Magnetic Flux Indicators TYPE II (Gold Plated)
These indicators are suitable for use in aerospace and general engineering applications.
Portable flux indicators are used to give clear indication of the direction of a magnetic field and a
guide as to the field strength when Magnetic Particle Testing is carried out according to various
standards including B.S. 6072.
Instructions for Use.
Portable flux indicators and other devices which respond to the external field H in air above the
surface of magnetized materials give excellent evidence of the direction of the magnetic field in
all instances. Where the indicators are used to give guidance to field strength this is only
applicable when current flow techniques including threading bar (central conductor) and prod
magnetization, induced current technique by use of a.c. Results when coil magnetization or any
other methods of magnetization which create air borne flux whether there is a magnetizable
sample present or not, d.c. electromagnets and permanent magnets are used are misleading with
respect to the field at the surface of the material for magnetic particle inspection.
1. One indicator is attached to a vertical area of the surface under test so that its major axis is
in the same direction as that of suspected defects in a vertical mode.
2. A second indicator is attached to the surface under test at right angles to the first indicator.
3. The component or material is magnetized in the normal way and Magnetic Particle
Inspection ink (either CTB3 colour contrast or CTF9 fluorescent) is applied.
4. A minimum of 5 seconds magnetization must be allowed for particle migration before the
flux indicator is examined with the magnetization on.
Testing is carried out according to various standards including B.S. 6072.
Interpretation
The direction of the magnetic field is seen readily from the indications.
If one indicator shows indications and the other none, the magnetic field is in the direction at right
angles to the indicator showing a response. If neither indicator responds there is insufficient
external magnetic field to cause a response and, in techniques where an external magnetic field is
created, the field is too low for magnetic particle testing to be carried out. If both indicators show
response they are both at an angle of around 45° to that of the induced field.
Interpretation of the strength of the field depends on the way in which the indicators are mounted.
When they are mounted on a vertical surface and one indication is seen the induced field in air
above the surface is above 2400 Amps per metre and when all three are shown the field strength
is above 6500 Amps per metre. Inspection must be carried out while the sample is magnetized.
When these indicators are mounted horizontally no assessment of the field strength can be made.