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San Juanico disaster

Coordinates: 19°31′26.7″N 99°06′27.8″W / 19.524083°N 99.107722°W / 19.524083; -99.107722
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San Juanico disaster
The PEMEX terminal after the accident, with the two surviving LPG spheres. In the foreground, part of the totally destructed housing area.
San Juanico disaster is located in State of Mexico
San Juanico
San Juanico
Toluca
Toluca
Mexico City
Mexico City
class=notpageimage|
Location of San Juan Ixhuatepec in the State of Mexico
Date19 November 1984 (1984-11-19)
VenuePemex LPG storage plant in San Juan Ixhuatepec
LocationTlalnepantla de Baz municipality, State of Mexico, Mexico
TypeMultiple boiling liquid expanding vapor explosions
Deaths> 500
Non-fatal injuries> 5000

The San Juan Ixhuatepec explosions of 1984, also known as the San Juanico disaster, was an industrial disaster involving a series of explosions at a liquefied petroleum gas (LPG) tank farm in San Juan Ixhuatepec (popularly known as San Juanico), Tlalnepantla de Baz, State of Mexico on 19 November 1984.[1] The explosions destroyed the facility and devastated the town of San Juan Ixhuatepec, part of Greater Mexico City, with 500–600 victims killed, and 5000–7000 suffering severe burns.[2] It is one of the deadliest industrial disasters in world history.[1]

Background

The incident took place at a storage and distribution terminal for liquified petroleum gas (LPG) belonging to the state-owned oil company Pemex. The facility consisted of 54 LPG storage tanks: six large spherical tanks (four with capacity of 1,600 cubic metres (57,000 cu ft) and two with capacity of 2,400 cubic metres (85,000 cu ft)) and 48 smaller horizontal bullet-shaped tanks of various sizes, for a total plant capacity of 16,000 cubic metres (570,000 cu ft),[3] representing one third of Mexico City's entire liquid petroleum gas supply.[4][5] Contrary to good practice, the sphere support legs were not fireproofed. Tanks were divided in several clusters by concrete walls about 1 metre (3.3 ft) tall. It received LPG through three underground pipelines from remote sites: a 12 inches pipeline from Minatitlán (576 km; 358 mi), a 4 inches pipeline from Poza Rica (235 km; 146 mi) and another 4 inches line from the Azcapotzalco refinery (8 km; 5 mi).[6]

There were two ground flare pits and a fire protection system including a pond, fire pumps and water spray distribution.[5]

Adjoining the terminal to the east, there was a Unigas plant with further LPG storage and distribution capacity. Immediately further east was a Gasomático facility for bottling the LPG and dispatch it by truck.[5] The Pemex terminal distributed LPG to these two plants via underground pipelines. Further away from this cluster, five more gas distribution companies imported gas from the Pemex terminal using tank trucks and bottles.[7]

The town of San Juanico surrounded the site and consisted of 40,000 residents, with an additional 60,000 more living in nearby communities.[1] Housing surrounding the facility began to materialize only after the construction of the installation started in 1962,[7][8] although this is disputed.[9] The closest houses were at a distance of 130 metres (430 ft) from the storage tanks. However, the two largest spheres were added to the plant only recently, when the plant was already surrounded by the densely populated neighborhood.[6] Most of the houses were simple brick or wooden buildings.[7][10]

The events

Liquefied gas Horton tanks similar to the six spherical tanks involved in the San Juanico disaster
LPG bullet tanks. There were 48 tanks of this type in the Pemex plant.

In the early hours of 19 November 1984, the plant was being filled from a refinery 400 kilometres (250 miles) away. At that moment, two of the spheres and the 48 cylindrical vessels were filled at 90% of their capacity and the rest of the spheres at 50%.[11] Overall, the plant held about 11,000–12,000 cubic metres (390,000–420,000 cu ft) of LPG,[10] i.e., in excess of 300 TJ of energy equivalent,[12] roughly five times the energy released by the atomic bomb of Hiroshima.[13] Shortly before 5:40 a.m., the control room operators and those at the pipeline pumping station, sited 40 kilometres (25 miles) away,[3] noticed a decrease in pressure. A pipe between a sphere and the cylinders had ruptured, resulting in a continuous release of LPG. For 5–10 minutes, with the cause of the leak not identified, the resulting gas cloud built up, reaching an estimated size of 200 × 150 × 2 metres (660 × 490 × 7 ft). The cloud eventually reached one of the waste-gas flare pits at 5:45 a.m, and ignited.[11]

A flash fire ensued, which immediately transitioned to a violent vapor cloud explosion (VCE), likely due to its flame front acceleration being enhanced by the especially congested geometry of the plant. The blast (like the ensuing boiling liquid expanding vapor explosions (BLEVEs)) was felt and recorded by a seismometer at a National Autonomous University of Mexico lab located some 32 km (20 mi) away in Mexico City.[5][10] In a textbook case of domino effect accident,[10] the explosion damaged further piping and storage tanks, which resulted in a massive conflagration fed by multiple LPG leaks. About 90 seconds after the VCE blast, the first tank BLEVE occurred.[4] The explosion was witnessed by the pilot of a Pan Am flight on its approach to the airport. He immediately contacted air traffic control, worried that the deflagration might be from a nuclear bomb.[14] Eight separate BLEVEs were recorded by the seismometer, with the last one at 7:01 a.m. The first and the sixth registered the highest strength, at 0.5 on the Richter scale.[4] The BLEVE fireballs were up to 300 metres (980 ft) in diameter, and they had a duration of some 20 seconds.[3] Smaller explosions continued until 11 a.m.,[7] while the flames on the last large sphere was extinguished at 11 p.m.

The four smaller spheres were completely destroyed, with fragments propelled around the plant, some at a distance of 350 metres (1,150 ft) in public areas. The larger spheres collapsed to the ground, with their legs buckled due to the heat radiation they received. Only four of the bullet tanks survived. 12 of those that failed were launched from their supports with the furthest landing at 1,200 metres (3,900 ft). Missile fragments ejected weighed up to 30 tons. Gas explosions also occurred inside the plant buildings and the surrounding houses.[1][10] At the Gasomático site, 100 parked trucks loaded with LPG household cylinders weighing 20–40 kilograms (44–88 lb) were completely burned-out and hundreds of secondary explosions took place.[7]

An area of a few square kilometers was affected, with varying degrees of damage from the fires and the missiles. Around 150 homes were estimated completely destroyed, with a few hundred sustaining lesser damage.[7] It is estimated that the thermal radiation produced by the BLEVEs was in excess of the threshold of pain (4.0 kW/m2) within a radius of 1,850 metres (1.15 mi).[15]

Five plant workers perished, but the majority of the victims died in the housing area surrounding the plant, mostly within 300 metres (980 ft) from the centre of the storage area.[7] Most of the casualties were surprised in their sleep. The disaster resulted in 500 to 600 deaths, and 5000–7000 severe injuries. Radiant heat generated by the fire incinerated most corpses to ashes, with only 2% of the recovered remains left in recognizable condition.[1]

Emergency response

The first call to the emergency services was made at 5:45.[3] More than 200 firemen were deployed to the affected area in the six hours after the first explosion. Firewater was provided to the site by tank truck normally used for domestic potable water distribution.[14] A major rescue operation mounted, which reached its climax between 8:00 a.m. and 10:00 a.m. Around 4000 people participated in rescue and medical activities, among whom 985 medics, 1780 paramedics, and 1332 volunteers. 363 ambulances and five helicopters were involved.[3] After the last BLEVE, the firemen kept cooling the two larger, unexploded spheres. While this was undoubtedly an act of bravery, they were exposing themselves to further potential BLEVEs that would have surely killed them.[14][16] 200,000 people were evacuated from the area.[5][6]

Investigation

Initially, director-general of Pemex Mario Ramón Beteta and government officials attempted to shift the responsibility for the accident onto the gas-distributing businesses adjoining the terminal.[17][9] No results from a public inquiry or a Pemex investigation have ever been made available, except for a declaration of the Attorney General[6] released on 22 December 1984, which pointed to the gas escape having occurred at the row of bullet tanks next to the spheres. In this press release, it was also stated that the responsibilities were not to be sought in the lack of plant maintenance by Pemex.[18][19][20]

On TNO's initiative and through mediation of the local Netherlands embassy, a Dutch team reached the accident site two weeks after the facts. This investigation was not instigated by the Mexican authorities or Pemex, but rather was a scientific mission whose purpose was testing physical models used in safety studies for the prediction of damage from industrial explosions, and examining the emergency response to the accident. The investigation was also participated by the Mexican Petroleum Institute (IMP).[5] IMP stated that the cause of the accident was already known, pointing to a disgruntled employee that had allegedly sabotaged the plant. They also added that further investigation would not be necessarily very useful.[6]

The TNO report was issued in May 1985. Although the Dutch team did not primarily focus on the causes of the accident, the final report hypothesizes that the initial leak may have been caused by overpressure and rupture of a pipe to one of the cylindrical vessels (possibly due to the high discharge pressure (> 60 bars (870 psi)) of a booster pump in one of the underground pipelines), possibly combined with a tank overfill and the consequent opening of a tank relief valve discharging to atmosphere. The report also stresses how it was the fires that brought about most of the destruction, with blast overpressures playing only a secondary role. It further calls attention to the congested plant layout as a factor that greatly contributed to the rapid escalation of the accident, and to the fact that poor land-use planning led to housing built within the credible damage radius from accidents originating from the plant. It also commends the work of the emergency services.[7]

An informal investigation was conducted by the U.S. Department of Transportation, which corroborated the TNO's findings on the cause of the accident, additionally pointing out that the overpressure should have been prevented by relief valves placed on the receiving pipelines, but these had not been installed. Their report also called attention to an earlier statement by Pemex that the pipelines were not isolated, with LPG being pumped into the terminal at the usual rate until 6:40 a.m., long after the onset of the accident. This further aggravated the fire, with an estimated additional fuel inventory of roughly 500 cubic metres (18,000 cu ft). The USDOT concluded that the main causal factors were "the human element, maintenance problems, and inadequate relief capacity and pressure control." They also identified two more contributing factors: multiple tanks being lined up (i.e., not isolated from) a common header, which increased the effectiveness of the chain reaction; and the failure of piping underneath the spheres as a consequence of the initial vapor cloud explosion, which meant that the consequent tank heating ultimately escalated to the BLEVEs.[18]

Aftermath

"SHOCK": The November 21 cover of La Prensa

President of Mexico Miguel de la Madrid and other high-ranking government officials drew criticism for not attending either the funeral ceremony or the mass burial of 272 of the victims.[9] Some sources point to Pemex officials and public authorities potentially hampering the relief and investigation efforts. The parish priest of San Juan Ixhuatepec may have been removed to elsewhere in the State of Mexico by church authorities, after complaining that much of the financial aid allocated to the affected families was quickly disappearing. In a speech in Guadalajara, head of Pemex Mario Ramón Beteta likened criticism directed at the company to cannibalism, declaring that Pemex's tax money was key in keeping Mexico afloat.[20] Barely six weeks after the events, with no official investigation results, the Government started payment of indemnifications to those affected by the disaster. Loss of life was indemnified "at a flat rate", without taking into account the age, family situation, or employment conditions of the deceased.[17] Indemnifications amounted to US$10,400 per each fatality.[20] The state of Mexico gave 167 families new homes in the complex of Valle de Anáhuac, each being valued at around US$8,000.[20] A park was quickly built south of the accident site, where most of the destroyed houses used to be.[17]

The disaster was detrimental to the ruling Institutional Revolutionary Party (PRI), as inadequately maintained Pemex infrastructure was identified as responsible for the explosions, although the events would in part be overshadowed by the 1985 Mexico City earthquake.[21] In the years following the accident, the government's actions (or lack thereof) were criticized in several respects. For example, concerns were raised on the uncontrolled growth of the housing areas immediately adjoining the LPG terminal, which was against the Ley del Petróleo (Petroleum Act), establishing minimum safety distances and mandating approvals from the Secretariat of Health and Assistance. While the Government made an official communication to the effect that all gas plants in San Juan Ixhuatepec should be shut down, as of 2020 six out of 12 were still in operation.[17]

Although the accident became well-known worldwide in the technical domain of process safety, it had relatively little mainstream resonance outside of Mexico (e.g., as opposed to the Bhopal tragedy, which followed it by merely two weeks), likely due to the fact that no non-Mexican companies were involved.[20][22]

Lessons learned in process safety

San Juanico had a notable impact on process safety.[15] TNO's contributions were used[6] by the API to support their standard on Design and Construction of LPG Installations.[23] Some of the lessons learned, or in certain cases re-learned, were:

  • The fundamental role of land-use planning and its rigorous enforcement, which must be supported by robust risk assessment and accident models.[3] Based on models that did in part benefit from validation provided by the accident itself, safety distances of 300 metres (980 ft) have been proposed between an LPG plant the size of San Juanico's and the nearest houses.[8]
  • Barriers that failed included an inherently safer layout, with good natural ventilation and limited congestion; emergency isolation; and water spray system, designed to withstand credible accidental loads. The accident stressed their importance to the safety of plants storing and processing flammable materials.[3]
  • The plant did not have a gas detection system. This prevented early detection of the leak and safe isolation of the plant, thus contributing to a much greater inventory being available to the raging fires.[3]
  • Firemen exposed themselves futilely and at great risk to BLEVEs when trying to cool the unexploded sphere. It is important that emergency services be aware of the dangers of liquefied gas vessels exposed to impinging fires.[3]

The San Juanico tragedy, which followed other destructive BLEVE events such as those of Feyzin and Los Alfaques, resulted in a much higher awareness of the destructive potential of BLEVEs and the necessity to manage effectively the risk associated to these phenomena.

Later accidents

In 1996 another Pemex site in San Juan Ixhuatepec suffered a serious accident, this time involving a petrol tank, which led to the death of a fireman and the evacuation of around 5000 people from their homes.[17]

See also

References

  1. ^ a b c d e Arturson, G. (1987). "The Tragedy of San Juanico—the Most Severe LPG Disaster in History". Burns. 13 (2): 87–102. doi:10.1016/0305-4179(87)90096-9. PMID 3580941.
  2. ^ "Accidente de San Juan de Ixhuatepec" [The San Juan de Ixhuatepec Accident]. Universidad de Zaragoza (in Spanish). Archived from the original on 1 July 2007. Retrieved 11 June 2008.
  3. ^ a b c d e f g h i Mannan, Sam (2014). Lees’ Process Safety Essentials: Hazard Identification, Assessment and Control. Oxford and Waltham, Mass.: Butterworth-Heinemann. pp. 462–465. ISBN 978-1-85617-776-4.
  4. ^ a b c López-Molina, Antioco; Vázquez-Román, Richart; Díaz-Ovalle, Christian (2012). "Aprendizajes del accidente de San Juan Ixhuatepec, México" [Lessons Learned from the San Juan Ixhuatepec, Mexico Accident]. Información tecnológica (in Spanish). 23 (7): 121–128. doi:10.4067/S0718-07642012000600013. ISSN 0718-0764.
  5. ^ a b c d e f Pietersen, C.M. (1988). "Analysis of the LPG-disaster in Mexico City". Journal of Hazardous Materials. 20: 85–107. doi:10.1016/0304-3894(88)87008-0.
  6. ^ a b c d e f Pietersen, C.M. (2013). 25 Years Later: The Two Largest Industrial Disasters with Hazardous Material. Nieuwerkerk aan den Ijssel: Gelling Publishing. ISBN 978-90-78440-42-0.
  7. ^ a b c d e f g h Pietersen, C.M.; Cendejas Huerta, S. (1985). Analysis of the LPG Incident in San Juan Ixhuatepec, Mexico City, 19 November 1984 (PDF). R 85/0222. Apeldoorn: Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek. Archived from the original (PDF) on 14 August 2023. Retrieved 14 August 2023.
  8. ^ a b Ballesteros Gómez, Zuilly Annais (2018). Riesgos en asentamientos habitacionales por la cercanía con áreas de almacenamiento de Gas L.P. en San Juan Ixhuatepec [Risks in Residential Settlements Due to the Proximity to LPG Storage Areas in San Juan Ixhuatepec] (PDF). Graduate dissertation (in Spanish). Ciudad de México: Instituto Politécnico Nacional. Archived from the original (PDF) on 20 August 2023. Retrieved 20 August 2023.
  9. ^ a b c Orme Jr, William A. (26 November 1984). "Mexican Blast Stirs Anger, Criticism". The Washington Post. Archived from the original on 9 October 2019. Retrieved 20 August 2019.
  10. ^ a b c d e Atherton, John; Gil, Frederic (2008). Incidents That Define Process Safety. Hoboken, N.J.: Center for Chemical Process Safety and John Wiley & Sons. p. 61. ISBN 978-0-470-12204-4.
  11. ^ a b Marmo, Luca; Fiorentini, Luca (2019). Principles of Forensic Engineering Applied to Industrial Accidents. Hoboken, N.J. and Chichester: Wiley. pp. 60–64. ISBN 9781118962817. LCCN 2018034915.
  12. ^ "Convert Liter of LPG, Higher Heating Value (Liquefied Petrolium Gas (LPG) Energy Equivalent) to Watt Second (W × s, Common Units)". convert-me.com. Archived from the original on 13 August 2023. Retrieved 13 August 2023.
  13. ^ Ochiai, Eiichiro (2013). Hiroshima to Fukushima: Biohazards of Radiation. Heidelberg: Springer. doi:10.1007/978-3-642-38727-2. ISBN 978-3-642-38726-5.
  14. ^ a b c Skandia International Insurance Corporation. El día que el cielo se incendió [The Day the Sky Caught Fire] (Videotape) (in Spanish).
  15. ^ a b CCPS (1994). Guidelines for Evaluating the Characteristics of Vapor Cloud Explosions, Flash Fires, and BLEVEs. New York, N.Y.: American Institute of Chemical Engineers. pp. 35–36, 184–185, 308–311. ISBN 0-8169-0474-X.
  16. ^ Skandia International Insurance Corporation (1985). BLEVE! The Tragedy of San Juanico. Stockholm: Skandia International. If a BLEVE had occurred during the later morning, a large number of those 3000 people who were engaged in rescue and guarding would have been killed.
  17. ^ a b c d e Álvarez, Carlos (12 August 2020). "La tragedia de San Juanico. Infierno en la tierra" [The San Juanico Tragedy. Hell on Earth]. La Prensa (in Spanish). Archived from the original on 11 August 2022. Retrieved 15 August 2023.
  18. ^ a b "Interpretation Response #PI-85-003". PHMSA (Pipeline and Hazardous Materials Safety Administration). Archived from the original on 10 December 2022. Retrieved 16 August 2023.
  19. ^ Procuraduría General de la República (1984). Boletín de prensa [Press Release]. 488/84 (in Spanish). Ciudad de México: Procuraduría General de la República (published 22 December 1984). Petróleos Mexicanos hizo entrega de la documentación en la que se analizan los problemas de mantenimiento ordinario de esta planta, y se concluye que aquéllos no pudieron causar por sí mismos los hechos sujetos a examen [Petróleos Mexicanos handed over the documentation in which the ordinary maintenance problems of this plant are analyzed, and it is concluded that they could not have caused the events under examination by themselves]
  20. ^ a b c d e Vasquez, Juan M. (28 January 1985). "Mexico Furor Over Gas Blast Is Quickly Over". Los Angeles Times (21 January 1985). Retrieved 19 August 2023.{{cite journal}}: CS1 maint: url-status (link)
  21. ^ De Anda Torres, Martha Abigail (2010). La reconstrucción de la identidad de San Juan Ixhuatepec, Tlalnepantla de Baz Estado de México, 1984-2006 [The Rebuilding of the Identity of San Juan Ixhuatepec, Tlalnepantla de Baz, State of Mexico, 1984-2006]. Graduate dissertation (in Spanish). Ciudad de México: Universidad Nacional Autónoma de México. Retrieved 12 August 2023.
  22. ^ Pearce, Fred (18 July 1985). "After Bhopal, Who Remembered Ixhuatepec?". New Scientist (1465): 22–23.
  23. ^ API (2001). Design and Construction of LPG Installations. API Standard 2510 (8th ed.). Washington, D.C.: American Petroleum Institute.

Further reading

19°31′26.7″N 99°06′27.8″W / 19.524083°N 99.107722°W / 19.524083; -99.107722

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