How to deal with the leakage of the bottom plate of the 10,000-ton sulfuric acid tank in my company
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The bottom plate of our company’s 10,000-ton sulfuric acid tank has leaked again; this is already the third time it has leaked. For the first two leaks, all welds were removed and rewelded; after passing the hydrostatic test, the component was put back into use. This time, we want to use non-destructive testing methods to identify the leakage points, without having to reprocess all the welds. Which testing methods can be used to solve this problem?
Please analyze it from various perspectives to determine whether it is merely a weld issue. Such as material selection, welding structure type, bottom plate joining method, etc...
The weld here should be a fillet weld. It should be impossible to detect it using ultrasound or radiation. Only penetrant testing or magnetic particle testing can be used, and they are only surface inspections that cannot detect internal defects. It is estimated that this is caused by corrosion over time. It is recommended to apply PTFE spray internally after welding repairs. It won’t be leaked anymore. (Provided that the quality of perfluorospray is ensured)
All welds were rewelded; the original welding areas were completely removed, notched, and then welded again. After welding, flaw detection is performed; once no defects are found, PTFE spraying is carried out.
For the welds of such storage tanks, if shims are placed underneath, they are butt welds； Otherwise, it is a lap fillet weld; for inspection, extended testing can be considered, as well as magnetic particle and penetrant testing.
The size must be extremely large; I’ve seen tanks weighing 1,000 tons, but I’ve never seen ones that weigh 10,000 tons. This problem is likely caused by a design flaw. Generally, small storage tanks don’t leak again in a short period of time after welding, provided that the welding quality is good. For a tank of this 10,000-ton scale, the welding work must be carried out with high quality – it’s unlikely that workers with insufficient skills would be assigned to carry out such work.
It is likely a problem with the welding process, as the welding method used for the bottom plate is different from that used for the wall panels; however, there is no leakage in the wall panels
In the case of multiple leaks, it is necessary to check not only the welding issues but also the strength of the base plate and any problems with the foundation. It is necessary to determine whether the leak is caused by a hole, an eye in the sand, or a crack. Once the cause is identified, it’s possible to analyze what the problem is.
For highly corrosive media such as sulfuric acid, all bottom welds of the tanks should be fully penetrative butt welds with gussets