"A cleaning "pig" for a 28-inch oil pipeline. The blue plastic disks seal against the inside of the pipe to propel the device and to remove loose sedimentation or scale buildup. The black rectangles at the top and the circular disks in the center are magnets to attract and remove any loose metal objects in the pipe." They can squeak and squeal when being rammed through the pipeline. (I had to look it up.) https://en.wikipedia.org/wiki/Pigging
I’m familiar with cleaning pigs. The intelligent pigs have things like eddy current sensors to detect any defects such as corrosion and cracking.
I have also seen pigs used in pipelines for product separation. One pipeline where I did some terminal work handled gasoline (several grades), butane, and propane. I installed the custody transfer measurement systems.