On kinetics and mechanism of crack growth in steam boiler drums

The maximum crack growth rate in drums of 22 K steel (v=1.7-2.4· mm/h), which does not depend on operation conditions and the level of static stesses, is recorded as a result of experiment under operation conditions. Thermal variations (thermocycles) related to the mixing of feed and boiler water with different temperatures produce the determining effect an the process of crack propagation. Corrosion thermal fatigue is the main mechanism of the drum metal fracture. In the process of identification of operation fracture surface the secondary changes in relief owing to a strong effect of corrosion medium should be taken into account