Failure analysis of perforation in salty water-wall tubes of a power plant

Perforation of water-wall of saline panels in Shahid-Montazeri power plant led to some systematic serious problems. XRD and XRF investigation along with spectrometric and metallographic analysis proved that perforation is mainly due to caustic corrosion. Moreover; it was concluded that significant amount of copper ions entered into the water circulation line and caused higher corrosion rate. It’s evident that variation in oxygen concentration and base metal decarburization were also effective in corrosion deterioration. Reduction in water-wall over-deposition and regular descaling along with modification of heating rate and replacing lithium hydroxide and ammonia with suitable modifiers, helped to overcome the problem.

► Perforation of a water-wall panel was investigated.
► XRD, XRF and metallographic techniques were used to find source of problem.
► Alkaline corrosion and copper deposition were found to be main source of failure.
► Control of heating pattern and replacing modifier were useful to solve the problem.