常减压蒸馏装置的电脱盐设备中电极棒断裂分析

Study on Fracture of Electrode Rod of Electro-static Desalter in Atmospheric-vacuum Distillation Unit

某常减压蒸馏装置的电脱盐设备中电脱盐罐中的6根电极棒于2009年3月更换,2011年1月1号正极棒发生断裂。电极棒鼻根部分的内外两层套管均断裂。宏观检查发现1号正极棒外管球头的腐蚀麻坑象"虫子"咬过,呈典型的电蚀特征。内管及芯部铜导线有腐蚀坑,含Cu元素,表面有铜绿,都发生电蚀。断口有二次裂纹及孔洞,显示脆性断裂特征,而外管断口及蚀坑处横截面未发现裂纹、晶间腐蚀迹象,说明是外力造成1号正极棒断裂。电极棒、高压电连接器和电极板之间的软性连接接触不良,使正极棒与电极板间的电路阻断,电流成为杂散电流,正极棒作为阳极,很快发生电蚀。在流体冲击下因电蚀减薄,强度不足在支点处断裂,宜定期检查、更换并采用新型电脱盐设备。

Six electrode rods in the electro-static desalter of an atmospheric-vacuum distillation unit were replaced on March 2009, and No. 1 electrode rod fractured during operation on January 2011. The two conduit tubes on the nose root of the electrode rod all fractured. The macro examination found many pits on the end of electrode rod, looking like to be bitten by worms and showing electrical erosion characters. Covered with Cu and patina, the inner tube and copper lead also suffered from electrical erosion. There were subcracks and cavities on the fracture, which featured brittle rupture. On the cross section of outer tube no cracks and intergranular corrosion were found, which indicated that the fracture of No. 1 electrode rod was induced by external force. Due to the bad contact of soft join connection among the electrode rods, high voltage coupler, electrode boards, working current becoming stray current and the positive pole becoming anode, the positive rod as anode would suffer from rapid electric erosion. As corrosion thinning lowered the strength, the electrode rod fractured on pivot point under liquid impingement. Therefore, the system should be periodically inspected, equipment should be replaced or new equipment should be applied when necessary.