A Flash Fire on the Hydrogenation Unit
The event occurred while starting a new production cycle. The production supervisor issued specific instruction on a new production cycle to a technician. The technician did not follow them in the right sequence as indicated in the verification instructions before staring production: to save time when pressurizing the device at 9 bar of nitrogen, he simultaneously made several adjustments and carried out several checks (opening the manual H2 valves of the storage tank, the emergency shutdown valve just in front of the workshops, etc.). The reactor and safety process valves in front of the reactor were protected by a check valve that remained closed. The reactor was pressurized using nitrogen. The operator observed N2 leaking from a manhole. He decompressed the reactor and removed the fastening bolts from the lid to change the joint. During this operation, he heard a leaking noise at the joint. Believing it to be a H2-leak, he blocked the reactor and triggered the emergency shutdown. He was convinced that the reactor was clean and the residual volume in the pipe was low and proceeded to change the joint with assistance from a fellow technician. It followed an explosion that projected backwards the4two technicians.
Event Date
February 12, 2007
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes (Select all applicable options):
Cause Comments
The immediate cause was of the explosion was probably identified by the inspection in small quantity of hydrogen ignited by the catalyst in presence of oxygen coming from the manhole. Drying conditions could have increased the pyrophoric properties of the catalyst.The root cause was the operator not following the chronological order of checking as specified by the instruction.
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
Hydrogenation unit
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
Few day before the accident, the hydrogenation reactor had been cleaned up and dried to eliminate all residue of the preceding synthesis.
Number of Injured Persons
3
Number of Fatalities
1
Currency
Lessons Learned
The inspection expert found additional deficiencies in the procedures: no leak detection had been on the hydrogen valves and instructions were missing for opening of the manhole in normal or abnormal operation and exchange of the corresponding seal.Moreover, the design for sampling and introducing hydrogen was favoring formation of leaks on up-stream valves in presence of catalyst in the reactor.As corrective measures, changes have been planned:1) in the hydrogenation equipment: installation of pressure sensors and flame guards on regulator vents2) in the procedures: risk analysis, verification of the status of the hydrogen line, de-commissioning the H2 pipe before opening the manhole.
Emergency Action
A safety alert was sounded in the workshop. The Internal Operation Plan and the ETARE plan are launched. The operator decided to shut down the site for 48 hours.
Release Type
Release Substance
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
Event no. 32796 of the French database ARIA (accessed December 2020)