Today's KNOWLEDGE Share:Earthquake Effect on Spherical Storage Tanks

Today's KNOWLEDGE Share:

Earthquake Effect on Spherical Storage Tanks:

A major earthquake of magnitude 9 (Richter scale) hits eastern Japan at 14:46, a leak on a LPG pipe is detected at 15 h 35 in a refinery located within a large petrochemical complex in the bay of Tokyo . At 15 h 48, the leak ignites and spreads to the adjacent spherical tanks stocking liquefied butane and butylene.
The rapid development of the fire causes the fall of most tanks (broken foot support) and a cascade of BLEVE (BOILING LIQUID EXPANDING VAPOUR EXPLOSIONS).

The initial leak of LPG, by crushing of a pipe, resulted from the collapse of an overhanging sphere filled with water for a hydraulic test after the 1st aftershock of the main earthquake.
The main earthquake weakened the supporting structure by cracking the crosspieces, and then led to the failure of the support legs during the 1st aftershock of magnitude 7.2 at 3.15 pm.

What Went Wrong???
The design of the structure adapted to the seismic risk for a gas (LPG) load did not take into account the overload due to the filling of the tank with water.
In addition, the automatic safety shutdown of the gas transport pipeline triggered by the seismometers was inoperative on this part of the pipeline, as the automatic cut-off valve was shunted open following earlier problems with the pneumatic control.(big mistake).The temporary procedure of manually closing this valve pending repair could not be implemented due to a large LPG pool.
As a result, the fire was uncontrollable.

What We Learned From This Accident?
-Reduction of the duration of the water presence in the spheres in hydraulic tests (judged abnormally long during the accident) ;
-In the new sphere design, additional loads from water, especially seismic loads, should be taken into account.
-Systematic isolation and draining of a gas pipeline close to the spheres under hydraulic test.
-Increasing the flexibility of new on site gas transport pipelines to accommodate large multidirectional displacements during major earthquakes.
- Emergency shut-off valves are critical equipment, their faults should be repaired in a short time.

Source:https://lnkd.in/dNpCnuw4/ Technical Engineering Portal
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