The paper analyzes features of the techniques for calculation of thermomechanically loaded reformer tube components in EP-300 pyrolysis furnaces under high-temperature creep. The patterns of the relationship between the tube wall temperature and coking during operation are analyzed. On the basis of the calculated temperature fields and the stress-strain field of the tubes, as well as the data on the deformation capacity and fatigue resistance of the material, the possible causes of premature failure of the reformers are considered. The authors propose a calculation method for analyzing the temperature and the stress-strain field of the reformer tube in relation to the growing coke layer, as well as the estimation of its serviceability according to the criteria of the deformation capacity and the cyclic strength.