Measurement verification f the stress reduction on a water vessel by shape modification of a welded part

Shortly before finalizing inspection, a problem was found on the internal wall of a feed water tank at a power station.

Shortly before finalizing inspection, a problem was found on the internal wall of a feed water tank at a power station. Cracks with a maximum depth of 4 mm (0.16 in) were found in welded mounting brackets alter a three-year operating period. The tank is 50 m (164 ft) long with a diameter of 4 m (13 ft). All the cracks on the welded parts were ground away and the brackets non-destructively tested again.

Metallographic examination showed that the cause of failure was strain-induced crack corrosion. This could be traced to cracks arising in the magnetite coating applied as corrosion protection to the area in question. The cracks were formed on the inside of the tank wall.