Seeking advice on the coverage of weld procedure qualification for heat exchanger tube sheets
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I would like to ask everyone about the welding process for heat exchange tube sheets (10 tubes + 16MN tube sheet), where TIG welding is used for the root pass and manual welding for the cover pass. I’m wondering what type of weld qualification tests are required. Normally, 4 types of weld qualification tests are needed; as discussed in the group, these include: 1) TIG welding for thin plates, and 2) shielded metal arc welding for thin plates, to cover the tubes. . . Welding of 3-mm-thick plates by shielded metal arc welding (for thicknesses over 38 mm) + welding of 4-mm-thick plates by TIG welding (for thicknesses over 38 mm, whether in combination or separately) ~~My current problem is that I have not established a weld assessment for welding 4-mm-thick plates by TIG welding (for thicknesses over 38 mm, whether in combination or separately). According to Table 9, Item 1 of NB/T47014, for thicknesses over 13 mm, TIG welding is used as the root pass; 1) the coverage thickness is determined based on the criteria for other filling welding methods, 2) however, the minimum coverage thickness cannot be less than the thickness of the heat exchange tubes. Here, I was thinking of using TIG welding on thin plates to provide the necessary coverage – is that possible? ?
To find out whether this post is helpful to you, please take a look: Questions regarding the evaluation of the welding process for heat exchanger tubes and tube sheets https://bbs.hcbbs.com/thread-2295317-1-1.html (Source: Haichuan Chemical Industry Forum)
Thank you. Seen. I didn’t explain my situation clearly; in that example, the tube sheet connection was made using strength welding, and there is a difference between the strength welding used there and the welding method that involves expansion as well. The understanding of the strength weld groove in that post is also a point of doubt
OP, your question isn’t clearly stated. Do you currently have an ARG welding assessment for a thin plate, and do you want to use item 1 in Table 9?
Yes, currently there is an ARG welding procedure specification with a thickness of 16 mm, which is intended for covering the tube sheet (thick plates). TIG welding for weld evaluation of covered thin tubes is now available as well
What is the base metal thickness for the GTAW weld evaluation of the thin tube you are working with? Your situation is a bit special. The prerequisite for applying the first item in Table 9 is that the base metal thickness for GTAW weld qualification must be greater than 13 mm, and the evaluation is conducted separately; when used as a root pass in product welds, the thickness of the thicker sides can be covered by other welding processes. As I understand it, this rule can be applied if the two separate GTAW weld evaluations have exactly the same all important variables and additional important variables, with the only difference being the thickness covered.
Take a look at this as well; find out how the weld evaluation thickness for heat exchanger tube sheets is determined: https://bbs.hcbbs.com/thread-1297654-1-1.html (Source: Haichuan Chemical Industry Forum)
I have another question. This weld is prepared with GTAW for the root pass and SMAW for the cover pass. For the base layer, the weld evaluation includes 16 mm all-GTAW specimens and 8 mm all-GTAW specimens. The important and secondary factors are consistent. Can this cover that base case here? I mainly consider that the 8mm specimen covers a shell thickness of 12mm, while the 16mm specimen uses item 1 in Table 9 to cover the tube sheet thickness, but it cannot cover the minimum weld thickness of 16mm. Some posts state that as long as a test piece of ≥13mm is used as the root pass for the weld, it corresponds to the full thickness of the weld. . http://bbs.toweld.com/simple/t50224.html
Even under conditions that require impact, I think your method of covering it is acceptable.