PSI - Issue 16

Roman Dzhala et al. / Procedia Structural Integrity 16 (2019) 218–222 Roman Dzhala , Vasyl’ Dzhala, Roman Savula, Oleh Senyuk, Bohdan Verbenets’ / Structural Integrity Procedia 00 (2019) 000 – 000 5

222

in n mgin R U i /  ,   м 2 ,

(11)

where

U in = U mg – U gg – U p . (12) The resulting value of the transient resistance U in includes the insulation resistance R in and the polarization resistance R pol on the investigated site. It can be used at calculating the cathodic polarization of the UP. According to the TR components, one can determine the average polarization resistance per unit of the UP surface using the following relation: R pol = R mgin – R in . (13) Taking into account the area of the insulation damages (Dzhala at al . (2018)), polarization resistance in the site of contact of the UP metal with the soil can be estimated. The obtained values of the UP polarization resistance can be used for the estimation of corrosion rate in the places of insulation damage of pipelines and other underground metal structures under operation. Examples of determining the distributions of TR and its components along the UP by measurements using the BVC and VPP at the inspection of gas transit pipelines are presented in the following papers: Nykyforchyn at al. (2009), Dzhala at al. (2017, 2018). 6. Conclusions Components of transient resistance of underground pipelines are required during the design and control of their anti-corrosion protection and diagnostics of their technical condition. Disadvantages of traditional contact methods of measuring TR are shown. The new possibilities for determining the distribution of TR "pipe – earth" and its components (resistance of insulation, soil, polarization) along the pipeline route by contactless measurements of current (by the BVC device) and contact measurements of potentials (by the VPP device) are described. Implementation of the developed method significantly increases the efficiency and informativeness of diagnostics of underground pipelines in order to prevent damages and prolong lifetime. References Dikmarova, L.P., Kornienko, V.Yu., 2002. Determination of dimensions of through-thickness damages in underground pipeline insulation. Information Extraction and Processing 16(92), 9 – 12. [In Ukrainian] DSTU 4219-2003. Steel main pipelines. General requirements for corrosion protection. Depzhstandart of Ukraine, Kyiv, pp. 74. [In Ukrainian] Dzhala, R.M., Dzhala, V.R., Ivasiv, I.B., Rybachuk, V.G., Uchanin, V.M., 2018. Electrophysical methods for nondestructive testing of defects in structural elements. in “ Technical diagnostics of materials and structures: Reference manual ”, Vol. 4. In: Nazarchuk, Z.T. (Ed.). Prostir-M, Lviv, pp. 356. [In Ukrainian] Dzhala, R.M.,Verbenets' , B.Ya., Mel’nyk, M.I., Mytsyk, A.B., Savula, R.S., Seмеnyuk , O.M., 2017. New methods for the corrosion monitoring of underground pipelines according to the measurement of currents and potentials. Materials Science 52(5), 732 – 741. Herasymenko, R.Yu., Vasylev, H.S. and Herasymenko, Yu.S., 2017. The increase of corrosion monitoring validity for low-carbon steel in tap water. Materials Science 53(3), 337 – 342. Mansfeld, F., 1976. The polarization resistance technique for measuring corrosion current, in “ Advances in corrosion science and technology ” . Springer, USA, pp. 163 – 262. Nykyforchyn, H.M., Polyakov, S.G., Chervatyuk, V.A., Orynyak, I.V., Slobodyan, Z.V., Dzhala, R.M., 2009. Strength and durability of oil and gas pipelines and storage tanks, in “ Fracture mechanics and strength of materials: Reference book ”, Vol.4. In: Panasyuk, V.V. (Ed.). Spolom, Lviv, pp. 504. [In Ukrainian] Strizhevsky I.V., Zinevich A.M., Nikolsky K.K., Glazkov, V.I., Kotik, V.G., 1981. Protection of metal structures from underground corrosion: Handbook. Nedra, Moskva, pp. 294. [In Russian] Zvirko, O.I., Mytsyk, A.B., Tsyrulnyk, O.T., Gabetta, G., Nykyforchyn, H.M., 2017. Corrosion degradation of steel of long-term operated gas pipeline elbow with large-scale delamination. Materials Science 52(6), 861 – 865.