The paper is concerned with the results of strain-stress state analysis for bent and steeply curved pipebends, using the modified formula of Soderberg for a long-term creep description. The computations were performed for the most common in steampipe production steel grades such as 12Х1М1Ф, 15Х1М1Ф, 10Х9МФБ. The results of computation are compared with allowable and reduced stress. The temperature dependence of the strength of bends for different materials is estimated. The out-of-roundness’ change is determined during operation.