Jet Fire at Refinery Isomerization Unit Due to Compressor Failure
An isomerization unit of a refinery was affected. The release was caused by the mechanical failure of one of the two compressors working in parallel at a pressure of 20 bars, conveying the gas mixture needed for the isomerization process. The jet fire was the consequence of the release and ignition of a gas mixture containing hydrogen. The jet fire headed towards the adjacent benzene saturation section hitting the nearest equipment (a pressure vessel) located 14 m from the release point. Due to the weakening of this benzene saturation structure, benzene leaked and contributed to the broadening of the fire, with substantial destruction of the section. The length of the original jet-fire could not be calculated with precision because the flame hit against the saturation unit, but was has been estimated having a length of approximately 30 m in absence of obstacles. Due to the fact that the process control records did not register significant changes in the process parameters it has to be assumed that the failure of the crank mechanism was caused by aspects linked to maintenance or by a material defect.Off-site fire brigade teams intervened extinguishing the fire within approximately 1 hour and a half of work. No damage was reported to persons or to the environment.
Event Date
December 27, 2002
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The immediate cause of the fire was the mechanical failure of a compressor.The root cause was the failure in considering the possibility of domino effects from the fire in the isomerization unit (whose risk had been considered in the risk assessment).
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
Isomerization unit, gas compressor
Storage/Process Medium
Actual Pressure
20
Design Pressure
20
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
The release occurred on own of the two compressors working in parallel at a pressure of 20 bars, conveying the gas mixture needed for the isomerization process. The aim of a isomerization unit is to converts linear molecules (e.g. pentane) into higher-octane branched molecules for blending into the end-product gasoline. It is also used to convert linear normal butane into isobutane for use in the alkylation unit. it requires the feed of hydrogen. Maximum amounts of substances registered in the plant inventory were:- approximately 25,000 m3 of hydrogen rich gas mixture, therefore 1,500 m3 of pure hydrogen (approximately 1,5 tons).- 147000 t of liquid automotive petrol.The establishment extends over a surface of 100 ha.
Number of Fatalities
1
Currency
Lessons Learned
Lessons Learned
Various requests were issued by the legal investigation to the plant owner. Some were of technical characters, such as the replacement of the two horizontally-opposed compressors with simple centrifugal compressors in order to enhance isomerization unit reliability.other recommendations were aiming at improving the emergency operations, such as the modification of the locations of fire-fighting posts, improvement of personnel training and drills during emergency situations, and revise intervention and shutdown procedures for emergency situations.Finally, other requests regarded the safety management, including a new and a more accurate risk assessment.
Event Nature
Emergency Action
The emergency lasted for approximately 1.15 hr, from the moment of the release to the extinction of the fire. The accident could have caused more severe damage without the adoption of effective response measures and the joint effort of the on-site personnel and the off-site fire brigades; even if the on-site emergency response organisation could be improved.
Release Type
Release Substance
Hydrogen Release Concentration (%)
70.00
Release Amount (kg)
3000.00
Release Pressure (bar)
20.00
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
References
Event from the European database eMars
https://emars.jrc.ec.europa.eu/en/emars/accident/view/8bb6d0cc-dd21-292…
Full investigation reprot from French database ARIA (event 26983)
https://www.aria.developpement-durable.gouv.fr/fiche_detaillee/26983_en…