An explosion rocked the boiler facility in a distillery. A specialised company was replacing valves, natural gas lines running to the boilers, modifying vents, and installing purge and inerting connections within the scope of preventive maintenance operations. The work began which began on 12/21/2005 was to be completed 01/02/2006 as the distillery was closed from 12/23 to 01/03. The gas line was replaced after the gas was shut off and purged, as planned. On 12/29, the maintenance technician felt that he had completed the work but did not conduct a leak test with compressed air or nitrogen. He opened the gas without closing a flange (dia. 80) on boiler No. 3, releasing a significant amount of gas into the building. Two heat sources may have created enough energy for the explosion: the halogen lighting in the false ceiling was on while the operator was welding on the other side of the wall from where the gas was.

The electricity and the gas were disconnected, and the firefighters and gendarmerie arrived at the scene. A security perimeter was set up. The 2 technicians were hospitalised for examination, and were released 2 hours later. The explosion raised the roof of the boiler facility, damaged a gable wall and the room’s electrical cables. Operations at the site were shut down considering the extent of the damage. The boiler was reworked, and the building, electrical wiring roof and false ceiling were renovated.

The gendarmerie and insurance reports indicated the subcontractor’s disregard for recognised trade practices and safety rules were responsible for this accident. The type of cause is not identified in the specific hazard prevention document which does not include human failures. In this respect, the prevention plan reiterates the risks and the protective means to be used without going in to detail with regard to operations that could be considered recognised trade practices.

In the future, the prevention plans for external companies shall be checked by the Industrial Director and the QSE Supervisor. The respect and application of the defined rules shall be followed by the QSE Supervisor who shall have the authority to stop job site operations as required. Delicate phases (reopening of gas lines…) shall be conducted in the presence of an independent organisation or technical representative from the subcontracting company