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Boilers are one of the most used units for both heat generation plants and industry systems. Their operation is subjected to different working loads and maintenance requirements. Exploitation experience points out critical boiler zones where failures and break downs typically occur. This paper analyzes critical zones in hot water fire-tube boiler. Experimental procedure was performed on the model of this type of boilers and its critical element. The tube plate of hot water boiler was identified as the most critical one. Experimental analysis and numerical model verification were performed using Aramis system based on 3-D digital image correlation method. Numerical analysis was done in ANSYS software package and verification of results was done based on measurements obtained by strain gauges and local measurements performed by the Aramis system. Stress-strain analysis indicates the critical zones of boiler tube plate. The character of change parameters such as strain and stress occurring in the critical zones can be verified both by experimental and numerical data. The paper presents a novel approach in experimental and numerical analyses that can be conducted in similar units and used for existing unit optimization, as well as for new product testing on different loads and provide opportunity for further development and improvement for practical industrial application. [ABSTRACT FROM AUTHOR]

Exploitation experience of hot water boiler plants indicates relatively frequent and permanent breakdowns resulting from the accident state of various elements of the boiler. In addition to the damages caused by the corrosion processes and inadequate management of the plant, the phenomena of fatigue of boiler elements exposed to high pressures and temperatures can occur. Due to high pressure and temperature certain boiler elements are exposed to, high strain and stress of these elements can eventually lead to breakdowns. In this paper, a hot water fire tube boiler, produced by "Minel-Kotlogradnja" Belgrade, type TE110V, installed within the plant "Technical Faculties" at Faculty of Mechanical Engineering in Nis, Serbia, is analyzed. Thermomechanical stress-strain analysis is performed with loads typically occurring during operation. Finite element analysis is performed using ANSYS Workbench 17 Software package, while the CAD model is formed using SOLID WORKS 2015. The results were used to investigate and to give recommendations for the thickness of tube plate of the first reversing chamber based on determined functional dependence of equivalent stress in the tube plate from the thickness of the plate. The noted functional dependence was determined by Kriging response surface based on results of virtual numerical experiment with different thicknesses of the tube plate. [ABSTRACT FROM AUTHOR]

The paper presents an application of the finite elements method for stress and strain analysis of the hot water boiler structure. The aim of the research was to investigate the influence of the boiler scale on the thermal stresses and strains of the structure of hot water boilers. Results show that maximum thermal stresses appear in the zone of the pipe carrying wall of the first reversing chamber. This indicates that the most critical part of the boiler are weld spots of the smoke pipes and pipe carrying plate, which in the case of significant scale deposits can lead to cracks in the welds and water leakage from the boiler. The non-linear effects were taken into account by defining the bilinear isotropic hardening model for all boiler elements. Temperature dependency was defined for all relevant material properties, i. e. isotropic coefficient of thermal expansion, Young’s modulus, and isotropic thermal conductivity. The verification of the FEA model was performed by comparing the measured deformations of the hot water boiler with the simulation results. As a reference object, a Viessmann-Vitomax 200 HW boiler was used, with the installed power of 18.2 MW. CAD modeling was done within the Autodesk Inventor, and stress and strain analysis was performed in the ANSYS software. [ABSTRACT FROM AUTHOR]