The Asme Field Indicator

This consists of eight sections of mild steel brazed together, the separating lines between the sections forming artificial discontinuities. One side also has a chromium coating applied, this has a greater sensitivity than the opposite side which shows surface breaking discontinuities.

When the indicator is placed on a magnetised component the magnetic field passes through the indicator. The separating lines between the sections become visible when the detecting media is applied. To determine the direction of the magnetic field the indicator should be rotated until one of the lines is perfectly visible, at this point the direction of the field is at 90° to the line.