Cauasl Analysis Of External Corrosion And Design Of Coating System For Crossing Gas Pipelines In Sichuan-chongqing Region

As one of the most abundant natural gas and shale gas resources in China,sichuan-chongqing region has a highly developed system of natural gas pipeline network.In the process of natural gas transmission,however,external corrosion always threatens the safe operation of natural gas pipeline.Especially in the across pipelines,which is exposed directly to high-risk open environments,the leakage ofcaused by external corrosion will cause disastrous accidents such as fire and explosion.Casualties of particularly major person or huge pecuniary loss is caused immediately.Therefore,it become an urgent problem for the natural gas industry to speed up the in-depth analysis of the causes of pipeline external corrosion and the study of anti-corrosion measures.External corrosion of buried pipelines has been extensively researched by scholars at home and abroad and great achievements have been achieved.But,there is little mention of the study with external corrosion in pipelines exposed to atmospheric environment.Aimed at the pipeline network of a specialized gas pipeline operation enterprise(A enterprise for short)in Sichuan Province,18 pipelines with typical crossing characteristics were selected for field investigation.Through the investigation and research of the target pipe segment,appearance grading,corrosion pit depth,thickness of the external anti-corrosion coating,pipe wall thickness,surface temperature measurement was conducted to obtain operation status parameters of pipeline.Combined with modern analytical instrument test of coating samples,such as scanning electron microscopy(SEM),Fourier transform infrared spectrometer(FTIR),X-ray powder diffractometer(XRD),X-ray Energy Dispersive Spectroscopy(EDS),the significant factors affecting the external corrosion of pipelines were determined.Then,considering the actual operation and maintenance status of the pipeline and the complicated climate in Sichuan,a reliable scheme of pipeline external coating system is designed.The results of this study are intended to understand the external corrosion of crossing pipelines to ensure the safe and stable supply of natural gas in long-distance pipeline,and to provide basis for improving the management of sichuan-chongqing region pipelines.Moreover,it also provides reference for further research on coating of ground pipelines and anti-corrosion work of across pipelines.