Study On Failure Analysis And Preventive Measures Of T23Water Cooling Wall

Ultra-supercritical unit has been widely studied and applied, due to its highefficiency, environmental protection, energy saving. But a lot of problems such ascracks have appeared in T23water cooling wall during service, and the issue has notyet been resolved.This reasons that cause cracking problems in the T23water cooling wall wereanalyzed by two aspects: the welding process and welding residual stress distribution.Since T23steel is very sensitive to welding process, the different welding processesmay result in large differences in joint performance. So the weld morphology andtissue were analyzed. The macro-and micro-fracture morphology and the elementalcomposition were analyzed. It was found that the welding process is not strictlycontrolled such as the gap between pipes is too big, heat input is too high, and argonis not sufficient, which is one of the factors leading to cracks.And the distribution of welding residual stresses was simulated. Weldingresidual stress distribution shows that the maximum stress appears at6o’clock and12o’clock and3o’clock and9o’clock direction of the pipe. In addition the changes ofthe residual stress and creep strain during service are simulated. The results found that:welding residual stresses are soon released during service, and the creep strainincreases rapidly during welding residual stress releasing. And the equivalent creepstrain maximum occurs at6o’clock and12o’clock direction. Therefore, the weldingresidual stress promotes creep, which is another cause of cracks.Finally, the process of slot opening is simulated by the use of life and death celltechnology. The results show that life and death cell technology can effectivelysimulate the process of slots opening. And slots opening are effective for stressreleasing and adjusting the distribution of the local area significantly. With theincrease of slot length, the stress value is also getting lower and lower. But whenslotting length is longer than305mm, the stress does not change. Only when the slotposition is close to weld, the release of residual stress is effective. Stress release valueincreases also with slot width increasing.