Safety issues in the maintenance of cryogenic liquid oxygen storage tanks
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Equipment condition: Cryogenic liquid storage tank. The design pressure of the inner tank is 0.42 MPa, while the external pressure on the outer tank is 0.1 MPa. Design temperatures: -196°C for the inner tank, and normal temperature for the outer tank. Working media: Liquid oxygen, liquid nitrogen, liquid argon for the inner tank; pearlescent sand for the outer tank. During this year’s routine equipment inspection, a weld bead resulting from surfacing was found on the lower head, with a diameter of 20 mm and a height of approximately 30 mm. It was not mentioned in any of the previous regular inspections. After this regular inspection, an inspection report was issued requiring the issues to be resolved. May I ask, during normal storage and maintenance, can the weld bead in question be simply ground smooth? . Magnetic particle or penetrant testing is performed after grinding. May I ask what other effects might occur if sparks are generated during grinding, or if certain areas of the tank head become overheated? We suspect that the holes were drilled incorrectly at the time of production and then blocked off. If it gets smoothed out and there is a vacuum leak, what should be done next? I would appreciate it if experienced users could help answer this question; I’m a complete novice in the field of chemistry! !
This post was last edited by sdwfsgyykai on 2018-9-1 at 17:53. Maintenance is carried out during normal storage; as you said, there are electric sparks when grinding, and it’s no joke. Can the contents inside be drained first before carrying out repairs?
It is best to contact the equipment manufacturer to handle this. It should be possible to use this only after it has been inspected by the safety supervision department. Everything related to this is registered. But one thing is for sure: regardless of the value of the medium safety factor, as long as it is a pressure vessel, such scars cannot be simply polished away. It’s necessary for it to be approved by the manufacturer. Once it’s worn out, welding won’t work the same way.
My personal suggestion is to communicate with the original manufacturer to determine the true cause of this weld bead before taking appropriate action
This opinion is worth discussing; maintaining the integrity of the jacket structure of cryogenic liquid storage tanks is essential to ensure the vacuum level in the interlayer. Since it does not constitute a primary pressure-bearing component, its repair welding should not be regulated as part of the repairs for special equipment. Furthermore, as long as the vacuum level remains intact, it is possible to maintain the temperature of the liquid inside the inner cylinder, thereby ensuring the pressure within it; from the perspective of the equipment’s suitability for use, no action may be necessary. In summary, it can be discussed with the routine inspection personnel; there is no need to take any action.
The weld bead should be on the jacket; according to the inspection specifications, it must be ground smooth, after which surface non-destructive testing is performed. Before carrying out any repairs or modifications, the seller’s consent must be obtained, and qualified entities must be engaged to carry out such work.
Thank you all for your replies and discussions! !
It is recommended not to make any changes during normal operation; it is a high-risk welding task and very dangerous
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