What are the hazards of welding boiler tubes with different inner diameters?
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During minor boiler repairs, it is sometimes necessary to replace some of the thinned superheaters, economizers, evaporator screens, and water wall tubes. My question is: if the outer diameter of the tubes is the same but their thicknesses differ (for example, a superheater tube with an original diameter of φ34×4.5 welded to one with a diameter of φ34×5.0), is it permissible to weld such tubes together? What are the harms?
Welding is possible, but from a technical perspective, an increased wall thickness leads to higher thermal resistance, a smaller inner diameter, greater flow resistance, and ultimately a reduced heat conduction capacity. It is recommended to use original standard pipes for welding.
There should be no problem, right? The wall thickness difference is within 0.5, and the theoretical edge deviation is 0.25; heat exchange should also be fine
According to Article 4.3.3.4 of TSG G0001-2012 \"Regulations on the Safety Technical Inspection of Boilers\", there is no need to thin out the wall thickness deviation in your case.
4.3.3.4 This clause refers to the boiler drum; are there any standards for the butt welding of heat-exposed pipeline?
4.3.3.4 This clause refers to the boiler drum; are there any standards for the butt welding of heat-exposed pipeline?
Paragraph 4.3.3.4 specifies in the original text “the boiler drum…………or two components”. Moreover, you can think of it this way: the main reason for avoiding excessive misalignment is to prevent high edge stresses at those areas of misalignment. In the case of a boiler drum, its diameter is large, so the risk associated with it is much greater compared to pipes with smaller diameters. Therefore, it makes sense to apply stricter standards when evaluating components for which relatively looser standards are sufficient.
:Handshake, thank you for your explanation.