Investigation of pitting corrosion monitoring using field signature method

An Overview of Major Experimental Methods and Apparatus for Measuring and Investigating Erosion-Corrosion of Ferrous-Based Steels

“…Although electrochemical techniques can gain the corrosion current easily and rapidly, they are not suitable for erosion-corrosion monitoring in the field, especially for energy pipelines, due to the inability to directly measure the non-Faradaic part of the metal loss [9,37]. Therefore, electrical resistance (ER) probes as shown in Figure 8 are used to monitor the total metal loss caused by erosion-corrosion in most industrial applications [76,77,[79][80][81][82][83][84][85]. Figure 8a shows a typical erosion-corrosion ER probe with its sensing part in a rectangular form.…”

“…Therefore, some modified ER sensors are developed to monitor the non-uniform corrosion in pipelines. Figure 10 shows two kinds of modified ER sensors which are defined as the field signature method (FSM) [81] and ring pair electrical resistance sensor (RPERS) [82], respectively. The basic principle of these sensors involves dividing the pipe into small sections, and the resistance of each section is on-line monitored.…”

Current deflection NDE for the inspection and monitoring of pipes

“…Potential Drop (PD) methods are able to successfully monitor crack growth from the change in resistance between two electrodes as the increasing defect size lengthens the path of the current [37]. The Field Signature Method (FSM) is based on potential drop methods, and has been used to monitor internal erosion, corrosion and cracking [38], and more recently the ability to characterise pitting has been improved [39]. Galvanic contact with the conductor is required for both PD and FSM, hence insulation must be removed and the methods are not suitable for scanning.…”

Inner defect depth detection using a multifrequency alternating current potential drop technique

“…10 Low-frequency ACPD or DCPD should be used in these cases. There may be many defects in a measured pipe and their locations are random, so a reference voltage cannot be measured.…”

“…In this case, a reference plate, which is insulated from the outer surface of the measured pipe so that defects cannot occur, is electrically connected in series with the injecting electrodes, as shown in Figure 2. 10,11 Any temperature difference between the pipe and reference plate can, however, significantly affect the measurement results. Use of equations (2) and (3) can eliminate the effect of temperature because V 1 and V 2 are measured under the same temperature conditions.…”