Upon leaving an industrial gas production plant around 11 am, a 40,000-litre capacity tanker lorry carrying liquid hydrogen tipped over into a ditch on a curve in an intersection while travelling on a municipal road at the edge of town. The cistern was retained by an electrical tower and did not completely overturn. A whitish cloud dispersed through the degassing chimney on top of the cistern. First responders set up a 200-m safety perimeter and took 4 hours to evacuate 3 local residents. Fire-fighters controlled the container’s internal pressure, which was held to 0.1 relative bar. From 11:30 am until 2 pm, the explosimeter measurements conducted at the degassing chimney outlet, at a height of 3-4 m, remained positive. At 2:30, fire-fighters extended the safety perimeter to 600 m and lifted the cistern, thereby allowing technicians with the transport company to access the cistern control box. Responders closed the hydrogen degassing valve, which had been slightly opened due to the shock produced by the accident. The explosimeter measurements then turned negative. Around 5:30 pm, the semitrailer was placed back on the road and escorted into the industrial gas production plant, which was equipped with a degassing unit. During the emergency intervention, power and phone lines were cut, and the plant had to stop all production and evacuate its personnel. For the most part, the cloud was composed of nitrogen in liquid form in order to maintain the hydrogen at a cold temperature, with the inclined position of the cistern causing spillage into the degassing circuit. The cryogenic cloud dissipated thereafter.

The Classified Facilities Inspectorate visited the site. Given the presence of nitrogen protoxide storage, only empty semitrailers could be accommodated for degassing. According to the operator, the implicated rig driver came to the site of his own volition looking for replacement hoses. He accessed the site without waiting for the shift foreman’s approval and entered through the door that had not immediately closed following entrance of the previous vehicle. In recognising that the tanker lorry loaded with liquid hydrogen had accessed the site without authorisation, the foreman asked the driver to back up. During the manoeuvre, the lorry bumped the gate. The foreman then requested he exit the site by the rear; in advancing along this path, the driver missed a turn. Nitrogen protoxide production resumed on 30th June.

The Inspectorate noted a procedural problem in the industrial site’s safety management system (SMS), as the vehicle filled with liquid hydrogen never should have entered. Inspectors requested that the site operator issue a report analysing the causes of this incident. A follow-up inspection was ordered to ensure that new organisational measures had indeed been implemented as part of the operator’s SMS.