Mobile magnetizing devices
HELLMAG-series mobile magnetizing devices are heavy current generators designed for current flow and field flow magnetisation, coil magnetization, pulse magnetization as well as for demagnetization.
During current flow magnetization the contact electrodes are being attached to the edges of the test piece, thus the part itself becomes a current-carrying conductor. The circular magnetic field generated around the part allows the detection of longitudinal cracks between the contact poles. This technique makes it also possible to find the defects which are located at an angle of up to 60 degrees off the axial line. In order to avoid overheating, burns or electric arcs in the contact area it is important to ensure proper current transition by using copper braid pads or melt-off electrodes.
When using HELLMAG equipment for field flow magnetization, power cables are being used as inner or outer conductors or as a cable coil respectively. Inner conductor: this way of magnetizing is used for testing ring shaped work pieces. Thereto the power cable should be put through the center hole (bore) of the work piece. Thereby cracks that are located mainly parallel to the conductor are being detected. Outer conductor: this way of magnetizing is often used for testing weld seams. Here one or more power cables should be positioned parallel to the weld. Thereby longitudinal cracks are being detected. In order to avoid field compensations, the current reverse flow cable is to be located as far away as possible from the magnetizing cable. Cable coils: while coil magnetizing, a current-carrying conductor should be wound like a coil with an appropriate number of windings. After energizing the coil, circular magnetic fields will be generated around each coil winding. In the center of the coil these magnetic fields add on to a general longitudinal magnetic field, therefore cracks located across the magnetic field i.e. transversal cracks are being indicated.
HELLMAG devices can be combined with a variety of testing equipment such as the chain testing device, closed or hinged coils, trapezoidal coils for testing of railway wheels.
The testing current can be infinitely adjusted through a foot switch operated potentiometer (when the magnetizing circuit is closed). A selector switch changes between the different modes: Magnetizing – Demagnetizing – Pulse. The devices are equipped with 230 V plug sockets for connecting additional equipment such as an UV lamp or a suspension pump.