MPI Testing Lab in Bangalore | NABL & NADCAP MT In lab & Onsite Services in Hosur & Mysore

Magnetic particle testing (MPT), also called MT or magnetic particle inspection (MPI), is a non-destructive method that detects surface and slightly subsurface cracks and other discontinuities in ferromagnetic materials. The part is magnetised and fine iron particles are applied. They gather where the magnetic field leaks out of a flaw and form a visible indication in white light or, for fluorescent particles, under UV-A light.

Yes. Trinity NDT’s laboratory in Peenya, Bangalore is accredited by NABL to ISO/IEC 17025:2017 for non-destructive testing, and our aerospace division is accredited by NADCAP for MPI and FPI. The accredited scopes can be downloaded from our website. Ask us to confirm that your specific technique and standard are within scope before you place an order.

MT detects cracks, laps, seams, inclusions and other discontinuities on or near the surface of ferromagnetic materials, including fatigue cracks, grinding cracks, quench and heat-treatment cracks, and weld cracks such as crater, toe, transverse and longitudinal cracks. It finds only slightly subsurface flaws, so deep internal flaws such as porosity or lack of fusion inside a weld need ultrasonic testing or radiography.

MT works on ferromagnetic materials: iron, nickel and cobalt alloys, including carbon and low-alloy steels and ferritic and martensitic stainless steels. It cannot be used on non-ferromagnetic materials such as austenitic stainless steel, aluminium, copper and magnesium. For those materials, dye penetrant testing is the usual surface method for finding cracks.

The weld and adjacent base metal are cleaned and magnetised with an electromagnetic yoke or prods. Particles are applied during magnetisation, and the yoke is repeated at about 90 degrees so flaws in all directions are covered. Common standards are ASME Section V Article 7, ISO 17638 for the technique with ISO 23278 acceptance levels, AWS D1.1 and ASTM E3024, with acceptance from the construction code.

Shafts are tested on a stationary bench unit in two directions. A head shot passes current through the shaft to find longitudinal flaws, and a coil shot creates a longitudinal field to find transverse flaws such as fatigue cracks. Hollow shafts can also use a central conductor. Large forged crankshafts are commonly accepted to ASTM A456/A456M, and parts are demagnetised and cleaned afterwards.

A flaw leaks magnetic flux only when it lies roughly across the magnetic field. A circular field finds flaws that run along the part, and a longitudinal field finds flaws that run across it. Because the orientation of a flaw is not known in advance, specifications normally require the part to be magnetised in at least two directions, with the results checked after each.

Wet fluorescent particles are suspended in a liquid and viewed under UV-A light in a darkened area. They give the highest sensitivity and are used on the laboratory bench for critical and aerospace parts. Visible particles, wet or dry, are viewed in white light. Dry powder is used on site on rough surfaces and welds, with lower sensitivity to very fine flaws.

ASTM E1444/E1444M is the practice for magnetic particle testing for aerospace applications. ASTM E3024/E3024M is the practice intended for industrial applications, and ASTM E709 is a guide that can be used with it. For welds, ASME Section V Article 7 and ISO 17638 with ISO 23278 are commonly used. Your contract or specification decides which applies.

Often yes. MT can be used through thin non-magnetic coatings such as paint, but the allowable thickness depends on the standard or specification, and the inspector must demonstrate the required sensitivity on the coated part. If the coating is too thick, it must be removed first. Nickel plating is itself ferromagnetic and needs special consideration, so tell us the coating type and thickness.

Magnetic particle testing can leave residual magnetism in a part. Residual fields can attract swarf, damage bearings and gears, interfere with instruments and are restricted on aircraft assemblies, where limits of 3 gauss or less are common. Demagnetisation reduces the residual field, which is then verified with a calibrated gauss meter. It is done after inspection is complete and indications are recorded.

It depends on the material. MT is quicker, is less sensitive to pre-cleaning, can find slightly subsurface flaws and can work through thin coatings, but it works only on ferromagnetic materials. Dye penetrant testing works on any non-porous material, including austenitic stainless steel and aluminium, but finds only surface-breaking flaws and needs careful cleaning. Many specifications use one or the other depending on the material.

Only slightly subsurface ones. MT is intended for flaws on or near the surface, and sensitivity falls quickly with depth. Alternating current gives the best sensitivity to surface cracks, while rectified current gives deeper field penetration. For internal flaws deeper in a weld, casting or forging, use ultrasonic testing or radiography, often together with MT for full coverage.

Yes. Our Level II inspectors test on site with portable AC or DC yokes, prods and permanent magnets, and mobilise from Peenya to Bangalore, Hosur, Mysuru and Tumakuru, and across India for larger projects. Fluorescent testing needs a darkened area and UV-A lamps, so it is normally done in our laboratory. We confirm the mobilisation time when we quote.

The cost depends on the technique (bench, yoke, prod), part size, weight and quantity, the standard and acceptance criteria, whether NABL or NADCAP-scope reporting is needed, demagnetisation and residual-field verification, lab or on-site testing, and urgency. We quote after reviewing your drawing, standard and quantity so the price reflects the real scope. Send the details on WhatsApp for a quotation.

We typically reply with a quotation within two hours of receiving complete details on WhatsApp or email. Lab jobs are scheduled as soon as parts and the purchase order arrive, and we confirm the date when we quote. Urgent jobs can be prioritised. Report timing depends on quantity, part size, standard and the report format required.

Send the drawing or sketch, material and heat-treatment condition, dimensions, length and weight of the largest part, quantity, the standard, specification and acceptance criteria or your MT procedure, surface finish and any coating, whether testing is in the lab or on site, any third-party or aerospace approval requirement, and your deadline.

The report identifies the part, material and condition, the standard, procedure and acceptance criteria, and the technique, current, particle type, bath details and lighting, including UV-A intensity for fluorescent testing. It lists each recordable indication by location, type and size, gives the accept or reject evaluation and the residual field after demagnetisation if required, and carries the inspector’s level and Level III approval.

Yes. Structural bolts, studs and aerospace fasteners are batch-tested on the bench using the wet method, with a head shot and coil to cover both crack directions. Parts are demagnetised afterwards and the residual field is checked with a gauss meter if the specification requires it. Send the drawing, quantity and specification and we will confirm the technique.

Yes. Our aerospace division is NADCAP-accredited for MPI and FPI, and procedures are approved by an in-house NAS 410 Level III. Aerospace inspection uses wet fluorescent particles on stationary equipment in a darkened area with verified UV-A lamps, followed by demagnetisation and residual-field verification. ASTM E1444 is the practice written for aerospace applications, and we test to your OEM or customer specification

Yes. Our laboratory measures magnetic field strength with digital gauss and Tesla meters that use Hall-effect probes, reading up to 10,000 gauss, and reports results in gauss or Tesla. The service is used to check the strength of separator magnets, for example in rice and pulse mills, and to verify residual magnetism on demagnetised components.

Testing is performed by MT Level II inspectors qualified to ASNT SNT-TC-1A and ISO 9712, and to NAS 410 for aerospace work. In-house ASNT NDT Level III and NAS 410 Level III specialists approve the technique and procedure, check calibration status and acceptance criteria, and approve the report before release. Inspectors also train at Trinity Institute of NDT Technology.