FBG-Based Nonintrusive Monitoring Method for the Impact Force on 90° Pipe Elbow

Abstract

Elbow pipe is one of the components in pipeline transportation. The impact force caused by the liquid flow in the pipe elbow produces the strain on the wall. So, the monitoring of impact force can be realized by measuring strain. This article developed a new nonintrusive method to detect the impact force on the 90° horizontal bend pipe by measuring the axial strain and the hoop strain on the outer wall of the pipe elbow. Taking three typical cross-sections (i.e. $\theta = 0^{\circ }$ , $\theta = 45^{\circ }$ , and $\theta = 90^{\circ }$ ) of the pipe elbow as examples, the impact forces were adjusted by the inlet velocity in the bend pipe based on a specific relationship. The nonintrusive method was based on fiber Bragg grating (FBG) sensors, measuring the axial strain and hoop strain on the outer wall of the elbows caused by the impact force accurately. In this article, the theoretical study and numerical analysis by ANSYS Fluent based on the finite-element method were detailed in our initial work. Then, strain gauges were used to verify the effectiveness and accuracy of FBG monitoring. The results demonstrated that the FBG sensors had good performance on the strain measurement and were sensitive to the variation of the impact force caused by different velocity levels. The lightweight and easy networking of this method make it have a wide range of application prospects.