How to Pig a Pipeline – Gas Pipeline Pigging Procedure
The gradual buildup of debris, grease, corrosion, and fractures within gas pipelines is a serious problem that affects flow integrity and can result in accidents. A special tool, known as a “pipeline pig,” can help prevent these problems to ensure optimal flow assurance.
This article will outline the pipeline pigging procedure, types of gas line pigs, and common applications.
What is a Pipeline Pig?
Pipeline “pigs,” a backronym for “pipeline intervention gadget” are devices used to clean or inspect pipelines in upstream, midstream, and downstream O&G operations. Interestingly, the name may have originated from the “squealing” sound early pig models (made of straw and wire or leather) produced while traveling through pipelines.
What Is Pigging in Oil and Gas Pipelines?
Pigging in the oil and gas industry is a form of flow assurance where pipeline pigs are used to purge, clean, and/or inspect pipelines to keep them running smoothly. Since the operation is hazardous, pigging must only be carried out by experienced professionals.
Purpose of Pipeline Pigging
The following are some justifications for pigging gas pipelines:
- Keeps pipelines clean and free of obstruction
- Ensures optimal flow integrity of pipelines
- Can be used to inspect internal sections of pipelines to plan for remedial operations
How Does Pipeline Pigging Work?
The typical pigging system consists of a pig, a launcher, and a receiver, collectively known as the “pig trap.” The pig is a cylindrical device that travels the length of a pipeline by being pulled by a string or using the force of a fluid flowing through the line.
The pig launcher releases the pig from one end of the pipeline (launcher station) and the receiver retrieves it at the other end (receiver station). Pipeline pigging is a potentially hazardous procedure that must be carried out by competent professionals.
Pipeline Pig Types
For the most effective results, it is essential to select the appropriate pipeline pig for the job. The following are some common pipeline pig types used in the oil and gas industry today:
Utility Pigs
Utility pigs are used for cleaning, dewatering, and sealing of gas pipelines. To flush a gas line, a utility pig sweeps through the internal section, scraping off debris and semi-solids that obstruct or limit the flow of hydrocarbons.
When used for dewatering or sealing, the pig provides air and moisture-tight coupling to flush liquids from the line or separate different in-line media.
Utility pigs can be further divided into the following types:
- Mandrel Pigs – Consist of a steel mandrel body with a series of replaceable cups and discs (sealing elements). Mandrel pigs contain special brushes that remove debris from the internal sections of pipelines. A key benefit of this type of pig is its cost-effectiveness – worn-out components can be replaced resulting in a brand-new pig.
- Solid Cast Pigs – Consist of a single piece of polyurethane polymer or steel.
- Foam Pigs – Consist of a combination of polymer foam embedded with solid abrasive materials.
- Spherical Pigs – Consist of hollow, spherical balls made from polyurethane or neoprene. Spherical pigs are mostly inflatable and filled with liquids such as glycol or water to retain their shape when exposed to the high pressures within gas pipelines.
Gel Pigs
Gel pigs consist of chemical substances such as rigid polymers and high-viscosity gels. They are typically used during pipeline commissioning or maintenance. They are the ideal option for so-called “unpiggable” lines – pipelines containing internal valves, sharp bends, and/or special structures that could result in a stuck pig.
Unlike other pig types, gel pigs do not require a launcher and receiver system. Gel pigs are often used alongside other types of pigs to improve the efficiency and prevent deterioration of the primary pig components. They can also help to retrieve a pig stuck in a pipeline.
Inspection Pigs
Inspection pigs also called “smart pigs,” are used for inspecting internal sections of gas pipelines ahead of remedial activities. They contain electronic components such as ultrasonic sensors, RF modules, and pig gauge plates, and can measure parameters such as diameter, curvature, thickness, pressure, metal loss, and temperature. Newer inspection pigs can detect issues in pipelines such as leaks, cracks, wax deposition, and corrosion with a high degree of accuracy.
Specialty Pigs
These types of pigs, also called “plugs” are used to seal off entire sections of pipelines while remedial activities are being carried out. Specialty pigs are used by pipeline maintenance service companies for pipeline cleaning without completely restricting the flow of fluids through them.
NiGen Can Solve Your Pipeline Pigging Needs!
Are you in need of pipeline pigging services? NiGen provides pipeline decommissioning and commissioning services, including pipeline pigging operations for several petrochemical industries. Our team of highly-trained technicians provide expert advice on choosing suitable pipeline pigs for any operation.
Contact us online today to learn more about our services or request a quote.