锅炉电动气动泄放阀阀体螺柱断裂原因探讨

Study on the Fracture Causes of Valve Studs of Boiler Electro-pneumatic Discharge Valve

某电厂1号锅炉在整套启动运行过程中过热器出口电动气动泄放阀螺柱发生断裂,通过宏观形貌分析、化学成分分析、金相组织检测、断口微观形貌探测及力学性能测试等综合性试验分析,结果显示:1号锅炉过热器出口电动气动泄放阀螺柱断裂的主要原因,一是电动气动泄放阀阀体连接螺柱选材等级偏低,所用的SA193-B16材质不能满足设计温度下的强度极限及疲劳极限要求;二是锅炉运行过程中电动气动泄放阀反复开闭,在形成的交变拉—压冲击载荷作用下,在应力集中的螺纹牙底部形成疲劳开裂并扩展导致螺柱断裂失效。

The studs of the electro-pneumatic discharge valve at superheater outlet were broken during the start-up and operation of boiler No.1 in a power plant.Comprehensive test analysis such as macroscopic morphology analysis,chemical composition analysis,metallographic structure testing,fracture microscopic morphology detection,mechanical properties testing,and so on,is carried out.The results show that the main causes for the fracture of the studs of the electro-pneumatic discharge valve at the superheater outlet of boiler No.1 are as follows:first,the material grade of the connecting studs of the electro-pneumatic discharge valve is low,and the SA193-B16 material used cannot meet the requirements for strength limit and fatigue limit at the design temperature;second,during the operation of the boiler,the electro-pneumatic discharge valve is opened and closed repeatedly.Under the action of the alternating pull-pressure impact load,fatigue cracking is formed at the bottom of the thread teeth with stress concentration,which expands gradually and finally leads to the fracture and failure of the studs.