High-temperature low-cycle fatigue: A summary of industry and code work

Many of the pressure-vessel and piping systems of the power and process industries operate in the creep range of metals. These structures may be subjected to severe cyclic loading conditions from startup and shutdown operations and to less severe temperature and pressure fluctuations from load-level control and process operational characteristics. In many cases, the number of cycles is small, but the stresses are high. Thus, the cyclic life of this equipment must be evaluated to establish safety requirements in relation to its expected life history. Presently used procedures for the construction of this equipment is discussed as applied either to the ASA (B31.1) Piping Code or to the ASME Power Boiler and Pressure Vessel Code. Considerable cooperative research in the field of high-temperature low-cycle fatigue has been undertaken by the Pressure Vessel Research Committee of the Welding Research Council, the Metals Properties Council, and various industrial and government groups. The effort of the PVRC and the Metals Properties Council is reviewed.