The high-pressure buildup inside the boiling liquid steel caused by ‘entrapped gas’ is said to be the main reason for the explosion at the Rashtriya Ispat Nigam Limited-Visakhapatnam Steel Plant (VSP) on June 8, according to the plant sources.

This critical detail was said to have been shared by the VSP officials with the three-member team of Central experts who ate probing the accident.

The tragic accident has claimed nine lives so far—five permanent employees and four contract workers.

What ‘trapped gas’ caused the blast?

Making steel is an extreme process where iron ore is melted down to a boiling liquid at temperatures reaching 1,600°C. To turn this melted iron into steel, workers blast pure oxygen at high pressure into the liquid to burn away impurities like carbon and silicon, turning them into a waste layer of slag.

However, dangerous consequences are likely if this process is rushed to meet high production targets. The sprayed oxygen may get chemically trapped inside the heavy liquid metal, creating highly pressurised pockets.

Sources from the VSP told The Hindu that this specific batch of molten steel was moved to the next process before these gases were given enough time to dissolve.

As an overhead crane carried the giant ladle container, the trapped gas pressure became so intense that it violently blew the mechanical slide-gate assembly at the bottom of the ladle, pouring tonnes of hot steel onto the shop floor where the workers were working, the sources said.

Lucky escape

Sources also claimed that a similar container explosion had happened in the Steel Melt Shop-2 (SMS-2) at 3:57 p.m. on Monday, less than half an hour before the fatal blast.

A ladle exploded, spilling about 60 tonnes of molten steel after a transport car suddenly stopped working. Luckily, a group of 16 people—including four permanent staff, two supervisors, and ten helpers—managed to run away just in time.

“This incident was even shared among the colleagues on WhatsApp,” a source claimed. Just 28 minutes later, at 4:25 p.m., the second and much bigger explosion occurred in Steel Melt Shop-1 (SMS-1), leaving no room for escape, he said.