| Summary: | Failure of carbon steel boiler tubes from waterside has been reported in the utility
boilers and industrial boilers for a long time. In industrial boilers, most waterside tube
cracks are found near heavy attachment welds on the outer surface and are typically blunt,
with multiple bulbous features indicating a discontinuous growth. These types of tube
failures are typically referred to as stress assisted corrosion (SAC). For recovery boilers
in the pulp and paper industry, these failures are particularly important as any water leak
inside the furnace can potentially lead to smelt-water explosion.
Previous research shows that metal properties, environmental variables, and stress
conditions are the major factors influencing SAC crack initiation and propagation in
carbon steel boiler tubes. A significant volume of work has also been published to show
that the use of carbon steel in high temperature water applications strongly depends upon
the formation and stability of a protective magnetite oxide film on the waterside of boiler
tubes.
This present study is aimed at evaluating above stated variables individually and
interactively to identify SAC crack initiation and crack propagation behavior in carbon
steel boiler tubes. Other goal of this research is to understand the mechanism of bulbous
SAC crack formation under industrial boiler operating conditions, thus to figure out a
practical way to predict and prevent SAC type failures in the industrial boilers.
|
|---|
