乙烯装置氢气加热器U形弯管失效分析

某乙烯装置氢气加热器系外置式夹套换热器。该设备在检修时发现,U形弯管内侧有泄漏现象。通过取样进行化学成分、金相和腐蚀产物分析发现,U形弯管上存在的外表面裂纹是由内壁向外扩展至外壁所形成的,且呈多源裂纹特征,裂纹呈树枝状扩展,系典型的应力腐蚀裂纹。

Failure Analysis for Hydrogen Gas Heater U-bending in the Ethylene Plant

The hydrogen gas heater in ethylene plant is an external jacketed heat exchanger. During the equipment maintenance, leakage occurred in the inside of the U-bending. By sampling, a series of analytic tests were conducted as follows： chemical composition analysis, microstructure analysis as well as corrosion product analysis, and found that the outside surface crack on the U-bending was formed by the crack extending outward from the inner wall to the outer wall. The crack had multiple sources and showed dendritic extension, it belonged to typical stress corrosion crack.