FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 5. Nondestructive Inspection (NDI) | 4. Magnetic Particle Inspection | 5-51. Demagnetization and Postexamination Cleaning
9/8/98
AC 43.13-1B
small parts such as rod end fittings in a con-
tainer of suspension, which has just been
stirred for about 30 seconds, is an excellent
method.
(5) Check for the presence of particle
accumulation in the sharp radii. It is necessary
that the level of magnetization and the particle
application result in the formation of nonrele-
vant indications. Lack of indications will re-
quire remagnetization to a higher level, more
care in applying the particles, or both.
(6) Wash the parts in a clean suspension
vehicle only enough to remove the weakly-
held particle accumulations causing the non-
relevant indications. Particles at true cracks
will be more strongly held and will persist if
the washing is gently done. This can be ac-
complished by flowing or directing a stream of
liquid vehicle over the part, or for a small
component, by gently stirring in a container of
the vehicle. Closely observe the removal of
the nonrelevant particle accumulations in the
region to be examined to avoid excessive
washing. If washing is prolonged beyond the
minimum needed to remove the nonrelevant
indications, the small defect indications may
also be washed away. A few trials will help to
develop the best method and time required for
washing.
(7) Check for crack indications with
optical magnification and ample lighting. The
smaller indications that are attainable by this
procedure cannot be reliably seen or evaluated
with the unaided eye.
5-51. DEMAGNETIZATION AND POST-
EXAMINATION CLEANING. Parts should
be magnetized longitudinally last before de-
magnetizing.
NOTE: Circular magnetism cannot
be read with a field meter since it is an
internal magnetic field. However, if
the last shot, was a coil shot the meter
can read it if a magnetic field is pres-
ent.
a. Demagnetization. Demagnetize be-
tween successive magnetization of the same
part, to allow finding defects in all directions,
and whenever the residual magnetism inter-
feres with the interpretation of the indications.
Also, demagnetize all parts and materials after
completion of magnetic particle examination.
Test all parts at several locations and parts for
residual magnetism of complex configuration
at all significant changes in geometry. Repeat
demagnetization if there is any appreciable de-
flection of the field indicator needle.
(1) AC method. Hold the part in the
AC demagnetizing coils and then move the
part slowly and steadily through the coils and
approximately 3 to 4 feet past the coils. Re-
peat this process until the part loses its residual
magnetism. Rotate and tumble parts of com-
plex configuration as they are passed through
the coils.
(2) DC method. Place the part in the
same relative position as when magnetized and
apply reversing DC current. Gradually reduce
the current to zero and repeat the process until
the residual magnetic field is depleted.
b. Post-Examination Cleaning.
(1) When oil suspensions are used, sol-
vent clean or remove the part until all magnetic
particles and traces of oil are removed.
Par 5-50
Page 5-27