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.

• See Article  -  Pipeline Pigging Glossary
• Tags:  Pipeline Pigging Pipe Corrosion Advantages and Disadvantages Pipeline Glossary

Pipeline Pigging Index

• Pipeline Pig Types
• Pipeline Pigging Advantages and Disadvantages
• Overview of how Pipeline Pigs Operate
• Pipeline Pigging Procedures
• Pipeline Pigging Standards

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.

Pipeline Pig Types

• 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.

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.

Pipeline Pigging Procedures

• During Construction
  • Removing construction debris from the line.
  • Acceptance testing (water filling, dewatering, etc.)
  • Commissioning

• During Operation
  • Pipe wall cleaning
  • Condensate removal
  • Product separation (batching)
  • Applying inhibitors

• For Inspection
  • Check for physical damage (geometry)
  • Detect corrosion, laminations or cracking
  • Leak detection
  • Sampling
  • Line cover and spanning (subsea)

• For General Maintenance and Repair
  • Corrosion inhibition
  • Pre-inspection cleaning
  • Decommissioning
  • Isolation
  • Recommissioning

• During Renovation/Rehabilition
  • Gel pigging
  • Applying in situ coatings
  • Chemical cleaning
  • Scale removal
  • Cleaning for product conversion

• Decommissioning
  • Product removal
  • Pipe wall cleaning
  • Inspecting/testing
  • Inerting

Pipeline Pigging standards

ASME Standards

• ASME B16.5 - Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24 Metric/Inch Standard
• ASME B16.9 - Factory-Made Wrought Buttwelding Fittings
• ASME B16.47 - Large Diameter Steel Flanges, NPS 26 Through NPS 60
• ASME B16.36 - Orifice Flanges
• ASME B31.4 - Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids
• ASME B31.8 - Gas Transmission and Distribution Piping Systems

NACE Standards

• NACE ISBN 51316-7023 - Methodology for the Evaluation of Cleaning Pigs on Sludge Deposits from Corrosion Pits
• NACE ISBN 96034 - A Portable Pig Launcher and Receiver to Enable Maintenance and Smart Pigging of Production Pipelines
• NACE ISBN 96035 - Use of Intelligent Pigs to Detect Stress Corrosion
• NACE ISBN 96041 - Smart Pig Philosophy
• NACE ISBN 96048 - Solid Gel Pigs for Cleaning Production
• NACE ISBN 96049 - Intelligent Pigging: Policy, Recent Experience and Needs of a Petroleum Poerator
• NACE SP0102 - In-Line Inspection of Pipelines
• NACE SP0106 - Control of Internal Corrosion in Steel Pipelines and Piping Systems
• NACE SP0204 - Stress Corrosion Cracking (SCC) Direct Assesment
• NACE SP0206 - Internal Corrosion Direct Assesment Methodology for Pipelines Carrying Normally Dry Natural Gas
• NACE SP0208 - Internal Corrosion Direct Assesment Methodology for Liquid Petroleum Pipelines
• MTI Publication No. 14 - Manual on Closure Bolting for the Chemical Process Industries