At a site producing industrial gases (O2, N2), a valve opened on a vaporised O2 circuit supplied by a liquefied oxygen tank (LOX). The unit had been shut down (a high energy consumption day) and the customer supplied on line was scaled back. The LOX vaporisation station maintained the O2 pressure in the network. During the day, the operator replace his FOXBORO software which drives the unit with a compatible “Year 2000” version.

At around 7 pm, with the unit still shut down and without the operator’s knowledge, the restart of the system stopped a water pump used to vaporize the LOX. An hour later, the temperature of the O2 from the vaporisation pool was too low, causing the safety system to be triggered: a valve closed downstream from the vaporisation bundle, the LOX pump shut down and the FOXBORO software alerted the supervisor on duty. The trapped LOX vaporised, and one of the unit’s 2 valves opened. The noise alerted a local resident living nearby. The police and fire department arrived at the scene and the incident was brought under control in 15 minutes.