Failure analysis of an electric arc furnace off-gas system

The water-cooled ductwork of an electric arc furnace direct evacuation system, installed in a steelmaking plant, experienced premature failure.The damaged pipe was investigated by means of optical microscope, scanning electron microscope equipped with energy dispersive X-ray spectroscopy micro-analysis and differential scanning calorimetry, in order to find out the failure causes and to suggest preventive solutions.The study shows that failure was mainly due to sulphur dewpoint corrosion formed in the hot service and continued also during furnace shutdown. Some modifications to the process were recommended to cope this problem.

► Failure of water cooled tubes in contact with high temperature off-gas.
► No overheating or corrosion phenomena promoted failure.
► Failure was mainly due to sulphur dewpoint corrosion.
► Corrosion was exacerbated by the presence of thick fly ash deposits.