In an urban boiler room located inside an incineration plant, the bottom valve of an oil tank suddenly ruptured at 1:55 p.m. At the time, the tank contained 778 m³ of heavy fuel oil. The fuel oil discharged into the retention tank at a rate of 40 m³/h. The liquid presence alarm in the retention tank’s low point and the level detection alarm were triggered. The technicians went to the site and discovered the leak.

Eight trucks took turns pumping out the fuel contained in the retention tank. With a capacity of 450 m³, it was unable to hold the entire volume of the tank. The leak was brought under controlled at 10:00 p.m. after a clamp was installed. In all, 280 m³ of heavy fuel oil had been spilt. The fuel remaining in the tank was drained out by gravity the following day. Tests conducted on the groundwater and soil revealed no trace of pollution.

The tank, built in 1992, had undergone a thorough inspection in 2010. The analysis of the causes of the sudden rupture of the valve made it possible to rule out the possibility of corrosion-related degradation. No trace of mechanism was observed on the valve, either internally or externally. The tank filling line, filled with fuel oil, had been steam-heated 2 hours before the rupture. This pipe had been closed at both ends. The operator determined that the liquid’s thermal expansion would have resulted in an increase in pressure-related stresses on the valve. These stresses, which exceeded the mechanical limits of the valve, would have caused a clean break between the valve body and the pipe’s connecting flange.