A gaseous oxygen (O2) pipe failed at around 4 am in a liquid oxygen production unit located in a port area. This pipe, most of which was buried underground, crossed the River Rhine to supply a German steelworks.

The pressure of 30 bar in the neighbouring pipe was within the operating pressure range at the time of the incident. The establishment’s internal emergency plan was activated. Relatively significant damage was subsequently observed: 4.6 t of O2 (as the pipe emptied) were discharged in 13 minutes, stones and gravel were blasted throughout an area 40 m in length and 20 m in width, ending up embedded in the neighbouring buildings and installations.

Significant external corrosion of the pipe, where it entered the ground, had caused the rupture. According to various appraisals, this corrosion was caused by the detachment of the waterproof protective lining following a faulty installation. Analyses carried out by the operator also revealed the presence of chloride ions on the steel in the area surrounding the point of rupture (de-icing salt?). Finally, cathodic protection was in operation at the time of the incident, but the hypothesis of electrical disturbances related to the damage caused by lightning on this protection were also considered shortly after the accident.

The resumption of the installations’ activities was subject to the prior repair of the pipe, as well as the recording and checking of the integrity and proper working order of the safety and control equipment of the installations that may have been damaged by the projections of materials.

Several measures have been implemented to reduce the likelihood of such an accident recurring: repair of the lining, creation of a 1 m deep shaft around the pipe, in the vertical part at the beginning of its buried section, modification of the maintenance plan to include an annual inspection of the lining, measurement of stray currents around the pipe’s interface with the ground, and improvement of the system to detect excess oxygen in the air, etc. Furthermore, all of the plant’s pipe inlets and outlets in the ground that were cleared and examined will be periodically inspected.

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