At around 1 p.m., the fire source on an incineration plant line went into overpressure (3mbar), causing a significant release of smoke in the plant and then outside via the smoke control systems. The standby technical personnel were called in and an attempt to retrieve a vacuum pressure was made by the operations manager until 2.30 p.m. A further peak at 3.7mbar caused the insertion of wastes to be stopped in order to shut down the line. At 3 p.m., the firefighters arrived on the site, alerted by an outside person, but did not intervene. At 6 p.m., the line was shut down and the furnace was empty.

By testing the fire’s draught and vacuum pressure with the empty furnace it was found that unclogging in automatic operation was no longer working. Monitoring of the sensors measuring the upstream/downstream pressure difference in the bags which actuates unclogging showed that the pressure sensor mounting flange was separated from the body of the bag filter, giving a distorted measurement. In the absence of unclogging, the filtration sleeves were filled with dust at an exponential rate until they no longer let any flow through.

Following the event, the operator:

• checked the flanges of the sensors on the other incineration line;
• planned verification of the condition of the flanges during annual technical inspection and maintenance;
• stepped up training concerning analysis of the malfunction found based on data reported in the supervision centre and the phenomenon observed;
• revised the organisation of emergency response in conjunction with the emergency responders.