PEMEX LPG Terminal, Mexico City, Mexico. 19th November 1984

Accident summary

At approximately 05:35 hours on 19 November 1984 a major fire and a series of catastrophic explosions occurred at the government owned and operated PEMEX LPG Terminal at San Juan Ixhuatepec, Mexico City. As a consequence of these events some 500 individuals were killed and the terminal destroyed.

Three refineries supplied the facility with LPG on a daily basis. The plant was being filled from a refinery 400 km away, as on the previous day it had become almost empty. Two large spheres and 48 cylindrical vessels were filled to 90% and 4 smaller spheres to 50% full.

A drop in pressure was noticed in the control room and also at a pipeline pumping station. An 8-inch pipe between a sphere and a series of cylinders had ruptured. Unfortunately the operators could not identify the cause of the pressure drop. The release of LPG continued for about 5-10 minutes when the gas cloud, estimated at 200 m x 150 m x 2 m high, drifted to a flare stack. It ignited, causing violent ground shock. A number of ground fires occurred. Workers on the plant now tried to deal with the escape taking various action. At a late stage somebody pressed the emergency shut down button.

About fifteen minutes after the initial release the first BLEVE occurred. For the next hour and a half there followed a series of BLEVEs as the LPG vessels violently exploded. LPG was said to rain down and surfaces covered in the liquid were set alight. The explosions were recorded on a seismograph at the University of Mexico.

Failings in technical measures

• The total destruction of the terminal occurred because there was a failure of the overall basis of safety which included the layout of the plant and emergency isolation features
• Plant Layout: positioning of the vessels
• Isolation: emergency isolation means
• The terminal's fire water system was disabled in the initial blast. Also the water spray systems were inadequate.
• Active / Passive Fire Protection: survivability of critical systems, insulation thickness, water deluge
• The installation of a more effective gas detection and emergency isolation system could have averted the incident. The plant had no gas detection system and therefore when the emergency isolation was initiated it was probably too late.
• Leak / Gas Detection: gas detection
• Hindering the arrival of the emergency services was the traffic chaos, which built up as local residents sought to escape the area.
• Emergency Response / Spill Control: site emergency plan, access of emergency vehicles

References

Lees, F.P., 'Loss Prevention in the Process Industries – Hazard Identification, Assessment and Control', Volume 3, Appendix 4, Butterworth Heinemann, ISBN 0 7506 1547 8, 1996.

Marsh and McLennan, 'Large Property Damage Losses in the Hydrocarbon-Chemical Industries a thirty-year Review', 16th Edition, Marsh and McLennan Protection Consultants, 1995.