Residual argon-linked 'fire bubble' may have caused Vizag Steel Plant blast, says preliminary probe

Visakhapatnam: A preliminary investigation into the Vizag Steel Plant tragedy, in which nine workers were killed, suggested that the accident was triggered by the presence of residual argon gas retained within the casting system during maintenance or operational activities.Argon, commonly used as an inert shielding medium in steelmaking to prevent oxidation and assist in refining, can turn problematic if not fully vented or purged from the system.Investigators believe that retained argon pockets contributed to the formation of a fire bubble within the molten steel environment. When disturbed during ladle rotation and slide‑gate opening, the bubble expanded rapidly and ignited, producing an explosion. The resulting fire propagated through the casting zone, damaging equipment and causing severe injuries to workers. The overhead crane above the continuous casting machine‑II was also engulfed in fire, intensifying the spread of flames and debris.Sources indicated that the possible use of substandard or unsuitable chemical materials is also being investigated as a factor in the fatal mishap at the plant on Monday. “Defective refractory linings, moisture-contaminated material, malfunctioning porous plugs, or abnormalities in the purging arrangement can lead to pressure build-up or instability during high-temperature operations,” said Kolli Ramesh Naidu, an industrial safety expert.According to a report available with TOI, at around 4.15pm on June 8 (Monday), the incident occurred while the continuous casting machine-II was under operation, and a ladle full of molten steel from the non-casting side was being rotated and positioned for pouring in the steel melting shop-I. As the slide gate was opened, an explosion occurred. The intensity of the event was such that the exact point of origin — the ladle or the tundish — could not be immediately determined.Witnesses reported that flames quickly engulfed the workspace as molten steel spilt to the ground. The overhead crane was also damaged due to the extreme heat and debris generated by the blast.A worker stationed near machine-IV observed a massive plume of incandescent molten material rising towards the ceiling, while workers near machines-II and III were struck by the blast, falling debris, and intense heat. The confined workspace descended into chaos, with multiple cases of severe burn injuries reported. Emergency response teams rushed to the scene to rescue and evacuate the workers amid flames, smoke, and hazardous conditions. The catastrophic explosion of the ladle carrying 150 tonnes of molten steel was the first incident of its kind in any steel plant in India.Meanwhile, a three-member committee appointed by the Union ministry of steel has initiated an inquiry into the accident. The committee comprises Priya Ranjan, director-in-charge, Bokaro, SAIL; Jitendra Kumar, chief general manager, SAIL; and Gopal Singh, former chief general manager, SAIL.Local technical experts are also assessing compliance with standard operating procedures, refractory conditions, and the effectiveness of safety monitoring systems that were in place before the accident. The findings of these investigations are expected to determine the cause of the incident and identify measures to prevent similar occurrences in future.