Corrosion Monitoring Technology for Bellows in Petrochemical Pipelines

This study proposes a method for monitoring the corrosion condition of metal bellows based on geometric characteristic and natural frequency, targeting the issue of corrosion-induced wall thinning in metal bellows within petrochemical pipelines. First, an axial tensile-compression testing apparatus was designed and constructed. This apparatus can perform axial tensile and compressive operations on the bellows at a predetermined rate and displacement. Second, a feature points extraction algorithm based on positional extrema was developed to precisely extract the coordinates of the corrugation peaks points in the bellows image, leveraging the geometric features of the periodic distribution of corrugation peaks on the bellows. Finally, an experimental system was established. Corrosion simulation tests were conducted on the bellows to investigate the effects of corrosion severity on geometric characteristic and natural frequency. The test results indicate that as the corrosion area increases, the degree of planar instability of the bellows under compression gradually increases, while the first natural frequency shows a decreasing trend. Both are significantly correlated with the corrosion severity, enabling the corrosion condition of the bellows to be determined by analyzing its planar instability and natural frequency.