Detection of bolt connection deterioration in closed pipeline networks

Bolted connection loosening poses significant risks to structural load-bearing capacity, yet reliable detection remains challenging due to geometric complexity and material discontinuities. This study develops an innovative transient impact-response method for bolt loosening detection through vibrational energy analysis. The approach utilizes controlled steel ball impacts on pipe exteriors combined with piezoelectric sensor arrays to capture flange vibration signatures. Experimental results demonstrate a strong correlation between received signal energy attenuation and bolt torque reduction from 50 N·m to complete loosening. The method provides four significant benefits: (1) non-invasive operation without disassembly requirements, (2) highly cost-effective implementation using minimal equipment, (3) rapid assessment capability with high detection efficiency, and (4) simplified operation requiring minimal operator expertise. Validation tests confirm the technique’s superior performance for pipeline integrity monitoring compared to conventional non-destructive testing methods, offering an optimal balance of accuracy and practicality for industrial applications.