PSI - Issue 40

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

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

Figure 5. Calculation of the residual life of the main gas pipeline to change the speed of sound.

The residual life, presented in Figure 5, is determined by plotting the function V (t) “sound speed - operation time” using formula 2. Two curves are constructed: the first V, the second V 1 as the lower bound of the function V with an accuracy interval of minus 0.5%. In the same coordinates, two straight lines V f and V cr are built parallel to the abscissa axis and straight line t f = 50 years parallel to the ordinate axis. The t cr is the abscissa of the intersection point of the curve V 1 and the straight line V cr . The point of intersection of V f and t f is marked by the point Z. This point must fall within the interval of the function accuracy between V and V 1 or over the V curve, in this case the difference t cr – t f = t con gives the desired value of the residual service life. In the case when the point Z does not fall within the accuracy interval, i.e. below the V 1 curve, the parameter λ should be clar ified or, instead of t f , used to calculate t uf , the conditionally actual operation time, equal to the abscissa of the intersection point of the V 1 curve and the straight line V f . In this case, t res = t cr – t f .   t V t V e     0 , (2) where λ = 0.000457 is a parameter reflecting the process of ageing relative to the initial value V 0 , which is determined on the basis of the available experimental data by approximating it and is constantly being updated when new data are received. For the investigated section of the pipeline for V 0 = 3242 m/s, the value of the speed of sound obtained on the pipes from the emergency reserve used in the construction of this section is taken, the value measured during diagnostics and V f = 3081 m/s for V f = 3169 m/s is the speed limit value sound for this material. According to Figure 5, the residual service life due to the change in the speed of sound was t res = t cr – t f = 112-50 = 62 years. Based on the obtained correlation dependence, a scheme was developed for monitoring the change in the toughness of steel of the main gas pipeline during long-term operation (Fig. 6). Periodic monitoring allows assessing the real physical state of the object, as well as predicting the residual resource and the rate of flow of the ageing process of the material. In places of control, the speed of sound is measured in four sectors and recorded in the measurement protocol. Using correlation, we estimate the impact strength of the material at a given time. In the next diagnostics, we re-fix the values of the velocities at the same points and, compared with the initial values, we evaluate the condition of the pipe material. This technique was tested during the technical state of the main gas pipeline in the framework of research. The values of the parameters under study were obtained and a database was created for their further monitoring. The disadvantages of these studies can be attributed to the fact that studies were conducted on only one grade of steel,