Pollution
Humain
Environnement
Economique

A test was performed on the boiler of a cheese factory at around 8 a.m. No incidents were reported until 8:15 a.m. when a loud noise occurred. The electrician was alerted by the power alarm at 8:20 a.m. The boiler had shut down, and its rear door had come off its hinges. The cover of the front burner had also been ejected, suggesting that an overpressure had occurred inside the boiler. The gas supply valve was locked out, and the boiler’s electrical cabinet was switched off. An examination of the chimney’s structure was conducted to determine its integrity, and the boiler was locked out. The manufacturer was called, and a request was made to immediately send over a technician to note and explain the accident.

The boiler was in its start-up phase. The accident suggests that gaseous residues were still present in the combustion chamber when the electrodes were ignited. This hypothesis must be verified by blank (gas-free) tests by the manufacturer.

The action plan recommended by the boiler manufacturer was as follows:

  • inspection of the burner’s start-up phases;
  • inspection of boiler components by magnetic particle inspection and ultrasound inspection of welding points;
  • removal of the boiler’s insulation and full overload testing;
  • complete replacement of the gas ramp including valves, expansion valve, pressure switch, control box or new burner;
  • inspection of the smoke extraction ducts to check for blockage.

The operator reminded its authorised personnel of good boiler room practices. Purging operations during the burner start-up phase were formally prohibited. The boiler purge piping was modified so that the technician purging the boiler is no longer exposed to the rear door in the event it falls due to a similar accident.