PSI - Issue 81

Roman Dzhala et al. / Procedia Structural Integrity 81 (2026) 98–101

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transition resistance and its components (insulation, soil, polarization resistances) in different sections of the UP (Dzhala et al. (2019)). The purpose of this work is to substantiate a new method of comprehensive non-destructive testing of ACP UP based on NCM in combination with contact electrometry. We will analyze the shortcomings of traditional methods. We will show the advantages of non-contact methods and the synergy of using non-contact and contact methods of non-destructive testing together. This article shows the possibilities of the electromagnetic method for the prompt detection of UP sections with unsatisfactory anti-corrosion protection. Let us show an example of practical non-destructive testing of anti-corrosion protection parameters during diagnostic inspections of a main gas pipeline. 2. Analysis of the shortcomings of traditional methods of the ACP UP testing The complexity of diagnosing UP is due to the lack of a single point of access to the pipes and their long lengths. The importance of the problem determines the large number of various studies and scientific and technical developments. The problem currently does not yet have sufficiently complete solutions that would satisfy all the needs of practice. Traditionally, the ACP of the UP is monitored by contact electrometric methods from the ground surface (Ostapenkoet al. (1988), DSTU (2003)). Electrochemical corrosion protection of underground metal structures is controlled by contact measurements of electric potentials. The disadvantages are the local nature of the control and the need for a large number of contacts with the pipe metal and the environment (soil). Contact measurements make it possible to detect local damage to the insulation of the UP, but do not provide their quantitative estimates. Internal pipelines inspection (ILI) only detects existing damage to the pipe metal, but does not provide the necessary information about the state of protection against soil corrosion. It is important that the currently available regulatory documents do not contain methods for determining a number of important indicators (parameters) of the state of the cathodic protection system of pipelines, such as: - distribution of cathodic protection current consumption between branches and sections of pipelines, which makes it possible to control the efficiency of the operation of cathodic protection systems (CPS) and identify and eliminate irrational current consumption; - cathodic protection current density in sections of the UP (and not averaged over the area of the CPS, which has no clear boundaries); - pipe-to-ground transition resistance and its components (specific resistances of insulating coatings and polarization) in different sections of the UP. In particular, it should be noted that according to the method of monitoring the condition of the protective coating of the UP during operation, the transient electrical resistivity of the coating on a section of the pipeline length, determined by the length L of the zone of action of one CPS, is calculated by the ratio of the average value of the ohmic component of the protective potential on the length of the zone of action of this CPS, to the current density i (A/m 2 ), which is calculated by the ratio of the CPS current strength I(A) to the pipe surface area (m 2 ) on the named section L. However, in real operating conditions, since the protective potential changes along the UP non-monotonically (there are many minimum and maximum values), it is practically impossible to determine the length L of the zone of action of one CPS with sufficient accuracy, and therefore, it is impossible to determine the real value of the current density i. Therefore, as a result, some value of the coating resistance is obtained for a rather long (tens of km) section of the UP, and the benefit of such an estimate is doubtful. The mentioned shortcomings are eliminated by using non-contact methods of UP examinations. The efficiency and informativeness of UP examinations are significantly increased by using methods of NCM (Dzhala et al. (2024)). 3. Non-destructive testing of the UP ACP. Advantages of non-contact methods To implement non-contact current measurements (NCM), theoretical and experimental studies were conducted. The physical model of the problem is an underground pipeline with an insulating coating and cathodic polarization, electric currents and components of the electromagnetic field. Based on the developed mathematical model, the connections of informative field characteristics with UP parameters were investigated. Methods for quantitative non-destructive testing of the values of parameters of the NDT ACP were developed. Functional and schematic diagrams have been developed, and special portable devices have been manufactured. NCM equipment is intended for non-contact measurements of currents and depth of UP. MPP devices are intended for contact measurements of alternating and direct electric voltages and determination of ohmic and polarization potentials (Dzhalaet al. (2024)). The devices are equipped with a GPS system for determining coordinates during diagnostic examinations of UP.