Safety issues related to the maintenance operations in a vegetable oil refinery: A case study

•We described an incident occurred to a packed column of a vegetable oil refinery.•We characterized the column mechanical damage caused by residual fouling combustion.•We characterized the column residual fouling material.•We reproduced on small scale the conditions leading to the residual solid ignition.•Lessons learned were determined by fishbone analysis on the incident causes.

The present work was focused on maintenance hazards related to vegetable oil refining. An incident occurred in an Italian vegetable oil refinery was presented to evidence this safety criticality. The incident took place during a maintenance shut down, and was associated to the ignition of the solid residual in a packed column. No fatalities or injuries were reported, but the column was strongly damaged and removed from the plant. A specific experimental characterization of the solid residues accumulated in the column, sampled both from the damaged and undamaged parts of the column, was carried out in order to determine the conditions leading to unwanted combustion of the residues. At the same time, samples taken from the damaged column steelwork were subjected to metallurgical analysis aimed at the thermal and mechanical characterization of the steel, obtaining information about the incident duration and temperature reached during the combustion phenomenon. The study evidenced the need of adequate maintenance procedures and safety management in the generic framework of food industry, identified as key lessons learned.