Scholarly record

ENHANCEMENT OF PIPELINE CATHODIC PROTECTION DESIGN PROCEDURE

В. А. Гриневич

Abstract

Underground pipeline corrosion protection is an urgent task to be addressed by the companies that operate gathering and transmission pipeline systems. The key component of pipeline protection procedure is a feasibility study of the planned cathodic protection program, which, in its turn, poses a number of requirements for calculating basic parameters of the entire system. The regulatory calculation procedures do not allow resolving all tasks. The same can be stated about modern software which is based on the same regulatory procedures or the universal finite-volume method for modeling and calculation. As a result, the accuracy of this software significantly depends on the validity of the initial data. The present article examines the simple analytical method for calculating potential distribution along the transmission pipeline with regard to the impact of the voltage cone around the anode bed. The voltage cone occurs due to current discharge from the anode. According to the simple analysis, the potential distribution along the pipeline is governed by the exponential law in the absence of shielded electrical grounding, while the decrease in potential is registered in the vicinity of the anode ground bed. Thus, specific electrical resistivity of soil within the field of cathodic protection currents covering the same area as the so-called anode voltage cone around the anode ground bed is regarded as a key factor that significantly decreases the length of the protected zone. In addition, resistivity-to-soil along the entire length of pipeline can be neglected without prejudice to design quality as compared with the transient resistivity of pipeline coating. In order to enhance the quality of design calculation, it is proposed to improve the credibility of resistivity-to-soil calculation within the field of cathodic protection currents, while the number of soil resistivity measurements along the pipeline route can be decreased by confining the area of measurements to the radius defined by the multi-factor numerical analysis.

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