Abstract
There is considerable economic incentive to extend the life of aging industrial plant equipment. For components such as high-energy piping and turbogenerators, safety and reliability are of major concern. Life extension involves determining whether materials which have been exposed to elevated temperatures for many years are suitable for continued service. Obtaining physical specimens is critical to assessing the degradation of mechanical properties of components in service and permitting detailed examination of microstructure and surface flaws. This information permits a reduction in the uncertainty of remaining life estimates to avoid premature and costly retirement decisions.
This paper describes the operation and application of a recently developed material sampling device which machines and recovers an undeformed specimen from the surface of rotor bores or other components. The removal of the thin, wafer-like sample has a negligible effect on the structural integrity of the component, due to the geometry and smooth depression. Samples measuring up to 2.5 mm thick by 2.5 cm diameter can be removed. The device is operated remotely and can be used externally or internally on any surface for which there is at least 7.5 cm working clearance. Two examples of the application of the sampler are described. The first involved evaluating the level of graphitization in a power plant main steam line, and the second involved evaluating surface flaws in the bore of a turbine-generator rotor.
