ii) The detonation in a drip leg transmits a shock wave through the unburned gas to crack the pipe without the presence of combustion at the crack site.
iii) For this work, one important point is that high pressures are sufficient to blast a shock wave out through the newly formed crack to explode a jet of flammable methane and air.
8. The explosion splits the pipe into two sections for a massive release of energy as gas pressures suddenly decrease at the crack site (Explosion 1).
i) Since the blast wave from the drip leg is already located downstream when the pipeline ruptures, there is no available spark source yet to ignite the plume of gases.
ii) Methane jets out of the pipe through the soil. Gas burrows/blasts a hole, or excavation, up through the soil to the ground surface.
iii) A crater is formed, which is much smaller than the final crater size that erupts from subsequent gas detonations.
iv) A re-investigation of the deadly Swan Bruno explosion shows that this explosion was measured at the time and not recognized as an explosion, but was incorrectly believed to be caused by valve operations.
9. Reflected shock waves return from distant locations in the pipeline, while methane entrains air into the jet above the pipeline.
10. An explosive shock wave exits through the crack to autoignite a flammable methane fuel/air mixture.
11. This ignition creates a detonation (Explosion 2). This second detonation explodes to ignite a towering jet of flame that burns near 1970 C (3594 F).
i) The incoming detonation wave, coupled with substantial air, blows the pipeline out of the ground.
ii) This second detonation transmits a shock wave back into the pipeline to send shock waves in in both directions from the pipeline rupture.
iii) Low pressures in the wake of this shock also draw large amounts of air into the pipeline.
12. Not shown, reflected waves from other distant points in the pipeline enter the explosion crater and create retonation wave detonations (Explosions 3 and 4).
13. After explosions 3 and 4 or other reflected wave explosions, multiple smaller explosions ignite as fresh fuel is continually supplied to mix with the air within and above the crater. These subsequent, smaller detonations are a series of deflagration to detonation transition explosions.'
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