PSI - Issue 40

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Burnashev A.V. at al. / Structural Integrity Procedia 00 (2022) 000 – 000

* Corresponding author. Tel.: +79681548286. E-mail address: l.prokopyev@yandex.ru 1. Introduction

A.V. Burnashev et al. / Procedia Structural Integrity 40 (2022) 90–96

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The fast industrial growth in the Far East in particular, and Russia in general, is associated with the construction of extensive industrial facilities, most of which belong to the category of hazardous industrial facilities. These are long-distance main oil and gas pipelines, storage tanks for oil and oil products. The smooth operation of these complex technical systems must be ensured by the reliability and dependability of the structures and requires close attention from the supervisory authorities. On the territory of Yakutia, Taas-Tumus – Berge – Yakutsk gas pipeline has been in operation since the 70s. It provides the city of Yakutsk and surrounding areas with natural gas. This gas pipeline is a unique metal structure, laid and operated in difficult geological conditions, in areas of permafrost and with great temperature fluctuations. In such conditions, the gas pipeline is exposed to additional non-project loads, which are periodic and manifest themselves mainly in the winter. Under the influence of these factors and long service life, today the pipeline is considered to be almost exhausted. Every year, gas consumption increases. It requires the pipeline to work at the maximum possible pressure. Operating the pipeline with an exhausted resource poses a significant danger at such pressure: there is a threat of brittle fractures due to structural degradation of the pipe metal, which reduces the resistance of the material to crack propagation. In addition to calculations based on the assessment of the residual resource, such situations require periodic monitoring and collection of information about the real state of the object using methods sensitive to structural changes. Despite the sufficient knowledge of the problem of assessing the reliability, resource and material degradation of long-running structures, this topic is one of the central issues to ensure technological safety, since the types of calculations available today do not fully take into account the change in the structural state of pipe material. This paper aims to develop a method for the rapid assessment of the resistance of metal of long-running main gas pipelines to brittle fracture using a non-destructive method of control, for monitoring and improving operational reliability. Nomenclature - impact strength - crack resistance V - the speed of sound admiss - admissible cr - critical 2. Materials and methods of experiment To accomplish this goal, we performed the tests on the impact bending of samples from steel of the main gas pipeline and studies of the acoustic properties of steel pipes. In all experiments, samples from 530x9 mm pipes of the same manufacturer and one type of rolling were used. It was normalized pipe steel made (according to the certificate) in 1964 from 09G2S steel according to the technical specifications of VTU ChMTU-UKRNITI 537 – 64 at the N.V. Ilyich Zhdanovskiy Metallurgical Plant. The steel was investigated in various states: 1 — emergency stock (stored in conservation for more than 50 years), 2 – after 50 years of operation, 3 - after 50 years of operation with additional thermal deformation ageing (deformation 10%, subsequent annealing at 650 С, s co oling in the oven). Thermal deformation ageing was performed in order to imitate the achievement of limits of chosen material. As a limit state we consider the value of impact toughness, which is less than or equal to the standard value specified