Pipeline Pig
A pipeline pig is a device inserted into a pipeline and propelled by the flowing product to clean the line, separate batches, gauge the bore or inspect the pipe, usually without stopping operation. Utility pigs include foam, mandrel and solid-cast types fitted with cups, discs, brushes or scrapers that remove wax, scale, debris and accumulated liquids. Gauging pigs carry a deformable plate to confirm the minimum internal bore after construction, while intelligent pigs, or in-line inspection (ILI) tools, use magnetic flux leakage, ultrasonic or geometry sensors to detect metal loss, cracks and dents. Pigs are launched and received through pig traps fitted with quick-opening closures. Selection parameters include line size and wall thickness, minimum bend radius, valve bore restrictions, product type, available differential pressure and the pigging objective. API 1163 addresses qualification of in-line inspection systems.
Examples
- Bi-directional disc pig for liquid removal in a gas line
- Foam pig for cleaning after hydrotesting
- MFL intelligent pig for corrosion inspection