19 Aug Magnetic Flux Leakage – ASNT Level 3

What is Magnetic Flux Leakage?

Magnetic Flux Leakage is a type of non-destructive inspection which uses electromagnetism for the inspection of flaws, corrosion, pitting, wall loss or material degradation in steel structures. In the field of oil and gas this method can be used to detect the flaws in aboveground storage tanks also. This involves temporary magnetisation of the structures. This magnetic field will detect the flaws by showing the distortions which signals the defects like corrosion, pitting, wall loss etc. 

How does it work?

MFL or Magnetic Flux Leakage mainly uses a powerful magnet to magnetize the conductive sample or material for the test which might be steel usually So that when any defects like corrosion or wall loss comes, the magnetic field will leak from the steel. A magnetic detector is placed in between the poles of the magnets so that it can detect the leakage field. While performing the test, a magnetic field is formed and get saturated until it can hold no more flux. The flux will overflow and leak out of the wall in the case where there is a defect. This time the sensors placed strategically will measure the 3D vector of the leakage field accurately. Since the magnetic flux leakage is a vector and the sensor will measure only one direction, there must be three sensors to accurately measure the radial, axial and circumferential components of the signal (MFL). If there is no defect then the magnetic flux lines will pass through the inner side of the ferromagnetic material.

Advantages and Disadvantages of Magnetic Flux Leakage

Advantages

• Sensitive to pits in carbon steel
• Test results are reliable and reproducible
• Less skill required
• Small defects even as 0.1 mm can be detected
• Can use on fin tubes
• Easy and Efficient operation
• Well sustained indication of corrosion on tank floor
• Powerful scanning of large floor area
• Highly sensitive for the detection of longitudinal defects on black steel bars
• Coupling liquid is not required

Disadvantages

• Result can be obtained only by achieve complete magnetic saturation of the pipe wall
• Responses form top side and bottom side indications cannot be differentiated
• Axial long and narrow inspections will be limited
• Reliable quantitative indication is not possible
• Anti-interference ability is poor and is susceptible to the pipe wall
• There is limitation in physical access, so the coverage will not be accurate
• The height of the defect depends on the experience of the trainer sometimes

Applications

• Used for Flaw detection on large tank floor area within a time frame
• Used in petrochemical industries to provide high speed inspections of storage tank as well as carbon steel pipes
• Used to inspect finned Tubes
• Used in all ferromagnetic materials 

Enroll for 1 month preparatory classes for ASNT level 3 Magnetic Flux Leakage Testing Certification

Gamma NDT academy offers NDT preparatory classes for candidates who intend to appear for the ASNT 3 Magnetic Flux Leakage Testing Certification exam. 

We will cover all the syllabus under ASNT for Magnetic Flux Leakage Testing and conduct mock tests to prepare you best for the certification exam. We will also share study materials and sample questions which you need to revise. We have a 100% success rate for NDT level 2 and 3 certification courses.

Gamma NDT academy training institute is located in Kerala, India. We provide online classes for candidates who cannot attend our training sessions in-person.