Weibin Wang

Using Computer Software to Simulate AC Interference and Mitigation Measures of Buried Pipelines

Due to rapid development of HVAC transmission lines, AC electric railways and oil and gas pipelines, these lines will inevitably cross or lie parallel to each other. At these positions, pipelines will be subject to serious interferences. In most situations, only the results of an interference are detectable, with no clue as to what caused the problem. This paper presents a new method designed to solve AC interference. When the interference source cannot be determined, AC voltages of buried pipelines are first measured and the AC interference is simulated. Furthermore, a mitigation method is built using computer software. After mitigation devices are installed on the pipeline, AC voltages are simulated once more and compared with field-measured values. The result shows that the simulated AC interference and the subsequent mitigation method built with computer software are more efficient.

Study of Numerical Simulation of Region CP System in a Large Pipeline Station

Newly built pipeline stations in China have widely used a cathodic protection system using flexible anodes and grid anodes. However, there may be some places in a pipeline station where the lack of protection may not be apparent because the data collected from several test posts cannot accurately represent the entire protection system in the station. After numerical simulation of an ideal case without interference from other metals, the results show uniform distribution in a flexible anodes system. But, if a grounding system exists in the model, interference will greatly influence the potential distribution. The result shows the potential distribution is no longer uniform and portions of pipe near the grounding system may not be protected. Due to the differences between characteristics of polarization in the grounding system and the pipeline, the addition of a sacrificial anode system is advised.

Design Cathodic Protection Ground-bed Arrangement with Finite Element Analysis Method

A more flexible grounding resistance calculation method, based on finite element analysis (FEA) method, is suggested, which is especially suitable for optimization cathodic protection (CP) ground-bed arrangement. As compared with traditional grounding resistance evaluation method, which is only suitable for the case of each anode rod in a straight line, the FEA method can calculate grounding resistance of ground-bed at any arrangement. Moreover, a realistic soil resistance rate, usually varying with depth, can be included in calculation model. The detailed steps for this method can be summarized as follow: building a 3D geometric model according to general design, meshing the geometric model, setting reasonable boundary conditions, solving and post-solving the grounding resistance with ohmic law. To further explain this procedure, a realistic CP ground-bed displacing project is presented, which includes displacing the original CP ground-bed firstly and re-designing a new ground-bed within a limited area (5m×30m). A new CP ground-bed design, compared with traditional design, 2×7, 14 anode rods dispersed in two parallel groups, are calculated firstly. The results show that this design can not meet the grounding resistance requirement. Another 4 designs, with anode rods arranged as 2×6, 2×8, 2×9, 3×6 are calculated respectively. Finally, the design 2×8 is recommended from the view of economy and practicability.

Safe Evaluation of AC Interference on an Oil Products Pipeline

Stray current interference may cause pipeline corrosion, which will result in premature failure of pipeline and potential safety problem to the persons who would touch the pipe during the work. The results of systematic field survey of the AC interference on an oil products pipeline showed that the range of quasi-stable AC interference was more than 20 km. Moreover, the risk of two separate pipeline sections among them was medium or worse. The relationship among corrosion rate, AC interference voltage, and AC interference current density was summarized after on-site tests. Finally, some mitigation suggestions were proposed.