Pipeline pigging is a method of cleaning, inspecting, and maintaining pipelines used for transporting liquids or gases, such as oil, gas, or water.  A pipeline pig is a cylindrical device that is inserted into the pipeline and propelled through the pipeline by the flow of the product being transported.  A Pipeline Inspection Gauge, abbreviated as PIG, can be made from a variety of materials, including foam, rubber, or metal, and can be configured in different ways depending on the specific application.

PIG's scrape the inside of the pipeline and perform various maintenance jobs like cleaning, clearing, maintenance, inspection, dimensioning, process and pipeline testing operations on new and existing pipelines.  Smart PIG's inspect the integrity of the line for any potential problems.  Pipelines need to be cleaned regulary to prevent debris or buildup from occuring that may slow down the movement of the fluid inside.  The process of pigging is normally performed without stopping the flow of the product in the pipeline.  The diameter and lengths of the pipelines determine the pig size and tend to be much larger than in liquid processing and manufacture.  PIG launchers and receivers need to be installed at the approperate locations.

Pigging is an important part of maintaining the integrity and safety of pipelines, as it helps to prevent blockages, corrosion, and other issues that can cause leaks or failures.  It is widely used in the oil and gas industry, as well as in other industries that rely on pipelines for transportation of liquids or gases.

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Pipeline Pig Classification

In-line inspection tool (ILI)  -  Also called intelligent pigs or smart pigs, that inspect the interior wall of the line.  When a pipeline is inspected through processes that examine the interior of a pipeline.  These pigs are used for: burial & coating, caliper, crack detection, internal inspection, leak detection, metal loss, line damage due to construction equipment.

• Configurations  -  A pig that is used to gather data about the internal pipeline wall.
  
  • Camera Pig  -  A pig with a camera and light source recording the inside of the pipeline for visual inspections.
  • Geometry Pig  -  Designed to record conditions, such as dents, wrinkles, ovality, bend radius and angle, and occasionally indications of significant internal corrosion by making measurements of the inside surface of the pipe.
  • Mapping/ GPS Pig  -  A mapping pig uses technology, often inertia sensing, to produce a plan view of a pipeline’s route. 

Utility Pig  -  These pig perform simple mechanical functions, such as cleaning the pipeline, are called utility pigs.

• Types
  • Foam  -  There is a wide variety of styles, drying, wiping and scraping pigs to accommodate almost any application.
  • Inflatable
  • Solid Cast  -  These pigs have the same flexibility and handling advantage of foam pigs.  The cups and discs found on steel pigs can offer excellent sealing which makes them very efficient as general purpose pigs for batching, displacement, and routine pipeline pigging operations.
  • Gel  -  Utility pig composed of a highly viscous gelled liquid.  These pigs are often used for pipeline cleaning.  Sometimes called gelly pigs.
• Utility pigs are used for:
  • Batching Pig  -  A utility pig that creates a tight seal as it moves through the pipeline seperating liquids from gasses or other products being transpotred.
  • Cleaning Pig  -  Is used to remove solid or semi-solid debris or build-up inside a pipeline.
  • Cup Pig  -  A utility pig that is supported and driven by cups made of a resilient material such as neoprene or polyurethane.  At least one of the cups forms a piston-like seal inside the pipe.
  • Fill Pig  -  The pig runs through a pipeline during various testing processes like during a pipeline filling procedure.  The pig is propelled by a column of test water, ensuring that air in the pipeline is eliminated.
  • Gauging Pig  -  Utility pig permanently deformable by obstructions in the pipeline.  Upon retrieval from the line, the gauging pig provides evidence of the worst-case obstruction in a given pipeline segment.
  • Sealing Pig  -  Used to provide a good seal in order to either sweep liquids from the line, or provide an interface between two dissimilat products in the pipeline.
  • Sphere Pig  -  Can be solid or inflated to their optimum diameter with glycol and/or water.