At 7:23 a.m., a gas leak was detected by a sensor in an LPG storage depot. The operator secured the site by isolating the area of the leak. The police set up a security perimeter around the industrial estate, stopped traffic, and the employees were asked to evacuate the site. The site’s emergency responders were able to dissipate the gas cloud by spraying it with water. The security perimeter was lifted once the explosive gas level measurements confirmed that it was no longer dangerous and the site’s activity resumed during the day.

It is presumed that the leak was caused by a release from a valve on an LPG transfer line between the refinery and a distribution site. A power failure on an inverter caused all the installations on the distribution site to be shut down. The motor-operated LPG valves, which are fail-safe valves, were therefore closed while LPG was being transferred from the refinery. The increased pressure in the pipeline, coupled with a possible calibration defect on the thermal expansion valve (opening at 13 bar instead of 16 bar) upstream of one of the closed motor-operated valves, led to the release of LPG into the atmosphere. Due to the total absence of wind, the LPG migrated to a low point where a gas detector was tripped.

Following this incident, the operator:

• replaced the valve and modified its calibration pressure,
• checked its electrical installations and had any modifications verified by an authorised body,
• implemented regular calibration verifications on valves located upstream of the ¼ turn valves,
• updated its alert procedures and its telephone directory.