Application of special calculation techniques in the design of all-welded gastight structures of boiler units

Introduction. Improving the calculation methods of mechanical engineering facilities is an urgent and in-demand task. This fully applies to the techniques of calculating the strength of all-welded gastight boiler structures. Normative calculation techniques are based on simplified models that give limited possibilities for optimizing these structures. The low calculation accuracy inherent in such techniques is unacceptable under real design conditions, when an engineer is faced with the task of developing competitive structures in a short time, i.e., reducing metal consumption while providing the strength of these structures with limited development time. The use of simplified models was justified in the past, under conditions of insufficient development of computer technology. Application of the most advanced techniques based on computer modeling makes it possible to increase the accuracy of calculations, provide the optimization of such structures, and improve the quality of design. The objective of this study was to develop a new special procedure for calculating the strength of all-welded gastight structures based on computer modeling, using the most advanced methods of modeling the membrane wall and factors affecting it. The accompanying task was to verify the developed procedure based on comparing the results of calculations using the developed technique and the normative method.Materials and Methods. The developed technique is based on the replacement of the membrane wall with an orthotropic plate or shell. Computer modeling was used applying the finite element method of all-welded gastight structures, and the impacts to which they were subjected during operation, as well as an effective method for assessing the technical condition of these structures.Results. A new two-stage technique for calculating the strength of increased accuracy of all-welded gastight boiler structures was developed and patented. The calculation results were compared according to the proposed procedure and the normative method. It was shown that the proposed technique made it possible to increase the accuracy of modeling and calculation. The error in calculating all-welded gastight structures of a high-power boiler was reduced by more than 30% for the recommended steps between stiffeners. For specially reinforced membrane walls with steps exceeding the permissible values, the error reduction reached 70% or higher.Discussion and Conclusion. The developed technique is used in the modeling and calculation of all-welded gastight structures. Its application makes it possible to optimize the step between the stiffeners of the structure of the support and connecting nodes of gastight membrane walls. Based on the results of the application of the two-stage calculation procedure, new designs were developed and patented. The developed technique has been used in the real design of boilers since 2014.