For economic reasons, the power industry is now operating its 500 MW coal-fired plants on a two-shift cycle in which the turbines are on-load for 16 hours per day and off-load overnight and at weekends. The concern with ‘two-shifting’ is the impact on environment assisted cracking of the associated transients in stress, water chemistry and temperature. On-load, with well-controlled water chemistry, the condensate on the low-pressure turbines will be free of oxygen with chloride and sulphate levels both up to about 300 ppb. Off-load, the condensate would essentially be pure water but aerated unless there is nitrogen blanketing. The stress off-load would be zero. Ideally, to fully simulate two-shifting in laboratory testing, the combined influence of transient stress and water chemistry would be evaluated but there are technical difficulties in synchronising the changes in the stress, temperature, oxygen, and anion (chloride and sulphate) concentrations. For the purpose of assessing the impact of transient stress on crack propagation, the environment was held constant, viz. deaerated 300 ppb Cl
+300 ppb SO
solution at 90 °C. Separate measurement to examine the effect of transient water chemistry at constant stress are underway.