Pollution
Humain
Environnement
Economique

A release of liquid oxygen and subsequent fire occurred on a air separation plant, killing one employee. Before sending liquid oxygen into a cryogenic storage tank, the pipe was cleaned using a flush of oxygen. After the flush, the valve did not close correctly ; instead of entering the tank, 2.4 t oxygen were released on the gravel bed near the tank and vaporized into the atmosphere. At 17 pm a fire broke out inside the building, killing one employee, who had been sent to check for an oxygen alarm in the nitrogen cooling circuit.

The fire spread rapidly despite the response of fire detectors ; it destroyed most rooms on the ground floor and on the first floor of the building. The fire brigade brought the fire under control around 18 h. The damages amount to 250 000 euros. No environmental pollution has been reported.

The pneumatic flush valve, did not close correctly because the relief pipe for the expansion of the compressed air was iced up due to atmospheric conditions and insufficient sizing of the pipe cross-section and did not allow the compressed air to expand. The display on the control monitor indicated erroneously that the valve was closed, not allowing the personnel to identify the failure. It was indeed assumed that the valve would close after the set flushing time and the real status of the flush valve was not monitored : no end point control device was installed.

The operator modified its process : he installed an end point monitoring device on the flush valve to display the real position of the valve in the control room, and modified the compressed air relief pipe. He sat up a monitoring system of the on-site ambient air oxygen content both in the open air and inside the buildings. The alarm will be visually displayed on the control monitor and acoustically signalled on the whole site. The employees will be trained on how to react to that new alarm.