Analysis of pipeline flange bolt loosening characteristics under vibration conditions

Due to the effects of vibration, pipe flange bolts are susceptible to loosening, which weakens the system’s constraints on the pipeline and potentially causes accidents such as leaks. Therefore, monitoring pipeline flange bolt loosening is imperative. A novel approach for detecting flange bolt loosening is presented, in which a Fiber Bragg Grating (FBG) acceleration sensor is mounted on the upper surface of the flange clamps of a cantilever beam structure to ascertain both the quantity and locations of loose flange bolts. An artificial setup replicated bolt loosening in a controlled environment, enabling validation of the proposed detection technique under different configurations of bolt loosening. The test results demonstrate that the FBG acceleration sensor effectively identifies fault signals associated with loose pipe flange bolts. The feasibility of this detection method in identifying the number and location of loose bolts was confirmed through the analysis of these fault signals using time-domain and frequency-domain characteristic analysis methods. These findings establish a quantitative framework for assessing bolt loosening severity and identifying fault types with precision.