PSI - Issue 59

Roman Hrabovskyy et al. / Procedia Structural Integrity 59 (2024) 112–119 Roman Hrabovskyy et al. / Structural Integrity Procedia 00 (2024) 000 – 000

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 The revealed hydrogen residual concentration in 17H1S and 10H2BТ steels is not sufficiently determinative for the critical fracture of the gas pipeline; obviously, a set of factors are dominant during fracture (defect size, operating pressure, environment, temperature, etc.). In general, the obtained results of experimental investigations of the mechanical characteristics of the studied steels of main gas pipelines (17H1S and 10H2BТ ) are consistent with the known literary data (Kryzhanivs’kyi et al. (2013); Bolzon et al. (2021)). However, the hydrogen influence on the change in the strength and plasticity characteristics, and therefore on the operating capacity and durability of long-term operated 17H1S and 10H2BТ steels of main gas pipelines require additional study (Dmytrakh et al. (2020). Besides, the minimization of emergency and man-made situations for the population and the environment is one of the main tasks during the main gas pipelines operation. At the same time, it is important to establish the cause and type of the emergency and a possible scenario of their development, as well as determine the consequences, since fires occur in 50 – 60% of cases during the catastrophic damage of main gas pipelines (Gas pipeline incidents (2011); Babadzhanova et al. (2011)). The following types of accidents are possible:  Depressurization of the pipeline section (fistula formation), which is accompanied by leakage of natural gas into the environment; It is worth noting that in the case of main gas pipeline catastrophic damage due to a significant reserve of elastic energy in the pipe material during its depressurization, a crack, which propagates along the pipe for tens and hundreds of meters at a rate of 1 000 m/s, develops (Mandryk (2015)). According to the first scenario, pipeline damage occurs in dense soils such as clays and loams. At the place of the breaking, a foundation pit with an equivalent diameter of 15 – 60 m is formed, from which a near-vertical leakage and burning of the gas flow occurs. The second scenario is typical for pipeline damage in river floodplains or peaty soils. In this case, due to inertial forces, the pipe can be pulled out from the ground in relatively large areas with the throwing about the gas pipeline ends and the formation of two independent “ floor ” of gas streams coming out of the pipe. Calculation of gas losses during an accident on the main gas pipeline was carried out according to the formula (Babadzhanova et al. (2011)) 0 0 0 Q V PT PTZ  , (4) where V 0 is the volume of gas in the pipeline, m 3 ; P is the operating pressure, MPa; T 0 is the nominal temperature, 293 K; P 0 is the nominal pressure 0.131 MPa; T is the operating temperature, K; Z is a constant, equal to 0.93. To estimate the damage area in case of catastrophic damage of the main gas pipeline, a formula in (Babadzhanova et al. (2011)) was proposed, which was built on the basis of fire models, gas leakage rate, threshold value of thermal radiation intensity  The pipeline section breaking, accompanied by a gas explosion without ignition;  The pipeline section breaking, which is accompanied by a gas explosion with the fire.

,

99 R D p 

(5)

max

where R is the radius of damage area, m; p max is the maximum operating pressure, MPa; is the outer diameter of the gas pipeline, m. Table 6 presents calculation results and literary data (Mandryk (2015)).

Table 6. Emergency consequences on main gas pipeline (Pipeline safety (2003)). Gas pipeline diameter ( D ), mm Mean radius of thermal effect ( R average ), m Radius of damage area ( R ), m

Gas loss (Q×10 6 ), m 3

Size of pit ( c × b × a ), m

1220 1420

275 288

281 382

11.0 13.9

49×22×12 65×40×10