A magnetic Yoke is a portable device for detecting surface and sub-surface cracking in any ferro-magnetic material. Magnaflux Yokes handle the most demanding inspection jobs with ease; their portability makes them ideal for in-plant inspection and repair of welds, automotive components, steel and gray iron castings, and many other applications.

Magnaflux manufactures several types of Yokes:

• Y-2 – an ergonomic lightweight AC electromagnetic Yoke
• Y7 – an AC/DC lightweight Yoke
• Y8 – a battery powered DC Yoke

There are two methods to test the performance of a yoke: one is a lift test using standard test weights, the other is to measure the field strength (according to DIN EN ISO 9934) between the two yoke legs.

Several current forms can be used in magnetic particle inspection. Alternating current (AC) is used to detect surface defects, whereas rectified current and direct current (DC) are used when defects are likely to be sub-surface.

The ability to detect sub-surface defects and the limit of the defect is a contentious subject. This depends on many factors, not least of which is the test environment itself. For example, defects detected within a laboratory set-up on an ideal specimen will almost certainly not relate to a welder’s findings on-site in the middle of winter. Coupled with this, the size and orientation of a sub-surface defect can potentially have a major effect because the flux leakage on the surface will be present as a broad outline. This may not be easily detectable against the background.

The correct orientation for a Yoke is perpendicular to the direction of the defects.