Caliper pigs, also known as dimensional pigs, are a type of inline inspection (ILI) pig used in pipelines to measure the internal diameter and geometry of pipelines.

They are designed to detect changes in the diameter and geometric profile of the pipeline, such as dents, deformations, or ovality, which can indicate potential problems with the pipeline's integrity.

Caliper pigs use several sensors and measurement technologies to gather data about the pipeline's internal dimensions and shape. These sensors may include mechanical arms, cameras, laser scanners, or electromagnetic sensors. The sensors are positioned along the pig body and are used to measure the diameter, wall thickness, and geometric profile of the pipeline as the pig moves through it. The data collected by the sensors is then processed and analyzed to identify any potential problems with the pipeline.

One of the key advantages of caliper pigs is that they can provide very accurate and detailed information about the internal dimensions and shape of pipelines. This information can be used to assess the pipeline's overall condition, detect potential problems, and make decisions about maintenance or repairs. Caliper pigs are also capable of detecting changes in the pipeline's diameter and shape over time, which can be a valuable tool for monitoring the pipeline's long-term performance and ensuring its reliability.

Caliper pigs are typically used in pipelines that carry liquids, gases, or other types of fluid. They can be used to inspect pipelines of various sizes and materials, including carbon steel, stainless steel, and plastic pipelines. Caliper pigs are also capable of inspecting pipelines that contain bends, tees, reducers, and other types of fittings.

In conclusion, caliper pigs are a type of inline inspection pig used to measure the internal diameter and geometry of pipelines. They use sensors and measurement technologies to gather data about the pipeline's internal dimensions and shape, which is used to assess the pipeline's overall condition, detect potential problems, and make decisions about maintenance or repairs. Caliper pigs are typically used in pipelines that carry liquids, gases, or other types of fluid and are capable of inspecting pipelines of various sizes and materials.