In-Loop Tests of Probe for Flow-Accelerated Corrosion Monitoring in Power-Plant Feedwater

Abstract

Flow-Accelerated Corrosion (FAC) is a serious problem for power plants. A monitoring technique was developed to determine pipe wall thickness from electrical resistance measured along the pipe length. As the pipe wall thins and the electrical resistance increases, the corrosion rate can be estimated. Although average resistance represents wall thickness well, the data can be highly scattered, reflecting electrical noise and leading to poor sensitivity for corrosion rate. To reduce the problem, the three-point delta method has been investigated in two parts; 1) in the air in a furnace; 2) in water in a recirculating loop. The new method improved the variance, R², and data scattering in both furnace and loop tests. At ~140°C, the standard deviation of resistance was reduced from ±0.58 μΩ to ±0.11 μΩ and from ±0.24 μΩ to ±0.09 μΩ respectively. The new technique resulted in significantly improved sensitivity of FAC monitoring.