Magnetic particle testing
(MT)
Even a small weld crack can grow into a critical fracture – especially dynamically
in loaded structures. Magnetic particle inspection (MT) is a standardised non-destructive
non-destructive testing (NDT) method that detects surface and near-surface flaws
quickly, cost-effectively and without radiation.
- SFS-EN ISO 9712 certification
- The whole process from pre-treatment to audit-ready reporting
METHOD
PRINCIPLE
The ferromagnetic component to be inspected is magnetised in a controlled manner. A surface defect causes
disturbance where the applied magnetic powder gathers to form a visible indication.
Using the fluorescent wet method under ultraviolet light, even down to the micrometre level
The cracks stand out clearly.
Note
Austenitic stainless steel, aluminium and other non-ferromagnetic materials
are not suitable for MT testing. For these materials, it is recommended
jack test (PT).
SUITABILITY
SUITABLE MATERIALS AND STRUCTURES
- Carbon steel and low-alloy steels
- Cast steel and forgings
- ferritic stainless steel
AUDIT PROCESS STEP BY STEP
The surface is cleaned of oil, grease and loose material in accordance with standard ISO 17638. Sufficient cleanliness is a prerequisite for a reliable inspection.
The component is magnetised with an electric current (direct magnetisation) or an external magnetic field (indirect magnetisation). The direction of magnetisation is optimised according to the expected defect orientation – often two mutually perpendicular ones are needed
Either dry powder or the wet method is used, either colored or fluorescent.
A certified inspector assesses the indications in accordance with applicable standards and acceptance criteria. Ambiguous cases are meticulously documented.
The inspection report contains a description of the area inspected, the parameters used, indications observed and the acceptance decision – ready to be attached to the QA/QC documentation.
TYPICAL APPLICATIONS
01
Welded joints in the steel structure and pressure equipment industry
02
Supporting structures for cranes and lifting appliances (SFS-EN 15011)
03
Shafts, flanges and gears in mechanical engineering
04
Bridge and offshore structures
05
Quality assurance of castings and forgings
06
In-service inspections and maintenance NDT
MT BESIDES NDT METHODS
The following comparison helps to select the most suitable method or combination of methods for the situation:
| Feature | MT | UT | PT |
|---|---|---|---|
| Pintaviat | ✓ Excellent | Limited | ✓ Excellent |
| Subsurface defects (≤3 mm) | ✓ Good | ✓ Excellent | ✗ Not suitable |
| Deep internal faults | ✗ Not suitable | ✓ Excellent | ✗ Not suitable |
| Non-ferromagnetic materials | ✗ Not suitable | ✓ Suitable | ✓ Suitable |
| Pace on the pitch | ✓ Fast | Moderate | ✓ Fast |
| Freedom from radiation | ✓ Yes | ✓ Yes | ✓ Yes |
Magnetic particle testing
UT — Ultrasonic Testing
Turku University Neuropsychological Rehabilitation Test
The combination of MT and UT is a common solution for critical welded structures where required
comprehensive inspection of both surface defects and volumetric defects.
Customer benefits
Safety
Detect critical surface cracks before they propagate – protect your personnel, structures and reputation.
Lifecycle management
Supports predictive maintenance: regular inspection identifies fatigue cracks at an early stage.
Cost-effectiveness
Prevents costly production downtime, repair welding and warranty claims. Faster than many alternative methods.
Flexibility
Suitable for both factory production lines and field conditions – even in confined spaces or
to hard-to-reach locations.
Compliance with standards
Reporting complies with SFS-EN ISO 9712, ISO 17638 and project-specific EN/ISO requirements – audit-ready documentation.
QUALIFICATION
STANDARDS AND CERTIFICATION
NDT Aura Oy's inspectors operate in accordance with the standards listed below — a technically competent and legally acceptable inspection result.
NDT programme
NDT Comprehensive Programme by MT Osana
A single inspection method covers only a specific set of fault types. Comprehensive quality assurance often requires different methods:
NDT Aura Oy can consult on the formation of the most suitable inspection programme for the object
based on the risk assessment and applicable standards.
FREQUENTLY ASKED QUESTIONS (FAQ)
MT reliably detects surface-breaking and potentially up to a few millimetres deep
deep subsurface defects. Deeper internal defects require ultrasonic or radiographic inspection.
An individual weld or machine part is inspected very quickly. Larger assemblies naturally take more time.
Not necessarily. MT is a field-proven method that is in many cases suitable to be carried out alongside production.
Yes. MT does not contain ionising radiation and does not damage the object being inspected. The fluorescent wet method requires the use of UV light, but no special protection areas.
A written inspection report is supplied, in which the inspected object, parameters used, observed indications and the approval decision are recorded. Photo and other attachments as necessary.
A rough description of the object (material, welding method, area to be inspected) and the applicable standard or project-specific requirement as well as the scope of inspection is sufficient. Drawings will speed up the preparation of the quotation.
Request for quotation
Request a quotation for magnetic particle testing
(MT) — quick response, audit-ready documentation
Tell us about the inspection object, material, applicable standard and schedule — we will respond to your request for quote quickly. Send the drawings or a short project description, and we will help you choose the technically correct NDT method or combination of methods.
