A leak of heavy fuel oil was discovered around midday in the hydrocarbon storage area of a thermal power station. The leak originated on a pipe downstream from a transfer pump. The fuel oil was sprayed against the wall of the retention tank, causing the liquid to mist. The operator stopped the transfer pump as soon as it was detected. Pollution barriers were set up around the site and several on-call teams were brought in to assist in the intervention. 10 m3 of fuel oil was released but remained within the confines of the site.

The operations to clean-up and recover the fuel oil began at approximately 2 p.m. The piping was repaired. The operator excavated 20 m3 of polluted land.

The cause of the leak was attributed to fatigue failure of a branch connection on the heavy fuel oil transfer pipe. This rupture was localised upstream of a shut-off valve of the branch connection. Improper installation of the branch connection (excessive offset) and strong vibrations in the piping led to excessive fatigue stress on the fitting.

The operator eliminated the unnecessary connections on the installation. Modifications were carried out on the retention basins to reinforce their tightness. He also decided to make transfers during business hours.