Event
- Event ID
- 895
- Quality
- Description
The fire occurred on the tube plate gaskets of 3 of the 4 exchangers loaded with catalytic reforming effluent. The fuel (500°C and p=30 bar) was a mixture of 30% hydrocarbons and 70% hydrogen.
After depressurisation of the unit and nitrogen flushing (some problems to access the valves), the exchangers being cooled (overall flow 600 m³/h on 3 units), the fire was controlled until extinction by nitrogen injection.
The accident was apparently due to incorrect tightening of the threaded rods; only 1/5 were correctly tightened on one of the heat exchangers involved. Three threaded rods break and the gasket surfaces were poorly prepared.
- Event Initiating system
- Classification of the physical effects
- Hydrogen Release and Ignition
- Nature of the consequences
- fire
- Macro-region
- Europe
- Country
- France
- Date
- Component involved
- heat exchanger (flange)
- Failure mode
- rupture & ignition
- Initiating cause
- loss of tightness (wrong operation)
- Root CAUSE analysis
The INITIATING cause was the release of hydrogen at a flange.
The ROOT (or INTERMEDIATE) cause was the wrong execution of the flange joint (incorrect tightening, bad quality of the gasket surface)- Root causes
- Date entry in HIAD
- 01/01/2018
Facility
- Application
- Petrochemical industry
- Sub-application
- Catalytic reforming processes
- Hydrogen supply chain stage
- All components affected
heat exchanger of the catalytic reforming unit
- Process temperature range [C]
- Very high temperature (500°C to 1000°C)
- Location type
- Open
- Location
- industrial area
- Operational condition
Emergency & Consequences
- Number of fatalities
- 0
- Number of injured persons
- 0
- Post-event summary
The tightening procedure is reviewed (hot tightening procedure: 340 °C and 8 bar) before the
charge is introduced again.- Emergency action
The unit was depressurised, nitrogen flushed (with some problems to access the valves), the exchangers being cooled (overall flow 600 m³/h on 3 units), the fire was controlled until extinction by nitrogen injection.
Lesson Learnt
- Corrective Measures
The flange tightening process was reviewed and improved.
In-depth data
- Release type
- gas mixture
- Involved substances (% vol)
- H2 70%
hydrocarbons 30% - Release temperature [°C]
- 500
- Probable IGNITION SOURCE
References
- Sources categories
- ARIA
- Reference & weblink
Event description in the French database ARIA
https://www.aria.developpement-durable.gouv.fr/accident/26616/
(accessed September 2020)
