PSI - Issue 16

Lubomyr Poberezhny et al. / Procedia Structural Integrity 16 (2019) 141–147 /XERP\U 3REHUH]KQ\ et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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serviceability. Similar regularities were earlier noted for material of drill pipes and sea pipelines (Maruschak et al. (2013); Kryzhanivskyy et al. (2014)). 4. Conclusion Corrosion behaviour of the low carbon ferrite pearlite St 20 steel of gathering pipeline under the mutual effect of the corrosion environment, mechanical stresses and hydrate formation was studied. The regularities of corrosion degradation of the steel under investigated conditions were determined. A change in the mechanism of corrosion in chloride media was found at increasing chloride concentration from 2.5 mol/L to higher concentration. The revealed more significant influence of mechanical stress on localized corrosion rate than on uniform corrosion one was associated with the formation of local galvanic elements on the metal surface and intensification of the metal dissolution in the tensile zone due to the weakening of interatomic interaction caused by increase the distance between grains. A negative effect of the preliminary exposure of the steel to gas hydrates on the durability of the pipe steel in air and in corrosion environment was defined. The durability of the pipe steel in air was reduced by 25%, and in the ME5 solution – by 15%. The reason of a significant decrease in durability of the steel specimens after exposure in gas hydrate was obviously associated with increasing of corrosion damaging of the specimen surface as a result of the aggressive action of gas hydrates. References Chernov, V.Y., Makarenko, V.D., Kryzhanivs'kyi, E.I., Shlapak, L.S., 2002. Causes and mechanisms of local corrosion in oil-field pipelines. Materials Science 38, No. 5, 729 – 737. Hrabovskyy R., Mazur M., Hrytsanchuk A., Habinskyy V., 2017. Assessment of destruction conditions of the long-term operation gas pipeline. Scientific Journal of TNTU (Tern.) 87, No. 3, 38 – 47. Kryzhanivskyy Ye.I., Poberezhnyy L.Ya., 2001. Perspektyvy vykorystannya avtomatyzovanykh vyprobovuvalnykh system z EOM dlya otsinky koroziyno-mekhanichnykh vlastyvostey materialiv morskykh truboprovodiv. Problemy sozdanyya novykh mashyn y tekhnolohyy. Nauchnye trudy K·HPU. No. 1 (10), 21– 23. (In Ukrainian) Kryzhanivskyy Ye.I., Poberezhnyy L.Ya., 2004. Metodolohiya doslidzhennya deformatsiyi ta ruynuvannya truboprovidnykh system. Materialy III mizhnarodnoyi konferentsiyi. Mekhanika ruynuvannya materialiv i mitsnist konstruktsiy. Lviv, pp. 419 – 424. (In Ukrainian) Kryzhanivs’kyi, E.I ., Hoisan, I.M., Student, O.Z., 2014. Specific features of the growth of a tigue cracks in 36G2S steel of drill pipes after there covery heat treatment. Materials Science 50, No. 1, 92 – 97. Kryzhanivskyi, Y.I., Ivasiv, V.M., Rachkevych, R.V., Vasylyshyn, V.Y., 2015. Fatigue strength of oil well tubings screwed joints in wells curvelinear sections. Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu 5, 14 – 21. Maruschak, P., Poberezhny, L., Pyrig, T., 2013. Fatigue and brittle fracture of carbon steel of gas and oil pipelines. Transport 28, No. 3, 270 – 276. Maruschak, P., Panin, S., Danyliuk, I., Poberezhnyi, L., Pyrig, T., Bishchak, R., Vlasov, I., 2015. Structural and mechanical defects of materials of offshore and onshore main gas pipelines after long-term operation. Open Engineering 5(1), 365 – 372. Obanijesu, E.O., Pareek, V., Gubner, R., Tade, M.O., 2011. Hydrate formation and its influence on natural gas pipeline internal corrosion. Nafta 62(5 – 6), 164 – 173. Poberezhny, L., Maruschak, P., Hrytsanchuk, A., Poberezhna, L., Prentkovskis, O., Stanetsky, A., 2017a. Impact of gas hydrates and long-term operation on fatigue characteristics of pipeline steels. Procedia Engineering 187, 356 – 362. Poberezhnyi, L.Y., Marushchak, P.O., Sorochak, A.P., Draganovska, D., Hrytsanchuk, A.V., Mishchuk, B.V., 2017b. Corrosive and mechanical degradation of pipelines in acid soils. 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Electrochemical methods for the evaluation of the degradation of structural steels intended for long-term operation. Materials Science 52(4), 588 – 594. 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, No 6, 861 – 865.