Magnetic Flux Leakage (MFL) - Assessing Metallic Pipelines

Magnetic flux leakage (MFL) is an electromagnetic method of nondestructive testing that is used to detect corrosion, pitting and wall loss in lined and unlined metallic pipelines



  • Potable Water
  • Raw Water
  • Wastewater
  • Oil & Gas

Pipe Materials

Pipe Diameters

8" (200mm) and larger

Case Studies

The most accurate method of metallic pipeline condition assessment is MFL in-line inspection (ILI) using advanced nondestructive electromagnetic methods to scan the full circumference and length of the pipeline for damage by corrosion and other causes.

This technology, commonly known as ‘smart pigging’, has become the industry standard condition assessment vehicle in unlined steel pipelines in the oil and gas industry.

Until now, the presence of mortar lining in water pipelines has limited the accuracy and use of ILI inspection and hindered development of practical ILI methods for large diameter, mortar-lined metallic pipelines. With MFL from Pure, pipeline owners can now clearly see through mortar linings up to an inch thick.

What is MFL?

With MFL technology, permanent magnets are used to temporarily magnetize the steel pipe and the magnetic field changes are recorded and analyzed. The magnetic flux is uniform if there are no flaws in the wall of the pipe. If internal or external flaws are present, such as pitting, corrosion or other forms of damage, the magnetic flux is distorted beyond the wall of the pipe, and this distortion or ‘leakage’ is measured by Hall Effect sensors.

See Through Lined Pipes

Pure's MFL tools inspect lined pipe through liner up to an inch thick. These tools have industry-leading computational capacity and speed, world-leading inspection resolution of the pipe wall and unique data analysis algorithms using advanced applied mathematics to accurately determine defect characteristics and shape.

Benefits of Pure MFL

  • Provides high resolution data of entire circumference of the pipe wall allowing for comprehensive structural evaluations of the pipe
  • MFL tool is capable of collecting high resolution data through interior mortar linings
  • Recognized as an industry standard for metallic pipe wall assessment
  • May be deployed manned or free-swimming

Available Tools

8 Inch XHR MFL In-Line Inspection Tool

# Primary Sensors: 96
Tool Length (ft): 7.1
Tool Weight (lbs): 280

10 Inch XHR MFL In-Line Inspection Tool

# Primary Sensors:120
Tool Length (ft): 7.4
Tool Weight (lbs): 320

12 Inch XHR MFL In-Line Inspection Tool

# Primary Sensors: 144
Tool Length (ft): 7.7
Tool Weight (lbs):580

24 Inch XHR MFL In-Line Inspection Tool

# Primary Sensors:288
Tool Length (ft):4.75
Tool Weight (lbs):650

56-78 Inch XHR MFL In-Line Inspection Tool

# Primary Sensors:672-936
World Largest MFL Tool

Pure offers a wide variety of MFL tools for assessing the condition of metallic pipelines. These range from large diameter manned entry tools to free-swimming small diameter tools. Contact your Pure representative to find out which solution is best for your needs.

Extra High Resolution (XHR)

Our MFL tools use Extra High Resolution (XHR) data in order to provide a visibly improved view of defects and better analytical characterization of their size. XHR is the newest generation of MFL tools where systems have a very high number of sensors. Hall Effect sensors are positioned at 1/4" (6.25mm) intervals along the circumference of the tool, and in conjunction with higher sampling rates, guarantee maximum data resolution.

Extra High Resolution (XHR) MFL means:

  • Better magnets and better sensors
  • Tighter sensor spacing for maximum resolution
  • Uniform sensor spacing on the entire circumference
  • Higher sampling rates for the best quality data

Featured Projects

State-of-the-art Extra High Resolution Magnetic Flux Leakage (MFL) Tool Scans California Utility's Pipeline

Built in the 1950's, this 73 and 76-inch mortar lined steel pipeline serves an important link between Metropolitan Water District and the San Diego County Water Authority. The inspection employed a custom high resolution magnetic flux leakage (MFL) tool, owned by the San Francisco Public Utilities Commission (SFPUC), to detect corrosion, pitting and wall loss in the lined metallic pipeline.

Hetch Hetchy Water and Power Project (SFPUC) - Magnetic Flux Leakage

San Francisco Public Utilities Commission (SFPUC) operates three parallel cement mortar-lined steel pipelines 47.5 miles long, otherwise known as the San Joaquin Pipelines, which range in size from 56- to 78-inches in diameter. In 2008, the SFPUC contracted Pure Technologies to perform the in-line "smart pigging" inspection of the lines utilizing advanced MFL technology.

Data Analysis

The highest quality tools produce the highest quality data. The world-class data gathered by Pure's MFL tools provides a clean and clear view of pipeline conditions.

  • Hall Effect Sensors are only .66cm (¼") Apart
  • Each Sensor is Sampled 1400 Times per Second
  • XHR Shows Clear Delineation of Minute Defects - ¼" Diameter Defects shown




Pit Corrosion (A<3tx3t) (Preliminary) Minimum Identifiable Defect Depth
Minimum Quantifiable Defect Depth
Depth Accuracy
Length Accuracy
Width Accuracy
±8% WT
General Corrosion (A>3tx3t) (Preliminary) Minimum Identifiable Defect Depth
Minimum Quantifiable Defect Depth
Depth Accuracy
Length Accuracy
Width Accuracy
±8% WT
Location Accuracy Axial
±1% of distance from nearest recognizable pipeline feature or ±3" when referenced to a girth weld on the same pipe joint



Learn More

Managing Metallic Pipelines

Managing Metallic Pipelines

Pure offers a number of leading edge technology options for assessing the condition of ferrous water and wastewater mains.