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This data is from the European Hydrogen Incidents and Accidents database HIAD 2.1, European Commission, Joint Research Centre.

Explosion of a Hydrogen/Oil Mixture in a Refinery
The event started at the effluent pipe of one of the hydro-cracking reactors, which broke and released a mixture of hydrogen, light gases (methane, butane), light gasoline; heavy gasoline; gas oil. The mixture instantly ignited upon contact with air, causing an explosion and fire.The explosion caused one fatality a several injuries The pipe ruptured due to excessively high temperature, in excess of 14000 F (760 C). This high operating temperature was initiated by a temperature excursion in one of the a catalyst beds of the reactor which raised the temperature in the reactor effluent pipe. The runaway event was a consequence of the failure of initiating the shut down procedure which is foreseen by operating procedures in case the reactor temperatures exceeded the 800 F temperature limit (425 C). This procedure foresaw the full depressurization of the reactor.The cause of the temperature excursion was probably related to poor flow and non-uniform heat distribution.
Event Date
January 27, 1997
Record Quality Indicator
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
According to the EPA report (see references), the immediate cause of the rupture of the effluent pipe due to excessively high temperature.Contributing cause was the fact that the operators did not activate the emergency shutdown procedure because they were confused about whether a temperature excursion was actually occurring (difficult interpretation of the signals). The investigators identified the following root and contributing causes:(1) The conditions to support employees to operate the reactors in a safe manner inadequate.(2) Human Factors, poorly considered in the design and operation of the reactor temperature monitoring system.(3) Supervisory management inadequate.(4) Operational readiness and maintenance inadequate.(5) Operator training and support inadequate.(6) Procedures outdated and incomplete.(7) Inadequacy of the process hazard analysis (8) Barriers against hazardous work conditions inadequate.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
Hydrocracking unit, pipe
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Consequences
Number of Injured Persons
2
Currency
Lessons Learned
Lessons Learned
The EPA investigators developed recommendations to address the root causes of this accidents. Among those, the following ones are related to general lesson learned:(1)Process instrumentation and controls should be designed to consider Human Factors, consistent with good industry practice. For example, a hydro-processing reactor temperature controls should be consolidated with all necessary data available in the control room. (2)Backup system of temperature indicators should be used so that the reactors can be operated safely in case of instrument malfunction. Each alarm system should be designed to allow critical emergency alarms to be distinguished from other operating alarms. (3)Adequate supervision is needed for operators, especially to address critical or abnormal situations, ensuring that all required procedures are followed. (4)Facilities should maintain equipment integrity and discontinue operation if integrity is compromised. Maintenance and instrumentation support should be available during start up after equipment installation or major maintenance. (5)Management must ensure that operators receive regular training on the unit process operations and chemistry. (6)Management must develop written operating procedures for all operations. The procedures should include operating limits and consequences of deviation from limits. (7)Process hazard analyses (risk assessments) need to be based on actual equipment and operating conditions that exist at the time of the analysis. (8)A Management of Change review should be conducted for all changes to equipment or the process, as necessary, and should include a safety hazard review of the change.
Event Nature
Emergency Action
A hundred of firemen intervened. The fire was extinguished after 3 days. The emergency measures implied confinement of 1000 people in the surroundings.
Release Type
Release Substance
Hole Shape
Hole Length (mm)
6000
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
References

Event description in the French database ARIA
https://www.aria.developpement-durable.gouv.fr/accident/11934/
(accessed December 2020)

The EPA (US Environmental Protection Agency) Chemical Accident Investigation Report, downloaded from https://nepis.epa.gov/

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