Pipeline integrity, efficiency, and cleanliness are vital in industries ranging from oil and gas to food processing and chemicals. One of the most widely used solutions for maintaining these pipelines is a pigging system. At the heart of these systems lies the pipeline pig, a simple yet essential device used for cleaning, inspecting, and maintaining flow inside pipes.
However, not all pigs are created equal. Depending on the pipeline’s design, product type, cleaning goals, or inspection requirements, different pipeline pig types are available to serve specific functions. Understanding these types is crucial for selecting the right tool for optimal performance and minimal disruption.
In this article, we’ll explore the various pipeline pig types, their unique features, and how they serve different industries and applications.
What Is a Pipeline Pig?
A pipeline pig is a device inserted into a pipeline to perform a particular task while moving through it, usually propelled by the flow of the product or an external gas or fluid. It may clean the pipeline, separate batches, recover product, or inspect the internal condition of the pipeline.
Modern pigs are made from materials like foam, urethane, metal, or a combination of these. Depending on their task, pigs may include sensors, brushes, discs, or blades.
Now, let’s explore the pipeline pig types used across various applications.
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1. Foam Pigs
Foam pigs are among the most versatile and cost-effective pipeline pig types Constructed from open-cell polyurethane foam, these pigs are lightweight, flexible, and available in a range of densities.
Key Features:
- Soft structure prevents damage to pipe walls
- Can pass through bends, valves, and diameter changes
- Often used for drying, cleaning, or dewatering
- May be coated with polyurethane or embedded with abrasives for scrubbing
Common Applications:
- Initial line cleaning and drying
- Removing water after hydrostatic testing
- Pipeline commissioning and decommissioning
Foam pigs are popular for their simplicity and adaptability, especially in pipelines that are not regularly pigged or contain challenging geometries.
2. Mandrel Pigs
Mandrel pigs, also known as steel-body pigs, have a strong central shaft or mandrel with attached sealing discs and cups made from urethane or rubber. These pigs are durable and reusable.
Key Features:
- Replaceable components (cups, discs, brushes)
- Ideal for aggressive cleaning tasks
- Can handle high pressures and long-distance pigging
- Suitable for multi-diameter pipelines
Common Applications:
- Heavy-duty cleaning
- Debris or wax removal in crude pipelines
- Product separation in multiproduct pipelines
Mandrel pigs are one of the most widely used pipeline pig types in oil and gas pipelines due to their high durability and customizable configurations.
3. Cup Pigs
Cup pigs are similar to mandrel pigs but usually have flexible urethane cups without the central steel shaft. The cups provide excellent sealing and propulsion.
Key Features:
- Flexible design to navigate bends
- Efficient in pushing out fluids or displacing products
- Often used with multiple cups for better sealing
Common Applications:
- Batch separation
- Product displacement
- Water and condensate removal
Cup pigs are reliable and are often used where high sealing and product recovery are critical.
4. Disc Pigs
Disc pigs use multiple urethane or rubber discs instead of cups. These discs make contact with the pipe wall, scraping and pushing residue forward.
Key Features:
- Suitable for long-distance pigging
- Creates a tight seal to maximize cleaning
- Can be combined with brushes for additional cleaning
Common Applications:
- Line scraping and deposit removal
- Preparing pipelines for inline inspection
- Removing wax or scale buildup
Disc pigs are effective for pipelines that require rigorous cleaning or are preparing for inspection.
5. Brush Pigs
Brush pigs are designed to mechanically scrub the inside of pipelines. They can be foam pigs or mandrel pigs fitted with steel or nylon brushes.
Key Features:
- Removes stubborn deposits and scaling
- Can be aggressive or soft depending on brush type
- Used in conjunction with cleaning fluids
Common Applications:
- Removing wax, rust, or solidified product buildup
- Cleaning before coating or internal corrosion inspection
- Debris removal in crude or refined pipelines
Brush pigs are used when pipelines have not been cleaned regularly or are known to have heavy deposits.
6. Spherical Pigs
Spherical pigs are inflatable balls made of polyurethane or rubber. They are used primarily in gas pipelines and are effective at removing liquids.
Key Features:
- Self-centering and can pass through valves
- Can be pressurized for precise sealing
- Minimal resistance to flow
Common Applications:
- Liquid removal in natural gas pipelines
- Monitoring pipeline flow
- Preventing slugging in gas pipelines
Because of their unique shape and low wear characteristics, spherical pigs are common in gas transmission lines.
7. Smart Pigs (Intelligent Pigs)
Smart pigs are the most technologically advanced pipeline pig types. These pigs are equipped with sensors and electronics to perform inline inspections (ILI).
Key Features:
- Use ultrasonic, magnetic flux, or electromagnetic sensors
- Detect internal/external corrosion, dents, cracks, and wall thickness
- GPS and data logging for tracking and analysis
Common Applications:
- Pipeline integrity assessment
- Regulatory compliance inspections
- Predictive maintenance and risk analysis
Safety and Operational Considerations
All pipeline pigging operations must follow strict safety protocols. High pressure, trapped pigs, or incorrect launch/receive procedures can lead to injuries or equipment damage. Operators should be trained and use control systems to manage pressure, flow, and pig tracking accurately.
Additionally, pigs should be inspected after each run and replaced or maintained according to manufacturer guidelines.
Final Thoughts
The evolution of pipeline pig types has made pigging a highly effective and adaptable solution for pipeline maintenance and inspection. Whether it’s recovering expensive food product from process lines or ensuring safe transportation of oil across thousands of miles, there’s a pig for every job.
By understanding the capabilities and ideal applications of each pig type, industries can enhance efficiency, reduce costs, and protect vital pipeline infrastructure. As technology continues to advance, we can expect pipeline pigging tools to become even more intelligent, reliable, and essential to operations worldwide.
