MT Magnetising equipment
Magnetic Particle Testing
MT, Magnetic particle testing, Fluxing, MP testing
Magnetic particle testing is a simple, sensitive test procedure. It is used to detect inhomogeneities on the surface of ferromagnetic materials (surface crack detection).
The surface to be tested is first cleaned before magnetisation. During magnetisation (e.g. with one of the magnetisation devices shown below), a magnetic particle suspension is sprayed onto the surface to be tested. These suspensions contain ferromagnetic particles. The magnetic flux leakage generated over the material separations (e.g. cracks) during magnetisation result in accumulations of these particles. In this way, material separations can be made visible. The black ferromagnetic particles stand out well over a white background colour. Particles coated with a fluorescent layer are easily visible in a darkened environment by UV irradiation. Sufficient magnetisation is checked with a field strength meter.
Magnetising devices
Hand yoke magnets
For the magnetisation of construction components, there are available, for example, handy yoke magnets or cross yokes which are placed on the component surface to be tested (e.g. for magnetic particle testing of weld seams). Since the field lines run from one pole to the other, only indications whose areal extent is transverse to the field lines can be displayed. For a complete test in all directions, the yoke must be set up twice with an offset by 90°.
Hand yoke magnets differ by
- Mains or battery operation
- the medium pole distance
- the leg length
- the lifting force
- the weight
Hand yoke magnet UM 10 / HANSA-230
The HANSA series of HELLING hand yoke magnets consists of lightweight, handy and powerful AC and DC devices. The narrow handle and the roughened surface support long and fatigue-free work.
The hand yoke magnets meet the requirements of the current regulations:
- DIN EN ISO 9934-3 "Non-destructive testing - Magnetic particle testing - Part 3: Equipment".
- ASTM E709 "Standard Guide for Magnetic Particle Examination".
- ASTM E1444 "Standard Practice for Magnetic Particle Testing".
They also meet the requirement of the regulations that the tangential field strength should be at least 20 A/cm. The lifting force is greater than 265 N (27 kg), thus meeting the requirement of ASTM E1444 (minimum 225 N / 22.5 kg).
All AC and DC hand yoke magnets at a glance
Cross yoke
With a HELLING cross yoke, surface and near-surface defects can be detected in a single operation, regardless of their direction of expansion. Cross yokes are equipped with two AC yokes which are arranged crosswise. These are fed by two alternating currents of equal strength but shifted by 90°. A rotating magnetisation vector is created. Its field strength is the same in all directions. The wheels on the poles are adjustable. This allows the air gap between the poles and the test object surface to be kept constant. This also allows the cross yoke to be moved effortlessly on the component surface.
With an air gap of 5 mm, the tangential field strength is still 24 A/cm.
For the weld seam testing of fillet welds, there are corresponding special designs for optimum adaptation of the poles to the component surface.
The mobile cross yoke consists of two AC yokes. These create a rotating magnetisation vector whose field strength is the same in all directions.
Mobile magnetisation devices – cross yokes
HELLING Center for Technology - Magnetising facilities
The "Blue Hall" - HELLING Center for Technology
Magnetisation bench HELLMAG
At the HELLING Center for Technology, magnetisation systems especially adapted to specific testing problems are developed. These include various designs of magnetisation benches, e.g., for series testing or training purposes.
Crack test bench HELLMAG Universal 500 AC / 700 AC / 1000 AC with mechanical clamping of the test object via two quick clamping facilities and with two individually switchable magnetisation circuits (alternating current flooding / alternating current yoke magnetisation).
This also includes testing facilities adapted to the components to be tested, such as:
Chain testing facility
Mobile chain testing facility for testing sling chains in accordance with the German Regulation on Industrial Safety and Health, Section 2BGR 500.2.8, (formerly UVV 18.4.) and DIN 685-5 "Tested round steel chains, individual parts and accessories - Part 5: Use of chain slings and hoist chains". The test facility is equipped with:
- Collection container for the fluorescent test agent
- Flushing device with high performance pump
- Closed magnetising coil
- High current generator
Mounted on a test trolley, the test facility can be easily moved to the test location.
Chain testing facility: Testing of sling chains according to German Regulation and standard DIN 685-5 with the fluorescent magnetic particle testing
Wheelset testing facility ROD-A-MAT
Simultaneous testing of wheelset axle and wheelset wheel by means of two magnetising systems that can be operated in parallel. The ROD-A-MAT allows a combined magnetic particle testing of wheelset axle and wheelset wheel with fluorescent magnetic particle suspension.
Wheelset testing facility ROD-A-MAT for combined fluorescent magnetic particle testing (half/segment coil and trapezoidal coil) of wheelset axle and wheelset wheels.
The magnetisation is contactless. A half/segment coil is used for testing the wheelset axle and a trapezoidal coil with several turns for testing the wheel tread.
Segment/half coil for contactless magnetisation of wheelset shafts, test medium: fluorescent magnetic particle suspension.
Trapezoidal coil with 5 turns for contactless magnetisation of wheelset wheels, test medium: fluorescent magnetic particle suspension.
The wheelset inspection system is equipped with a semi-automatic test system with integrated rinsing, UV-A backlighting and the HELLING HCC documentation system.
Documentation system HELLING Connect Control (HCC)
HCC documentation system
The HCC system generates a test protocol. This contains:
- Test parameters
- Test data
- Original images of the tested surface
- Copies of the processed indication images
In addition, the Indications are measured and evaluated:
- Position (x/y, inclination)
- Size (mm/pixel)
- Evaluation (IO/NIO)
- Defect type (longitudinal/transverse)
HCC protocol
The system is easy to use and can be adapted to the customer's requirements.
It ensures traceability of the indication acquisition and supports the operator of the plant in optimising the test process control and the analysis of the manufacturing process.
Stationary and mobile magnetisation facilities for magnetisation of specific components such as shafts, wheel sets, sling chains, …
