A leak of over-pressurised and overheated glycol water occurred at a chemical plant after the rupture of a pipe joint. At 2 am, a technician recorded a drop in coolant temperature (150°C), preventing vacuum drying operations from continuing. On-call staff diagnosed a loss of communication link between the utility automation feature and the plant’s digital control system. A specialist in such systems confirmed the defect of a card on the utilities automation, whose replacement had been postponed until the next morning. Once the specialist left the premises confident of his diagnosis, the on-call technician decided to restart the unit. He short-circuited all of the safety mechanisms for hot fluid, as noted by the supervisor, and replicated the corresponding settings in manual mode. Called by another workshop an hour later, the technician abandoned the post for 30 min. Upon his return, the hot fluid had exceeded 180°C, and a noise resembling a detonation shook th e plant. After joint rupture, the glycol water vaporised on the premises, which were closed immediately thereafter. The only consequence of this incident was a production loss. A plant working group suggested several remedial measures: revise access to the various system levels; reduce the number of staff members certified to take part in the programme and prioritise access ; train subcontracted personnel depending on their access authorisation; install cabled safety systems ; improve decision-making system reliability at night or outside of the normal schedule.