Magnetic Particle Testing

Magnetic particle testing (MT/MPI) in Dubai, Abu Dhabi and across the UAE — surface and near-surface crack detection in ferrous materials using yoke, prod and bench techniques, visible and fluorescent, to ASTM E1444, ISO 9934 and ASME V Article 7, carried out by ISO 17020 accredited inspection personnel. Last reviewed: August 2026.

Magnetic particle inspection finds cracks at and just below the surface of ferrous components. It detects tight defects that a penetrant test would miss — in-service fatigue cracks that have closed under load, and creep cracking in high-temperature piping — because it does not depend on the defect being open enough to admit liquid.

How the method works

The component is magnetised, either by applying an external field or by passing current through it, producing magnetic flux within the material. A discontinuity distorts that flux and forces some of it out of the surface, creating a leakage field at the defect. Fine ferrous particles applied to the surface are drawn to that leakage field and accumulate along the edges of the discontinuity, forming an indication considerably larger than the defect itself.

Because the field must be perpendicular to the defect to produce a usable leakage field, every area is examined in two directions at approximately ninety degrees. An examination performed in one direction only will miss cracks running parallel to the field — this is the most common cause of a defect being missed by an otherwise competent operator.

Magnetising techniques

• Electromagnetic yokeThe most widely used field technique. An articulated yoke is placed on the surface, producing a longitudinal field between its legs. Portable, requires no electrical contact with the component, and leaves no arc strike risk — which is why it is preferred on finished and in-service equipment. Yoke lifting power is checked against the standard before use.
• Prod techniqueCurrent passed directly through the component between two electrodes, producing a circular field. Effective on heavy sections and large weldments, but carries a risk of arc strike and local heating, so it is restricted or prohibited on some materials and finished surfaces.
• Bench techniquesHead shot through contact heads, encircling coil and central conductor or threaded bar magnetising, carried out on a magnetic particle bench. Used for manufactured components where controlled, repeatable magnetisation in both directions is required.
• Permanent magnets and coilsApplied where power is unavailable or the geometry suits, with field strength verified using a flux indicator, artificial flaw shim or Hall effect meter as the procedure requires.

Visible and fluorescent particles

Colour contrast MPI uses visibly coloured particles against a contrasting background lacquer and is examined under white light (minimum 500 lux at the surface). Fluorescent MPI uses particles coated with fluorescent dye, examined under UV-A (minimum 1000 µW/cm² at the surface) in a darkened area, and offers substantially higher sensitivity for fine cracks. Both dry powder and wet suspension methods are used, with wet fluorescent generally applied where the smallest detectable defect matters — aerospace and rotating component work in particular.

Field strength verification and demagnetisation

Field adequacy is verified rather than assumed, using a flux indicator, artificial flaw shim or a Hall effect meter as the procedure requires, and yoke lifting power is checked against the standard. Components are demagnetised after examination where residual magnetism would interfere with machining, welding, instrumentation or service performance, and residual field is measured to confirm it.

Standards applied

• ASTM E1444 — standard practice for magnetic particle testing
• ASTM E709 — guide for magnetic particle testing
• ISO 9934 series — general principles, detection media and equipment
• ASME Boiler and Pressure Vessel Code, Section V, Article 7, with acceptance to the relevant construction code section
• AWS D1.1 for structural steel welding
• Client, project and manufacturer specifications where more stringent

Personnel qualification

Examination and interpretation are carried out by technicians qualified to ISO 9712, ASNT SNT-TC-1A Level II and PCN as the work requires, with NAS 410 qualification for aerospace components and Level III oversight of procedure approval and technique validation.

Typical applications

• Welded joints in pipework and structures
• Pressure vessel welds and nozzles
• Crankshafts, camshafts and connecting rods
• Engine blocks, bearing caps and gears
• Landing gear and aerospace components
• Crane hooks, pins and lifting components
• Motor and drive shafts
• Studs, bolts and threaded bar
• Castings and forgings
• Steam piping and high-temperature components

Limitations

Magnetic particle inspection applies only to ferromagnetic materials. It cannot be used on aluminium, copper, titanium or austenitic stainless steel — for those materials, penetrant or eddy current examination applies instead. Detection is limited to surface and near-surface defects; deeper flaws require ultrasonic or radiographic methods. Coatings must generally be removed or their thickness accounted for, and surface condition affects sensitivity. Where MT is the wrong method for the defect you need to find, we will say so rather than perform a test that cannot answer the question.

Accreditation and approvals

ITMAD is accredited to ISO/IEC 17020 as an inspection body, is an ADNOC approved inspection contractor, and is listed on the Abu Dhabi City Municipality register of Approved Third Party Inspection Bodies. Certificates are issued in the format required by the governing authority, including Dubai Municipality and the Dubai free zone authorities, and inspection is carried out across Dubai, Abu Dhabi, Sharjah and the northern Emirates. Examination is carried out on site, in fabrication yards, offshore or at ITMAD premises.

What you receive

• A report identifying components examined, by weld number or part reference
• The magnetising technique, particle type and field direction applied
• Field strength verification records and equipment calibration traceability
• Indications recorded with location, dimension and character, supported by photographs
• Assessment against the acceptance criteria in your specification
• Demagnetisation confirmation and residual field readings where applicable
• Technician qualification level and certification reference