Metallurgical Case Studies of Early-in-Life Failures in Three Watertube Boilers

This paper presents three case studies involving early-in-life failures in water-tube boilers, with an emphasis on the metallurgical analysis utilized in determining the root causes. The three failures presented here demonstrate the variety of failure modes boilers can suffer, even after operating for just a fraction of their design lives. The first case presents a large rupture in baffle header that occurred two years after plant startup. The failure exhibited the classic signs of hydrogen damage, likely caused by deficient water chemistry control program. The second case summarizes weld reheat cracking that appeared within the first six months of operation in a supercritical boiler constructed from SA-213 Gr. T-23 steel. This material requires great care during welding, and in this case the manufacturer was inexperienced with the alloy and failed to implement the controls necessary when welding this material. Finally, the third case presents a classic case of moderate, long-term overheat in a boiler that had been operational for three years.