1000MW超超临界机组高压旁路阀减温水喷嘴焊缝开裂失效机理与设计优化OA

To address the issue of frequent cracking in the weld of the desuperheating water spray nozzle of a high-pressure bypass valve in a 1 000 MW ultra-supercritical unit,the failure mechanism of the weld was revealed and a structural optimization scheme was proposed by means of metallographic structure analysis,microhardness testing,and other physical and chemical inspection methods combined with finite element numerical simulation technology.The results show that the high hardness of the weld between the desuperheating water inlet pipe and the nozzle,together with the low-cycle strain fatigue induced by structural constraints,mutually superimposed to promote the rapid initiation and propagation of cracks in the fillet weld,thereby leading to leakage of the desuperheating water pipe.For the optimization scheme of lengthening the vertical desuperheating water pipe to enhance pipeline flexibility,finite element analysis shows that when the vertical pipe length is increased to 380 mm,the stress at the fillet weld significantly decreases to 65 MPa,effectively avoiding stress concentration.The research results can provide reference for the structural design and safe operation of similar high-pressure bypass valves.