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

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

Modeling of the buckstay system of membrane walls in watertube boiler construction

Membrane walls are very important structural parts of water-tube boiler construction. Based on their specific geometry, one special type of finite element was defined to help model the global boiler construction. That is the element of reduced orthotropic plate with two thicknesses and two elasticity matrixes, for membrane and bending load separately. A global model of the boiler construction showed that the high value of stress is concentrated in plates of the buckstay system in boiler corners. Validation of the new finite element was done on the local model of the part of membrane wall and buckstay. A very precise model of tubes and flanges was compared to the model formed on the element of a reduced orthotropic plate. Pressure and thermal loads were discussed. Obtained results indicated that the defined finite element was quite favorable in the design and reconstruction of the boiler substructures such as a buckstay system

Modeling of the buckstay system of membrane walls in watertube boiler construction

Membrane walls are very important structural parts of water-tube boiler construction. Based on their specific geometry, one special type of finite element was defined to help model the global boiler construction. That is the element of reduced orthotropic plate with two thicknesses and two elasticity matrixes, for membrane and bending load separately. A global model of the boiler construction showed that the high value of stress is concentrated in plates of the buckstay system in boiler corners. Validation of the new finite element was done on the local model of the part of membrane wall and buckstay. A very precise model of tubes and flanges was compared to the model formed on the element of a reduced orthotropic plate. Pressure and thermal loads were discussed. Obtained results indicated that the defined finite element was quite favorable in the design and reconstruction of the boiler substructures such as a buckstay system

Dynamic Nonlinear Temperature Field in a Ferromagnetic Plate Induced by High Frequency Electromagnetic Waves

The subject of this paper is the thermal-behavior of an elastic metallic plate influenced by several harmonic electromagnetic plane waves at the upper and lower surfaces. The direction of wave propagation is normal to the surfaces of the plate. As a result of a time-varying electromagnetic field conducting currents appear in the plate. Distributions of eddy-currents and hysterisis power losses across the plate thickness are obtained using complex analysis. It is of the exponential type and depends on the plate thickness, wave frequency, electric conductivity, magnetic permeability and magnetic intensity. By treating this power as a volume heat source, differential equations governing distribution of the temperature field are formulated. The temperature field across the plate thickness is assumed to be in nonlinear form and a system of three coupled differential equations governing the temperature field is formed. Equations are solved in analytical form using the integral-transformation technique (Double Fourier finite-sine transformation and Laplace transformation). The influence of the skin depth, plate thickness, wave frequency and characteristic times of an impulse on the dynamic temperature field are considered. Nonlinear distribution of the temperature across the plate thickness is obtained. Strain and stress fields are obtained using the finite element method (FEM). Depending on the plate thickness thin shell finite elements (for a thin plate) or volume finite elements (for a thick plate) were applied

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