Energy producing power plants are designed for an operational period of 20-30 years. During this period, inspections are realized to investigate the operational capability of the respective components and the plant as a whole, and when the designed time is approaching its limit, crucial questions are raised with respect to the continuing possible operation, and its safety and risks that stem from the fact that the continuous degradation of material property has occurred during the lifetime of service as a result of service conditions, e.g. high temperatures, fatigue loading etc.The inspection of the boiler and the assessment of its future operational capability should ensure the safe operation and minimization of the failure risks that can cause not only economic losses.This paper summarizes the results of non-destructive (NDT) and destructive mechanical and metallographic tests performed in order that the degradation of material property of the decisive Steam Turbine Boiler Components due to service conditions could be evaluated and the resulting residual lifetime assessed. On the basis of performed examination, the results provided the customer with recommendations relating to the future safe and reliable operation of the boiler.
The fatigue phenomenon is said to be responsible for more than 80% of structural failures and operational accidents. One of the most important branches of industry, where unexpected outages can cause extremely expensive costs is the power producing industry. The steam turbine rotors represent large, expensive and, in the case of failure, potentially dangerous components. Their local properties generally differ from one forging to another, or if we compare head and bottom parts of the original ingot, or central and circumferential locations of one rotor body respectively, or if we compare the properties of separate discs, e.g. in the case of welded rotors. These differences stem from both even slight changes in the chemical composition (of separate heats or even within one ingot), heat treatment and in the differences in technology with respect to the real shape and size of the forgings in question.At present, questions on quantitative evaluation of remaining lifetime (to avoid failure) become urgent and, because fatigue is the most frequent cause of material degradation and resulting structural components failures, the remaining lifetime assessment is based on the evaluation of mechanical properties before and after some time of service. The original material data are usually tested by means of classic test specimens, which can hardly be used in the case of components in service, where there is no possibility to withdraw a sufficient volume of representative material for the manufacturing of a classic test specimen. In such cases today, methods of semi-destructive removal of a small volume of test material are utilized. This makes it possible to produce miniature test specimens. This paper describes the results of fatigue tests performed on miniature test specimens in comparison with the classic fatigue tests for several alloys applied in the power producing industry. The miniature test specimens were produced by water-jet cutting from the large test specimens. With respect to the specimen shape, stress concentration had to be taken into consideration for the purposes of comparison with the classic test specimens.
Abstract. In city of Pilsen (Czech Republic) modern transport engineering is developed. The Skoda Transportation (production company) has successfully been producing rail and road vehicles for many years (electric locomotives, trams, metro cars, trolleybuses, battery buses).
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