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Jun 22, 2012

Blast and fire in Vizag Steel Plant

In an incident of explosion and resultant fire in Vizag Steel Plant, 16 persons died and  property worth crores of rupees is damaged. It is reported that the incident happened in oxygen plant of the recently commissioned steel melting shop-II during trials. The hot metal from blast furnace will be sent into a mixer where oxygen will be blown at 17 kg/cm2 pressure to remove impurities and then convert into blooms. It is reported that the back pressure caused the explosion.
As per the reports, following are my observations:
  1. Impurities from hot metal will be burnt in the mixer with oxygen.
  2. Operators could not get the oxygen pressure of 17 kg/cm2 and instead they got about 14 kg/cm2.
  3. They tried to admit oxygen at this lower pressure 2-3 times.
  4. While people went closer to the unit to see reasons for low pressure, explosion occurred.
  5. The pipeline for oxygen is of 5 mm thick instead of 10 mm
  6. The oxygen container and associated piping got burst
  7. The fire after explosion led to fire causing injuries/fatalities and property damage
  8. Vehicles flew of about 50 m from the incident site
The above indicate nonavailability or failure of check valve / non-return valve in the connecting line; non-availability or failure of safety relief valve in the oxygen container and or mixer. The back pressure could be due to sudden reaction of impurities like carbon, etc with more oxygen supplied (2-3 times as low pressure was there) and the reaction product gases could have builtup pressure and non-venting of these gases as they are formed could have led to pressure buildup and back pressure.
As the plant is being commissioned/started for trial runs, many people including top level management was present and so many people thus got exposed.
Why so many vehicles including autorikshaws and scooters were available near the site is not known.

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