Critical crack assessment procedure for high pressure steam turbine rotors

Abstract

Abstract A critical crack assessment procedure for high pressure steam turbine rotors is introduce and applied. The processes relating to low‐cycle thermal fatigue (LCTF), high‐cycle fatigue (HCF) and creep are considered and the critical crack length is determined in accordance with its shape and position, based on a linear elastic fracture mechanics criterion. Taking this critical crack length as the final value, two mechanisms of crack growth are analysed, LCTF and creep, with the aim of defining the initial value of crack length. Alternatively, LCTF and creep are analysed as crack initiation processes with the aim of defining the appropriate time and number of cycles which can be used in relation to crack growth. The worst‐case materials data are used in order to obtain a conservative estimation of the critical crack length. The procedure is also applicable, directly or modified, to other power plant components, e.g. intermediate and low pressure rotors, steamlines and castings.