Internal subsidies found during inspection of used pressure vessels
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Check a tower with 20g of material, about 470 degrees Celsius, and 0.2Mpa pressure. The internal corrosion thinning is in good condition, and no cracks were found during non-destructive testing. However, there is a patch inside, and it is patched from the inside. A patch is attached to the cylinder with a fillet weld. I remember that regular inspection regulations do not allow patching. What are the specific harms of such a patch structure? Generally, subsidies are provided from the outside, so what’s the disadvantage of applying them from the inside?
Generally, it is done on the outside, just like the reinforcing ring. It is not allowed to stick it on the inside. It will easily cause stress concentration and accelerate the corrosion rate.
This post was last edited by qldch2306 on 2010-8-30 14:56. The lap weld formed after the update is a serious stress concentration, which can easily lead to corrosion, cracking, etc.； What is formed after excavation and repair is a butt weld, which has better stress resistance and is recommended by the specification. During the inspection of some old refineries and chemical plants, I have encountered several times - the situation you mentioned exists in low-voltage equipment. Personally, I think that under normal circumstances, after adding surface flaw detection or buried flaw detection methods here, no new defects are found. It can only be regarded as having an unreasonable structure and can be rated as Level 3. If there are special circumstances, such as harsh usage conditions, high temperature and high pressure, or stress corrosion environment, it is recommended that the factory repair it. Some people may think that this is a very conservative approach, haha, benevolence is in the eyes of the beholder and wisdom is in the eye of the beholder. . .
Generally, if there is an insulation layer on the outside, it is added to the outside. If not, it is added to the inside.