Common Pipeline Pigging Terminology to Know

The pigging pipeline process is a unique one. If you’ve ever found yourself curious about various pigging and pipeline terminology, you aren’t alone. When looking to maintain your pipelines, obtaining key information about various pigging terms can provide beneficial insights. 

What types of pipeline corrosion should I know about? What’s the difference between a caliper pig and a configuration pig? What do dents in my pipeline look like, exactly? 

By and large, the art of pigging can best be understood by examining various pigging and pipeline terminology. 

To give you an idea of what pigging is all about, we’ve defined the following pigging and pipeline terminology. 

Pigging and Pipeline Terminology to Know

Camera pig: A camera pig is a configuration pig. The configuration pig uses a camera and light sources inside a pipe to photograph the pipe’s inner surface.

Caliper pig: A caliper pig is similar to a gauging pig. A caliper pig tool is a pig designed with mechanical sensors or arms on the pig’s body. These mechanical sensors record the internal structure of the pipeline. 

Cleaning Pig: The purpose of running a cleaning pig is to remove debris or build-up inside a pipeline. Running a cleaning pig increases cleaning efficiency. 

Configuration Pig: A configuration pig is a pig that is used to gather data about the internal pipeline wall. There are several types of configuration pigs, such as a camera pig. 

Corrosion: There are several types of pipeline corrosion, which are defined as the following:

External: External corrosion of a pipeline is a chemical or electrochemical reaction of a pipeline’s metal to the surrounding environment. When corrosion of a pipeline occurs on the pipe’s external surface, it is external corrosion. Rust, or the formation of iron oxides, is a common electrochemical corrosion process. 

Internal: Similar to external corrosion, internal corrosion differs due to the location of the corrosion. 

Pit, or Pitting Corrosion: A pit in a pipeline is caused by a process known as pitting corrosion. This is a localized form of corrosion that can occur on the internal or external surface of a pipeline. A pit, also referred to as a cavity, is the result of localized corrosion process.   

Selective Seam Weld Corrosion: Another form of localized corrosion is selective seam weld corrosion. This type of corrosion is selective because it affects the weld metal instead of the pipe’s base metal.  

Stress Corrosion Cracking: Within a corrosive environment, cracks can occur. This is referred to as stress corrosion cracking. These cracks can be the cause of a pipe’s sudden failure due to pressure on the pipe. 

Cracks: In pipeline terminology, there are three types of cracks: 

Fatigue: Fatigue of a pipeline occurs when the pipeline’s material is weakened. The weakening of a pipeline’s material is the result of regular use. Accordingly, the pipeline experiences localized structural damage, and cracks begin to grow in the pipe. 

Girth Weld Crack: A girth weld is a type of arc welding that joins together a pipeline. When a pipeline has cracks along its girth weld, it is known as girth weld cracks.  

Seam Weld Crack: A seam weld is another type of arc welding that joins together a pipeline. Similar to girth weld cracks, when a pipe has cracks along its seam weld, it is seam weld cracks.  

Dent: When a pipeline’s surface has a depression, typically the result of mechanical damage, it is known as a dent. A dent is identified partly by the fact that it does not reduce the wall thickness of the pipeline. 

Fill Pig: A fill pig is a type of pig run through a pipeline during various testing processes. Specifically, the fill pig is used during a pipeline filling procedure. The pig is propelled by a column of test water, ensuring that air in the pipeline is eliminated.

In-Line Inspection (ILI): In-line inspection is when a pipeline is inspected through processes that examine the interior of a pipeline. 

In-Line Inspection Tool: The tool used in in-line inspections is known as an in-line inspection tool. This device is also referred to as a “smart” pig or an “intelligent” pig. The focus of this tool is the inspection of a pipeline’s walls. 

Instrumented Pig: An instrumented pig is a tool equipped with instruments such as sensors or records, to examine a pipe’s interior. There are two main types of instrumented pigs: configuration pigs and in-line inspection tools. 

Mapping Pig: One type of configuration pig is a mapping pig. A mapping pig uses technology, often inertia sensing, to produce a plan view of a pipeline’s route. 

Metal Loss: Metal loss refers to numerous types of pipeline anomalies. These anomalies are identified by the loss of metal in a pipeline’s surface. This metal loss can be the result of pipeline corrosion or gouging. 

Obstructions: Any foreign objects or general restriction that reduces a pipe’s flow is an obstruction. Obstructions can be identified through the visual inspection of a pipeline’s interior. 

Pig: A pig is a universal term referring to a device used in pipeline pigging procedures. A pig tends to be self-contained, such as an instrumented pig like a configuration pig. The general purpose of using a pig is to clean, inspect, or measure a pipeline. 

Swab: The first pig used in a pigging process is often referred to as a swab. A swab tends to be made of soft foam and is meant to be malleable, as it must navigate potential pipeline obstructions. Once a swab arrives at a pipeline receiver, it is known as a “prover pig.” The condition in which this pig emerges indicates the internal condition of a pipeline. 

Trap: A pipeline trap is used for either a pig launcher or a pig receiver. The use of these devices is integral to pigging procedures. 

Launcher: A launcher, or pig launcher, is part of a pig trap used to introduce a pig into a pipeline. A pig is forced into a pipeline without interrupting the pipeline’s flow with a launcher. A pig can also be inserted from a launcher into a pipeline by towing it with a device or cable. 

Receiver: A pipeline receiver is used alongside a pig launcher. The receiver is used to remove a pig from a pipeline. The receiver is important because examining the pig, such as a prover pig, can help identify the next steps of the pigging process. 

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