- Model
- KY-CJE220 series, Y series and the CDX-III bench unit
- Magnetising pole spacing
- 0 to 220 mm on the portable range; 0 to 160 mm, 0 to 255 mm, 100 mm and Φ120 mm across the four bench probes
- Detectable depth
- 3 mm below the surface on AC supply alone; 5 mm on the variants carrying a DC or inverter power pack
- Lifting force
- AC 45 N or better on the direct-supply yokes; AC 69 N and DC 215 N on the inverter model; the material also states AC 69 N and DC 215 N for the Y series
- Sensitivity
- A1 standard test piece, 15/50 groove, clearly indicated
- Supply
- Single-phase AC 220 V 50 Hz, or an interchangeable DC or inverter battery pack
- Duty cycle
- 50 %
- Working current
- AC 2.2 A; DC 1.5 A on the pack-supplied variants and the bench unit at about 8 to 12 A
- Working environment
- -10 to +40 °C, temperature rise under 18 °C, relative humidity below 80 % without condensation
- Forms
- A hand-held yoke for direct supply, the same yoke with a white or ultraviolet lamp, and pack-supplied variants including an inverter type
A magnetic particle inspection yoke is bought because a surface crack has to be found on a part that is too large, too heavy or too firmly installed to be brought to an inspection station. The yoke is carried to the joint, the joint is magnetised between its poles, particles are applied, and any crack that interrupts the field shows up as an indication on the surface.
It is one of the fastest ways to cover a weld or a casting face, and one of the easiest to carry out badly, since what makes an indication appear is a field that has been established in the right direction and at the right strength.
What the equipment is
A magnetising yoke and the means of driving it. The yoke is the hand-held part: a laminated core with two poles that are placed on the work, carrying a coil that is switched on for the few seconds the particles need. The body of the arrangement is the supply - the mains, a battery pack, or an inverter pack that produces alternating current away from an outlet.
The range in this material has three layers. The direct-supply yokes run from a 220 V single-phase outlet and are the simplest and lightest arrangement. The pack-supplied variants add a battery box and reach deeper into the material. The bench unit brings the same principle to a fixed station for small parts, with four interchangeable probes covering different pole spacings and lifting forces.
Magnetisation is directional. A crack is detected best when the flux crosses it at a large angle, so a crack running along the axis of a part needs the field applied around it and a crack running around the part needs the field applied along it. In manual work both directions are applied in turn, because assuming the orientation of a defect that has not been found yet is how one gets missed.
The current form sets the depth. Alternating current concentrates the field near the surface through skin effect and is the right choice for cracks that break the surface; direct current and rectified current from an inverter penetrate further, which is why the pack-supplied variants in this range are stated at 5 mm where the direct-supply yokes are stated at 3 mm. The yoke itself does not change between those two figures - what changes is what is driving it.
The indication, the particles and the light
The indication is produced by particles, not by the instrument. Dry powder is convenient and tolerant of rough surfaces and elevated temperature; a wet suspension in a carrier fluid is more sensitive and is what code work usually specifies. For white-light inspection the particles are coloured and read against a prepared contrast background. For fluorescent inspection they are coated so that they fluoresce under ultraviolet light, and the indication is read in a darkened area - which finds weaker indications at the cost of a darkened bay and a lamp whose output has to be maintained and checked.
What the equipment has to demonstrate is that the field was adequate. In this range that is done against an A1 standard test piece with a 15/50 groove, described as clearly indicated. A field indicator - which shows both the strength and the direction of the field - is not listed in the material, and where a standard requires one it is asked for separately.
The direct-supply yokes are the right answer where a mains outlet is within reach of the work and the defects being looked for break the surface. The pack-supplied variants exist for two reasons that are often the same reason: the work is away from an outlet, or the defect may lie just under the surface and needs the deeper field.
Within the pack-supplied forms the choice is largely about the lamp, since white-light and ultraviolet variants are otherwise the same instrument. The inverter model is the exception, carrying a higher stated lifting force than the others, which matters on thicker sections where a stronger field is needed to reach the same field density. The bench unit is a different decision altogether: it is bought when the parts are small enough to be handled and the volume justifies a fixed station.
Measurement limitations and selection considerations
The material gives two different alternating-current lifting forces - 45 N on the direct-supply yokes and 69 N on the inverter and Y-series models - without reconciling them, and it gives the yoke weight as 2.5 kg in one place and 2.4 kg in another. Both are carried as open items rather than resolved here, because both affect whether a claimed field strength can be met on a given section.
A third gap is the method rather than the specification: the material names no acceptance standard at all. Field strength requirements, the particle medium, the light level and the reporting format are normally set by the standard the inspection is carried out to, and without it the equipment selection is being made against nothing in particular. That standard is the first thing an enquiry should name.
The limits of the method belong here too. It works only on ferromagnetic material, so austenitic stainless steel, aluminium, copper and their alloys produce no indications however well the equipment is set up. It reaches a few millimetres, so an internal defect deeper than that is found by another method. And it leaves the part magnetised, which has to be dealt with before the part is machined, welded or put near instrumentation - a step that is easy to omit and expensive to discover later.
Ordering
The items that fix the answer are the material and grade, and confirmation that it is ferromagnetic; the part or weld to be inspected; whether the work is in a workshop or on site, and whether a mains supply is available there; whether the defects being looked for break the surface or lie beneath it; whether white-light or fluorescent inspection is called for and whether the area can be darkened; whether the parts must be left demagnetised; and the acceptance standard together with the level of acceptance to be worked to. The standard is not optional in practice - it decides the field strength that has to be demonstrated, and the material behind this page names none. Quantity, destination port and required delivery date complete the enquiry.
Every value below is taken from source documentation. Where a parameter is not stated in the available material it is marked as information required rather than estimated.
