Pigging Services

Pipeline pigs are tools that are placed into and travel throughout the length of a pipeline, driven by product flow. They were originally developed to remove deposits which could obstruct or reduce flow through a pipeline. Today, pigs are used during all phases in the life of a pipeline, and for many different reasons.
Although each pipeline has its own set of characteristics which affect how and why pigging is used, there are basically three reasons to pig a pipeline:

• Internal inspection
• Batch or separate different products in the line
• Displacement.
Pigs used to accomplish these objectives are divided into three categories:
• In-line inspection tools. Provide information on the condition of the line, as well as the extent and location of problems or potential problems.
• Utility pigs. Used to perform functions such as cleaning, separating, or dewatering.
• Gel pigs. Used with conventional pigs to optimize pipeline de-watering, cleaning, and drying tasks.
The type of pig to be used and the pig’s configuration for a particular task in the pipeline is determined based upon several considerations, including:
• Purpose. This covers location and volume of the material in the pipeline to be displaced or removed during conventional pigging applications; information to be gathered from an intelligent pig run; and objectives and ultimate goals for the pig run.
• Line content. Here, consideration is given to product—natural gas, crude oil, refined petroleum products—in the line during the pig run; and available pressure driving the pig, and pig velocity.
• Pipeline characteristics. The characteristics that are considered include minimum and maximum internal pipeline diameter, total distance of the pig run, and the minimum bend radius and angles. Then, there are other features that come into play such as type of valve, pipeline lateral connections, and the profile of the pipeline’s elevation.

Utility Pigs
These pigs can be divided into two groups based upon how they are to be used:

• Cleaning pigs. Used to increase throughput by removing solid or semi-solid material or debris from the pipeline, or to reduce corrosion or clean the line prior to a corrosion tool inspection.
  
• Sealing pigs. Used to seal the pipeline to perform a variety of functions such as removing liquids from the line, or to provide a seal between two dissimilar products within the line.

In-line Inspection Tools
The ultimate objective of in-line inspection tools is to facilitate cost-effective decisions regarding repair, replacement, preventive maintenance, or even new procedures for pipeline construction. This necessitates accurate and reliable in-line surveys that gather information on the condition of the pipe, which is then analyzed by engineers to assess and determine the relevant condition of the line with confidence.

Gel Pigs
These are a series of gelled liquid systems that have been developed for use in pipeline operations, usually at the time of commissioning. However, these pigs can be used as an important part of a continuing maintenance program.

For the most part, pipeline gels are water-based, but there are also chemicals, solvents, and acids that can be gelled. Some chemicals can be gelled as the bulk liquid and others only diluted in a carrier.

For pipeline applications, four primary gel types are used—batching gel, debris pickup gel, dehydrating gel, and hydrocarbon gel.

The gel pig can be moved through any pipe-line which accepts liquids. They can be used in liquid pipelines in place of batching pigs, or they can be used with conventional pigs. When used with conventional pigs, these pigs can improve overall performance.