A caliper pig (geometry pig) is an inline inspection (ILI) tool designed to measure the internal diameter, ovality, and geometric profile of a pipeline.

A caliper pig (also known as a geometry pig or dimensional pig) is an inline inspection (ILI) tool designed to measure the internal diameter, ovality, and geometric profile of a pipeline. Caliper pigs detect dents, deformations, buckles, and wall thickness variations as they travel through the pipeline — providing critical data for pipeline integrity assessment.

Caliper pigs use mechanical arms, laser scanners, or electromagnetic sensors to capture geometry data with high precision. This information helps pipeline operators identify sections at risk of failure, plan maintenance, and comply with regulations such as ASME B31.8S and API 1163.

However, caliper pigs can only be used in piggable pipelines — those with pig launchers/receivers, consistent diameter, and no sharp bends. For unpiggable pipelines, EMPIT’s Current Magnetometry Inspection (CMI) provides an aboveground alternative that delivers 3D geometry mapping, depth of cover measurement, and deformation detection without internal tools or pipeline shutdowns.