Questions for help! How to select the design temperature for external pressure verification of cryogenic vessels?
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I am currently designing a cryogenic vessel. The reference standard is of course GB/T 18442-2011 "Fixed Vacuum Insulated Cryogenic Pressure Vessel". As shown in the figure, in GB/T 18442.3 4.2, it is stated that the inner container and outer shell need to withstand external pressure loads: As for the external pressure load endured by the shell, the following explanation is given in the engineering master's thesis of South China University of Technology "Research on Strain Strengthening Design and Manufacturing of Stationary Cryogenic Vessels": In this paper, during the external pressure check of the shell cylinder and head, it was determined that the design temperature was selected as 150°C. Right now: During the process of vacuum extraction, the shell needs to be heated to 150°C, and the corresponding explanation is also given in GB/T 18442.3 4.6.3 Design Temperature: This paper provides an explanation for the selection of the external pressure verification design temperature of the outer shell, but does not provide an explanation for the external pressure verification design temperature of the inner vessel. So the question now is: 1. Is it correct to select 150°C as the design temperature for external pressure verification of the cryogenic vessel shell? 2. How should the design temperature for external pressure verification of the cryogenic vessel be selected?
Still learning now* stage, this is a task assigned to me by my business mentor, and I have to think about it myself
Help! ! ! ! :hug:
First question, I suggest you consult the vacuum container manufacturer to see what the actual vacuum heating temperature is. Personally, I think 150°C is about the same. Even if there is a deviation, it will not be too big and has little impact on the value of the allowable stress.； The second question is actually to find out what is the possible maximum temperature of the inner cylinder when it is subjected to external pressure? Under normal working conditions, it is impossible for the inner cylinder to withstand external pressure. There is only one extreme case where a leakage failure occurs in the inner cylinder, causing a large amount of internal cryogenic liquid to leak out, and then rapidly lose pressure and flash, so that the jacket cavity is rapidly pressurized. When it reaches 0.1Mpa, if the cryogenic liquid in the inner cylinder leaks, it will instantly withstand external pressure at this time. When the pressure is high enough to trigger the activation of the jacket explosion-proof device, a large amount of gas will be rapidly discharged, and the inner cylinder will gradually no longer bear external pressure. During the entire hypothetical process, the flash evaporation of the cryogenic liquid in the inner cylinder will absorb a large amount of heat. Not only will it not exceed 150°C, but it will be lower than 0°C. Therefore, I personally feel that 150 degrees Celsius is sufficient for the maximum temperature for inner cylinder and external pressure calibration.
Great answer! ! Thank you for your participation!