PSI - Issue 20

Marina Zakharova / Procedia Structural Integrity 20 (2019) 108–112

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Marina Zakharova / Structural Integrity Procedia 00 (2019) 000 – 000

3. Risk analysis of gas pipeline accidents in the Arctic zone The operational risks of gas pipelines are increased by the presence of many welded joints and flange joints, as well as gates and control valves. In addition, the pipelines operate continuously at high internal pressure and move large volumes of gas over a long working life. Even slight fluctuations in the operating conditions may lead to accidents. Therefore, it is very important to analyze the operational risks of gas pipelines, especially at low air temperatures. The main reasons for accidents of gas pipelines are considered in Bolshakov and Zakharova's work (2016) where pipeline crack is 27 %; corrosion – 18 %; pipe wear – 9 %; pipe deformation due to metal fatigue – 9 %; pipe deformation due to the temperature difference – 9 %; gate failure, ball - valve destruction, and unsealing of the junction between an insulating component and a flange of the supply gas line – 14 %; and 14 % for pipe damage. Thanks to the failure of gas pipelines, damage to joints, and malfunctioning of gates and control valves, explosive gases may be released. The magnitude of the emissions will depend on the quantity of gas present, its temperature, its pressure, and the size of the holes; it will also depend on the preventive measures that have been adopted. In the Siberian region of the Arctic, at low air temperatures, the abnormal conditions determined by formation of powerful long temperature inversions in combination with calm are considered. These abnormal conditions complicate dispersion of gas in the atmosphere and lead to its congestion to dangerous concentration, in the presence of an ignition source, air-gas mix can ignite and an explosion may occur. According to the results of the analysis of the known failures in the gas pipelines which occurred at low temperatures " event trees" of gas leakage from a gas pipeline with implementation frequencies assessment of the emergency scenarios intended for quantitative assessment of risk is developed, fig 3.

Injured people

Scenario 1: H(S )=2.32 · 10 -5 1/( км год )

Damage to neighboring facilities

Р =1

1

Scenario 2:

Р =0.11

No injured people

With further in? ammation

H (S )=0 1/( км год )

Р =0

2

Injured people

Scenario 3:

Р =0.66

No damage to neighboring facilities

Gas leakage in the gas pipeline Р =1

H(S )=2.26 · 10 -5 1/( км год )

Р =0.12

3

Scenario 4:

Р =0.89

No injured people

H(S )=1.65 · 10 -4 1/( км год )

Р =0.88

4

Formation of an explosive cloud of air-gas mix of methane

Scenario 5:

-4

Without further in? ammation

H (S )=1.00 · 10 H (S )=1.07 · 10 2 5 H (S )=1.02 · 10 -4 3 5 H (S )=9.03 · 10 -5 4 5 5 1 -4

1/( км год ) 1/( км год ) 1/( км год ) 1/( км год )

Dispersion of gas mix without formation of dangerous concentration Р =0.98 (december) Р =0.92 (november) Р =0.94 (january) Р =0.83 (february) 1 2 3 4

Р =0.34

Scenario 6:

-6

H (S )=8.71 · 10 1 6 H (S )=2.18 · 10 -6 2 6 H (S )=6.53 · 10 -6 3 6 H (S )=1.85 · 10 4 6 -5

1/( км год ) 1/( км год ) 1/( км год ) 1/( км год )

(november) (december) (january) (february)

Р =0.08 Р =0.02 Р =0.06 Р =0.17 1 2 3

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Fig. 3. Event tree for gas leakage from a gas pipeline at low temperatures