Study of the mechanical properties of the gas pipeline metal after long-term operation in conditions of the North

The residual strength and technical condition of the material of 530-mm steel pipe (14KhGS) of main gas pipeline are estimated to ensure the safety of long-term operation of pipelines in climatic conditions of the North. The mechanical properties are determined using standard methods of mechanical testing in laboratory conditions. A full-scale pressure test up to failure is used to determine the actual values of the fracture toughness and safety factor of the pipe. Full-scale tests were carried out on a test bench, a computer-measuring complex which displayed the reaction of the object to the load. A pipe fragment was cut from the linear part of the main gas pipeline and welded with spherical plugs. The outer surface of the pipe was notched along the pipe axis. The depth of the notch was calculated such that the breaking load on the ligament section at the notch site corresponded to the working pressure of the gas pipeline. No significant changes in the mechanical properties of the pipe metal were revealed in the absence of visible corrosion and deformation damage during long-term operation of the pipe in the North. Impact tests did not reveal embrittlement of the metal of the tested pipes. Full-scale tests of a pipe with an artificially applied defect made it possible to calculate the value of the critical stress intensity factor, which allowed us to estimate the residual strength of a pipe with a longitudinal crack. The value of the strength criterion of the fracture mechanics indicates the preservation of a sufficiently high viscosity of sheet metal pipes. Similar tests of the pipes (of other size and made of other materials) operating in the main gas pipelines should be continued taking into account temperature ranges and material degradation after long-term operation.

1. Lubenskiy S. A., Yamnikov S. A. The influence of the duration of operation on the properties of metal pipes / Probl. Anal. Riska. 2013. Vol. 10. N 1. P. 58 – 63 [in Russian].

2. Kapitonova T. A., Struchkova G. P., Tarskaya L. Ye., Yefremov P. V. Analysis of risk factors for pipelines laid in the permafrost using GIS-technologies / Fundam. Issl. 2014. N 5. P. 954 – 958 [in Russian].

3. Sleptsov O. I., Struchkova G. P., Kapitonova T. A., Stepanov A. A. Influence of the natural fibrous additive on properties / Proceedings of VIII Eurasian Symposium on the problems of the strength of materials and machines for cold climate regions EURASTRENCOLD-2018. — Yakutsk: Tsumori Press, 2018. P. 604 – 607 [in Russian].

4. Makhutov N. A., Lebedev M. P., Bol’shakov A. M., Zakharova M. I. Features of emergency situations on gas pipelines in the North / Vestn. RAN. 2017. Vol. 87. N 9. P. 858 – 862. DOI: 10.7868/S0869587317090158.

5. Golikov N. I., Ammosov A. P. Strength of welded joints of tanks and pipelines operating in the conditions of the North. — Yakutsk: Izd. SVFU, 2012. — 323 p. [in Russian].

6. Filippov G. A., Livanova O. V., Dmitriev V. F. Degradation of metal properties during long-term operation of trunk pipelines / Stal’. 2003. N 2. P. 84 – 87 [in Russian].

7. Mochernyuk N. P., Krasnevsky S. M., Lazarevich G. I., Sorokhin Ts. D., Gerasimchik I. I. The influence of the operating time of the main gas pipeline and the working gas pressure on the physicomechanical characteristics of pipe steel 19G / Gaz. Promyshl. 1991. N 3. P. 34 – 36 [in Russian].

8. Lyakishev N. P., Kantor M. M., Voronin V. N., Timofeev V. N., Sharygin Yu. M. Investigation of the metal structure of gas pipelines after their long-term operation / Metally. 2005. N 1. P. 3 – 6 [in Russian].

9. Makhutov N. A., Permyakov V. N., Kravtsova Yu. A., Botvina L. R. Assessment of the condition of the product pipeline material after its long-term operation / Zavod. Lab. Diagn. Mater. 2007. Vol. 73. N 2. P. 35 – 43 [in Russian].

10. Syromyatnikova A. S. Degradation of physical and mechanical condition of the main gas pipeline metal at long operation in the conditions of the cryolitozone / Fiz. Mezomekh. 2014. Vol. 17. N 2. P. 85 – 91 [in Russian].

11. Golikov N. I., Litvintsev N. M. Change in mechanical properties and structural parameters of metal structures operated in the North / Zavod. Lab. Diagn. Mater. 2015. Vol. 81. N 12. P. 60 – 65 [in Russian].

12. Makhutov N. A., Bolshakov A. M., Zakharova M. I. Possible scenarios of accidents in reservoirs and pipelines at low operating temperature / Inorganic Materials. 2016. Vol. 52. Issue 15. P. 1498 – 1502.

13. Ivanov A., Bolshev K., Bolshakov A., Syromyatnikova A., Alexeev A., Burnashev A., Andreev Y., Prokopiev L., Grigoriev A., Cheremkin M., Efimov V., Golikov N., Makharova S., Zhirkov A. The corrosion damage mechanisms of the gas pipelines in the Republic of Sakha (Yakutia) / Collector: E3S Web of Conferences. 2019. P. 03002.

14. Bol’shakov A. M., Syromyatnikova A. S. Destructions and Damages of Objects of the Main Gas Pipeline at Long Operation in Conditions of the Arctic / Nauka Obrazov. 2015. N 4(80). P. 94 – 99 [in Russian].

15. Makarov G. I. Quality control of welded pipes for gas pipelines for compliance with regulatory requirements for static and dynamic crack resistance / Nauka o zemle. 2018. N 3(292). P. 112 – 124 [in Russian].

16. Varlamov N. V., Polikarpov K. V., Makarov G. I., Goritsky V. N. Field tests of pipes and repair structures at the testing range of VNIIST OJSC / Truboprovod. Transport. Teor. Prakt. 2010. N 6(22). P. 4 – 6 [in Russian].

17. Krasovsky A. Ya., Krasiko V. N. Crack resistance of steel pipelines. — Kiev: Naukova Dumka, 1990. — 176 p. [in Russian].

18. Larionov V. P. Electric arc welding of structures in the northern version. — Novosibirsk: Nauka, 1986. — 256 p. [in Russian].