GAUGING PIGS/PROFILE PIG
Gauging Pig is a pig used to check whether there is a reduction in the internal diameter of the pipe.
Basically a
gauging pig is just a utility pig with a gauging plate attached to it.
This "gauging plate" is a component/part in the form of a circular soft aluminum material, the way it works is that the gauging plate will deform if there is a reduction in the pipe diameter exceeding the minimum pipe diameter or the diameter of the gauging plate.
The diameter of the gauging plate is 95% of the nominal inside diameter of the pipe. This is intendedto allow/tolerate some ovality of pipe that the pipe may have under unpressurized conditions as well as for any ovality caused by field bends
Gauging is a simple form of 'geometry' or 'caliper' PIG, the difference is that gauging pig only provides information that there is or is not deformation of the diameter of the pipeline beyond the minimum diameter and its location (for gauging pigs equipped with tracking devices), but does not provide information how much deformation was detected and the shape and size of the deformation as given by 'geometry' or 'caliper' PIG.