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

Explosion and Fire in a Petrochemical Plant
The explosion occurred in a Litol benzene unit, when it was being restarted following a scheduled shutdown for maintenance. The explosion followed the release of about 30 kilograms of hydrogen gas into a compressor shed from a burst flange operating at 4.8 MPa (700 psig). Two men were killed and two more were injured. The investigation is reported in the referred scientific article, and arrived to these conclusions: 1. the hydrogen was released through a failed flange gasket 2. it accumulated and ignited under the roof of the compressor shed. It also escaped from this semi-confined structure and accumulated under the roof of an adjacent building.3. Probably the cloud under the roof of the compressor shed ignited first, and deflagrated to the rest of the cloud.4. the total estimated cloud mass was 30 kg, however the force of the blast suggest a much higher energy. 5. Flange and gasket were of he correct type. Perhaps the gasket was displaced and/or the bold improperly tightened. This leak could not have been detected, because the leak test procedure use gas only up to 0.7 MPa. .
Event Date
April 20, 1984
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The immediate cause was the failure of a gasket on hydrogen compressor.The immediate cause was the failure of a gasket on hydrogen compressor. According to MacDiarmit 1989 (see reference), the real cause of the gasket failure could not be found, despite establishing that the gasket was not catered. This could have been caused by the use of a lubricant when installing the gasket, and the use of a gasket type not corresponding to the original specification (but which demonstrated good performance for many years).According to the already mentioned source, a contributing or root cause were unauthorized or improperly considered modifications, which clearly played a major role in this incident. There had been several modifications carried out in the Litol unit which were not adequately documented or for which documented authorization was not available. For example the installation of a valve drain and the addition of gables and a wall to the compressor shed originally consisting of only a roof over the compressors. The walls were likely added to aid in winter operation and maintenance, but hindered the dispersion of the gas.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
litol benzene conversion unit, hydrogen compressor
Storage/Process Medium
Storage/Process Quantity
30
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
After a maintenance outage, the plant was starting up for a new production run. The accident occurred after the hydrogen system pressurization past 600 psig. The incident occurred on a plant holiday, and all the offices were empty. The plant produced styrene monomers. The plant used a hydro-de-alkylation process on coke oven light oil to make the benzene needed for a styrene production process, by means of Litol a catalyst . This complex, single-step process achieves desulfurization, removal of parafns and naphthenes, and saturation of unsaturated compounds, in addition to de-alkylation and dehydrogenation.
Currency
Lessons Learned
Lessons Learned
According to MacDiarmid et al (see references), following the accident and the investigation, the following safety measures were implemented in the plant: (1) Operative procedures were reviewed and improved, (design and engineering safety checklists, material specifications) (2) Blast and Fire Resistance was improved (separation standards for buildings and facilities, more resistant components for building components) (3) Management of change procedure was adopted, with a focus on closure technologies (4) To avoid full emptying of storage unit during accidents, emergency shut-off valves were installed (5) Safety awareness was increased by better communication and training. One additional conclusion coming from the investigation (see MacDiarmid et al.) is that the use of the TNT-equivalent method for quantifying hydrogen explosion must be done with great caution. The prediction of blast effects can be complicated by real-world factors.
Event Nature
Emergency Action
Major fires in the unit burned themselves out in few minutes but one fire lasted for eight hours, was fuelled by benzene flowing out of a tank connected to a damaged flange which could be isolated.
Emergency Evaluation
According to the referred source, the outside response was very effectively coordinated through the local Chemical Valley Emergency Control Organization. The emergency response was rapid and neighboring companies and the neighbouring city provided additional fire-fighting equipment ,such as a directed-foam truck, Since the power to the affected unit was shut off, the oily water separator pumps stopped and caused firewater to back up on the unit. This water plus debris and scaffolding from theturnaround combined to hinder firefighting.
Release Type
Release Substance
Hydrogen Release Concentration (%)
100.00
Release Amount (kg)
30.00
Release Pressure (bar)
48.00
Hole Shape
Ignition Source
Ignition Delay (s)
10
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References

Cadwallader and Herring
Safety Issues with Hydrogen as a Vehicle Fuel
September 1999
Idaho National Engineering and Environmental Laboratory, INEEL/EXT-99-00522
The event described here is summarised at page 42

Prof. J. Lee presentation at 1st European Summer School on Hydrogen Safety (ESSH)
available at the HySafe project site
http://www.hysafe.org/science/eAcademy/php/1stesshsprogram.php
(see slides from 13 to 15, accessed October 2020)

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