Pipeline installation issues
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In oil refining process pipelines, in some cases, instead of using tees for connections, the branches are welded directly at the open ends. I would like to ask how such openings should be handled? Is it also TIG backing and welding for the root?
As long as the welding process (welding pressure level) is maintained, it is possible to weld tees with openings; TIG welding is used for the root pass in order to ensure that the inside of the pipe remains clean (free of slag) during welding. If cleanliness inside the pipe is not a concern, electric welding can be used directly.
Ensuring cleanliness is just one aspect; the main thing is to ensure full penetration
T-joints are particularly difficult to inspect on-site, and it is hard to clean the flux from the inner surface after double-sided welding; therefore, TIG welding for the root pass is recommended as it ensures better quality (primarily by guaranteeing full penetration and reducing welding defects). Shielded metal arc welding can be used for the cover pass.
Pay attention to the details in the work; it is recommended to use TIG welding for the base layer and manual arc welding for the finishing layer, as this reduces the likelihood of problems
To ensure cleanliness inside the pipe, attention must be paid to the cutting process when making holes; after drilling, it is essential to keep the area clean. Using TIG welding for the root pass helps maintain cleanliness inside the pipe. As for ensuring full penetration, this can only be verified through radiographic inspection after welding is completed.