Condition and behavior diagnostics of boiler constructions

U radu je prikazana metodologija dijagnostike stanja i ponašanja kotlovskih konstrukcija, koja je neophodna pri donošenju odluka o njihovom daljem radu. Definisan je algoritam koji ilustruje metode prikupljanja podataka neophodnih za dijagnostiku: analiza konstrukcije, vizuelna kontrola, ispitivanje bez i sa razaranjem, inženjerska analiza, eksperimentalna merenja i ekspertska ocena stanja - dijagnostika ponašanja. Dijagnostika se može značajno poboljšati primenom metode konačnih elemenata. Osnovna prednost ove numeričke metode u odnosu na proračun definisan normama je prikazana kroz mogućnost određivanja skoro realne slike deformacija i napona, i pouzdane procene i predviđanja ponašanja kotlovske konstrukcije u uslovima opterećenja. Primena metode konačnih elemenata je ilustrovana na primeru projektovanja novog plameno-dimnocevnog kotla i pri dijagnostici ponašanja vodocevnog kotla pri održavanju.In the paper the methodology of condition and behavior diagnostics of boiler constructions is presented, which is necessary to perform in order to make decision on further operation. An algorithm is defined that illustrates the methods for collecting data needed for the diagnostics: analysis of construction, visual inspection, non-destructive and destructive examinations, engineering analysis, experimental measurements and expert condition assessment-diagnostics of behavior. The diagnostics can be significantly improved by the application of finite element method-FEM. The main advantages of this numerical method over the calculation by design norms are expressed through possibilities of determining a nearly realistic image of deformation and stress, and reliable assessment and prediction of boiler construction behavior under service condition. The application of FEM is illustrated by the examples of designing a new firetube boiler and behavior diagnostics of water-tube boiler in service

Condition and behavior diagnostics of boiler constructions

U radu je prikazana metodologija dijagnostike stanja i ponašanja kotlovskih konstrukcija, koja je neophodna pri donošenju odluka o njihovom daljem radu. Definisan je algoritam koji ilustruje metode prikupljanja podataka neophodnih za dijagnostiku: analiza konstrukcije, vizuelna kontrola, ispitivanje bez i sa razaranjem, inženjerska analiza, eksperimentalna merenja i ekspertska ocena stanja - dijagnostika ponašanja. Dijagnostika se može značajno poboljšati primenom metode konačnih elemenata. Osnovna prednost ove numeričke metode u odnosu na proračun definisan normama je prikazana kroz mogućnost određivanja skoro realne slike deformacija i napona, i pouzdane procene i predviđanja ponašanja kotlovske konstrukcije u uslovima opterećenja. Primena metode konačnih elemenata je ilustrovana na primeru projektovanja novog plameno-dimnocevnog kotla i pri dijagnostici ponašanja vodocevnog kotla pri održavanju.In the paper the methodology of condition and behavior diagnostics of boiler constructions is presented, which is necessary to perform in order to make decision on further operation. An algorithm is defined that illustrates the methods for collecting data needed for the diagnostics: analysis of construction, visual inspection, non-destructive and destructive examinations, engineering analysis, experimental measurements and expert condition assessment-diagnostics of behavior. The diagnostics can be significantly improved by the application of finite element method-FEM. The main advantages of this numerical method over the calculation by design norms are expressed through possibilities of determining a nearly realistic image of deformation and stress, and reliable assessment and prediction of boiler construction behavior under service condition. The application of FEM is illustrated by the examples of designing a new firetube boiler and behavior diagnostics of water-tube boiler in service

PRIOR KNOWLEDGE BASED NEURAL MODELING OF MICROSTRIP COUPLED RESONATOR FILTERS

The design of microstrip coupled resonator filters includes determination of the coupling coefficients between the filter resonator units. In this paper a novel modeling procedure exploiting prior knowledge neural approach is proposed as an efficient alternative to the standard electromagnetic (EM) simulations and to the neural models based purely on the artificial neural networks (ANNs). It has similar accuracy as the EM simulations and requires less training data and less time needed for the model development than the models based purely on ANNs

Numerical calculation of the water-tube boiler using finite element of the orthotropic plate

Norme uglavnom pokrivaju proračun delova pod pritiskom, ali uglavnom bez uticaja termičkih opterećenja. Primena metode konačnih elemenata predlaže se pri proračunu svih komponenti koje norme ne obuhvataju. U radu je prikazan detaljan numerički proračun vodocevnog kotla tipa VU60 - Minel kotlogradnja. Na osnovu numeričkih modela određena su polja napona i deformacija za različita opterećenja. Razmatran je uticaj natpritiska i termičkog opterećenja. Primenjeni su i parametri dijagnostike čvrstoće kao što su raspodela membranskih i savojnih napona po podstrukturama i raspodela energije deformacije. Membranski zidovi (cevni paneli) vodocevnih kotlova izloženi su veoma velikim opterećenjima. Modelirani su elementima tanke ortotropne ploče. Razmotren je uticaj pojaseva ukrućenja na ponašanje konstrukcije kotla.Norms handle the issues concerned with calculation of pressurized boiler components, however not considering the influences of thermal strains. Application of FEM in boiler design is suggested in calculating all components that are not covered by the norm. Detailed numerical calculation of the water-tube boiler type VU60-Minel Kotlogradnja is presented in the paper. Stress and strain fields are obtained based on numerical models for various types of loading. The influences of the over-pressure and thermal loading are discussed. Distribution of membrane and bending stresses for substructures and distribution of deformation energy are involved in the analysis. Membrane walls (tube panels) of the water-tube boilers are exposed to large loads. They are modelled using elements of a thin orthotropic plate. The influence of the buck-stays on the structural behaviour is discussed

Numerical calculation of the water-tube boiler using finite element of the orthotropic plate

Norme uglavnom pokrivaju proračun delova pod pritiskom, ali uglavnom bez uticaja termičkih opterećenja. Primena metode konačnih elemenata predlaže se pri proračunu svih komponenti koje norme ne obuhvataju. U radu je prikazan detaljan numerički proračun vodocevnog kotla tipa VU60 - Minel kotlogradnja. Na osnovu numeričkih modela određena su polja napona i deformacija za različita opterećenja. Razmatran je uticaj natpritiska i termičkog opterećenja. Primenjeni su i parametri dijagnostike čvrstoće kao što su raspodela membranskih i savojnih napona po podstrukturama i raspodela energije deformacije. Membranski zidovi (cevni paneli) vodocevnih kotlova izloženi su veoma velikim opterećenjima. Modelirani su elementima tanke ortotropne ploče. Razmotren je uticaj pojaseva ukrućenja na ponašanje konstrukcije kotla.Norms handle the issues concerned with calculation of pressurized boiler components, however not considering the influences of thermal strains. Application of FEM in boiler design is suggested in calculating all components that are not covered by the norm. Detailed numerical calculation of the water-tube boiler type VU60-Minel Kotlogradnja is presented in the paper. Stress and strain fields are obtained based on numerical models for various types of loading. The influences of the over-pressure and thermal loading are discussed. Distribution of membrane and bending stresses for substructures and distribution of deformation energy are involved in the analysis. Membrane walls (tube panels) of the water-tube boilers are exposed to large loads. They are modelled using elements of a thin orthotropic plate. The influence of the buck-stays on the structural behaviour is discussed

Numerical and experimental strength analysis of fire-tube boiler construction

Norms, such as EN 12952-3 and EN 12953-3 handle the issues concerned with calculation of the pressurized boiler components, not however considering the influences of thermal strains that are often of vital importance for the integrity of boiler's construction. Application of FEM in boiler design in EN is suggested in calculating all components that are not covered by the norm. In this way, the calculation of thermal stress is left to the free will of designer and technical inspectorate which supervises and approves placement of a boiler into operation. This paper demonstrates that the influence of thermal stresses is great and that it must be taken into consideration when the boiler's construction is designed and its working life evaluated. It is shown that for every construction a numerical-experimental behaviour diagnostics should be conducted prior to putting it into operation. First, a numerical model must be experimentally verified and then it can be used in considering different parameters of strength diagnostics, such as distribution of membrane and bending stresses for substructures, and distribution of deformation energy. They indicate, in an optimal way, root causes of insufficiently good behaviour of the construction. Also, a dynamical calculation of natural oscillations should always be suggested

Numerical and experimental strength analysis of fire-tube boiler construction

Norms, such as EN 12952-3 and EN 12953-3 handle the issues concerned with calculation of the pressurized boiler components, not however considering the influences of thermal strains that are often of vital importance for the integrity of boiler's construction. Application of FEM in boiler design in EN is suggested in calculating all components that are not covered by the norm. In this way, the calculation of thermal stress is left to the free will of designer and technical inspectorate which supervises and approves placement of a boiler into operation. This paper demonstrates that the influence of thermal stresses is great and that it must be taken into consideration when the boiler's construction is designed and its working life evaluated. It is shown that for every construction a numerical-experimental behaviour diagnostics should be conducted prior to putting it into operation. First, a numerical model must be experimentally verified and then it can be used in considering different parameters of strength diagnostics, such as distribution of membrane and bending stresses for substructures, and distribution of deformation energy. They indicate, in an optimal way, root causes of insufficiently good behaviour of the construction. Also, a dynamical calculation of natural oscillations should always be suggested

CYTOKINE PROFILE IN RENAL TRANSPLANT PATIENTS IN A LONG-TERM PERIOD AFTER SURGERY

In the long-term period after kidney transplantation, a certain level of tissue inflammation and therefore the production of proinflammatory cytokines, including TNF-α, IL-1β, IL-18 and IL-2 can be found. The aim of our study was to determine the concentrations of TNF-α, IL-1β, IL-18, IL-2 and its soluble receptor (IL-2R) in renal transplant patients, regarding the length of the postoperative period. The study involved 65 patients, transplanted at least 12 months prior to our investigation, divided into three groups, regarding the time passed since the transplantation (12-24, 24-48, and >48 months consecutively). Concentrations of the cytokines in the plasma of the subjects were measured using ELISA method. Group I showed significantly higher concentrations of IL-1b compared to the III (p<0.05), IL-18 compared to the II and III (p<0.05) and TNF-a compared to the II (p<0.05). Cytokine concentrations correlated with the time passed since the transplantation (p<0.05), except for TNF-a. Interleukin-2 correlated negatively with IL-18 and immunosuppressant dosage (p<0.05). Interleukin-1b, IL-18 and TNF-α measurements should be considered for monitoring and detecting potentially subclinical allograft damage in the second year after surgery. However, the dynamics of the change of cytokine concentration may also have been altered by the components of the immunosuppressive protocols used, such as tacrolimus, which is a link that is yet to be examined

Influence of furnace tube shape on thermal strain of fire-tube boilers

The aim of this paper is to use numerical analysis and fine element method-FEM to investigate the influence of furnace tube shape on the thermal strain of fire-tube boilers. Thermal stresses in corrugated furnace tubes of different shape, i.e. with different corrugation pitch and depth, were analysed first. It was demonstrated that the thermal stresses in corrugated furnace tube are significantly reduced with the increase of corrugation depth. Than deformations and stresses in the structure of a fire-tube boiler were analysed in a real operating condition, for the cases of installed plain furnace tube and corrugated furnace tubes with different shapes. It was concluded that in this fire-tube boiler, which is of larger steam capacity, the corrugated furnace tube must be installed, as well as that the maximal stress in the construction is reduced by the installation of the furnace tube with greater corrugation depth. The analysis of stresses due to pressure and thermal loads pointed out that thermal stresses are not lower-order stresses in comparison to stresses due to pressure loads, so they must be taken into consideration for boiler strength analysis