During the pre-turnaround hydrostatic test, multiple tube leaks were
discovered in the original water wall tubes of a 680 psig industrial boiler
installed in 1954. Inspection of the water wall tubes of the boiler revealed
significant pitting corrosion on the high heat ff ux side warranting tube
repair or replacement, while the cold-side of the tube maintained close to
original wall thickness. Metallurgical analysis determined the mode of
failure to be caustic corrosion. Further investigation concluded that the
physical root cause was localized higher heat flux due to the operation of
low NOx burners installed in 1996.