Around 10:30 a.m., a tank of petroleum overflowed at a flammable liquid storage facility. The quantity transferred to the tank was greater than the capacity available. The petroleum flowed into the tank’s retention basin. The operator was alerted by the hydrocarbon detection probe located in the retention basin and the transfer was stopped. The 5 m³ of product that had spilt into the retention basin was recovered.

Causes of the incident

The tank is equipped with an internal floating screen, a high-level sensor and a very high-level sensor. No sensor had functioned. The screen sank, damaging the internal reference rod. Also, the operator in charge of the transfer had overestimated the time needed for the transfer. The transfer procedure includes 1 hour of monitoring after it has begun, which was not observed.

Measures taken by the operator

The operator drained the tank. He conducted his assessment and checked the level probes. The following corrective measures were taken:

• the transfer procedure was modified:
  • the transfer duration calculation was double-checked,
  • the dipping operations are conducted every half hour instead of every hour,
  • the flow rate of internal transfers was reduced to 300 m³/h.
• the frequency of level probe tests was reduced to 3 months instead of 6 months,
• a radar-based level measurement was implemented in order to provide back-up for the measurement technologies.