San Juanico: Pemex LPG blast killed 500+ — safety devices were bypassed

On November 19, 1984, explosions destroyed the Pemex LPG storage terminal in San Juan Ixhuatepec (San Juanico), a densely populated suburb of Mexico City. The disaster began when a pipeline between a storage sphere and cylindrical tanks ruptured, releasing LPG for 5 to 10 minutes. The gas cloud ignited at a waste-gas flare, triggering a massive vapour cloud explosion. Within 90 seconds, the first of eight BLEVEs — boiling liquid expanding vapour explosions — sent fireballs up to 300 metres across the neighbourhood. The energy released exceeded the Hiroshima atomic bomb by a factor of five.

The terminal was a disaster waiting to happen. 30-40% of the safety devices were bypassed or non-operational: firewater spray systems did not work, pressure gauges were inaccurate, a relief valve was missing. The plant was dangerously congested — 54 tightly packed LPG tanks (6 large spheres and 48 smaller bullets) with 1-metre-high bund walls that trapped the gas cloud instead of dispersing it. Tank support legs had no fireproofing. The pipeline flow rate had been increased without upgrading pressure relief. LPG continued to be pumped into the burning terminal long after the accident started.

Pemex was found responsible by the Attorney General, but no public inquiry results were ever released. The government paid a flat $10,400 per fatality and gave 167 families new homes worth about $8,000 each. Up to 200,000 people were evacuated. The disaster permanently changed international LPG storage standards: mandatory HAZOP reviews, fireproofing of tank supports, limits on tank clustering, and strict land-use planning around such facilities. But for San Juanico, 500 to 600 dead and 5,000 to 7,000 severely burned, the lessons were learned on the bodies of the neighbourhood.