Major Process Safety Incidents
Introduction
Major process safety incidents have left devastating marks on industrial history, reminding the world of the importance of rigorous safety management. Starting from the infamous Bhopal Gas Tragedy in India (1984), through the Texas City Refinery Explosion in the United States (2005), and the Deepwater Horizon Oil Spill in the Gulf of Mexico (2010), all were caused by system failures, human errors, and poor safety culture. All of them led to large-scale casualties, environmental damage, and financial losses. These major process safety accidents must be well known so that lessons can be learned from them to avert future calamities of a similar nature.
1. Bhopal Gas Disaster—India, 1984
The Bhopal Gas Tragedy on the night of December 2–3, 1984, is the world’s worst industrial disaster. It was the leakage of methyl isocyanate (MIC) gas from the Union Carbide India Limited (UCIL) pesticide factory in Bhopal, Madhya Pradesh. The tragedy led to immediate and long-term health emergencies, environmental pollution, and persistent legal and social issues.
The direct cause was the filling of water into Tank 610, which held about 42 tons of MIC. This caused an exothermic reaction, which filled the tank with heat and pressure in a short amount of time and finally ruptured safety valves to release a poisonous cloud of gas over Bhopal.​
Methyl Isocyanate properties
- Extremely dangerous compound
- Reactive, volatile, toxic, flammable
- Maximum exposure concentration off MIC over 8 hrs = 0.02ppm
- Exposure over 2.1ppm experiences severe irritation of nose and throat
- At large concentrations—death due to respiratory distress
- Physical properties
- Boiling point at atmospheric conditions is 39.1 °C
- Vapor pressure at 20 °C = 348 mmHg
- Vapor twice as heavy as air
- Chemical properties
- MIC reacts exothermically with water
- Slow reaction, but with inadequate cooling, temperature will increase and MIC will boil. So MIC storage tanks are typically refrigerated
Immediate Fatalities: Different estimates of immediate fatalities are mentioned, ranging from the officially reported at least 3,800 fatalities to different estimates of up to 8,000 fatalities in the initial two weeks.
Wikipedia
Injuries and Health Impacts: Over 500,000 people were exposed to the gas, with resultant respiratory distress, eye irritation, and other acute trauma. Respiratory disease, neurological disease, and increased rates of cancer and birth defects are long-term health impacts.
Environmental Pollution: The soil was extremely polluted over several decades with toxic chemicals that seeped into the water and soil, affecting the local agriculture and water supply.
Texas City Refinery Explosion—USA (2005)
On March 23, 2005, the Texas City Refinery Explosion was among the worst major process safety incidents to have occurred in the USA. It occurred at the refinery plant owned by BP in Texas City, Texas, and claimed the lives of 15 workers, injured over 180 other workers, and caused bad damage and harsh criticism of safety practices followed in the oil industry.
| Date | March, 23 2005 |
| Refinery Name | BP Texas city Refinery (British Petroleum) |
| City | Texas, USA |
| Manufacturing | Oil refineries (Isomerization units) used to raise gasoline octane |
British Petroleum’s Texas refinery at that time was the United States’ second-largest refinery, refining approximately 3% of the nation’s gasoline.
What Happened
Startup of ISOM Unit
It was the day of the accident when the ISOM unit raffinate splitter tower was in the process of start-up following shut-down.
Overfilling the Tower
Due to defective level sensors and ineffective monitoring, the tower had been overfilled with liquid hydrocarbons beyond its usual safe operating level.
Outdated Safety Equipment Used
Excess hydrocarbons were blown out to a blowdown drum and stack, an outmoded practice that was supposed to vent vapor—rather than liquids. Amazingly, this configuration was not connected to a flare to burn excess hydrocarbons in a safe manner.
Massive Release of Hydrocarbons
Nearly 76,000 liters (nearly 20,000 gallons) of flammable hydrocarbons were blown out into the atmosphere, producing a gigantic vapor cloud.
Ignition and Explosion
The cloud of vapor was most likely caused by the heat from the hot diesel engine of an approaching truck or by welding processes. This caused an enormous explosion that leveled structures in the devastated region, which comprised office trailers.
Fatalities
There were 15 fatalities, and all were in temporary office trailers, which incidentally just so happened to be situated immediately next to the blowdown stack. The trailers themselves were not explosion-proof. Over 180 injuries and thousands of lawsuits from affected workers and families.
Financial impact
over the $2 billion total cost, $50 million crime fine, and $87 million OSHA fine. This is history’s largest fine.
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Deepwater Horizon Oil Spill—Gulf of Mexico (2010)
The Deepwater Horizon oil spill is the largest in history, and one of the worst major process safety incidents was the largest oil spill ever and generated grisly environmental, economic, and human losses. On April 20, 2010, there occurred a case of this oil spill whereby millions of barrels of oil had been streaming out in the Gulf of Mexico for 87 days.
| Name of Incident | Deepwater Horizon Oil Spill |
| Date | April 20, 2010 |
| Location | Macondo Prospect, Gulf of Mexico (approximately 41 miles off Louisiana) |
Refinery name | British Petroleum |
| Rig Owner | Transocean Ltd |
| Rig Name | Deepwater Horizon (ultra-Deepwater, semisubmersible drill rig) |
| Fatalities | 11 workers |
| Depth of Well | ~5,500 ft water depth; ~18,000 ft total well depth |
| Duration of Spill | 87 days (through July 15, 2010) |
| Total Oil Released | 4.9 million barrels (206 million gallons) |
What Happened
April 20, 2010—Blowout and Explosion
- Following drilling that was close to completion, the team started to abandon the well temporarily.
- The blowout happened as high-pressure oil and gas encroached into the well, going around safety equipment.
- The blowout preventer (BOP), which is a fail-safe mechanism, failed to seal the well.
Gas caught fire on the rig, resulting in two explosions and an enormous blaze. 11 men lost their lives, and the rig burned for 36 hours.
April 22, 2010 – Rig Sinks
- The Deepwater Horizon rig went down and into the ocean.
- The wellhead was left open on the seafloor, pumping oil around the clock.
Reasons Behind the Disaster
1. Failure of Well Integrity
Cement that sealed off the well did not last, forming a pathway along which gas moved up the casing. BP chose a riskier, cheaper cementing method, despite warning signs.
2. Misinterpretation of Negative Pressure Test
One of the key tests designed to check well stability came back with anomalies. They were misinterpreted or disregarded, and complacency followed.
3. BOP Failure
The blind shear ram of the BOP—used to sever and seal the pipe—failed due to misalignment and hydraulic breakdowns.
4. Safety Culture Failure
BP and contractors put speed and cost above safety. Communication was poor, decision-making was poor, and risk assessment was poor.
5. Environmental Impact
Oil Released: 4.9 million barrels (approx. 780,000 m³). 1,300 miles of coastline were affected.
Gigantic destruction of sea life : fish, turtles, dolphins, and birds.
Coral reefs, marshes, and deep-sea environments were devastated.
Thousands of marine wildlife and birds were killed or contaminated.
Economic Impact
Tourism and fishing industries in Gulf nations were devastated.
Fishing grounds were shut down; livelihoods were lost.
Estimated economic loss: over $60 billion (including clean-up, settlements, and fines).
Legal and Financial Impacts
BP Penalties and Payments
$20.8 billion settlement (largest in U.S. history) with the Department of Justice and five Gulf states.
Made billions more in payments to businesses, governments, and individuals.
Various lawsuits were filed against BP, Transocean, Halliburton, and other contractors.
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