某气田集输管线失效原因分析
Analysis of Failure Causes of Gathering and Transportation Pipeline in a Gas Field

某气田集输管线热缩套下存在严重外腐蚀导致管线失效，经开挖发现，集输管线热缩套普遍无粘结力并剥离，多处发现热缩套内有水存在，钢管表面布满腐蚀坑，腐蚀速率0.08 mm/a~0.88 mm/a，通过化学成分分析、金相分析、硬度分析、强度性能分析、防腐层理化测试与形貌分析、腐蚀形貌分析、腐蚀产物截面分析、腐蚀产物成分分析等方法对其失效原因进行分析。结果表明：失效直接原因为管体外壁发生了严重的氧腐蚀，根本原因管线运行温度(>50℃)超过防腐层设计耐温能力，导致防腐层老化严重，失去保护作用。根据造成失效的原因，提出了具体对策。
There is serious external corrosion under the heat shrink sleeve of a gas field gathering pipeline, which leads to the failure of the pipeline. After excavation, it is found that the heat shrink sleeve of the gathering pipeline generally has no bonding force and is peeled off. Water is found in the heat shrink sleeve in many places, and the surface of the steel pipe is covered with corrosion pits, and the corrosion rate is 0.08 mm/a~0.88 mm/a. The failure causes were analyzed by chemical composition analysis, metallographic analysis, hardness analysis, strength analysis, physical and chemical test and morphology analysis of anti-corrosion layer, corrosion morphology analysis, corrosion product cross section analysis, corrosion product composition analysis and other methods. The results show that the direct cause of failure is serious oxygen corrosion in the outer wall of the pipe, and the root cause is that the operating temperature of the pipeline (>50？C) exceeds the designed temperature resistance of the anti-corrosion layer, resulting in serious aging of the anti-corrosion layer and loss of protection. According to the causes of failure, the specific countermeasures are put forward.