Seek help with the selection of low-temperature valves and the choice of flange gaskets for pairing
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The medium is liquid nitrogen, with a minimum operating temperature of -198 degrees Celsius. What model of gate valve should be selected? What material is the valve body made of? What are the options for gaskets and bolts/nuts? Thank you~~~
1. The boiling point of nitrogen is -196°C; at normal atmospheric pressure, a liquid nitrogen state is formed when the temperature drops below this value. If pressure is applied, liquid nitrogen can be obtained at higher temperatures. I don’t know where the poster got the -198℃ figure from. 2. Liquid nitrogen is at an ultra-low temperature, so ultra-low temperature valves must be used. Taking the ANSI gate valve of CL150 as an example here: 1) The valve body, gate, and stem are made of austenitic stainless steel; the forgings are of types 304/304L/316/316L, while the castings are of types CF8/CF3/CF8M/CF3M, etc. 2) Sealing surface API#5. 3) Graphite filler. 4) 304+flexible graphite wound gasket. 5) The valve cover/valve body bolts are also made of austenitic stainless steel and are fully threaded. For pipe flanges, gaskets and stud nuts are used, just like for valves. 3. Requirements to be met: 1) An extended valve stem structure should be used. 2) The manufacturer shall take measures to prevent pressure buildup in the middle chamber, which may include, but are not limited to, installing pressure relief holes on the inlet side. (When the valve has pressure relief holes, the valve body should have arrows indicating the flow direction of the fluid.) 3) The valve cover should be equipped with a drip tray for isolation. 4) The valve shall undergo a low-temperature test after passing the normal temperature test, and the low-temperature test shall be conducted in accordance with MSS SP-134. 5) The valve must undergo cryogenic treatment. Other requirements can be proposed as appropriate.
First of all, thank you for providing such a detailed explanation of this issue~~~ The temperature mentioned is the actual temperature measured on site, and there is likely some error involved~~~ The valve gaskets, bolts, and nuts can be the same ones that were used in the previous pipeline system~~~ Thank you again~~~
After the rough machining of the components, cryogenic treatment is carried out, followed by fine machining
Just contact the manufacturers of low-temperature valves and tell them your requirements~~