某型中压燃气蒸汽锅炉在近期一次持续低负荷运行后，其高温段过热器部分管排出现横向裂纹。根据该锅炉的设备参数、历史运行数据及流程结构特点，分析其运行中可能致使炉管泄漏的主要风险因素，并进一步利用硬度检测、渗透检测、拉伸试验和金相检测等试验检测技术，排除换热管材质使用不当，汽水品质造成炉管内部结垢以及低负荷运行期间金属局部过热等造成缺陷的可能，对其失效机理进行分析和对比，最终确定导致本次换热管开裂的主要原因是氯离子影响下的持续应力腐蚀。针对本锅炉给水流程的结构特点提出增设氯离子监测措施，避免装置异常串料污染锅炉给水的品质。

Aiming at the abnormal increase of pressure in the bearing cavity of a gas turbine, through data analysis,on-site investigation, appearance inspection, dimension measurement, fracture analysis, simulation analysis and other methods, this paper successfully locates the cause of the fault, and puts forward an improvement scheme for the valve of pressure drop regulator from line contact pin structure to surface contact gasket structure,so that the contact stress is reduced from 235.5 MPa to 0.88 MPa,Moreover,the gas turbine did not fail again after 1 200 hour of assessment test,and the improvement scheme is reasonable and effective.

TK224.9+1

船舶与海洋工程动力系统国家工程实验室——海洋工程燃气轮机实验室；国家科技重大专项（2017-Ⅰ-0007-0008）