In a chemical factory, a boiler built in 1962 that was producing 100 tonnes/hr of vapour at 82 bar and 475°C exploded 3 days after restart following a 3-month shutdown for maintenance. The energy created cut 23 tubes out of the 470 present on the installation (A37 steel, diameter: 63 to 76 mm, thickness: 4-5 mm) less than 20 mm from the lower and upper drums. The screen burst open and was moved. Tube debris and refractory masonry were ejected a distance of 100 m and slightly injured a technician. This accident might have been caused by the simultaneous bursting of several corroded tubes (2-mm diameter) due to acid deposits (composed of metal sulphates), within a heterogeneous overlapping zone, followed by erosion as a result of a perforated tube. The cost of repairs was valued at 15 MF.