Technique of magnetic particle inspection of rail transport parts.

E. Dubovoi, Engineer of "Promprylad" LLC

 The magnetic particle inspection is widely used in aviation, chemical engineering, at testing large-sized constructions, main pipelines, shipbuilding, automotive and other branches of industry. But mostly it is applied in rail transportation. Magnetic particle inspection has high efficiency and sensitivity and is capable of displaying the testing results. If the parts testing is appropriately performed, this technique can help to detect fatigue cracks and other defects at early stage of their development. This way, using magnetic ink with black powder, the surface microcracks with width from 0,001 mm and more, depth from 0,01-0,03 mm and more are detected.

 The principle of this technique is the following: magnetic flaw doesn't change its direction on the flaw-free item area. On the areas of decreased permeability, for instance, metal discontinuity (cracks, nonmetallics etc.), a part of magnetic field lines come out of the component and then return inside, creating this way magnetic poles (N and S). As a result, there appears the magnetic field over the flaw. As the magnetic field is nonuniform over the flaw, the magnetic particles, that have entered this field, come under the power that draws them to the place of the greatest concentration of magnetic field lines that is to the flaw. The particles in the flaw filed area are magnetized and attracted to each other as magnetic dipoles, so that creating chain structures oriented along the magnetic field lines.

 There are two testing techniques subject to the material magnetic properties, size and shape of the testing part and nonmagnetic cover on it:

  • Testing by means of remanent magnetization
  • Testing in the applied field

 Magnetic particle technique is widely used in the testing of rolling stock parts, locomotive parts and multiple-unit rolling stock of Ukrainian railways. Magnetic particle technique is the only possible technique for many parts. At the same time, the installation and equipment base of magnetic particle inspection in depots and car repair plants is out-of-date and obsolescent.

 Meeting the market requirements, "Promprylad" LLC began to pay special attention to the development and production of magnetic particle testing equipment.

 Having considerable scientific potential, talented design engineers and substantial manufacturing capability, "Promprylad" LLC supplies its customers with the equipment of unique technical specifications at high quality and moderate prices.

 "UMPK-1 rail wheels system", manufactured and delivered to order of "Interpipe" Nizhnedneprovsk tube-rolling plant", is one of such company developments. "Interpipe" Nizhnedneprovsk tube-rolling plant" OJSC (NTRP, Dnepropetrovsk, Ukraine) is one of three manufacturers operating in CIS. It produces over 240 dimension-types of wheels and tyres for rail transport that are delivered to railways in more than 60 countries of the world.

 The system meets the requirements of such regulatory documents as GOST 21105, PrEN 13262, ISO 6933, ААR M107, DIN EN ISO-9934-1,2,3. The conditional sensitivity level of magnetic particle testing system is "B" according to GOST 21105. The system carries out semi-automatic magnetic-luminescent testing of 55 dimension-type rail wheels with diameter from 650 mm to 1300 mm, testing speed of up to 40 wheels per hour.


 Structurally, UMPK-1 system consists of the following main parts connected by one control system:

  • mechanical part;
  • hardware and computing complex, which comprises:
    1. operator's console;
    2. hardware and computing unit;
  • system of preparation and oiling with magnetic-luminescent suspension;
  • system of wheel magnetization and demagnetization;
  • UV illumination system.


 Main technical specifications:

  • magnetic particle inspection techniques are performed in accordance with:
    1. GOST 21105 "Nondestructive testing. Magnetic particle technique";
    2. ISO 6933;
    3. PrEN 13262;
    4. DIN EN ISO – 9934 – 1,2,3;
    5. AAR M 107.
  • conditional sensitivity of magnetic particle testing is "B" according to GOST 21105;
  • assures the detection of surface flaws with min. conditional length of 2 mm, opening width of no less than 25 μm;
  • testing of 55 dimension-type wheels with diameter from 650 to 1300 mm;
  • time of system reset for another dimension-type is up to 30 min.
  • wheel inspection time is up to 1,5 min.
  • testing efficiency is 40 wheels per hour.
  • registration of testing results;
  • possibility of video surveillance system integration for remote control of testing process.

 MD-83 PK ІІ U magnetic particle flaw detector is also one of major developments (see fig.5).Magnetic particle flaw detector is used as universal for magnetic particle testing of steel ferromagnetic cylindrical items with holes (e.g. springs, axlebox unit parts, pipe segments etc.) as well as for large-sized parts testing by current transmission. Magnetization is performed with pulse current.


Fig.5. MD-83 PK ІІ U magnetic particle flaw detector

 Main technical specifications of flaw detector:

  • Max. value of pulse current is:
    1. in copper bar, at least 10000 А;
    2. in testing part, at least 1500 А;
  • Magnetic field induction is:
    1. when transmitting current via copper bar, at least 1,3 T;
    2. when transmitting current via spring, at least 1,3 T;
  • Electrical supply of flaw detector ……….. 220 V, 50 Hz;
  • Time of continuous operation of flaw detector, at least 8 hours.
  • Flaw detector dimensions, up to ……….. 100 mm x 120 mm x 75 mm.
  • Flaw detector weight, up to ……… 200 kg.

 Flaw detector successfully functions at "Donetskgormash" OJSC (Donetsk, Ukraine) affiliating "Mining machines" SIC OJSC, association of large machine-building manufactures of coal and mining equipment.

 "Promprylad" LLC also produces the whole range of universal portable manual magnetic particle flaw detectors, such as MD-01PK electromagnet (magnetic П-shaped contour), MD-4К, МD-4KМ, UniMAG-01. These flaw detectors can be applied for the testing of bolsters and side frames of trolleys, welded joints etc.

 МD-01 PK III U manual magnetizer (magnetic П-shaped contour) is intended for the detection of surface and subsurface flaws, such as metal discontinuities, with the help of magnetic particle technique on the local areas of large-sized items by creating applied alternate or magnetostatic field. Magnetizing unit is an electromagnet with adjusted poles that allow to create alternate and magnetostatic field on the surfaces of any ferromagnetic materials and to demagnetize testing parts.


Fig.6. МD-01PK magnetic particle flaw detector (magnetic П-shaped contour)

 Magnetic conductors are made from soft magnetic material; the surface of magnetic conductors is protected from corrosion by electroplate. Flaw detector can be used for the testing of industrial products quality during their production and operation in different branches of industry. Flaw detector is manufactured in two variants: 1) mains supply 220V; 2) storage battery supply 12V.


 Main technical specifications:

  • Flaw detector type……………………………………portable;
  • Size of testing section while inspecting the item surface..0 – 320 mm;
  • Max. operating current …………5(3*) А;
  • Operating voltage…………230(12*) V;
  • Frequency…………50 – 60 Hz;
  • Overall dimensions…………185х175х65 mm;
  • Operating temperature range………… from minus 40 °С to +50 °С;
  • Flaw detector weight in a set, up to …………5 kg.

 * Magnetic flaw detector operating from the storage battery of 12 V.

 МD-4K flaw detector (on permanent magnets) is intended for the testing of local areas of large-sized ferromagnetic parts with the help of magnetic particle technique. Permanent magnets are used as magnetizing elements. That is why flaw detector doesn't need power supply what enables to use it in field conditions in explosive and flammable mediums and building areas.


Fig.9. МD-4K flaw detector

Main technical specifications:

  • Flaw detector type……………………………………portable;
  • Magnetizing units are completed with round permanent magnets (МD4-4K)
  • Average size of testing section while inspecting the item surface ….120 mm
  • Max. field density at magnetizing units poles, at least………1100 А/cm
  • Pullout force of magnetizing units from ferromagnetic surface ………35-40 kg-force.
  • Flaw detector weight ……….. 70 kg

 For operation ease there have been produced an improved МD-4KМ flaw detector equipped with the set of terminal caps and cable bridge that make it possible to carry out the quality testing of parts of different shapes and to simplify an operator's work.



Fig.10. МD-4KM flaw detector

 One of the last company developments, an ultra light magnetizer on UniMAG-1 permanent magnets, is intended for the magnetization of welded joints areas and surfaces of ferromagnetic material items. It is performed by applying magnetic field when detecting surface and subsurface defects in the process of NDT execution with magnetic particle technique. Magnetizer can be used in workshop, laboratory and field conditions, altitude objects, in places where power supply is hindered or prohibited according to the safety measures, at the ambient temperature from minus 30° to +50°C and relative humidity of up to 95% at the temperature of 35°C.


Fig.11. UniMAG-01 flaw detector

 Main technical specifications:

  • Flaw detector type……………………………………portable;
  • Magnetizing units are completed with permanent magnets from Fe-Nd-B alloy
  • Average size of testing section while inspecting the item surface ……200 mm
  • At nominal space of 200 mm between poles there is the magnetic field strength, at least … 20 А/cm
  • Max. field density of magnetizing units poles, at least……… 2400 А/cm
  • Overall dimensions of flaw detector:
    • cylindrical plastic cases with diameter of 35 mm and length of 120 mm,
    • flexible magnetic conductor of 400 mm in length,
  • Weight ……….0,8 kg.

 Our company suggests the customers a wide range of accessories for magnetic particle testing:

  • dry magnetic powder and powder for magnetic ink preparation: PzhV5-71, and also of other leading foreign manufacturers, such as Ely Chemical and others.
  • Suspensions in sprays;
  • Tools for quality spraying of magnetic suspension;
  • Milliteslameters;
  • etc.

 "Promprylad" LLC designs and produces both universal and special-purpose magnetic particle complexes. If you face the task of nondestructive testing of items surface, our specialists will develop and offer you a product that you need in this specific case.