperature valves specified with long-neck valve covers include low-temperature emergency shut-off valves, low-temperature globe valves, low-temperature check valves, low-temperature valves dedicated to LNG, and low-temperature valves dedicated to NG, etc. They are mainly used in chemical plants such as those for producing 300,000 tons of ethylene and liquefied natural gas. The liquid cryogenic media produced, such as ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, and liquefied petroleum products, are not only flammable and explosive but also vaporize when heated; during vaporization, their volume expands by hundreds of times. The use of a long-neck valve cover is specified for the following reason: (1) A long-neck valve cover provides protection for the packing gland of low-temperature valves, as the sealing performance of the packing gland is one of the key factors in low-temperature valves. If there is a leak at this stuffing box, it will reduce the insulation effect, causing the liquefied gas to vaporize. At low temperatures, as the temperature drops, the elasticity of the packing gradually disappears, resulting in a decline in its sealing capabilities. Medium leakage causes freezing at the junction between the packing and the valve stem, which hinders the proper operation of the valve stem; moreover, the up and down movement of the valve stem can scratch the packing, leading to severe leaks. Therefore, it is necessary to ensure that the temperature at the filler station remains above 8°C. (2) The long-neck valve cover structure facilitates the wrapping of insulation material to prevent heat loss from the valves at low temperatures. (3) The long-neck structure of the low-temperature valve facilitates the quick replacement of the valve’s main components by removing them through the valve cover. Since the process pipes and valves in the cold section of the equipment are often installed within the ’cold box’, the long-necked valve cover can extend through the wall of the ’cold box’. When replacing the main components of the valve, it is sufficient to carry out the replacement through the valve cover, without the need to disassemble the valve body. The valve body is welded to the pipeline, minimizing leaks in the cryogenic tank and ensuring the valve’s sealing performance.