某船用主锅炉过热器胀口处渗漏故障分析与排故措施

Fault Analysis of Leakage at the Expanded Tube Joint of a Marine Main Boiler Superheater and Measures Taken for Its Elimination

针对某船用主锅炉过热器胀口处渗漏问题 ,系统地进行了故障分析研究。通过胀口弹塑性有限元计算分析、不同材质的管子冷热态胀接性能对比试验和胀接接头应力释放试验 ,揭示了胀口渗漏的原因———管子与集箱材料不匹配 ,两种材料的热膨胀系数相差过大 ,胀口在经过多次启动、停炉的冷热循环后 ,残余接触应力大幅度下降 ,导致胀口渗漏。根据计算分析和冷热态试验结果 ,选用新研制的管材GH984 ,同时采取其它措施以提高安全可靠性 ,从而最终消除产生胀口渗漏的因素。

With regard to the leakage detected at an expanded tube joint in a marine main boiler superheater the authors have conducted systematically a fault analysis and research. An elasticity/plasticity finite element calculation and analysis of the expanded tube joint was performed. A contrast test was conducted of the cold and hot state expansion joint performance of tubes made of different materials followed by a stress release test of the expanded tube joint. On the basis of the above tests, the mismatch of tube and header material has been identified as the cause of the expanded tube joint leakage. Due to the excessively great difference in thermal expansion factor of two different materials the residual contact stress of the expanded tube joint has been drastically lowered after the latter had undergone alternating hot and cold cycles during numerous boiler startups and shutdowns. This ultimately led to the expanded tube joint leakage. Based on the results of calculation and analysis as well as cold and hot state tests the authors have selected a newly developed tube material GH984 to serve as a replacement. In addition, other measures were also taken to enhance operation safety and reliability, thus effectively eliminating all leakage causing factors.