Experimental validation of the limits of beam-based transverse vibration diagnostics in laboratory-scale pipe belt conveyor systems

Pipe belt conveyors enable enclosed bulk-material transport along complex routes, but their closed tubular cross-section and multi-point radial support create mechanical conditions that differ substantially from those of conventional flat or troughed conveyor belts. This study experimentally tests the transferability of a previously developed beam-based transverse-vibration frequency–tension methodology to a laboratory-scale pipe belt conveyor. A total of 72 steady-state acceleration records were acquired under empty-belt conditions for four axial-force levels (2000, 3000, 4000, and 5000 N), three belt velocities, and two consecutive measuring spans. The measured vibration signals were analyzed using Fourier-based peak detection, Rank-based frequency characterization, factorial statistical analysis, model-conditioned spectral correspondence, and cosine similarity of normalized power spectra. The amplitude-dominant Rank-1 frequency did not exhibit the monotonic increase with axial force predicted by the analytical beam model. The factorial analysis did not identify statistically supported main effects of axial force ( \(p=0.479\) ), belt velocity ( \(p=0.689\) ), or measuring span ( \(p=0.568\) ) on the Rank-1 frequency. Group-averaged spectra retained broadly similar spectral envelopes, with cosine similarities ranging from 0.890 to 0.972, whereas individual realizations exhibited substantially greater variability. Model-conditioned searches frequently identified spectral activity near the analytical reference frequencies, but these components were often secondary rather than amplitude-dominant and their proximity cannot be interpreted as independent model validation. The results show that, for the investigated empty-belt pipe-conveyor configuration, the global amplitude-dominant frequency alone does not provide a robust standalone indicator of axial force. The study establishes an experimental baseline for further investigations incorporating payload effects, contact-dependent boundary conditions, and larger-scale pipe-conveyor systems.