Discussion on the treatment scheme for misalignment of water wall headers in the radiant section of boilers
Thread Content
This post was last edited by qldch2306 on 2020-10-23 at 11:29. On-site feedback indicated that after installing the modules on the left and right sides of the water wall in the hoisting and radiation section, it was found that there was a height difference of around 10 mm between the interfaces of the two manifolds. The repair plan proposed by the manufacturer is shown in the diagram below (the diagram is on the 2nd floor): an open-round plate is added at the junction of the two collection boxes, and the two collection boxes are welded to this round plate. I personally disagree with this approach. Reason 1: The additional transition elements create resistance to the flow, similar to the orifice effect. Reason 2: The original butt weld formed a lap joint configuration, and it is unknown whether it can withstand the strength requirements. Reason 3: The industry has never seen such a repair method. There is no case or technical evidence to support it. I would appreciate it if netizens could advise me whether such a plan violates relevant regulatory provisions Is this acceptable? Thank you
Does the GB50273 Code for Acceptance of Boiler Installation Works not have any requirements in this regard either? I wonder whether it can be considered as not meeting the requirements of clauses 5.9–5.13 of JBT1613, which specify the welding technical requirements for pressure components in boilers.
GBT 16507/16508 standards for water-tube boilers and shell-and-tube boilers also do not meet the requirements.
It’s not clear what model the owner’s boiler is, but the misalignment is too large; it definitely does not meet the regulatory requirements.
Such defects leading to compromised acceptance means quality control fails (ー_ー)!! Leaving potential problems for the next person? Sigh\ud83d\ude14
Changing the original butt weld to a fillet weld results in a completely different load-bearing capacity; moreover, fillet welds have poor resistance to temperature changes and fatigue. Therefore, this modification plan is definitely not feasible.
Thanks for the comments from above. The question now is how to repair it? With such significant flaws in the pre-assembly at the manufacturing plant, and such poor weld quality, how should this be addressed? Did someone say scrap? Will the Special Inspection Agency step in to mediate? Can internal shims be used, with the outer wall welded using build-up welding, and the surface polished for a smooth transition? The slope should not exceed 1:3. Another ultrasound examination and MT test were conducted; the water pressure was within acceptable limits. Taking such actions amounts to pushing the homeowner to the brink, sigh╯﹏╰
At the original weld site, about 200 mm is cut off from each side, and then a new pipe section 400 mm in length is joined. The original single circumferential weld becomes two circumferential welds; the flaw detection is carried out using 100% radiography, with a qualification standard of grade II
I quite agree with your approach; this way, there are no changes to the interface of the pipe, and it involves butt welding. I’m not sure how the original poster ended up handling it