Vizag (LG Polymers), 2020: a monomer tank left alone
During the COVID-19 lockdown, styrene in a storage tank warmed up and began to polymerise. The heat vaporised styrene, which spread over nearby villages before dawn.
What happened
Styrene polymerises by itself if it gets warm: the reaction is exothermic and self-accelerating. It is stored cool, with an inhibitor (TBC) that needs dissolved oxygen to work and is slowly used up, faster at higher temperature. The plant had been shut since March for the lockdown, with a large styrene inventory sitting in old storage tanks.
The temperature in one tank rose over days (the refrigeration was operated intermittently, and temperature was measured only at the bottom of the tank). The inhibitor was depleted, polymerisation accelerated, and the heat released vaporised styrene, which escaped through the tank vents in the early morning and drifted over neighbouring villages. People were found unconscious in the streets. Investigations by the state high-power committee and an NGT-appointed committee found gross safety lapses: an outdated tank design, inadequate temperature monitoring and inhibitor management, no working alarm system, and a failed emergency response.
Sequence of events
Why it happened
- Reactive storage not treated as a reactor: a monomer tank is a slow chemical reactor and needs temperature, inhibitor and oxygen management.
- Poor instrumentation: temperature measured at one point only; no reliable high-temperature alarm or automatic cooling.
- Shutdown not managed: the lockdown changed conditions (unattended plant, idle refrigeration) without a hazard review.
- Emergency response failed: no siren, no timely warning to the community.
Lessons for your plant
- Treat stored monomers and unstable materials as reactions: monitor temperature at several levels, inhibitor content and oxygen, with alarms and emergency inhibitor/short-stop available.
- Run a hazard review (MOC) before any extended shutdown and before restart.
- Design the emergency plan with the neighbours: sirens, warning, shelter or evacuation.
Sources
- Official · National Green Tribunal order, O.A. No. 73/2020, 1 June 2020, quoting the joint committee findings (PDF)
- News · The News Minute: gross safety lapses caused the tragedy, says NGT committee
- News · The News Minute: state-appointed High Power Committee finds LG Polymers negligent
- News · Down To Earth: accountability of LG Polymers
- Secondary · Visakhapatnam gas leak: Wikipedia overview with references
Summary written for training. Figures are as published by the investigating bodies and widely cited sources; see the sources for full details.