Design issues (regarding periodic inspections)
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There is currently a low-temperature container used to store liquid oxygen, liquid nitrogen, etc. It consists of two layers: an inner layer that serves as the low-temperature pressure vessel, and an outer layer that acts as a thermal-insulating vessel at normal pressure. Thermal insulation is achieved using perlite. The container is designed and manufactured in accordance with new regulatory standards; however, its outer shell is sealed. It is not possible to conduct regular inspections on the inner cylinder. . Therefore, when a problem arises, it is necessary to inquire about possible solutions for the regular inspection of the inner cylinder. . . Please share your insights~～
If internal inspection is not possible, the proportion of flaw detection must be increased. This must be a vacuum insulated container.
Increasing the proportion of flaw detection may not be very effective, as there is a vacuum inside the interlayer, and the outer surface is typically made of Q235, which is ordinary carbon steel; even if 100% inspection of the outer surface is carried out, it won’t yield much practical benefit. The original poster mentioned that, as per the requirements, it is necessary to open the manhole for internal inspection, but since it’s not possible to shut down the system for such inspections, the checks can only be carried out while the system is running. The most important thing for a cryogenic container is to prevent heat from entering due to cracking of the inner cylinder. I believe that for a non-stop inspection method, it is necessary to measure the vacuum level in the interlayer and to use acoustic emission testing for the inner cylinder.
Regular inspections can only measure the vacuum level, as well as check the maintenance records and assess the condition of the inner cylinder.
This is not a vacuum insulated container, but rather a gas storage tank such as for liquid oxygen or liquid nitrogen, which is commonly used in air separation units.
The new regulatory requirements state that for equipment for which internal and external inspections are not permitted, a hydrostatic test can be used as a substitute