How to Pig a Pipeline – Gas Pipeline Pigging Procedure
Pipeline integrity is an essential consideration in downstream oil and gas operations. Over extended periods, pipelines used for transporting oil and gas and other process fluids could become clogged or begin to deteriorate internally due to corrosion. Therefore, periodic pipeline maintenance is necessary to ensure optimal flow and reliability.
What Is Pipeline Pigging?
Pipeline pigging is the use of maintenance devices called ‘pigs’ to ensure that the interiors of oil and gas lines are clean and free from obstruction as well as to ascertain pipeline integrity. Pigs can maintain pipelines without disrupting the flow of fluids through them.
The term ‘pig’ is a backronym for ‘pipeline inspection gauge.’ The name may have come about due to the squealing sound early models of the device (composed of straw and wire or leather) made while moving through oil and gas pipelines.
Components of a Pipeline Pigging System
While actual pipeline pigging procedures vary, a pigging system typically consists of the pig, launcher, and receiver. The pig is a cylindrical or spherical device propelled through a pipeline by the force of the fluid in motion or pulled with a string.
Nowadays, a wide range of materials can be used to make pigs including Polyurethane, Rubber, and Steel.
Functions of Pipeline pigs
- Internal cleaning of oil and gas pipelines
- Oil pipeline inspection*
- Physical separation of different process fluids flowing through a pipeline
*Special pigs with embedded electronics used to inspect the condition of oil and gas pipelines are known as ‘smart pigs.’
Pipeline Pigging Systems
As noted above, pigs serve more than one function in oil and gas operations. Below are some common types of pipeline pigging devices available today:
- Utility Pigs
- Inspection Pigs
- Specialty Pigs
- Gel Pigs
Choosing your Pig
When it comes to pigging oil and gas pipelines, every application is unique. Therefore, it is critical to know which pig type is suitable for a particular purpose.
Let’s take a closer look at the pig types listed above:
Utility pigs are used to remove debris, dirt, and other unwanted materials that could obstruct the flow of fluids through oil and gas pipelines. They are also used to separate products and for dewatering operations. Utility pigs travel the length of the line with the force of the moving fluid or electrically. Common utility pig types are foam pigs, spherical pigs, and mandrel pigs.
As the name implies, these pigs are used strictly for oil pipeline inspection. There are also called ‘Smart pigs.’ A pipeline inspection pig uses ultrasonic or electromagnetic technology to remotely monitor pipeline conditions such as thickness, diameter, and temperature. The R & D team can then use this information to pinpoint sections of the pipeline that require remediation.
Also known as plugs, specialty pigs can be used to isolate sections within a pipeline for remediation purposes. Specialty pigs come in a wide range of sizes and materials for various pipeline applications.
Gel pigs are made of chemical compounds and do not require a launcher/receiver system for pigging operation. They can be used alongside other pig types for effective cleaning, dewatering, and fluid separation in pipelines and also reduce wear and tear of primary pig components.
Gel pigs are especially advantageous for ‘hard-to-pig’ pipelines with sharp bends and changing diameters and can also help to remove a pig stuck in a gas pipeline.
Pipelines that contain internal valves cannot be maintained using conventional process pigging systems because these obstructions could lead to a stuck pig. In such cases, gel pigs can get the job done.
How to Pig a Pipeline
Below are a series of steps that form standard pigging procedures. The first step to successfully pig an oil and gas pipeline is to determine what type of operation the pig is to perform. This will help you determine the most suitable pig type for the job.
The basic pigging procedure requires a launcher and a receiver to clean a pipeline. The pig is inserted into the pig launcher which is slightly larger in diameter than the pipeline. The launcher is then closed and the force of fluid moving through the line propels it along the entire length of the pipe, clearing debris or material build-up within the pipeline. At the opposite end of the pipeline is a receiver device (or pig trap) which collects the pig before the debris is removed. During pigging pressure control is essential to avoid bodily injury.
NB: Pigging must be done by competent or experienced pipeline pigging contractors or professionals to mitigate the inherent safety risks.
NiGen Can Help!
To properly pig a pipeline and to ensure safe operation, you need the services of a seasoned pipeline pigging contractor. NiGen International has a team of highly-trained staff knowledgeable in various pipeline pigging procedures, applications, and devices.