阀室引压管放电烧蚀失效分析

近年来,我国油气管道沿线阀室遭受的交、直流电干扰日益严重,由此引发的阀室引压管放电烧蚀问题逐渐凸显,亟需开展相关研究来弄清阀室引压管放电烧蚀的规律和机制。为此,以西气东输天然气管道某阀室引压管的放电烧蚀为例,搭建了实验室放电烧蚀平台,采用实验室模拟实验、微观分析以及现场测试相结合的方法,对该阀室引压管放电烧蚀的规律和机制进行了研究。结果表明:(1)当两根引压管间的交直流电压差大于4 V且存在接触引弧时便可以观察到明显的放电现象;(2)随着引压管间电压差和回路电流的增大,其能量升高,引压管放电烧蚀越严重;(3)直流放电烧蚀情况下阴、阳极呈现出明显不同的烧蚀形貌,阳极区烧蚀更加严重,其烧蚀坑呈现凹坑且烧蚀坑中没有明显的烧蚀产物沉积,阴极区烧蚀深度较浅,表面沉积一层烧蚀产物,而交流放电烧蚀情况下阴阳极烧蚀区域形貌基本一致,无明显差异。结论认为:该阀室的引压管放电现象是一种弧光放电,可以通过固定引压管、增大引压管间距以及阀室的交直流排流等措施来避免该现象的发生。

Analysis of failures induced by the discharge ablation of pressure-guiding tubes in valve chambers

In recent years, the valve chambers along oil and gas pipelines suffer from AC/DC (alternating current/direct current) interference more and more seriously in China. The induced discharge ablation of pressure-guiding tubes in valve chambers gets serious gradually. Therefore, it is urgent to figure out the laws and mechanisms of discharge ablation of pressure-guiding tubes in valve chambers. In this paper, an experimental discharge ablation platform was established with the discharge ablation of pressure-guiding tubes in a certain valve chamber of West-to-East Gas Pipeline as an example. The discharge ablation laws and mechanisms were analyzed by means of laboratory simulation experiment, microscopic analysis and field test comprehensively. It is shown that the discharge ablation is apparent when the AC/DC voltage difference between two pressure-guiding tubes is over 4 V and there is touch striking arc. As the voltage difference between pressure-guiding tubes and the circuit current increase, the energy rises and the discharge ablation of the pressure-guiding tubes gets more serious. In the mode of DC discharge, the ablation feature at the positive pole is different from that at the negative pole. In the region of positive pole, the ablation is more serious and the ablation dent is concave without obvious deposit of ablation products. In the region of negative pole, the ablation is shallower and the ablation products are deposited on the surface. In the mode of AC discharge, the ablation features at the positive and negative poles are basically coincident without apparent difference. It is concluded that the discharge of the pressure-guiding tube in this valve chamber is a phenomenon of arc discharge, which can be avoided by fixing the pressure-guiding tube, increasing the spacing between them and performing AC/DC drainage of the valve chamber.