What is MFL pipeline inspection?

Safety and high efficiency are the main and basic requirements for oil and gas transport through the pipeline. Leaks on the pipelines can result in erosion, abrasion and unexpected damage. Inspecting oil pipeline systems is challenging because most are laid in the ground or underwater. However, various pipeline inspection methods can detect the proportion of damage.

Nowadays, there are systems for automatic control of industrial processes and oil pipelines that can detect any severe and significant damage in the oil pipeline system using various sensors.

Utilizing such systems, it is possible to detect the failure of certain system parts, such as pumping stations, valves, blockages, cracks in oil pipelines, and oil spills. Still, detecting corrosive metal loss or minor geometric deformation (ovalization) in the pipes is impossible. We use unique technologies and methods to detect such defects.

Magnetic flux leakage (MFL) is the most popular pipeline inspection method. It is also one of the oldest methods available since 1969. Over the years, several generations of MFL systems have been developed, each new with significantly improved performance.

MFL pipeline inspection technology has revolutionized the industry and greatly reduced costs, providing a more accurate overview of pipelines, tanks, and effective asset protection. This method uses magnetically sensitive sensors to detect magnetic field leakage on the inner and outer surfaces of the pipeline.

In this article, you will learn how to use a magnetic flux (MFL) measuring device to detect and locate defects in pipelines and tanks worldwide.

Types of devices for pipeline control and cleaning 

Inspecting the pipeline’s condition involves utilizing “in-line” tools and devices, specifically PIG devices (cleaners), to control the pipeline’s condition (Pipeline Intervention Gadget). Cleaners clean the pipeline, separate various fluids within the pipeline, and track and record the condition of pipelines.

For the control of oil pipelines, in industry we use the so-called “smart” cleaners. Depending on the type of damage, that needs to be determined, and the principle of measurement, several devices can be used to control the condition of the pipeline: 

MFL (Magnetic Flux Leakage): electromagnetic device for controlling the condition of pipelines, cracks and loss of pipe wall material.

EMAT (Electromagnetic Acoustic Transducer): acoustic device for monitoring the condition of pipelines. This technology is used to detect pipe wall material loss, damage to the protective coating of the pipe and to distinguish different types of coating.

Caliper: The caliper is used to detect all geometric deformations (ovalization) to pipelines, to give their exact location via GPS and to collect data on the size and shape of all geometric changes in the pipe.

What implies Magnetic Flux Leakage?

Magnetic Flux Leakage (MFL) is a magnetic non-destructive testing technique used to detect corrosion and pits in steel structures, most commonly pipelines and tanks, and accurately measure corrosion damage. The number of magnetic lines of force placed in a magnetic circuit determines magnetic flux.

The Magnetic Flux Leakage (Magnetic Flux Leakage, MFL) method and devices for determining the change in the geometry of the pipeline are used in in-line inspection (ILI).

The principle of operation is based on the induction of a magnetic field in the tube plate scattering between the two poles of the magnet. Anomalies are recognized by the scattering of magnetic flux in the wall. The larger the magnitude of the irregularity, the better the magnetic flux dissipation.

The dissipation of the magnetic field depends on several factors:

• the degree of magnetization of the wall,
• steel brushes,
• pipeline material,
• the distance between the two poles of the magnet,
• the speed at which the device moves through the pipeline, and other factors.

How does the MFL pipeline test method work?

High efficiency and security of pipelines and energy supply are important issues affecting all countries, the global economy, and the lives of people in general. To repair existing pipelines and prevent future damage, it is necessary to determine the location of the damage.

The petrochemical industry commonly employs magnetic flux leakage (MFL) for inspecting pipelines and tank floors. Corrosion of the tank floor can lead to product loss and cause environmental damage. To prevent such and similar problems, it is essential to conduct inspections of tanks and pipelines. 

The industry widely accepts MFL as a non-destructive method for detecting surface and subsurface anomalies. The MFL works by magnetizing the controlled pipeline using a strong magnetic field.

The method is based on the principle of magnetic induction. This is the formation of a magnetic field around a conductor, through which an electric current passes. As the magnetic flux passes through the cracks, there will be a concentration of magnetic forces and changes in the magnetic field on the test object’s surface. A leakage field will appear at the site of corrosion. The larger the corrosion, the greater the leakage field.

When corrosion or dents occur, the magnetic field “leaks” and the analysis determines the location and severity of the anomaly. In undamaged areas, the magnetic field forces stay undisturbed. When we find a loss of pipe wall material on the inside and outside, magnetic forces will go beyond the oil pipe.

Advantages of the MFL method:

• One of the few ways used to inspect corrugated pipes
• It can be used on all ferromagnetic materials
• Good sensitivity to pitting
• Cost-effective and quick review

How to successfully maintain pipelines?

To maintain reliable pipeline operation, it is necessary to conduct regular inspections of its technical condition to ensure safe use over a long time.

The first step in managing the system’s condition is to identify potential causes of damage to the oil pipeline system, i.e., disruption of its operation. System management aims to collect data on the system’s operation and condition. It assesses all possible risks of violating the system’s integrity and reduces them to an acceptable and minimum possible level.

How to control corrosion?

The most common cause of oil pipeline damage is corrosion. Corrosion is a natural process that occurs during the deterioration of the material due to environmental influences (presence of moisture, oxidant, etc.).

Controlling corrosion proves challenging, and it’s impossible to entirely eliminate the associated risks. Therefore, it is possible to take preventive measures to prevent its occurrence. Some of these measures include pipeline inspections, cathodic protection of oil pipelines, coating of pipes, and their regular cleaning.

The main challenge pipeline system operators face is comprehensive pipeline integrity management. The technology and devices used to control the condition of oil pipelines are extremely expensive. Some companies specialize only in pipeline system control, offering unique and modern solutions for the gas and oil industry.

Pipeline integrity management system software

One such solution is AYMO, a state-of-the-art pipeline integrity management system software. The AYMO pipeline integrity management system provides a comprehensive and integrated framework of norms and rules for effective pipeline network management integrated into software and automation.

Whichever method you choose, regular internal inspection of the pipeline is key to detecting damage to the pipeline. This way, you can avoid pipeline cracks, huge costs, and potential environmental disasters.

It is important to increase the accuracy of the data obtained by pipeline control and the effectiveness of corrosion protection to facilitate the preservation of the integrity of the pipeline system. Have any questions related to control, monitoring, analysis, and pipeline risk assessment? Contact us for more information about our services.