Hydrogen and methane release from a refinery plant

Event

Event ID: 790
Quality: 2
Description: In a petrochemical plant, a gas mixture at 270 bar made of 75% hydrogen and 25% methane leaked through the bottom valve of a dryer of a resin production unit.
After detection of the leak, the explosive zone near the equipment was estimated to be 7 m. Hydrogen sulphide (H2S) was detected around the leak. The installation was shutdown and depressurised, a nitrogen injection used to neutralise the gas mixture.
The emergency plan was called at 13:35, and terminated at 16:40, when the pressure in the dryer had dropped to 34 bar.
Event Initiating system: Non-Hydrogen system initiating event
Classification of the physical effects: Unignited Hydrogen Release
Nature of the consequences: leak no ignition
Macro-region: Europe
Country: France
Date: 31/05/2013
Component involved: reactor / oven / furnace / test chamber
Failure mode: rupture, no ignition
Initiating cause: unknown
Root causes: Unknown
Date entry in HIAD: 01/01/2020

Number of fatalities: 0
Number of injured persons: 0
Post-event summary: No ignition.
Emergency action: 13:10, The leak is detected, the installation is shut down and depressurised, a nitrogen injection neutralized the gas mixture.
13:35 The operator initiatives the emergency plan
14:00 The operator alerts the prefecture which informs the emergency services and the inspection of classified installations.
14:45 The prefecture decides to close the departmental road located 60 m from the unit accident because of the risk of explosion or fire (type "torch"); the plant staff is confined.
The pressure in the dryer drops to 34 bar.
16:00 The staff is de-confined
16:40 the emergency plan is terminated and the Crisis Staff at 17.15 pm.
The prefecture broadcasted several press releases during the event.