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Abstract:
Accurate determination of hanger rod tension in large suspended steam boilers of combined heat and power plants is essential for maintaining safe load distribution, preventing structural instability, and ensuring long-term operational reliability. This study proposes a vibration-based method for non-invasive tension identification, explicitly adapted to the boundary conditions and suspension configurations encountered in combined heat and power plants. The approach integrates in-house developed, battery-powered wireless accelerometers, deployed in an operational environment of combined heat and power plants, to acquire high-resolution, multidimensional vibration data suitable for both rapid inspections and continuous monitoring.
A comparative assessment of analytical formulations, including ideal string, Euler-Bernoulli beam and Timoshenko beam models, is conducted to identify the representation most appropriate for the dynamic behaviour of hanger rods under realistic operating constraints. The selected model is validated through experimental investigations on a full-scale installation of combined heat and power plants. Benchmarking against the industry-standard hydraulic “lift-off” method demonstrates the accuracy and reliability of the proposed procedure.
The results confirm that the developed system constitutes a robust, rapid, and cost-effective alternative to conventional techniques, reducing measurement time while preserving high accuracy. The findings address three critical questions: (i) the selection of a suitable vibration-based method analytical model for hanger rods of combined heat and power plants, including long-term operation units; (ii) the feasibility of quick and straightforward in situ tension measurements in rods without prior load history; and (iii) the potential for substantial reduction in measurement time compared with the “lift-off” method. The validated methodology provides a basis for future normative guidelines on hanger rod tension assessment in of combined heat and power plants.

Keywords:
Steam boilers, Structural health monitoring, Axial force estimation, Modal analysis, Industrial diagnostics