Types of Pipeline Pigs and Their Applications
Pipeline pigs are the workhorses of pipeline maintenance and inspection. From simple foam tools that clear water and soft debris to advanced smart pigs that measure wall thickness and metal loss, each pig type is designed for a specific purpose. Choosing the right one is the difference between a smooth run and a stalled tool, or worse, a missed integrity threat.
American Pipeline Solutions (APS) specializes in planning and executing pigging programs across water, force main, oil, gas, and industrial pipelines. We don’t manufacture pigs; we design and run pigging campaigns that match the pipeline, the service, and the integrity goal. This guide explains the main types of pipeline pigs, how they’re used in the field, and how APS applies them as part of integrated cleaning and pipe inspection programs.
What Is a Pipeline Pig?
A pipeline pig is a self-contained device that travels inside a pipeline, driven by differential pressure or flow, to perform mechanical tasks such as cleaning, separating, or inspection. In practice, most pigs fall into three broad families:
Utility pigs for cleaning, gauging, and separation
Intelligent (smart) pigs for inline inspection and data collection
Specialty pigs for more focused tasks such as dewatering, drying, or batching
APS uses these tools in combination with services like Pipeline Cleaning, Pipeline Inspection / Pipeline Condition Analysis, Pipeline Pre-Commissioning, Ice Pigging™, internal coating, and mapping to build full life-cycle programs for pressure pipe inspection and maintenance.
Utility Pigs – The Cleaning and Maintenance Workhorses
Utility pigs are the foundation of most pigging programs. Their job is to clean, sweep, separate, or gauge the line so that product flows efficiently and inspection tools can run safely.
Foam Pigs
Foam pigs are made from flexible polyurethane foam in various densities and configurations. Their flexibility allows them to navigate tight bends, minor diameter changes, and fittings more easily than rigid designs.
Typical applications include:
Dewatering and drying after hydrostatic testing
Sweeping construction debris before a new line is commissioned
Cleaning “soft” deposits in water, wastewater, or multiphase lines
Running through pipelines with complex geometry where stiffer pigs may not pass
For operators planning smart pig runs or pressure pipe inspection, APS often uses foam pigs as part of a staged cleaning program to remove loose debris before more aggressive cleaning or inspection tools are deployed.
Brush and Scraper Pigs
Brush and scraper pigs are designed for more demanding cleaning tasks. They use wire brushes or scraping elements to break up and remove wax, scale, rust, and other harder deposits that reduce internal diameter and increase friction.
These pigs are commonly used when:
Flow has dropped due to internal buildup
Water quality has deteriorated because of biofilm or mineral scale
An inspection run is planned and heavy deposits would interfere with sensor readings
APS selects brush and scraper configurations based on deposit type and pipeline condition, balancing cleaning performance with the need to protect pipe walls and coatings.
Solid Cast Pigs
Solid cast pigs (sometimes called solid urethane pigs) are robust, one-piece tools used for general maintenance, batching, displacement, and sealing. They offer strong wear resistance and can be configured with cups or discs to achieve specific sealing and cleaning profiles.
They are often used for:
Routine cleaning runs
Liquid removal in gathering or transmission systems
Separation between different batches or products in multiproduct pipelines
Where APS needs firm sealing and reliable drive through long sections, solid cast pigs are frequently part of the program.
Spherical Pigs
Spherical pigs—often simply called “spheres”—are hollow or inflatable balls used primarily for liquid removal, separation, and flow assurance. Their geometry helps them navigate certain bends and maintain contact with the pipe wall.
They are typically applied when:
Removing water slugs or accumulated liquids
Separating product interfaces
Supporting flow assurance in gas lines where liquid buildup is a concern
Intelligent (Smart) Pigs – Inline Inspection and Condition Analysis
While utility pigs clean and maintain flow, intelligent pigs provide data. These tools carry sensors and onboard electronics to measure wall thickness, detect metal loss and corrosion, and record geometric defects.
APS uses smart pigs as part of its Pipeline Inspection / Pipeline Condition Analysis services to give operators a detailed picture of pipeline integrity and remaining life.
Magnetic Flux Leakage (MFL) Pigs
MFL pigs magnetize the pipe wall and measure how the magnetic field changes as they pass. Variations in the field indicate metal loss, corrosion, or other wall defects.
Applications:
Internal metal loss and corrosion assessment
Corrosion growth monitoring when multiple runs are compared
Support for integrity assessments and repair planning
MFL is a common choice for ferrous pipelines in oil, gas, and some water and industrial systems.
Ultrasonic (UT) Pigs
Ultrasonic pigs use high-frequency sound waves to measure wall thickness directly and to detect internal or external defects. They can be highly accurate when the line conditions are suitable.
Applications:
Detailed wall thickness mapping
Detection of cracks and laminations in certain configurations
Pipelines where precise measurement is required for fitness-for-service decisions
APS considers line cleanliness, product, and operating conditions when recommending UT tools, often pairing UT runs with targeted cleaning beforehand.
Caliper and Geometry Pigs
Caliper or geometry pigs measure internal diameter and detect dents, ovality, wrinkles, and buckles. While they don’t directly measure corrosion, they provide crucial context for where mechanical damage interacts with metal loss.
They are often run:
Before or with MFL/UT tools to ensure passage and collect shape data
After construction or major repairs
In systems where deformation is a known threat (e.g., ground movement, third-party damage)
In APS programs, geometry information is integrated with corrosion and mapping data to support a complete condition analysis.
Specialty Pigs and Advanced Tools
Specialty pigs are built for more focused tasks than routine cleaning or inspection. They can be used in pre-commissioning, dewatering, rehabilitation preparation, and other niche applications.
Dewatering and Drying Pigs
After hydrostatic testing or maintenance, dewatering and drying pigs help remove water and residual moisture. They are used to:
Push out bulk water following hydrotests
Reduce internal moisture that can accelerate corrosion
Prepare lines for gas service or moisture-sensitive products
APS combines dewatering pigs with techniques like air or nitrogen drying as part of its Pipeline Pre-Commissioning and hydrostatic testing programs.
Batching and Sealing Pigs
Batching pigs are used to separate different fluids, chemicals, or products within a pipeline. Sealing pigs provide high differential pressure capability to push slugs, separate interfaces, or support certain maintenance operations.
While APS focuses on cleaning and inspection, batching and sealing pigs are often part of the broader pigging strategy when lines carry multiple fluids or when test segments need to be clearly defined.
Gel Pigs and Magnetic Pigs
In some systems, gel-based pigs or magnetic debris-collection pigs are used where rigid tools may struggle or where ferrous debris is a specific concern. APS reviews these options case-by-case and integrates them when they align with project objectives and pipeline constraints.
Matching Pig Type to Pipeline Application
Knowing the list of pig types is helpful, but the real value comes from matching the right pig to the right job. When APS designs a pigging program, we look at several factors:
Pipeline purpose and product – Drinking water, wastewater, oil, gas, and industrial fluids each create different fouling and corrosion risks.
Diameter and configuration – Bends, tees, valves, diameter changes, and “difficult-to-inspect” sections all influence pig selection and train design.
Condition and history – Known corrosion, past blockages, or prior inspection data help determine how aggressive cleaning should be and which inspection tools make sense.
Inspection objectives – Routine cleaning, pre-commissioning, corrosion assessment, or full pressure pipe inspection each drive different pig choices and run sequences.
Operational constraints – Available pressure, flow, access, and allowable downtime all shape what is realistic in the field.
Instead of starting from a catalog, APS starts from the pipeline and integrity goal—then selects and configures pigs to fit.
How APS Uses Pig Types in Integrated Programs?
Because APS provides more than one service, pig selection is always part of a bigger plan. For example:
A pre-commissioning program might use foam pigs, gauging pigs, and dewatering pigs, followed by hydrostatic testing and drying.
A cleaning and inspection program might start with foam pigs, move to brush or scraper pigs, and then run MFL or UT smart pigs for condition analysis.
A water and force main project might combine conventional cleaning pigs with Ice Pigging™, then follow with pipe inspection and internal coating to extend service life.
Pig types are tools inside that broader workflow. The goal is not just to move a pig from launcher to receiver; it’s to improve flow, verify integrity, and support safe, compliant operation over the long term.
Common Mistakes When Selecting Pipeline Pigs
Across industries, a few mistakes show up repeatedly:
Skipping cleaning before inspection – Sending a smart pig into a dirty line can produce poor data or risk a stuck tool.
Using an overly aggressive pig too early – Hard scraping elements in a heavily scaled or corroded line can damage the pipe or coatings.
Ignoring geometry constraints – Tight bends, valves, or internal restrictions can stall or damage pigs if they’re not considered in planning.
Treating pigging as a one-off event – Effective pigging is part of an ongoing integrity and maintenance program, not just a single run.
APS’s planning process is built to avoid these problems by aligning pig type, train sequence, and run parameters with the actual pipeline and objective.
FAQs: Types of Pipeline Pigs and Their Uses
What are the main types of pipeline pigs?
Most pigs fall into three broad families: utility pigs (cleaning, gauging, separation), intelligent or smart pigs (inspection and data collection), and specialty pigs (tasks like dewatering, drying, or batching). Within those groups are specific styles such as foam pigs, brush pigs, solid cast pigs, spheres, MFL pigs, UT pigs, and caliper pigs.
Which pig type is best for pipeline cleaning?
There is no single “best” pig. Foam pigs are excellent for general sweeping and dewatering, while brush and scraper pigs are better suited for harder deposits such as wax or scale. Often APS uses a sequence of pig types—starting soft and increasing aggressiveness as needed—to clean effectively without harming the pipe.
When should I use a smart pig instead of a cleaning pig?
Cleaning pigs remove debris; smart pigs measure condition. If you need to understand wall thickness, corrosion, deformation, or remaining life, a smart pig is required. APS typically runs cleaning pigs first, then smart pigs once the line is clean enough for accurate inspection.
Can all pipelines be pigged with every pig type?
No. Pipeline design, geometry, valves, fittings, and operating conditions all limit which pigs can safely run. Some lines are considered “difficult to inspect” or “unpiggable” with conventional tools. APS evaluates each system and recommends pig types and sequences that match its constraints.
How often should different pig types be used?
Cleaning pigs are usually run on a recurring basis as part of routine maintenance or pre-inspection preparation. Smart pigs are run less frequently, aligned with integrity management plans and regulatory requirements. The right interval depends on the pipeline’s age, service, environment, and risk profile.
Does APS manufacture pigs?
No. APS focuses on pipeline pigging services—planning, executing, and analyzing pig runs for cleaning, inspection, and pre-commissioning. We work with a range of pig types and technologies and select what best fits your pipeline and integrity objectives.
Work with APS on Your Next Pigging Program
Whether you’re planning pre-commissioning, routine cleaning, or a full inline inspection campaign, the pig types you choose will drive safety, performance, and data quality.
American Pipeline Solutions brings together decades of pigging experience with services that cover pipeline cleaning, Ice Pigging™, Pipeline Inspection / Pipeline Condition Analysis, Pipeline Pre-Commissioning, internal coating, mapping, and more.
If you need help selecting and running the right pigs for your pipeline, APS is ready to design a program that fits your assets, constraints, and integrity goals.
