At 6.10 am, a 3000 litre hydrogen gas tank dating back to 1939 (L=14 m, diam.=570 mm) exploded at 135 bar during hydrogenation in a chemical site. The technicians who witnessed the violent explosion followed by a red-orangey fire ball sounded the alert. The hydrogenation workshop was urgently shut down. The start of fire was quickly brought under control. The H2 station commissioned in 1986, located in an open underground pit with an asbestos cement roof assembly (L=16 m, B=5 m, depth= 4 m) and 20 m at the boundary of the site housed eight 1,000 to 3,300 litre forged cylinders in horizontal position mounted on metallic supports and connected by pipes with manual control valves. All cylinders were emptied. The single supply pipe was fitted with a pneumatic valve that closed upon lack of air and was controlled by a palm button. Its air supply, cut off by a projected horizontal hydrogen gas tank fragment (a 183 kg fragment was projected at 22 m, a 33 kg fragment was projected at 145 m) isolated the plant from the pressurised units.
No casualties were reported. Internal and external material damage were observed as far as 500 m in the storage axis, most of it being confined within a 350 m radius: rupture of claddings and asbestos cement roof assembly of exposed workshops, window panes, showcases of shops, displaced tiles. The explosion could have resulted in physical injury outside the site at a less favourable moment.
The expert report concluded the differed rupture (static fatigue) of the tank by the embrittlement of steel under the effect of hydrogen. The recycled cylinder was used on other sites mainly to store nitrogen. The site had two H2 plants to make up for the low flow rate during the various hydrogenation cycles as the compression station did not have a sufficiently high flow.
The use of the network and all pressurised hydrogen capacities (150 bar) of the plant was stopped and replaced with a direct supply under 35 bar.