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52 CHAPTER 3 Boiler tube failures: Some case studies
FIGURE 3.2
Boiler locations showing different types of failures.
FIGURE 3.3
Unusual short-term overheating failure. Excessive swelling but thick-edged fracture surfaces
are produced when a tube’s metal temperature exceeds its upper critical temperature (Ac 3 )
and the iron in the steel has been completely transformed from ferrite to austenite [3].
cavitation of the superheater/reheater tube due to exposure at higher temperature and
stress was shown by earlier investigators [10–12]. Figure 3.2 shows the locations of
the boiler where high-temperature creep can occur and Figure 3.4 shows fish-mouth-
type high-temperature creep failure.
