alloy that contains a high percentage of iron and can be
1. Monitoring compliance with NDI personnel
magnetized, it is in a class of metals called
qualifications, certification/recertification require-
"ferromagnetic," and it can be inspected by this
ments, safety precautions, and instructions.
method. If the part is made of material that is
2. Monitoring the organization's NDI training
nonmagnetic, it cannot be inspected by this method.
program to ensure it is current and comprehensive.
The magnetic particle inspection method will detect
Special emphasis should be placed on those areas of
surface discontinuities, including those that are too fine
NDI that are accomplished by personnel other than
to be seen with the naked eye, those that lie slightly
those assigned Navy enlisted classification (NEC)
below the surface, and, when special equipment is used,
7225/military occupational specialty (MOS) 6044.
the more deeply seated discontinuities.
Organizational Maintenance Activities
The inspection process consists of inducing a
magnetic field into a part and applying magnetic
O-levels responsibilities are as follows:
particles, in liquid suspension or dry powder, to the
surface being inspected. When the magnetic field is
1. Request NDI I-level support as required.
interrupted by a discontinuity, some of the field is
2. Obtain IMA NDI services in all situations
forced out into the air above the discontinuity, forming
where NDI results are suspicious.
a leakage field. The leakage field will be stronger and
more concentrated the closer the discontinuity is to the
3. Have an NDI technician verify defects dis-
surface. The presence of a discontinuity is detected by
covered by an NDI operator, whenever possible.
the ferromagnetic particles applied over the surface.
4. Inform the IMA, in advance, of scheduled NDI
Some of these particles will be gathered and held by the
requirements. Include these requirements in the
leakage field. This magnetically held collection of
monthly maintenance plan.
particles forms an outline of the discontinuity and
indicates its location, size, and shape.
5. O-level NDI technicians may be assigned to
the supporting IMA, as necessary, to maintain their
Electric current is used to create or induce magnetic
proficiency and to augment IMAs NDI capabilities.
fields in magnetic materials. The magnetic lines of
force are always aligned at right angles (90) to the
NDI INSPECTION METHODS
direction of the current flow. The direction of the
magnetic field can be altered, and it is controlled by the
The various NDI methods serve as tools of
direction of the magnetizing current. The arrangement
prevention that allow defects to be detected before they
of the current paths is used to induce the magnetic lines
develop into serious or hazardous failures. With the
of force so that they intercept and are as near as possible
NDI methods, a trained and experienced technician can
at right angles to the discontinuity.
detect flaws or defects with a high degree of accuracy
and reliability. It is important that you become fully
The magnetic field must be in a favorable direction
knowledgeable of the capabilities of each method. It is
to produce indications. When the flux lines are oriented
equally important that you recognize the limitations of
in a direction parallel to a discontinuity, the indication
the methods. Some of the defects found by NDI include
will be weak or lacking. The best results are obtained
corrosion, leaks, pitting, heat/stress cracks, and
when the flux lines are in a direction at right angles to
discontinuity of metals. The following paragraphs will
the discontinuity. If a discontinuity is to produce a
give a brief synopsis of the various NDI inspections.
leakage field and a readable magnetic particle indica-
For further information on NDI procedures, you should
tion, the discontinuity must intercept the flux lines of
consult the Nondestructive Inspections Manual,
force at some angle. When an electrical magnetizing
NA-01-1A-16, or the appropriate inspection manual
current is used, the best indications are produced when
pertaining to the type of aircraft or part that is to be
the path of the magnetizing current is flowing parallel
inspected by an NDI method.
to the discontinuity, because the magnetic flux lines are
always at an angle of 90 to the flow of the magnetizing
Magnetic Particle Inspection
current. The two types of magnetizing methods used
are circular and longitudinal.
Magnetic particle inspection is a rapid, non-
CIRCULAR MAGNETIZATION.--Circular
destructive means of detecting discontinuities in parts
magnetization is used for the detection of radial
made of magnetic materials. If the part is made from an
discontinuities around edges of holes or openings in
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