Why do low temperature valves use long neck covers?

Suitable for medium temperature – 40 ℃ ~ – 196 ℃ valve is called low temperature valve, and this kind of valve generally adopts long neck valve cover.

The long neck valve cover is adopted to specify low temperature valves, including low temperature emergency shut-off valve, low-temperature stop valve, low-temperature check valve, LNG special low-temperature valve, etc., which are mainly used in 300000 tons of ethylene, liquefied natural gas and other chemical plants. The output liquid low-temperature medium, such as ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, liquefied petroleum products, etc., is not only flammable and explosive, but also needs to be gasified when heating up. When gasifying, the volume expands hundreds of times.

Reason of using long neck valve cover for low temperature valve:

  • (1) The long neck valve cover has the function of protecting the stuffing box of the cryogenic valve, because the sealing performance of the stuffing box is one of the keys of the cryogenic valve. If the stuffing box leaks, it will reduce the cold insulation effect and cause liquefied gas gasification. At the same time, due to the leakage of the valve stem, the temperature of the valve stem will gradually decrease due to the leakage of the packing under the condition of low temperature, and the temperature of the packing will also decrease due to the leakage of the packing under the normal condition. Therefore, it is necessary to ensure that the temperature of packing standard position is above 8 ℃.
  • (2) The structure of long neck valve cover is convenient for winding cold insulation material to prevent cold energy loss of low temperature valve.
  • (3) The long neck structure of cryogenic valve is convenient for quick replacement of main parts of the valve by removing the valve cover. 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 extend through the wall of the cold box. When replacing the main parts of the valve, it is only necessary to remove and replace the valve cover without removing the valve body. The valve body and the pipeline are welded together to reduce the leakage of the cold box as much as possible and ensure the sealing of the valve.

Source: China Valves Manufacturer – Yaang Pipe Industry Co., Limited (www.pipelinedubai.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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