Residual Life Assessment of Pump Casing Considering Thermal Fatigue Crack Propagation

Thermal fatigue crack propagation is the main concern on the life assessment of the boiler feed-water circulation pump casings under cyclic operation. This paper describes the experimental and analytical studies on the thermal fatigue crack growth behavior, and the remaining life prediction of the casings.

First, it was confirmed by low-cycle fatigue test that the propagation behavior of surface cracks accompanied with the coalescence could be estimated by the da/dN-ΔJ relationship for long cracks. Secondly, the simplified J-integral estimation method for the thermal stress problem was discussed based on some bench mark calculations. Finally, the crack growth behavior in the casings was estimated and the results were compared with the field inspection data. Good agreement was found between them and, hence, these type of pump casings had adequate remaining lives to the final failure.