【Beginner in Static Equipment】Is it really necessary to perform magnetic particle or penetrant testing after root welding of pipes using TIG welding? ?
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Some pipeline design requirements call for magnetic particle or penetrant testing to be carried out after TIG welding as a backing process, but this interrupts the welding process. This is especially true for pipelines that require preheating. Is it really necessary to perform magnetic particle or penetrant testing on pipelines after TIG welding as a backing process? ?
In my opinion, it’s not necessary. Let’s see what the professionals have to suggest.
It should be necessary, as this allows for the early detection of any defects in the base layer, enabling prompt action to be taken. It is difficult to remove root defects that are detected during inspection after all the surface welding is completed. It needs to be dug all the way open. Especially in thick-walled pipes, if root defects are detected during inspection after welding, it is sometimes necessary to cut them open using a saw machine in order to address the issue
Thank you for your participation; happy New Year! ! !
Thank you for your participation; happy New Year! ! ================================= I have a question: The main defects in the root weld seam include lack of penetration, failure to fuse, inclusions, oxidation, and undercutting. Defects such as undercutting, surface oxidation, and inclusions do not require magnetic testing or dye penetrant testing for the root weld seam; experienced welders can detect them as well. These defects are removed by grinding during the filling process. However, failures to fuse and lack of penetration on the back side of the weld seam cannot be detected using magnetic testing or dye penetrant testing. That’s where my confusion lies
Magnetic particle testing can detect surface and near-surface defects such as cracks and inclusions; inclusions and edge cracks are generally visible to the naked eye, but cracks are likely to be difficult to detect with the unaided eye. As for incomplete welding or failure to fuse at the root, magnetic particle testing should not be able to detect it; for larger pipes, people can enter and repair the root area. As for whether it is necessary to perform magnetic particle testing on the base layer, one could consult a professional welding engineer
Why are such non-destructive testing requirements specified in the design? It mainly applies to structures or materials of certain containers that are prone to cold cracking; cracks can easily occur after TIG welding is used for the root pass, and if further welding is carried out without conducting inspections, these cracks will continue to spread.
The structure or material of some containers that develop cold cracks is prone to cracking after TIG welding as a base layer – could this be due to the thinness of the weld bead produced by TIG welding? Is it caused by the rapid cooling of the weld, which results in relatively high shrinkage stresses? If welding is to continue without interruption, can it be improved? ? For example, performing two TIG welds?
Well, that makes sense. Appropriate preheating can be considered, but due to the limitations of TIG welding operating conditions, excessively high preheating temperatures make it difficult for operators to carry out welding.
:Lol, the designers don’t know where they got the technical requirement template from. Then. . . .
There was such a rule in the previous specifications, but the conditions have changed