场指纹法(Field Signature Method, FSM)的本质是电位矩阵法。FSM管道腐蚀监测系统将测量电极矩阵布局在钢制管道外壁上, 并往管壁中通入恒定电流, 利用电极间电压与管壁厚度的对应关系, 通过测量极间电压的变化来实时监测管壁腐蚀。FSM系统已经成功应用于国内外的各种油气管道腐蚀监测, 在全面腐蚀、局部冲蚀监测方面有很好的精度(±0.5%WT, Wall Thickness, 壁厚), 但坑蚀监测精度较差(±15%WT)。本文在介绍FSM原理的基础上, 提出了小腐蚀坑的定义, 分析了小腐蚀坑不可识别问题形成的原因及其影响, 并提出了一种解决方法——主辅电压法(Major and Assistant Voltage Method, MAVM)。大量的仿真分析表明, 主辅电压法可以大幅提高坑蚀的监测精度, 对发展和完善FSM理论和实际应用有较大意义。

Field signature method (FSM) is an essentially potential-array method which arranges an array of measuring electrodes on external surface of pipeline and a constant current is injected into it. As there is a definite relationship between potential drop and wall thickness, FSM can monitor the degree of corrosion. FSM has been applied the field of oil and gas pipeline corrosion monitoring successfully because of its high-precision up to ±0.5%WT (wall thickness) in general corrosion monitoring and localized erosion monitoring. However, its precision in pit corrosion monitoring is relatively low (only ±15%WT). This paper introduces the principle of FSM, defines the small pit corrosion and points out the problem of unidentifiable small corrosion pits, and analyzes the cause and influence and presents a solution named major and assistant voltage method (MAVM). A large number of simulations demonstrate the feasibility of MAVM that is able to improve the precision of small pit corrosion monitoring greatly. It is significant for devolvement and perfection in FSM theory and practical applications.