After filling one diesel compartment of a road tanker and leaving the filling arm in place, a lorry driver installed a second arm on an empty tanker compartment. He inadvertently initiated a transfer using the wrong arm, into the already full compartment, and 1 m³ of product overflowed via the manhole safety valves. The driver then activated the emergency shutoff, and the oil depot was placed in safety mode. The effluent and rinsing water were collected on-site without causing a pollution incident.

Analysis revealed that the anti-spill probe (installed on the tanker) for the compartment that overflowed had become inoperable. This device should have halted the transfer automatically. Moreover, the loading station’s programming system displayed a design flaw, whereby it validated filling orders under the sole condition that the compartment was empty (via a dedicated sensor), yet without verifying that the selected arm was positioned on the appropriate compartment.

Subsequent to the accident, the oil depot operator implemented a weekly inspection plan covering all electronic devices connected to road equipment and furthermore requested lorry drivers allowed to operate on-site to control the anti-spill probes of their cisterns with the same weekly frequency. The operator also issued a reminder of relevant best practices and ran a driver training refresher course.