During a scheduled maintenance operation in a chlorochemical plant, in which the facilities had been shut down for several days, two subcontractors were installing steam traps on a steam line in the Vinyl Chloride Monomer workshop. The facilities had been made available to them by the operator. The facilities had been shut down during the maintenance operation. At about 11:30 a.m., while in the process of dismantling a 3/4″ valve, the first technician was hit by a jet of steam at 25 bar, severely burning him on his abdomen and legs. He was initially attended to by the firefighters from the petrochemical platform and then was evacuated by helicopter to a hospital. The second, surprised by the jet of steam, fell off the scaffolding from a height of 3 m, and was taken to hospital for observation. The leak was isolated, and the premises were secured, resulting in no impact on the environment or the facilities.

According to the establishment’s safety manager, the pressure equipment was not defective. The accident was the result of a deliberate venting operation when the valve was being dismantled. The facility operator prepared a press release in the afternoon.

The investigation conducted by the operator showed that the 3/4″ valve being worked on had been equipped with a very old and unreferenced “Prestofuite” type internal injection system (installed more than 20 years ago). Neither the unit’s technicians nor the subcontractors had been able to detect this invisible injection element from the outside the valve. This injection distorted the steam line’s energy reset diagnostics when the line was made available for the maintenance work. After the valve was disassembled, the valve and plug assembly were suddenly expelled by the residual steam under pressure.