The Shell Oil Norco VCE, Louisiana, 5 May 88 Presented to ES-317y at UWO in 1999. Dick Hawrelak

The Incident 20,000 lbs of hydrocarbons were released from the fractionating tower into the congested area of the Catalytic Cracker Unit (CCU). Within 30 seconds the vapor cloud ignited. The flames accelerated in the congested area and the event escalated into a detonation class VCE.

Plot Plan of Area

The Consequences 7 workers in the CCU were killed. 50 plant workers were sent to hospital. The CR disappeared. 4,000 people in Norco were evacuated. Building damage extended 8 blocks (3,750’) into the residential area of the city. Property damage was estimated at $300MM.

Events Leading to the Incident

Events Cont’d For 19 years operators had added methanol solution to the fractionating tower to prevent hydrate formation in the condenser. On engineering’s recommendation, operations replaced the methanol solution with a superior anti-fouling agent. Within 6 months of the change, an elbo downstream of the addition point corroded opening an 8 inch hole in the line.

Lessons Learned Engineering failed to test the corrosion characteristics of the new anti-fouling agent. The CCU was far too congested. The CR was too close to the CCU and was not hardened. The city of Norco was too close to the company fence line.

Similar Incident 9 Nov 92, major explosion at the Total, La Mede refinery near Marseilles, France. Major explosion in gas concentration section of the cat cracker. 7 dead, 10 injured. Damage to housing and shops 5 km. away. Unhardened control room was too near cracker and was completely demolished.