Pollution
Humain
Environnement
Economique

At around 9 a.m. in a chemical plant, 200 litres of 60% hydrogen peroxide (H2O2, a powerful oxidant) overflowed from the manhole on a storage tank while it was being filled by a delivery truck. The operator manually stopped the unloading operation when he noted that product was spilling onto the ground. The in-house first responders sprayed down the tank and the fumes. The intervention ended at 9:30 a.m.

The operator’s inquiry into the accident determined the following:

  • the tank’s high-level sensor had not functioned due to oxidation of its connector owing to the corrosive environment;
  • the co-operator of the hydrogen peroxide tank had not drawn off the foreseen volume and had not informed the operator who had ordered the delivery;
  • the operator’s technicians, therefore, began filling the 51.4 m³ tank, which already contained 35 m³), with the 24 m³.

The operator has implemented the following measures to prevent this type of accident from happening:

  • the unit’s operators were reminded to check the available volume in the tank before initiating the filling operation;
  • instructions for reading the tank’s available volume before the loading operation begins and recording of the volume reading on a tank level logsheet;
  • replacement of the level sensor and definition of its useful service life (the sensor in question was more than 4 years old);
  • increase in the level sensor’s inspection frequency (quarterly instead of yearly);
  • installation of a continuous level sensor for each tank at a high level, the old level sensor (float type) is used as an independent, very light level sensor;
  • improved communication with the co-user company of the hydrogen peroxide tank.