某气田弹簧管压力表失效与汞腐蚀

目的针对某气田井口压力表发生刺漏的情况,分析压力表弹簧管发生刺漏的原因。方法采用无损检测渗透法、金相显微镜、扫描电子显微镜及其能谱分析仪的方法或设备,检查其内部结构和弹簧管表面损伤情况,对损伤部位进行观察与分析。结果弹簧管上有一穿透性的裂纹,以沿晶方式扩展,并在断口的晶粒夹杂处和表面检测到少量的汞元素和CO_2腐蚀产物。结论确定该压力表弹簧管发生刺漏是其材质Monel合金中的合金元素Al和Cu与天然气中的汞形成汞齐而发生了汞腐蚀导致开裂的。

Failure of Spring Pressure Gage and Mercury Corrosion in Gas Field

Objective To analyze causes for leaking of spring tube of pressure gage based on leaking of pressure gage of certain gas field. Methods The inner structure and surface damage of spring tube were observed, and the damage regions were detected with permeating method of nondestructive testing, metallographic microscope, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Results There was a penetrative crack extending along the crystal in the tube. The mercury element and a bit of CO2 corrosion product were detected in the mixing region between and on the crystal grains. Conclusion The leaking of spring tube in the pressure gage is resulted from the mercury corrosion that the Al and Cu elements in the spring tube made from Monel alloy formed amalgam with Hg in the gas and the cracking of the tube under the inner pressure action.