PSI - Issue 36

S. Hryhorskyi et al. / Procedia Structural Integrity 36 (2022) 342–349

347

6

S. Hryhorskyi et al. / Structural Integrity Procedia 00 (2021) 000 – 000

3 3  1 1 j i = =

3  − d

4

j

i

;

−

G

A

q

(20)

=





inf

inf

, i j

i

- actual throughput of the investigated oil pipeline: ( ) 0 , Q Q Q Q A x B q  = +  + 

(21)

where i out Р is overpressure of oil at the beginning of the i-th stretch, provided that the linear part of the pipeline is tight ( 0 q = ), MPa; і inp Р is excess oil pressure at the inlet to the i-th intermediate OPS under the condition of tightness of the linear part of the pipeline ( 0 q = ), MPa; i х Р is overpressure of oil at a distance x , provided that the linear part of the pipeline is tight ( 0 q = ) and taking into account the actual profile of the route ( ) z f x = , MPa; 0 Q is capacity of the oil pipeline according to the set scheme of operation of pumping units at the NPS in the absence of oil leaks ( 0 q = ) along the entire route of the pipeline, m 3 /h; , i j out A , , i j out B , , i j inp A , , i j inp B , , i j x A , , i j x B , , i j l A , , i j l B , , inf i j A are coefficients of mathematical models (16) - (20) obtained by processing the results of multivariate calculations of the throughput of the investigated section of the oil pipeline by the least squares method, taking into account the physical properties of the transported oil (density and kinematic viscosity), pressure characteristics of OPS units and the profile of the pipeline route.

Fig. 1. Design diagram of the investigated section of the oil pipeline with applied hydraulic slope lines during depressurization of the second linear section of the pipeline ( 15 x km = , 3 300 / q m h = ).

For example, Tables 2 and 3 show the corresponding values of the coefficients in formulas (16) - (19) in the case of pumps operating according to the scheme 1.3‒2‒1.3 (at the first and last pumping station, pumping units with numbers 1 and 3, only one pump unit number 2 is operating at the second pump station) and depressurization of the first linear section of the oil pipeline. Table 4 summarizes the coefficients of the mathematical model (20) when a through hole is formed in the pipeline on the first linear section of the oil pipeline with the above pumping scheme at the pump station.

Table 2. The value of the coefficients of mathematical models (16) - (19) for calculating the dynamics of changes in oil pressure in the leak section and predicting the size of the hole diameter. Value i , j , i j x A , i j x B , i j l A , i j l B

3.356 ·10 -11 -1.718 ·10 -9 -9.836 ·10 -8

j = 1 j = 2 j = 3 j = 4

1. 145·10 -7 -2. 304·10 -5 -5. 237·10 -4

-5. 110·10 -7 4. 976·10 -5 -2. 308·10 -3 1. 742·10 1

1. 139·10 -6 -8. 868·10 -5 7. 177·10 -3 1. 421·10 -1

i = 1

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