Magnetic Particle Inspection (MPI) Systems & Equipment by ATG

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ATG designs and manufactures a complete range of Magnetic Particle Testing systems (MPI) and equipment for all industrial sectors, in any desired magnetization combinations: AC, HWDC, FWDC. These systems are applicable in mass production for the automotive industry (UNIMAG AC/AC series) as well as production and maintenance facilities in aerospace, among other industries (UNIMAG AEROTESTER, UNIMAG Basic, or MAGMAN series). The equipment can be utilized for low- and high-volume testing.
ATG develops advanced MPI and FPI equipment and systems for high-precision inspection in production and maintenance and across multiple industries.
Explore automated testing of aircraft wheels and other ET solutions designed for reliable inspection in aerospace maintenance.
Advance your professional qualification through internationally recognized ASNT 9712 certification through ATG CERT.
Verify your NDT lab Proficiency by accredited Proficiency Testing Provider. Verification of NDT personnel proficiency is also available.

How Magnetic Particle Inspection works

The principle of magnetic particle testing is based on magnetizing the component and applying ferromagnetic particles that gather at discontinuities (cracks, flaws). These indications become visible under UV light or white light, depending on the technique used.

What is Magnetic Particle Testing (MPI)?

Magnetic Particle Testing (MPI) is a non-destructive testing (NDT) method used to detect surface and near-surface discontinuities in ferromagnetic materials, such as iron or steel. It is one of the most widely used inspection techniques in industries such as automotive, aerospace, railway, and energy.

MPI Systems for Testing Various Parts

Gears, cogwheels and rings

For everybody who requires reliable, safe and fast inspection of big rotary parts, we can offer UNIMAG 2000 FLAT.

Application: Energy and other industries

Forgings (shafts, crankshafts, rings)

UNIMAG 5600 AC has been designed for testing diesel locomotives crankshafts as heavy as 6 t 5.6 m long..

Application: Railway

Crankshaft

UNIMAG 14000 AC/AC are among the longest MPI benches in the world. They are used to test crankshafts up to 14 m long and 35 t in weight.

Application: Maritime and power industries

Castings

Castings often have complex shapes and require detection of subsurface defects, which standard UNIMAG benches cannot always handle. For these castings, MAGMAN systems are used – mobile or stationary MPI.

Application: Energy

Bearings, forgings, chassis

UNIMAG AEROTESTER tests these parts, which ensures reliable testing of a wide range of ferromagnetic components – from wheel and engine shops to landing gear facilities and OEM applications.

Application: Aerospace

Geometrically complex components

UNIMAG TWIN system designed for “Y”, “V”, “U”, “T”, “X”-shaped, and other extremely complex geometries components.

Application: Automotive

Screws and bolts

ROBOMAG 1200 AC/AC is an MPI system designed for fully automatic testing of screws and bolts for the transportation industry, with an optional Automatic Defect Recognition (ADR) system external to the inspection bench.

Application: Automotive

Wheelsets

UNIMAG WST tests railway wheelsets according to VPI 09, increasing productivity from 60 to 18 minutes per piece while improving inspection quality and reliability.

Application: Railways

Axles

UNIMAG 2600 AC/AC/AC is a fully automatic MPI system for testing solid and hollow axles, with automatic loading for each processing station.

Application: Railways

MPI Systems and Equipment delivered by ATG

ATG is able to fulfill most Customer requirements by its own internal design floor, internal mechanical and electrical workshops, with special attention for improvements to testing productivity and safety.

Our MPI systems key advantages

  • Customized clamping and manipulation systems, with the ability to test parts ranging from pins, to rotor turbine blades, up through crankshafts of diesel ship engines, 15 meters in length

  • Design according to ASTM E1444

  • Quick Break function

  • Operator-friendly control system

  • Long-term stability with minimal servicing requirements

  • Internal calibration system with data acquisition system

ATG provides complete NDT solutions, offering not only equipment production but also support with qualification, certification, testing, inspection, and outside agency services. Holder a variety of certificates and approvals; ATG is committed to delivering NDT services of the highest quality.

Magnetic Particle Inspection machines in compliance with Standards and Specifications

Magnetic Particle Inspection (MPI) machines must comply with relevant industry standards and follow customer specifications to ensure reliable, accurate, and safe testing. This includes, for example, meeting NADCAP requirements, performing tests in accordance with ASTM E1444 – for Aerospace etc.

MPI systems references

Magnetic Particle Inspection Qualification and Training

The deliveries of these systems are joined with the possibility to qualify NDT operators and provide on-the-job training at ATG Training Center where there are disposable training MPI benches, or directly on delivered equipment at the customer ́s site.

Frequently Asked Questions (FAQ)

How does Magnetic Particle Inspection work?
The magnetic particle testing process starts by magnetizing the component and then applying fine magnetic particles, either dry or suspended in a liquid. If there are cracks, inclusions, or voids, these imperfections distort the magnetic field, creating leakage points where particles gather. This accumulation forms visible patterns that indicate potential flaws.
In practice, MT is widely used because it is quick, cost-effective, and highly reliable for detecting small yet critical defects. Industries like aerospace, automotive, and heavy machinery depend on MT to ensure structural integrity and prevent failures during service. Its ability to verify component safety without causing any damage makes it an essential tool in quality control and maintenance programs.

Magnetic Particle Testing offers several practical benefits that make it a preferred method in many industries. First, it excels at revealing both surface and shallow subsurface flaws, which are often most critical to structural integrity. The process itself is fast and straightforward, meaning inspections can be completed without long downtime—ideal for time-sensitive operations.

 

Another major advantage is cost efficiency: MT typically requires less investment than many other NDT techniques while still delivering highly reliable results. It’s also very adaptable, working on various ferromagnetic materials and accommodating various component sizes, from small machine parts up to large industrial structures.

 

Inspectors appreciate the immediate feedback MT provides—results are visible right after application, enabling quick decisions. In addition, portable systems make it possible to carry out checks on-site, even in remote locations. Finally, beyond simply detecting flaws, MT can help estimate their size and orientation, adding valuable detail for maintenance planning.

While Magnetic Particle Testing is a widely used and effective NDT method, it comes with certain constraints. One of the biggest is material dependency—MT works only on ferromagnetic materials, so it cannot be applied to non-magnetic metals or composites.

 

Proper surface preparation is another requirement; any dirt, oil, or paint must be removed before testing, which can add extra steps and time. Additionally, the method is best suited for detecting flaws on the surface or just beneath it, meaning deeper defects do not produce such obvious indications.

 

Finally, once the inspection is done, the component often needs to be demagnetized to prevent interference with its future use. This step demands extra time and, in some cases, specialized equipment, which can slightly increase the complexity of the overall process.

The size of components inspected by Magnetic Particle Inspection (MPI) is not fundamentally limited by the method itself. With the use of customized clamping and handling systems, a wide range of components testable – from small pins, springsm and turbine blades to very large parts such as marine engine crankshafts up to 15 meters in length.
Magnetic particle inspection systems are used across many industrial sectors. They are widely applied in automotive mass production, aerospace, power generation, and in the manufacturing and maintenance of railway vehicles among other critical mechanical components.

ASTM E1444 is the internationally recognized standard titled “Standard Practice for Magnetic Particle Testing.” It defines how magnetic particle inspection (MPI) should be performed to ensure accurate, repeatable, and safe results.

 

The standard covers the entire MPI process – from preparation and selection of equipment to magnetization techniques, inspection steps, and post-examination evaluation. Its main goal is to provide uniform guidelines so that technicians can reliably detect surface and near-surface discontinuities in ferromagnetic materials.

 

By following ASTM E1444, inspection laboratories and technicians ensure compliance with industry requirements and maintain consistent quality across all MPI tests, regardless of the application (automotive, aerospace, railway, or energy).

The main distinction lies in how deep the magnetic field penetrates the material. Alternating Current (AC) is primarily used when the goal is to find surface-breaking flaws, such as cracks in welds. AC produces a strong magnetic field on the surface but does not reach deep into the material, making it ideal for detecting fine, shallow defects.

 

On the other hand, Direct Current (DC) penetrates much deeper, which allows inspectors to identify discontinuities located beneath the surface. DC is commonly paired with wet magnetic particles for improved sensitivity and visibility during the inspection. This combination of techniques ensures that both surface and subsurface defects can be effectively evaluated.

A yoke is a handheld device designed to generate a controlled magnetic field in the inspected component. It features pole pieces connected to an electromagnetic coil. When placed on the surface and activated, it produces a magnetic field between the poles. The magnetic circuit is completed by the yoke through the component all the way around. The relevant magnetic field is within the component, running from one pole of the yoke to the other.

 

If the material contains a surface or subsurface discontinuity, such as a crack, the magnetic field is locally disturbed, creating a leakage field. When magnetic particles are applied, they accumulate at these leakage fields, forming clear indications of defects. Yokes are suitable for inspecting welds, joints, and hard-to-reach components due to their portability and simple operation.

The difference between HWDC (Half-Wave Direct Current) and FWDC (Full-Wave Direct Current) in magnetic particle inspection lies in penetration depth and current type. HWDC uses half-wave rectified AC, offering moderate penetration suitable for surface or near-surface flaws. FWDC uses full-wave rectified, providing stronger magnetizing force and deeper penetration, ideal for detecting subsurface defects in large or thick components.

Magnetic Particle Inspection (MPI) equipment, including yokes, should generally be calibrated at least twice a year to comply with standards like ASTM E1444, ISO 9934, or NADCAP guidelines. However, the exact frequency depends on how the equipment is used and the criticality of the inspections.

 

In addition to scheduled calibrations, daily functional checks—such as verifying magnetizing power before use—are performed, especially if the yoke has been dropped or repaired. For high-precision or safety-critical applications, more frequent calibration may be necessary. Regular maintenance and calibration help ensure accurate results and reduce the risk of downtime.

Yes, MPI can be integrated into automated production lines, especially for high-volume inspections. Automated MPI systems are designed to handle tasks such as magnetizing, applying particles, and inspecting components without manual intervention. These setups improve speed, consistency, and accuracy, making them ideal for industries like automotive or aerospace where throughput and reliability are equally critical.

 

Automation also reduces probability of human error and enables continuous quality control, but it typically requires customized equipment and higher initial investment compared to manual inspection.

Magnetic inspection laboratories are specialized facilities focused on non-destructive testing, mainly Magnetic Particle Inspection (MPI), to find surface and near-surface flaws in ferromagnetic materials. They use advanced equipment like magnetization benches to ensure the quality and safety of components without causing damage.

 

These labs serve industries such as aerospace, automotive, and defense, where material integrity is critical. Their work helps detect cracks, seams, or other defects and ensures that parts meet strict quality standards before being used in critical applications.

 

ATG provides services as an NDT proficiency testing provider and organizes interlaboratory comparisons in the field of Non-Destructive Testing (NDT). Interlaboratory comparisons within proficiency testing according to ISO/IEC 17043:2010 provide NDT laboratories with an independent tool for evaluating their technical competence and performance. These activities support laboratories in continuously assessing and improving the quality and reliability of their testing services and demonstrating competence to customers and certification bodies.

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