Explosion at the Cracking Unit of a Refinery
The accident occurred in the cracking unit and in the sulfur recuperating system, more exactly in a 90 curve of a 8" piping. Due to the crack of the curve a mixture of flammable gases was released from the tube; the gas/vapor cloud exploded and took fire. The released gas was recycle gas consisting of 80 vol% hydrogen, 14 vol% methane, 1.8 vol% hydrogen-sulfide , rest C2, C3 and C4 gases and water vapor. A large part of the plant was destroyed. The fire was mainly sustained by the petroleum derived. The smoke cloud was not toxic.
Event Date
June 15, 1992
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The results of investigations showed it was a spontaneous rupture in the curve. Through the hole in the curve the escaped gas exploded and took fire.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
sulfur recuperating system of hydrocracker
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
The operational values were 50 bar at 300C. The plant was built in 1974. The last shut down for a complete revision was in 1989. During those maintenance works it was changed a curve of the gas recycle system due to its corrosion. Other curves in the same piping were not corroded. In the period between the years 1989 and 1992 the thickness of the tube was regularly measured and never was found an abnormal corrosion
Consequences
Number of Injured Persons
100
Number of Fatalities
23
Currency
Lessons Learned
Lessons Learned
The installation was rebuild up, the use of 90 curves restricted and the gas speed decreased by increasing the tube diameter.
Event Nature
Emergency Action
As emergency response to the event, the plant was shut down, electrical supply was cut and loading/unloading operations were stopped. The internal emergency plan operated correctly.
Release Type
Release Substance
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
References
Event description in the European database eMARS (accessed December 2020)