System and method for predicting the rate of deterioration in one or more items of process equipment which are subject to deterioration by one or more deterioration mechanisms. The system includes a first item of process equipment which receives an inlet stream including a feedstock or derivative thereof, and discharges one or more outlet streams which can be fed to the item of process equipment. A data processor which is a programmed computer including at least one rate model for the first item of process equipment receives values of one or more properties of the feedstock and calculates predicted rates of deterioration by the one or more deterioration mechanisms for the first item of process equipment from the values of one or more of the feedstock properties. The data processor additionally provides an output containing information relating to the predicted rates of deterioration by the one or more deterioration mechanisms for the first item of process equipment.