Identification of Rub and Unbalance in a 320MW Turbogenerators

The paper presents two experiences of application of a model based fault identification method on real machines. The first case presented is an unbalance identification on a 320MW turbogenerator unit operating in a fossil power plant. In the second case, concerning a machine of the same size but of a different manufacturer, the LP turbine was affected by a rub in the sealings. This time, the fault is modeled by local bows. The identification of the faults is performed by means of a model based identification technique in frequency domain, suitably modified in order to take into account simultaneous faults. The theoretical background of the applied method is briefly illustrated and some considerations are presented also about the best choice of the rotating speed set of the run-down transient to be used for an effective identification and about the appropriate weighting of vibration measurements at the machine bearings

Use of Modal Representation for the Supporting Structure in Model Based Fault Identification of Large Rotating Machinery: Part 1 – Theoretical Remarks

Fault identification by means of model-based techniques, both in frequency and time domain, is often employed in diagnostics of rotating machines, when the main task is to locate and to evaluate the severity of the malfunction. The model of the fully assembled machine is composed by the submodels of the rotor, of the bearings and of the foundation, while the effect of the faults is modelled by means of equivalent force systems. Some identification techniques, such as the least squares identification in frequency domain, proposed by the authors, have proven to be quite robust even if the submodels are not fine-tuned. Anyhow, the use of a reliable model can increase the accuracy of the identification. Normally a supporting structure is represented by means of rigid foundation or by pedestals, i.e. 2 d.o.f. mass–spring–damper systems, but these kind of models are often not able to reproduce correctly the influence of the dynamical behaviour of the supporting structure on the shaft, especially in large machines where coupled modes are present. Therefore, peculiar aspect of this paper is the use of a modal foundation to model the supporting structure of the machine and the method is discussed in detail in this first part. The modal representation of the foundation is then introduced in the least squares identification technique in frequency domain

A sonic approach for the measurement of gas temperature in power generation boilers

The paper describes the recent improvements of a proprietary system for the estimate of temperature distributions inside gas flows by sonic methods, with special attention to applications in the steam boilers of power stations. In particular, together with a short review of the original configuration, the problem of installation and maintenance of the waveguides is first discussed and the newly devised solutions are shown. Then the revision of the signal processing algorithms, employedfor the determination of the temperature along the acoustic paths between any two transducers, is described; the aim was to reduce the scattering of the measurements and to improve their reliability, despite of the strong levels of background noise and of the highly non-stationary system under measure. Finally some results obtained by preliminary tests carried out on a coal fired 660 MW steam boiler are documented in some detail

Problematiche dell'identificazione strutturale nel settore dell'ingegneria elettromeccanica

Biblioteca Centrale CNR / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Gender-Related Differences in Presentation, Treatment, and Outcome of Patients With Atrial Fibrillation in Europe. A Report From the Euro Heart Survey on Atrial Fibrillation

Objectives: This study sought to investigate gender-related differences in patients with atrial fibrillation (AF) in Europe. Background: Gender-related differences may play a significant role in AF. Methods: We analyzed the data of 5,333 patients (42% female) enrolled in the Euro Heart Survey on Atrial Fibrillation. Results: Compared with men, the women were older, had a lower quality of life (QoL), had more comorbidities, more often had heart failure (HF) with preserved left ventricular systolic function (18% vs. 7%, p < 0.001), and less often had HF with systolic dysfunction (17% vs. 26%, p < 0.001). Among patients with typical AF symptoms (56% of women, 49% of men), there was no gender-related difference in the choice of rate or rhythm control. Among patients with atypical or no symptoms (44% of women, 51% of men), women less frequently underwent rhythm control (39% vs. 51%, p < 0.001) than did men. Women underwent less electrical cardioversion (22% vs. 28%, p < 0.001). Prescription of oral anticoagulants was identical (65%) in both genders. One-year outcome was similar except that women had a higher chance for stroke (odds ratio 1.83 in multivariable regression analysis, p = 0.019). Conclusions: Women with AF had more comorbidities, more HF with preserved systolic function, and a lower QoL than men. In the large group with atypical or no symptoms, women were treated appropriately more conservatively with less rhythm control than men. Women had a higher chance for stroke. Long-term QoL changes and other morbidities and mortality were similar. © 2007 American College of Cardiology Foundation

Antithrombotic treatment in real-life atrial fibrillation patients: a report from the Euro Heart Survey on Atrial Fibrillation

Aims To describe guideline adherence and application of different stroke risk strati. cation schemes regarding antithrombotic therapy in real-life atrial. brillation (AF) patients and to assess which factors influence antithrombotic management decisions.Methods and results The Euro Heart Survey enrolled 5333 AF patients in 35 countries, in 2003 and 2004. Prescription of antithrombotic drugs, especially oral anticoagulation (OAC), was hardly tailored to the patient's stroke risk pro. le as indicated by the joint guidelines of the American College of Cardiology, American Heart Association, and the European Society of Cardiology, ACCP guidelines, or CHADS(2) and Framingham risk scores. In multivariable analysis, only a limited number of the well-known stroke risk factors triggered OAC prescription. In contrast, less relevant factors, of which clinical type of AF and availability of an OAC monitoring outpatient clinic were the most marked, played a significant role in OAC prescription. Electrical cardioversions and catheter ablations clearly triggered OAC prescription, whereas pharmacological cardioversions even in the presence of stroke risk factors did not.Conclusion Antithrombotic therapy in AF is hardly tailored to the patient's stroke risk pro. le. Factors other than well-known stroke risk factors were significantly involved in antithrombotic management decisions. To facilitate this tailored treatment, guideline writers and physician educators should focus on providing one uniform and easy to use stroke risk strati. cation scheme