When starting and shutting down steam turbines or changing their power outputs, steam temperature variations are bound to occur that lead to temperature differences in and between the components. These temperature differences result in free expansions of the components relative to each other, deformations of the components themselves, and stresses in the components. If such expansions, deformations and stresses exceed certain limits set by design features or the materials used, both immediate damage - axial or radial rubbing - and long-time damage - inadmissible permanent deformation and crack formation - may occur. Finding solutions to this complex of problems is gaining importance in the field of steam turbine construction and operation. While component dimensions and thus the effects of major temperature differences inevitably become more pronounced as unit outputs increase, it is desirable to avoid availability losses due to thermal overloads. In addition, more stringent system requirements are now placed on the loadability and controllability of large turbo- generator sets. Last but not least, the expected increase in unit output and the fact that conventional, medium-size and large power stations are being pushed toward the peak and medium-load range by other, more economic stations - e.g. nuclear - providing the base load, lend greater importance to the problems mentioned here. Being aware of the relevance of the problems, scientists and engineers have made numerous theoretical studies, laboratory and field experiments in the past years which led to a better understanding of the processes involved and the possible damages that may occur.
The results have revealed that major parts of the brochure "The Warm-Up Process in Steam Turbines", issued by VDEW in 1961, are now obsolete. Thus the VGB Working Group "Turbine Development" has set itself the goal to describe the current state of the art.
*Dieses Produkt ist ebenfalls in deutscher Sprache erhältlich.