Overview of how Pipeline Pigs Operate

Pipeline pigs, also known simply as "pigs," are devices used in pipelines for various maintenance, inspection, and cleaning purposes.  The operation of pipeline pigs depends on their specific design and the purpose for which they are used.

Introduction into the Pipeline  -  Pigs are introduced into the pipeline through a pig launcher, which is a specialized facility designed for pig launching.  The launcher is equipped with a closure or launching mechanism that allows the pig to be inserted into the pipeline.
Propulsion  -  Pigs are propelled through the pipeline by the flow of the product (liquid or gas) within the pipeline.  Some pigs are equipped with their propulsion systems, such as brushes, discs, or cups that make contact with the pipeline walls and create a seal, allowing the pig to move through the pipeline.
Cleaning and Inspection  -  Cleaning pigs are designed to remove debris, scale, or other contaminants from the inside of the pipeline.  Inspection pigs may be equipped with sensors and tools to assess the condition of the pipeline, detect corrosion, and collect data.
Product Separation  -  In multi-product pipelines, pigs are used to separate different products, preventing cross contamination.  These are known as batching pigs.
Navigation  -  Pigs can navigate through bends, fittings, and changes in pipeline diameter, depending on their design and purpose.  Some pigs use magnetic or acoustic sensors to navigate and detect anomalies in the pipeline.
Retrieval  -  After completing their operation, pigs are retrieved from the pipeline using a pig receiver, a facility equipped for pig retrieval.  The receiver may have a closure mechanism that allows the pig to be captured safely.
Data Analysis  -  For inspection pigs, the data collected during the pigging operation, such as corrosion measurements or anomalies detected, is analyzed to assess the condition of the pipeline.

The specific design and operation of pigs can vary based on their intended use, the type of pipeline, and the nature of the products being transported.  Pigging operations are an essential part of pipeline maintenance and integrity management in industries such as oil and gas.