A method for accumulating stress damage induced by temperature differentials in a rotor of a high pressure steam turbine utilizes a representation of stress damage corresponding to a period of continuous temperature change. A counter variable associated with the representation of stress damage is incremented each time there is a significant change in direction of change in stress induced in the rotor. Accumulated stress damage is calculated by summing the products of each counter variable times a coefficient of stress damage corresponding to that counter variable. Accumulated stress damage is added to previously accumulated stress damage, calculated prior to resetting of the counter variables, to produce total accumulated stress damage. The total accumulated stress damage is printed on a permanent storage medium, such as paper, and it is compared with an alarm setpoint. If the alarm setpoint is exceeded, a message is sent to the operator and the operation of the steam turbine may also be adjusted.
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