Collisional vibration of PIGs (pipeline inspection gauges) passing through girth welds in pipelines

- An experimental setup was built to measure the collisional vibration of a typical PIG.
- A dynamic model of the PIG is introduced for understanding the collisional vibration.
- The girth weld greatly affect a PIG's dynamic behaviour.
- The vibration of a PIG passing through the girth weld is useful to locate the PIG.

The continuous collision between a running PIG (pipeline inspection gauge) and girth welds in a pipeline can induce significant vibrations on the PIG, which can harm its mechanical structure. The vibration response caused by the collision between a running PIG and a girth weld was studied both experimentally and theoretically. A two-dimensional dynamic model of the PIG is introduced to explain and understand the collisional vibration. Our results demonstrate that the girth weld, which can be regarded as an obstacle, can greatly affect the dynamic behaviour of a running PIG. The instantaneous acceleration when the PIG passed over the girth weld is larger than that of the PIG that collided with the girth weld. The distinct and regular vibration response signal of a PIG passing through a girth weld can be used to identify the obstacles inside a pipe to calculate and correct the pigging mileages with the help of a special algorithm based on the function of odometers during the pigging or inspection process.