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com

ML-M-11472
24 November 1952
HIL-I-6868E
8 March 1976

MILITARY STANDARD
INSPECTION, MAGNETIC PARTICLE

NO DELIVERABLE DATA REQUIRED BY THIS DOCUMENT

/AREA NDTI\
DISTf?IBUTIO!i
STATE.YENT
A Approved for publlc release; dlstrlbutlon unlimlted.

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HIL-STD-1949

DEPARTMENT OF DEFENSE
Washington, D.C. 20325

Inspection, Hagnetic Particle

1. This Military Standard is approved for use by all Departments and
Agencies of the Department of Defense.
2. Beneficial comments (recommendations,additions, deletions) and any
pertinent data which may be of use in improving this document should be
addressed to: Director, US Army Materials and Mechanics Research Center,
ATTN: AKXMR-SMS, Watertown, MA 02172-0001 by using the self-addressed
Standardization Document Improvement Proposal (DD Form 1426) appearing at the
end of this document or by letter.

ii

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KIL-STD-1949

FOREUARD

This standard 1s a procedural document describing wet and dry techniques

for magnetic particle inspection.

-----

iii

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Paragraph 1.

SCOPE...............***** *.**..*.* .***..***.***.* 1

1.1

Scope..................*........*........*.......

2*

REFERENCE DOCUMENTS....*..... .....*..*............ 2

2.1
2.1.1
2.2
2.2.1
2.2.2

Government documents.............................
Specifications, standards and handbooks..........
Other publications...............................
American Society for Testing and Materials.......
Society of Automotive Engineers: Aerospace
Mater~als Specifications.......................

2
2
2
2
3

DEFINITIONS........................................ 4
3.1
3.2
7.3
7.4
3.5
3.6
:*?
3.8
3.9
3.10
3.11
3.12
3.13
3.14
3.15
3.16
3.17
3.18
3.19
3.2G
3.21
3.22
3.23
3.24
3.25
7.26
4.
4.1
4.1.1
4.1.2
4.1.3

Alternating current (AC).........................

Black light.....,...................... .........
Classification...................................
Coil shot........................................
Conditioned water................. ..............
Continuous method...............................,
no--.$.
ucJeLb. ......,......... ........................
Flux leakage.....................................
Full wave direct current (FWDC)..................
Gauss............................................
Half wave direct current (HWDC)..................
Head shot........................................
Indication.......................................
Indication, false.............,..................
Indication, nonrelevant..........................
Magnetic flux....................................
Magnetlzatlun....................................
Permeability.....................................
Procuring activity...............................
p?ods............................................
Residual method..................................
Suspension..............,........................
Swinging field...................................
Water break test....................,............
Wet method.......................................
Other deflnltlons................................

4
4
4
4
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
~
5
5
5
5
5

GENERAL REQUIREMENTS.,............................. 6
Principles cf magnetic particle inspection.......
Intended use of magnetic particle inspection.....
Basic principle..................................
Magnetization and particle application...........

lV

6
~
6
6

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MIL-STD-1949

coNT~Ts (coNTINUED)

.-

Paragraph 4.1.4
4.2
4.3
4.4
4.5
4.5.1
4.6
4.7
4.8
4.9
4.9.1
4.9.2
4.10
4.10.1
4.10.1.1
4.10.1.2
4.10.2
4.10.3
4.10.4
5.
5.1
5.1.1
5.1.2
5.1.3
5.1.4
5.2
5.2.1
5.2.2
5.2.3
5.2.4
5.2.5
5.2.6
5.2.7
5.3
5.3.1
5.3.1.1
5.3.1.2
5.3.1.3
5.3.1.3.1
5.3.1.3.2
5.3.1.4
5.3.1.4.1
.

Classification, interpretation and evaluation.... 6

Responsibility for inspection........ ........0..
6
Qualification of inspection personnel........,.*
7
Acceptance requirements.**... .... ..............
7
Written procedure........ O... . ............*...
7
Elements of the written procedure ........ .... .
7
Record of inspection....... 0 ... ..... *.....,. 8
Magnetizing and demagnetizing equipment.......... 8
Inspection sequence ............................. 8
Lighting intensities. .. . .....*........,.,...
8
Visible light intensities....... ..0......... .. 8
Black light intensities.........*......... *..,..
8
Materials.....*................ ......*..*.. ...
8
Magnetic particle materials ............... ....,
Dry particle requirements..........0..... ...., ,
;
Wet particle requirements...............,.,..., O
9
Suspension vehicles.... .. ...............*...,..
9
Particle concentration......................... O 10
Conditioned water vehicle........................ 10

DETAIL REQUIREMENTS.... ........................... 11

Preparation of parts for test ***********..*...*. 11

Pre-inspection demagnetization................... 11
Surface cleanliness and finish................... 11
Coatings...................................O....* 11
Plugging and masking............................. 11
Magnetization methods............................ 11
Permanent magnets........................ ..*,., 11
Types of magnetizing current.***~................ 11
Magnetic field directions **.**.................. 11
Multidirectionalmagnetization .................. 12
Direct magnetization...........................
12
Indirect magnetization.........................,. 12
Induced current magnetization.................... 12
Magnetic field strength........................., 12
Magnetization current levels...............O ,,.* 12
Prod current levels........... ..........,.....,.
13
Direct circular magnetization.................... 13
Central conductor circular magnetlzatiun......... 13
Centrally located conductor ................,..
13
Offset central conductor
****.............. 13
Longitudinal magnetization
*******..*.*.*..... 13
Longltudi.nalmagnetization with lGw
fill factor coils.............................. 14

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141L-sTD-1949

CONTENTS (CONTINUED)

Paragraph 5.3.1.4.2
5*3.1*4.3

Longitudinal magnetization with cable wrap

or high fill factor coila...................... 14
Calculating the L/D ratio for a hollow or
15
cylindrical part.....
Particle application............................. 15
Continuous method ..... ..................*.
.. 15
Residual magnetization method.................... 15
Prolonged magnetization......................... 15
Dry magnetic particle application................ 15
wet magnetic particle application................ 16
Magnetic slurry/paint application................ 16
Magnetic polymer application..................... 16
Interpretation of indications.................... 16
Types of indications............................. 16
False mdlcationa ................................ 16
Nonrelevant indications.......................... 17
Relevant indications............................. 16
Recording of indications......................... 17
Written description.............................. 17
Transparent tape................................. 17
Strippable film.................................. 17
Photography...................................... 17
Post-inspection demagnetizationand cieaning..... i7
Demagnetization.................................. 17
Post-inspection cleaning......................... 18
Quality control.................................. 18
Inspection system verification................... 18
Use of test part with discontinuitles............ 18
Fabricated test parts with artificial
discontinuities................................ 18
Suspension vehicle tests......................... 18
Concentration tests.............................. 18
Determination of wet particle concentration...... 15
Determination of wet particle contamination...... 19
tiaterbreak test................................. 19
Equipment calibration............................ 19
Ammeter accuracy................................. 19
Timer control check.............................. 19
Magnetic field quick break check................. 19
Dead weight check................................ 20
Marking of inspected parts....................... 20
ImpressIon stamping or vlbro engraving .......... 20
Etching......*................................... 20
20
Dyeing..................
,.
Other ident~flcation............................. 20
Identifying symbols and cclor rnarkmgs
........... 20
100-percent impectlon ....... ................... Lo
Dyeing.* .,.. ,..,...*.....,..... ......,........ 20

5.4
5.4.1
5.4.2
5.4.3
5.4.4
5.4.5
5.4.6
5.4.7
5.5
5.5.1
5.5.1.1
5.5.1.2
5.5.1.3
5.6
5.6.1
5.6.2
5.6.3
5.6.4
~,7
5.7.1
5.7.2
5.8
5.8.1
5.8.2
5.8.3
5.8.4
5.8.4.1
5.8.4.1.1
5.E.4.1.2
5.8.4.2
5.8.5
5.8.5.1
5.8.5.2
5.8.5.3
5.8.5.4
5.9
5.9.1
5.9.2
5.9.3
5.9.4
5.9.5
5,9,5.~
5.9.5.1.1

.*..

vi

.*.

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MIL-STD-1949

CONTENm (CONTINUED)

Paragraph 5.9.5.1.2
5.9.5.2
5.9.5.2.1
5.9.5.2.2

Stamping, vibro engraving or etching............. 20

Lot inspection................................... 21
Dyeing ... ... ... .... ..........* . .. ..... 21
Stamping, vibro engraving or etching............. 21

NOTES

6.

.*.......

.....*. * . ..

....*..

... 22

Eye glasses......................................
Aircraft quality steel cleanliness...............
Acceptance requirements..........................
Safety. ..
Dark adaptation.......... .... ..............0 .

6.1
6.2
6.3
6.4
6.5

22
22
22
22
22

FIGURES
Figure

1....,..... . . ....
....... ..* .. . ..... ....0 . .... 0 . . ......
2 .
. ........ ......,..........
. *... . ......0..
......
3
..
...
.....
.
..
..
..
.*.
.
.
........
...*.... ...... .
4.
....*.*.
............0.....
........
......................*....
5
6 .................................*...........*..*......0......

Table
Table

23
23
24
24
25
25

26
I
II.....0.........0.0......,.**..**. .......... ................ 26

...*...*.

..0......

..*.*..***

..0....0..

..

0...0

Preparing activity............00.0...................0..0. 0... 27

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MIL-STD-1949

1. SCOPE

1.1 Scope. This standard establishes minimum requirements for magnetic

particle inspection used for detection of discontinuitiesat or immediately
below the surface of ferromagnetic material.

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MHJ-STD-1949

2. REFERENCE DOCUMENTS

2.1 Government documents.

2.1.1 Specifications, standards, and handbooks. Unless otherwise
specified, the following specifications, standards, and handbooks of the issue
l~sted in that issue of the Department of Defense Index of Specifications and
Standards (DoDISS) specified in the solicitation form a part of this
specification to the extent specified herein.
SPECIFICATIONS
Military
MIL-M-47230
MIL-I-83387
DOD-F-87935

- Magnetic Particle Inspection Soundness Requirements for

aterials, parts and weldments
- Inspection Process, Magnetic Rubber
- Fluid , Magnetic Particle Inspection, Suspension
(Metric)

STANDARDS
Federal
FED-STD-595

- Colors

Mliitarv
MIL-STD-41O

- Nondestructive Testing Personnel Qualification and

Certification
MIL-STD-2175 - Castings, Classification and InspectIon of

(Copies of specifications, standards, drawings and publications required by

contractors In connection with spec~flc procurement functions should be
obtained from the procuring activity or as directed by the contracting
officer.)
2.2 Other publicatlons. The following document(s) form a part cf this
specification to the extent specified herein. Unless otherwise specified, the
issues of the documents which are DoD adopted shall be those listed in the
issue of the DoDISS specified m the solicitation. The issues of documents
which have not been adopted shall be those in effect on the date of.the cited
DoDISS.
2.2.1 American Society for Testing and Materials.
ASTM A275

Magnetic Particle Examlnatlon of Steel Forgings

ASTM A456

Speclflcation for Magnetic Particle Examination of Large

CrankshaftFcrglngs

ASTM D93

Flash Pcint By Fensky-Martens Closed Tester

ASTM D96

Water and Sediment in Crude Oils

2

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HIL-STD-1949

ASTM D445
ASTM E125

ASTM E269

Kinematic Viscosity of Transparent and Opaque Liquids (and

the Calculation of I@amic Viscosity)
Reference Photographs for Magnetic Particle Indications on
Ferrous Castings.
Standard Definitions of Terns Relating to Magnetic Particle
Examination

(Applications for copies should be addreased to American Soci;;O~o; Testing

.
and Materials, 1916 Race Street, Philadelphia, Pennsylvania
2.2.2 Society of Automotive Engineers: Aerospace Materials Specifications.
Axs 2300

Premium Aircraft-QualitySteel Cleanliness

Magnetic Particle Inspection Procedure

A.Ms2301

Aircraft Quality Steel Cleanliness

Magnetic Particle Inspection Procedure

AMS 2303

Aircraft Quality Steel Cleanliness

Martensitic Corrosion Resistant Steele
Magnetic Particle Inspection Procedure

MS

Magnetic Particle Inspection Material

Dry Method

3040

AMs 3041

Magnetic Particles, Wet Method, 011 Vehicle

AMS 3042

Magnetic Particles
Wet Method, Dry Powder

AMs 3043

Magnetic Particles
Wet Method, Oil Vehicle, Aerosol Canned

MS

Magnetic Particles, Fluorescent

Wet Method, Oil Vehicle

3045

AMS 3046

Magnetic Particles, Fluorescent

Wet Method, Oil Vehicle, Aerosol Packaged

AMS 3161

Inspection Vehicle, High Flash, Odorlees

(Copies of publications may be obtained from the Society of Automotive

Engineers, Inc., 400 Commonwealth Drive, Warrendale, Pennsylvania 15096.)

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MIL-STD-1949

3. DEFINITIONS

3.1 Alternating current (AC). An electrical current that reverses its

direction of flow at regular intervals.

3.2 Black light. Electromagnetic radiation in the near ultraviolet range

of wavelength 320 to 400 nanometer (1 nm = 10-9 meters) with those
wavelengths near 365 nm predominating.
3.3 Classification. The initial review of a visible magnetic particle
accumulation to decide if it is held on the test piece by magnetic means or by
non-magnetic means (i.e. if it is a relevant, non-relevant or false
indication).
3.4 Coil shot. Production of longitudinal magnetization accomplished by
passing current through a coil encircling the part being inspected.
3.5 Conditioned water. Water with an additive or additives which impart
specific properties such as proper wetting, particle dispersion, or corrosion
resistance.
3.6 Continuous method. The continuous method of examination consists of
applying or otherwise making available on the surface of the piece, an ample
amount of magnetic particles to foxm satisfactory indications while the
current is being applied.
Defect. An unintended disCui-Ltiii-uit~Zocation which makes it detrimental to the useful service of the part,
j.?

iiith

--~AuG,

hnnn
CIA.uy-,

fiv.am+a+inn
.-b..-.-.-

Qy

3.8 Flux leakage. A local distortion of the normal magnetic flux pattern
of a magnetized part caused by a discontinuity in the part.
Full wave direct current (FWDC). A rectified three-phase alternating
3.9
current.
3.10 Gauss. This is the Unit of flux density or induction Ln the cgs
electromagnetic unit system. (1 gauss = 10-4 tesla) (In alr 1 gauss is
equivalent to 1 oersted which equals 79.58 amps per meter).
3.11 Half wave direct current (HWDC). A rectified single phase alternating
current that produces a pulsating unidirectional field.
3.12 Head Shot. Producing circular magnetization by passing current
directly through the part being inspected while being held in contact with the
head stocks in a horizontal wet machine.
3.17 Indication. An accumulation of magnetic particles on the test piece
that forms during the Inspection process.
3.14 Indication, False. An indication of magnetic particles on the part
held by gravity cr su~face roughness or which arises from improper processing.

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MIL-STD-1949

3.15 Indication, nonrelevant. An indication caused by flux leakage that

has no relation to a discontinuity that is considered to be a defect. (For
example, magnetic writing or a change in section due to part design).
3.i6 Magnetic flux. A conceptualization of the magnetic field intensity
based on the line pattern produced when iron filings are sprinkled on paper
laid over a permanent magnet. The magnetic field lies in the direction of the
flux lines and has an intensity proportional to the line density.
3.17 Magnetization. The process by which the elementary magnetic domains
of a material are aligned predominantly in one direction.
3.18 Permeability. The ratio of flux density produced to magnetizing
field. lHigh permeability materials are easier to magnetize than low
permeability materials.)
3.19 Procuring activity. The agency for which the system/equipmentis
built or service provided.
3.20 pr0d3. Hand held electrodes through which a magnetizing current is
applied resulting in a distorted circular field.
3.21 Residual method. The application of magnetic particles after the
magnetizing force has been discontinued.
3.22 Suspension. A two-phase system consisting of finely divided magnetic
particles dispersed in a liquid vehicle.
L

3.23 Swinging field. A magnetic field which periodically alters its

direction during a single magnetic particle test.
3.24 Water break test. A quallty control test for conditioned water to
determine that the surface tension of the water has been reduced sufficiently
by a wetting agent to satisfactorily cover the surface of the items to be
inspected.
3.25 Wet method. The inspection technique in which the magnetic particles
employed are suspended in a liquid vehicle.
3.26 Other definitions. Definitions not given herein shall be as specified
in ASTM E269.

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MIL-STD-1949

4.

GENERAL REQUIREMENTS

4.1 Principles of magnetic particle inspection,

4.1.1 Intended use of magnetic particle inspection. When specified, the
magnetic particle inspection method shall be used to detect cracks, laps,
seams, inclusions, and other discontinuities at or near the surface of
ferromagneticmaterials. Magnetic particle inspection may be applied to raw
material, billets, finished and semifinished materials, welds, and in-service
parts. Magnetic particle inspection is not applicable to nonferromagnetic
metals and alloys such as austenitic stainless steels.
4.1.2 Basic principle. The method is based on the principle that the
magnetic flux in a magnetized material is distorted locally by the presence of
discontinuities. This distortion of the internal field pattern, tezmed flux
leakage, is capable of attracting and holding an inspection medium of finely
divided magnetic particles. The resulting accumulation of particles will be
visible under the proper llghting conditions. Sensitivity is greatest for
discontinuitieswhich break the surface and diminishes rapidly with increasing
depth below the surface.
4.1.3 Magnetization and particle application. Magnetic particle inspection
consists of magnetizing the area to be inspected, application of suitably
prepared magnetic particles while the area is magnetized, and subsequent
classification,interpretation, and evaluation of any resulting particle
accumulations. Maximum detectability occurs when the discontinuity has a
~~T3~~f~.:c~~me~ ~~. ~per,ii,g,
at
ieasi equai to Its depth, and
a ~eIIg~lA
positioned perpendicular to the magnetic flux. Due to the importance of the
magnetic field orientation on sensitivity, magnetization is necessary in two
perpendicular directions, except when specifically exempted by the procuring
activity.
4.1.4 Classification, interpretation,and evaluation. Magnetic particle
patterns produced during the inspection process must be classified, interpreted
as to their cause, and then evaluated in terms of part integrity according to
requirements which define the type, size, location, orientation, and area
concentration of dlscontlnultleswhich are unacceptable In a speclflc part.
4.2 Responsibility for inspection. Unless otherwise specified in the
contract or purchase order, the contractor IS responsible for the performance
of all the inspections to the requirements specified herein. The contractor
shaii specify more stringent requirements than the minimum specified in this
standard when necessary to assure that a component will meet its functional
and rellablllty requirements. Except as otherwise specified, the contractor
may utilize his own facilities or any other facilities suitable for the
performance of the inspection requirements specified herein. The Government
reserves the right to perform any of the inspections set forth in this
standard where such InspectIons are deernednecessary to assure that supplles
and services conform to prescribed requirements.

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HIL-STD-1949

.-

4.3 Qualification of inspection personnel. All personnel performing

magnetic particle inspection shall be qualified and certified in accordance
with MIL-STD-41O. Personnel making accept/reject decisions in accordance with
the process described by this standard shall be qualified to at leaat a level
II per MIL-STD-41O. Personnel performing the processing steps descfibed in
this standard shall be qualified to at least a level I per HIL-STD-41O.
4.4
Acceptance requirements. The acceptance requirements applicable to the
part or group of parts shall be incorporated as part of a written procedure
either specifically or by reference to other applicable documents such as
MIL-PI-47230
containing the necessary information. Applicable drawings or
other documents shall specify the acceptable size and concentration of
discontinuities in high and low 8tress area8 of fabricated parts. These
acceptance requirements shall be as approved or as 8pecified by the procuring
activity

4.5 Written procedure. Magnetic particle inspection shall be performed in

accordance with a written procedure applicable to the parts or group of parts
under test. The procedure shall be in accordance with the requirements and
guidelines of this standard. The procedure shall be capable of detecting the
8mallest rejectable discontinuities specified in the acceptance requirements.
On approval of the procuring activity, or its authorized representative, the
written procedure may be a general one which clearly applies to the specific
parts being tested. All written procedures shall be approved by an individual
qualified and certified to MIL-STD-41O, Level III for magnetic particle
inspection, and shall be subject to the approval of the procuring activity.
-

4.5.i Ziements of the written procedure. The written procedure shall

include at least the following elements, either directly or by reference to
the applicable documents:
a.
b.
c.
d.
e.
f.
e.

h.

k.
1.
!2.

Identificationof the parts to which the procedure applies. This shall

include the material and alloy of which the parts are fabricated.
Areas of the part to be examined.
Directions of magnetization to be used, the order in which they are
applied, and any demagnetization procedures to be used between shots.
Method of establishing the magnetization (prods, yoke, cable wrap,
etc).
The type of magnetizing current (AC, HWDC, FWDC, etc.) and the
equipment to be used.
The current level, or the number of ampere-turns, to be used and the
duration of its application.
Part preparation required before testing.
Type of magnetic particle material (dry or wet, visible or fluorescent,
etc.) to be used and the method and equipment to be used for its
application.
Type of records and method of mark~ng of parts after inspection.
Acceptance requirements, to be used for evaluating indications and
disposition of parts after evaluation.
Post-inspection demagnetization and cleaning requirements.
The procedure identification number and the date it was written.
Sequence cf magnetic particle inspectifinas related to manufacturing
process operations.

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MIL-STD-1949

4.6 Record of inspection. The results of all magnetic particle inspections

shall be recorded. All recorded results shall be identified, filed, and made
available to the procuring activity upon request. Records shall provide for
traceability to the specific part or lot inspected, and shall identify the
inspection contractor or facility and the procedures used in the inspection.
4.7 Magnetizing and demagnetizing equipment. Performance of a satisfactory
magnetic particle inspection requires magnetization of the part tc a specified
level in a specified direction. Magnetization can be accomplished either by
passing an electric current directly through the material (direct method), by
inducing a current to flow in the part under test (induced current method), or
by placing the material within the magnetic flux of an external source such as
a coil (indirect method). The types of equipment available include yokes,
portable units, mobile units, stationary units, and special application units
(e.g. a unit to produces swinging field). The types of currents used for
magnetization are full-wave rectified three phase current (FWDC), half-wave
rectified single phase current (HWDC), and alternating current (AC). The
equipment used shall adequately fulfill the magnetizing and demagnetizing
requirements, as outlined herein, without damage to the part under test and
shall include the necessary features required for safe operation.
4.8 Inspection sequence. Magnetic particle inspection shall be performed
after the completion of operations that could cause surface or near-surface
defects. These operations include, but are not limited to, forging, heat
treating, plating, cold forming, welding, grinding, straightening,machining,
and proof loading. Magnetic particle inspection, unless otherwise specified,
shall not be performed with coatings in place that could prevent the detection
pcaiiit
of surface defects in a ferromagnetic suDstraie. Such coaiings iilcl-tide
or chrome plate greater than 0.08 mm (0.003 inch) in thickness or
ferromagnetic coatings such as electroplated nickel greater than 0.03 mm
(0.001 inch) in thickness.
4.9

Lighting intensities.

4.9.1 Visible light intensities. Visible light shall be used when testing
with nonfluorescent particles. The intensity of the visible light at the
surface of the parts undergoing inspection shall be maintained at a minimum of
2000 lux (200 foot-candles). Unless otherwise specified, fluorescent magnetic
particle inspection shall be performed In a darkened area with a maximum
visible light level of 20 lux (2 foot-candles).
4.9.2 Black light ntensities. Unless otherwise specified, the black light
intensity at the examination surface shall be 1000Aiw/cm2 or greater when
measured with a suitable black-light meter. Portable or hand held black
lights shall produce an intensity greater than 1000MU/cm2 when measured at
380 mm (15 inches) from the black light source.
4.10 Materials.

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MIL-STD-1949

4.10.1 Magnetic particle materials. The particles used in magnetic

particle inspection shall be finely divided ferromagneticmaterials which have
been treated tc impart visibility against the background of the surfaces under
inspection. They may be either colored for use with visible light or coated
with a fluorescent dye for use with black light. The particles may be
designed for use as a free flow~ng dry powder (dry method), for suspension at
a given concentration in a suitable liquld (wet method), for suspension in a
polymerizeablematerial (magnetic rubber method), or for suspension in a
slurry (magnetic palntlng). The particles shall be des~gned to have a high
magnetic permeability and a low retentivity. Careful control of particle size
and shape is required to obtain consistent results. The particles shall be
non-toxic, free from rust, grease, paint, dirt or other deleterious material
which might interfere with their proper functioning.
4.10.1.1 Dry particle requirements. Dry particles shall meet the
requirements of AMS 3040. In applylng AMS 3040 the particles shall show
indications as listed in Table I on the test ring specimen of Figure 1 using
the followlng procedure:
Place a conductor with a diameter between 25 and 31 mm (1 and 1.25 inches)
through the center of the ring and circularly magnetize the ring by
passing the current.speclfled in Table I through the central conductor.
Using a suitable squeeze bulb or other applicator, apply the particles to
the ring surface while the current 1s floulng. Examine the ring for
indications under the appropriate lighting conditions.

--

4.10.1.2 Wet parblcle requirements. Wet particles shall meet the

requirements of AMS 3041, AMS 3042, AMS 3043, AMS 3045, or AMS 3046, as
-applicable. In applylng these speclflcatlons, the particles shall show
indications as listed in Table I on the test ring specimen of Figure 1 us~ng
the following prccedure:
Place a conductor through the center of the rlne and circularly magnetize
the ring by passing the current specified in Table I through the central
conductor employlng the continuous method. Examine the ring for
indications under the appropriate lighting conditions.
4.10.2 Suspension vehicles. The suspension vehicle for the wet method
shall be a light petroleum distillate conforming to JU!S3161 or DOD-F-87935.
When approved by the procuring agency, suitably conditioned water may be
used. The v~sccslty cf the suspension shall not exceed 5.0 mm2s-1 (5.0
centistokes) at the temperature of use when tested in accordance with ASTM
method D 445. The flash point of the suspension should be a minimum of 930C
(200F) when tested In accordance with ASTM method D93 (see Paragraph 6.4 on
safety). The background fluorescence of the suspension vehicle shall be less
than the llmlt spec~fled in DOD-F-87935.

----

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MIL-STD-1949

4.10.3
Particle concentration. The concentration of particles in the test
bath shall be as specified in the written procedure but in no case outside the
range of 0.1 to 0.5 ml in a 100 ml bath sample for fluorescent particles and
1.2 to 2.4 ml for nonfluorescent particles. Fluorescent particles and
nonfluorescent particles shall not be used together.

4.10.4 Conditioned water vehicle. When water is used as a suspension

vehicle for magnetic particles, lt shall be suitably conditioned to provide
for proper wetting, particle dispersion, and corrosion protection (an example
would be tap water with approximately 12.8 percent wetting agent, 0.3 percent
antlfoaming agent, and 3.9 percent rust inhibitor). proper wetting shall be
determined by a water break test (see Paragraph 5.8.4.2). In general, more
wetting agent is required to wet smooth surfaces than rough surfaces.
Whenever possible, non-ionic wetting agent should be used. However, in all
cases, the amount of wetting agent added should be limited so as not to raise
the alkalinity of the suspension above a pH of 10.0. Use of conditioned water
vehicle on cadmium plated steels with tensile strength of 180 ksi or above is
prohibited.

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!41L-STD-1949

5. DETAIL REQUIREMENTS
--

5.1 Preparation of parts for test.

5.1.1 Pre-inspection demagnetization. The part shall be demagnetized
before inspection if prior operations have produced a residual magnetic field
which will interfere with the inspection.
5.1.2 Surface cleanliness and finish. The surface of the part to be
inspected shall be essentially smooth, clean, dry, and free of oil, scale,
machining marks, or other contaminants or conditions which might interfere
with the efficiency of the inspection.
5.1.3
Coatings. Thin non-ferromagneticcoatings, which do not exceed 0.08
mm (0.003 inch) in thickness and ferromagnetic coatings not exceeding 0.03 mm
(0.@l inch) in thickness which do not interfere with the inspection may be
left on in-service components during inspection unless otherwise specified.
When such coatings are non-conductive, they must be removed where electrical
contact is to be made. Unless otherwise specified, production parts shall be
magnetic particle inspected prior to application of coating.

-.

5.1.4 Plugging and masking. Unless otherwise specified by the procuring

agency, small openings and oil holes leading to obscure passages or cavities
shall be plugged with a suitable non-abrasive material which is readily
removed and, m the case of engine parts, is soluble in 011. Effective
masking shall be used to protect those components, such as certain
non-metallics, which may be damaged by contact with the suspension.
5.2 Magnetization methods.
5.2.1 Permanent magnets. Permanent magnets are not to be used for magnetic
particle inspection unless specifically authorized by the procuring activity.
5.2.2 Types of magnetizing current. The types of magnetizing current used
for magnetic particle inpection are full-wave rectified three phase current
(FWDC), half-wave rectified single phase current (HWDC), and alternating
current (AC). AC is to be used only for the detection of defects open to the
surface. FWDC has the deepest possible penetration and must be used when
inspecting for defects below the surface when using the wet magnetic particle
method. HWDC is advantageous for the dry powder method because this type of
current gives increased mobility and sensitivity to the particles due to its
pulsating unidirectional field.

-.

5.2.3 Magnetic field directions. Discont~nulties are difficult tc detect

by the magnetic particle method when they make an angle less than 45C to the
direction of magnetization. To assure detection of discontinuities in any
dlrectlon each part must be magnetized In a least two directions at right
angles to each ether. Depending on part geometq this may consist of circular
magnetization in two cr mere directions, of both circular and longitudinal
magnetization, or of longitudinal magnetization In two or mere directions.
tixce?t~cnsnecessltatec rIypar$ gecme?pry,size cr other factcrs require
speclflc apprcval cf the prficurlngactlvlty. When specifically approved by the
procuring actlvlt:f,multldlrectlc,na~.,
swlnglng fleldl magnetization may be
used to fulflll the requirement fcr magnetization 1P.twc d~rections.
11

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5.2.4
Multidirectional magnetization. With suitable circuitry a
multidirectional (swinging) field in a part may be established (for example,
by selectively switching the magnetizing current between contact pairs
positioned approximately 90 degrees apart). In using this method, the
particle application must be timed so that the magnetization reaches its full
value in all directions during the time particles are being applied to the
surface under test. Multidirectional magnetization is roughly equivalent to
AC or HWDC agnetization in two or more directions. Multidirectional
magnetization shall not be used unless specifically approved by the procuring
activity.

5.2.5
Direct magnetization. Direct magnetization is accomplished by
passing current directly through the part under test. Electrical contact is
made to the part using prods, clamps, magnetic leeches, or by other means.
Precaution shall be taken to assure that the electrical current is not flowing
while contacts are being applied or removed and that excessive heating does
not occur in the contact area. Prods shall not be used for inspection of
aerospace vehicle parts or on finished surfaces.

5.2.6 Indirect magnetization. Indirect part magnetization uses preformed

coils, cable wraps, yokes, or a central conductor to produce a magnetic field
of suitable strength and direction to magnetize the part under test.
5.2.7 Induced current magnetization. Induced current magnetization is
accomplished by inductively coupling a part to an electrical coil to create a
suitable current flow in the part as illustrated in Figure 2. This method
shall be used only with specific approval of the procuring activity.
5.3 Magnetic field strength. The applied magnetic field shall have
sufficient strength to produce satisfactory indications but must not be strong
enough to cause masking of relevant indications by nonrelevant accumulations
of magnetic particles. Factors which determine the required field strength
include the size, shape, and material permeability of the part, the technique
of magnetization, the method of particle application and the type and location
of defects sought. When using prods, or when testing cylindrically ghaped
samples using coils, cable wraps, central conductors, or direct magnetization,
current levels shall be as specified in Paragraph 5.3.1. For other
configurations,proper magnetization levels may be verified by testing parts
having known defects of the type size and location specified in the acceptance
requirements or with a gaussmeter capable of determining the peak values-of
the tangential field using a Hall-effect probe or equivalent. Tangential
applied field strengths in the range of 2.4 to 4.8 kAm-l (30 to 60 gauss)
are adequate magnetization levels for magnetic particle inspection. Assure
that field strengths in this range are present in all areas to be inspected on
the part.
When a current or field range is
5.3.1 Magnetization current levels.
given, the largest value listed shall be used unless such value causes
interference due to nonrelevant indications or overheating of the part. When
interference occurs, the current level may be lowered until the interference
disappears, but in no case outside the lower limit given.

12

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MIL-STD-1949

5.3.1.1 Prod current levels. When using prods on material 19 mm (3/4 inch)
in thickness or less, 3.5 to 4.5 amperes per mm of prod spacing (9O to 115
A/in) shall be used. For material greater than 19 mm (3/4 inch) in thickness,
4.0 to 5.0 amperes per mm of prod spacing (100 to 125 A/in) shall be used.
Prod spacing shall not be less than 50 mm (2 inches) or greater than 200 mm (8
Inches), The effective width of the magnetizing field when using prods is 1/4
cf the prod spacing on each side of a llne drawn through the prod centers.
5,3.1.2 Direct circular magnetization. When magnetizing by passing current
directly through the part (i.e. using head shots) the current shall be from
12 A per mm of part diameter to 32 A per mm of part diameter (300 to 800 A/in).
The diameter of the part shall be taken as the largest distance between any
two points on the outside circumference of the part. Normally currents will
be 32 A per mm (500 A/in) or lower with the higher currents (up to 800 A/In)
being used to inspect for inclusions or to inspect alloys such as 15-5 PH
steel.
5.3.1.3 Central conductor circular magnetization. Circular magnetization
may be provided by passing current through a conductor which pagses through
the inside of the part. In this case alternating current is to be used only
when the sole purpose of the test is to inspect for surface discontinuitieson
the inside surface of the part. If only the inside of the part is to be
inspected, the diameter shall be the largest distance between two points, 180
degrees apart on the Inside circumference. Otherwise, the diameter is
determined as in para 5.3.1.2.

5.3.1.3.1 Centrally located conductor. When the axis of the central

- ..-- - - L
LL..-A
Al-..
&L.
~~r,~.ti~~ur
GUL1CLIL
levels
bile CCiltT&l
&XiS
Gf
bile pal u bllc sacs
iS
lCICEt.~6
K56T
as given in paragraph 5.3.1.2 (Direct circular magnetization) shall apply.
5.3.1.3.2 Offset central conductor. When the conductor passing through the
lnslde of the part is placed against an lnslde wall of the part, the current
levels as given in paragraph 5.5.1.2 (Direct circular magnetization) shall
apply except that the diameter shall be considered the sum of the diameter of
the central conductor and twice the wall thickness. The distance along the
part clrcu.mference(lnterlor or exter~or) which is effectively magnetized
shall be taken as four times the diameter of the central conductor as
illustrated in Figure 3. The entire circumference shall be Inspected by
rotating the part on the conductor, allowlng for approximately a 10 percent
magnetic field overlap.
5.3.1.4 Longitudinal magnetization. Longitudinal magnetization is
accomplished by passing current through a coil.encircling the part, or section
of the part, to be tested (i.e. by using a coil shot). This produces a
rnagnetlcfield parallel to the axis of the coil. For low fill factor coils
the effective field extends a distance on either side of the coil center
approximately equal to the radius of the coil(see Figure 4). For cable wrap
or high fill factcr CO1lS, the effective distance of magnetization is 230 mm
(9 Inches) on either side of the coil center (see Figure 5). For parts longer
than these effective distances, the entire length shall be inspected by
repositioning the part within the coil, allowing for approxtiately 10 percent
effective magnetic field overlap.

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MIL-STD-1949

5.3.1.4.1 Longitudinal magnetization with low fill factor coils. When the
cross sectional area of the coil is 10 or more times the cross sectional area
of the part being inspected, then the product of the number of coil turns, N,
and the current in amperes through the coil, I, shall be:

.-

a. For parts positioned to the side of the coil;

NI=K -

(:10%)
L/JJ
where K = 45,000 ampere turns
L= length of the part
D = diameter of the part (measured
in the same units as the length)
b. For parts positioned in the center of the coil;
NI =

(: 10 %)
(6L?) -5

where R = radius of the COI1 m mm

K= 1690 ampere turns per mm
R is measured in inches)
L= the length of the part
D= the diameter of the part
in the same un~ts as the

(or m inches)
(43,000 ampere turns per inch if

(measured
length)

If the part has h~llfiwpcrtlons replace D with Deff ES given in Paragraph

only li L;D is greater than 3 and less than
5.3.1.4.3. These formulas hold
15. If L/D 1s less than 3, pole pieces (pieces of ferromagneticmaterial with
the same diameter as the part being tested) shall be placed on each end of the
part to effectively increase L/D to 3 or greater. If L/D 1s greater than 15,
the value 15 shall be substituted for L/D.
5.3.1.4.2 Longitudinal magnetization with cable wrap or high fill factor
coils. When the cross sectional area of the coil is less than twice the cross
sectional area (includlng hcllow portions) of the part under test, then the
product of the number of coil turns, N, ana the current m amperes through the
CC1l, I, shall be:

where K = 35,000 ampere turns

L = the length of the part
D = the diameter of the part (measured
in the same units as the length)
If the part has hollow pcrtlcns replace D with Deff as given l.nParagraph
!i.3.l.4.3. This formula holds cnly If LID is greater than 3 and less than
15. If L/D 1s less than 3, pcle pieces (pieces cf ferromwnet~c material With
the same diameter as the part being tested) shall be placed en each end of the
,,. b,
.J.-C+A.
..-l..
T? ~,,/~1
~~ gr~at.prf.han
~r,c~ssse,?.L
gre2te? ih?z :. ..
part tc CAL!SLLIVCL.V
f~r~/~1.
15, the value ib Sh?Al;be Sucstlt~tje(j

14
.-

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HIL-STD-1949

5.3.1.4.3 Calculating the L/D ratio for a hollow or cylindrical part. When
calculating the L/D ratio for a hollow or cylindrical part, D shall be
replaced with an effective diameter, Deff) calculated using:

Deff = 2 [(At - Ah) /~]1/2

where

At
Ah

=
=

the total cross sectional area of the part

the cross sectional area of the hollow
portions of the part

For cylindrical part this is equivalent to:

Deff
nhere

[ (OD)2 - (ID)2 ]1/2

OD = the outside diameter of the cylinder.

ID = the inside diameter of the cylinder.

!5.4 particle application.

5.4.1 Continuous method. In the dry continuous method, magnetic particles
are applied to the part while the magnetizing force ia present. In the wet
continuous method the magnetizing circuit shall be closed just before the
suspension is diverted from the part. Application of the magnetic particles
(see 5.4.4 and 5.4.5) and the magnetization method shall be as prescribed in
the paragraphs referenced herein.
L

5.4.2 Residual magnetization method. In the residual magnetization method

the magnetic particles are applied to the test part immediately after the
magnetizing force has been discontinued. The residual method is not as
sensitive as the continuous method but it can be useful, for example, to
detect in-service induced fatigue cracks on the surface of material with a
high retentivity. The residual method shall be used only when specifically
approved by the procuring activity or as an interpretation aid unless
otherwise specified.
5.4.3 Prolonged magnetization. When using polymers, slurrles, or paints,
prolonged or repeated periods of magnetization are necessary because of lower
magnetic particle mobility in the high-viscosity vehicles.
5.4.4 Dry magnetic particle application. When using dry particles the flow
of rnagnetlzingcurrent shall be initiated prior to the application of the
magnetic particles to the surface under test and terminated after powder
application has been completed and any excess blown off. The duration of the
magnetizing current shall be at least 1/2 second and short enough to prevent
any damage to the part due to overheating or other causes. Dry powder shall
be applied in a manner such that a light, uniform dust-like coating settles on
the surface of the test part while the part is being magnetized. Specially
designed powder blowers or shakers using compressed air or hand power shall be
used. The applicators shall introduce the particles into the air in a manner
such that they reach th,epart surfacem a uniform cloud with a minimum of

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MIL-STD-1949

force. After the powder 1s applied, and before the magnetizing force is
removed, excess powder shall be removed by means of a dry air current with
sufficient force to remove the excess particles, but not strong enough to
disturb particles held by a leakage field that is indicative of
discontlnulties. In order to recognize the broad, fuzzy, lightly held powder
patterns fclrmedby near surface discontinuities, the formation cf indlcation9
must be carefully observed during powder application and during removal of the
excess powder. Sufficient time for formation and examination of indications
shall be allowed during the testing process. The dry particle method shall
not be used to inspect aerospace components without specific approval of the
procuring activity.

5.4.5 wet magnetic particle application. Fluorescent or nonfluorescent

particles suspended in a liquid vehicle at the required concentration shall be
applied either by gently spraym.g or flowing the suspension over the area to
be inspected. Proper sequencing and timing of part magnetization and
application of particle suspension are required to obtain proper formation and
retention of indications. This generally requires that the stream of
suspension be diverted from the part simultaneously with, or slightly before,
energizing the magnetic circuit. The magnetizing current shall be applied for
a duration of at least 1/2 second for each application with a minimum of two
shots being used. Care shall be exerc~sed to prevent any damage to the part
due to overheating or other causes. Weakly held indications on highly
finished parts are readily washed away and hence care must be exercised to
prevent high-veloclty flow over critical surfaces.
5.4.6 Magnetic slurry/paint application. Magnetic paints or slurries are
-...
.m-l<=,a~G LL---L
..-&l_
IJ1lC
pal
u
NAbll
Fi
brush,
squeeze
l-L
uubbAe - UY u~iWtivl
UMIL vefvre
VT
during the magnetization operation. This method is for special applications,
such as overhead or underwater examination. This method shall be used only
when specifically approved by the procuring activity.

appALcu

5.4.7 Magnetic polymer application. Polymerizable material containing

magnetic particles shall be held in contact with the test part during the
period cf its cure. Before curing takes place and while the magnetic
particles are still mobile, the part shall be magnetized to the specifed
level. This requires prclorgedor repeated periods of magnetization. This
method is for special applications, such as bolt holes, which cannot be
readily tested by the wet or dry method and shall be used only when
specifically approved by the procuring agency. MIL-I-83387 established the
inspection process for magnetic rubber.
5.5 Interpretation of indications.
5.5.1 TYPes of indications. Indications are accumulations of magnetic
particles on the test piece that form during the inspection process. These
indications can be divided into false lndlcatlons, nonrelevant indications,
and relevant indications.
5.5.1.1 False indications. Indications which are not the result of
magnetic forces are termed false indications. Examples are particles held
mechamcally or by gravity In shallow depressions or particles wedged into
ru9t or scale on the 9urface.

16

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MIL-STD-1949

5.5.1.2 Nbnrelevant indications. Indications which adhere to flux leakage

areas created by intentional design factors such as keyways, drilled holes, or
abrupt cross-sectional changes, or which are due tb accidental causes such as
magnetic writing, are termed nonrelevant.
5.5.1.3 Relevant indications. Indications pruduced by any other flux
leakage fields are termed relevant. All relevant indications shall be
evalu~ted according to the applicable acceptance requirements specified in the
written procedure. Relevant indications which have been evaluated and
determined to be unacceptable discontlnulties shall be described in detail on
the appropriate rejection form and submitted for dispositionin accordance with
contract requirements.
5.6 Recording of indications. When required by the written procedure, the
location of all indications shall be marked on the part and permanent records
of the location, direction and frequency of indications may be made by one or
more of the following methods:
5.6.1 Written description. By recording the location, length, direction,
and number of indications by a sketch or in a tabular form.
5.6.2 Transparent tape. For dry particle indications, by applying
transparent adhesive-backed tape to which the ind~cations will adhere and
placing it on an approved form along with information giving its location on
the part.

k.

5.6,3 Strippable film. By covering the indicatlGn with a spray-on

.+...-...L1fi~r,:~,~~fix2~ ~y,eindications iiiplace and pluci[lgLhe resultant
o.L*yyuLG
reproduction on an approved fbrm along with information giving its locatlon on
the part.
5.6.4 Photography. By photographing the indications themselves, the tape,
or the strippable film reproduction and placing the photograph on a tabular
form along with information giving its locatlon on the part.
5.7 post-inspection demagnetizationand cleanlng. Unless directed
ctherwlse by the procuring activity, all parts shall be demagnetized, cleaned,
and corrosion protected after inspection.
5.7.1 Demagnetlzatlon. When using AC demagnetization the part shall be
subjected to a field with a peak value greater than, and in nearly the same
direction as, the field used during mspectlon. This AC field IS then
gradually decreased to zero. When using an AC demagnetizing coil, hold the
part about 30 cm (1 ft) in front of the CO1l and then move it slowly and
steadily through the coil and at least 100 cm (3 ft) beyond the end of the
Cell. Repeat this process as necessary. Rotate and tumble parts of complex
configuration while passing through the field of the CO1l. When using DC
demagnetization, the lnltlal field shall be higher than, and in nearly the
same direct~on as, the field reached during inspection. The field shall then
be reversed, decreased ~n nagnltude, and the process repeated (cycled) until
an acceptably low value of residual field 1s reached. Whenever possible parts
wh)ch have been circularly rnagnetlzedshall be magnetized In the lo~ltudlnal
dlrecticn befcre being demagnetized. After dernagnetizatlon,
a magnetic field
prcbe CT strength meter shall not detect fields greater than 240 Am-l (3
gauss1anywhere on the part.
17

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MIL-STD-1949

5.7.2 Post-inspection cleani~. Cleaning shall be by use of a suitable

solvent, air blower, or by other means. All traces of the magnetic particles
and magnetic particle test materials which might interfere with subsequent use
of the part shall be removed (chlorinated solvents shall not be used on partg
containing crevices). Care shall be taken to thoroughly remove all plugs in
holes and cavities and all asking. Parts shall be protected from any
possible corrosion or damage during the cleaning process and shall be treated
to prevent the occurrence of corrosion before continued processing.
5.8

Quallty control.

5.8.1 Inspection system verification. The overall sensitivity and

performance of the magnetic particle inspection system including the
equipment, materials and the lighting environment being used, shall be
verified initially and at regular intervals thereafter. The required
verification intervals are stated m Table II. Records of the verification
results shall be maintained. Personnel assigned to perform and audit the
verification shall be Identified.
5.8.2 Use of test part with discontinuities. A reliable method for
evaluating an inspection procedure is to use representative test parts
containing defects of the type, location, and size specified In the acceptance
requirements. If correct magnetic particle indications can be produced and
identified m these representative parts, then the overall system and
Inspection procedure is verlfled. Parts used for verification will be
thoroughly cleaned following the inspection and checked under black or white
llght, as appropriate to the inspection process, tc ensure residual
lnalcatlons du IiUt reiiiain.
5.8.3 Fabrlcatea test parts with artlflclal dlscontlnultles. When actual
production parts with known defects of the type, locatlun and size needed for
verification, are not available cr are Impractical, then ,upon the approval of
the procuring activity, fabricated test parts with artificial discontinuitles
suitable for verlflcatlon of the test procedure, the ple-field lndlcator L:
Figure 6, or the AISI Ketos tool steel ring as shown in F~gure 1 may be
substituted. Parts used for ver~flcatlon WI1l be thoroughly cleaned fcllowlng
the Inspection and checked under black Lr white light, a~ appropriate to the
lnspectlcr.prccess, tc ensure residual lndlcatlons ac not remain.
5.8.4 Suspension vehicle tests.
5.8.L.1 Concentratlcn tests. Particle concentration and contamination
shall be determined upon start up, at reg~lar intervals thereafter, and
whenever the bath is changed or adjusted. The required testing intervals are
stated in Table Il.

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MIL-STD-1949

5.8.4 .1.1
Determination of wet particle
concentration.
Agitate
the
particle suspension a minimum of 30 minutes to insure a uniform distribution
if particles-throughout the bath. Place a 100 ml sample of the agitated
suspension in a pear-shaped centrifuge tube (shaped and graduated as specified
in ASTM D96). Demagnetize the sample and allow the tube to stand undisturbed
for at least 30 minutes. Read the volume of settled particles. If the
concentration is out of the tolerance stated in the written procedure (or that
given in Paragraph 4.10.3) add particles or suspension vehicle, as required,
and redetermine the particle concentration. If the settled particles appear
to be loose agglomerates rather than a solid layer, take a second sample. If
the second sample also appears agglomerated, replace the entire suspension.

5.8.4,1.2 Determination of wet particle contamination. Perform the tests

specified in paragraph 5.8.4.1. In addition, examine the liquid above the
precipitate with black light. The liquid shall be essentially
nonfluorescent. Examine the precipitate. If two distinct layers can be seen,
read the volume of each layer. The top layer volume (contamination)shall not
exceed 30 percent of the bottom layer volume (magnetic particles) nor shall it
fluoresce. If either condition is unsatisfactory, the entire suspension shall
be replaced.
5.8.4.2 daterbreak test. In this test a part with a surface finish the
same as the Darts to be tested is flooded with the conditioned water and the
appearance o~ the surface is noted after flooding is stopped. If a continuous
even film forms over the entire part, sufficient wetting agent is present. If
the film of suspension breaks, exposing bare surface, insufficient wetting
agent is present or the part has not been adequately cleaned.
L.

5.8.5 Equipment calibration. Magnetic particle testing equipment shall be

checked for performance and accuracy at time of purchase and at intervals
thereafter as given in Table 11, whenever malfunction is suspected or when
specified by the procuring agency, and whenever electrical maintenance which
might affect equipment accuracy is performed.
5.8.5.1 Ammeter accuracy. To check the equipment ammeter, a calibrated
ammeter shall be connected in series with the output circuit. Comparative
readings shall be taken at three output levels encompassing the useable range
of the equipment. The equipment meter reading shall not deviate by more than
~10 percent of full scale from the current value shown by the calibrated
ammeter (when measuring HWDC, the current values shown by the calibrated DC
ammeter reading shall be doubled). The ammeter should be checked according to
the time frame indicated in Table II.
5.8.5.2 Timer control check. On equipment using a timer to control current
duration, the timer should be checked to within ~0.1 second using a suitable
electronic timer.
5.8.5.3 Magnetic field quick break check. On equipment which utillzes a
quick-break feature, proper function~ng of this circuit shall be verified.
The test may be performed using a su~table oscilloscope or other applicable
method as specified by the equipment manufacturer.

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MIL-STD-1949

5.8.5.4 Dead weight check. Yokes and permanent magnets (when allowed)
shall be dead weight tested. Alternating current yokes shall have a lifting
force of at least 45 N (10 pounds) with a 50 to 100 mm (2 to 4 inch) spacing
between legs. Direct current yokes and permanent magnets shall have a lifting
force Gf at least 135 N (30 pounds) with a 50 to 100 mm (2 to 4 inch) spacing
between legs or Z25 N (50 pounds) w~th a 100 to 150 mm (4 to 6 inch) spacing.
5.9 Marking of Inspected parts. Unless otherwise specified by the
procuring agency, parts which have been accepted using magnetic particle
inspection shall be marked in accordance with the applicable drawing, purchase
order, contract or as specified herein. Marking shall be applied in such a
manner and location as to be harmless to the part. The identificationshall
not be obliterated or smeared by subsequent handling and, when practicable,
placed in a location which will be visible after assembly. When subsequent
processing would remove the identification, the applicable marking shall be
affixed to the record accompanying the finished parts or assembly.
5.9.1 Impression stamping or vibro engraving. Impression stamping or vibro
engraving shall be used when permitted or required by the applicable written
procedure, detail specification or drawing, or when the nature of the part is
such as to provide for impression stamping of part numbers cr other
inspectors markings. Impression stamping shall be located only in the area
provided adjacent to the part number or inspectors stamp.
5.9.2 Etching. When impression stamping or vibro engraving is prohibited,
parts shall be etched using an etching fluld or other means and a method of
application acceptable to the contractor. The etching process and locatlon
mhol~
~,z~
.,*A*
5&-erwQti?~eci
the functioning 01the part.
5.9.3 Dyein~. #henstamping, vibro engraving or etching is not
permissible, identification shall be accomplished by dyeing.
5.9.4 Other identification. Other means of identification such as tagging,
shall be used for parts which have a construction or function precluding the
use of stamping, vibro engreving or etching, as in the case of completely
ground or polished balls, rollers, pins, or bushings.
5.9.5 Identifying symbols and color markings.
5.9.5.1 100-percent inspection. When items are inspected and accepted by
100-percent inspection, each item shall be marked as follows:
5.9.5.1.1 Dyeing. When dyeing is applicable, a dye of acceptable adherence
which is predominately blue (per FED-STD-595) shall be employed.
5.9.5.1.2 Stamying, vxbro engraving or etchi~. When impression stamping,
vibro engraving or etching is used to mark 100-percent inspected parts, the
letter M with a circle around lt shall be employed.

20

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MIL-STD-1949

5.9.5.2 Lot inspection. When Items are accepted by means of a sampllng

procedure, each item of an accepted lot shall be marked as follows:
.

5.9.5.2.1
Dyeing. When dyeing is applicable, a dye of acceptable adherence
which is predominately orange per FED-STD-595 shall be employed.

Stamping,vibro engraving or etchi~. When impression stamping,

vibro engraving or etching is used to mark lot-inspected parts, the letter M
with an ellipse around it shall be employed.
5.9.5.2.2

21

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MIL-STD-1949

6. NOTES
6.1 be glasses. When using fluorescent materials, inspectors shall not
wear eye glasses equipped with light sensitive lenses (i.e. lenses that darken
when exposed to ultraviolet light or sunlight).
6.2
Aircraft quality steel cleanliness. The inspection of aircraft-quality
steel for cleanliness using magnetic particle inspection shall be as specified
in AMS 2300, AMS 2301, or A.MS2303 as appropriate to the type of steel being
inspected. However, inspection of parts fabricated from this material shall
be in accordance with the requirements of this document.

6.3 Acceptance requirements. Methods for establishing acceptance

requirements for large crankshaft forgings are discussed in ASTM A456.
Methods for establishing requirements for steel forgings are discussed in ASTM
A275. Methods for classifying metal castings are given in MIL-STD-2175.
MIL-M-47230 provides a classification scheme for ferromagnetic forgings,
castings, extrusions and weldments.
6.4 Safety. Dry cleanlng solvents are not to be used for suspending
particles. Proper precautions must be taken to prevent the ignition of
hydrocarbon suspension baths by overheating, electrical arcing, etc.
Precaution shall be taken to prevent inhaling of dry particle materials. The
use of suitable face masks 1s recommended. It is the recommended that the
intensity of black light incident on unprotected skin or eyes not exceed
looo#fw/cm2.
Dn-.-..---l
.aV.,llc

~ti-~

... .

w=~~ SL Ieusi one minute after

entering a darkened area for their eyes to adjust to the low level lighting
before perfoming fluorescent magnetic particle inspection.
6,5

Dark

edent+isr.

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MIL-STD-1949

0.070 t 0.005
)iob$
Through
Typ.

Notms: All Tolerances

are 20.03
Except Where
Hole Numbers 8-12 are Optional

Shown

,
Iiolo

10

11

12

.07.14.21.20.35,42.49.56.63.70.77.84
D, Incttos
?0.005
i
Figure

1, AiSl KETOS tool steel ring for use-in magnetic particle system verification and
All dimensions are in inches. Material shall be
testing of magnetic particles.
AISI 01 toolsteel
from annealed round stock. Hardness shall be 90-95 Rockwell

----

,7

Multi.Tum
Magnetizing
coil
.~,::.,
.,,
J

/rl
.,$
:~ ,

Magnetic

,,

!!

,,.:

Prima~

,/

Particle
Indications

I:,

%L&Sk:
,? ,;

?
Under

v ,$

~.
Primaq
Current
(AC)

Figure 2.

Test

~ott

Iron Core

The primary current sets up an

Example of induced curren~ magnetization.
oscillating magnetic field. This primary magnetic field induces a current in
the ring shaped pafl under test.

23

B.

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MIL-STD-1949

,Effective
Region
of inspection

Central

Condu ctor

Figure 3.

The effective region of inspection when using an offset central conductor

equal to four times the diameter of the conductor as indicated.

is

n
I

\
~ \\\,,

Region
$pection

Figure 4.

Effec~we

region of inspection

for a IOW

ill-factor

mi[.

Downloaded from http://www.everyspec.com

MIL-STD-1949

Effective

Region

of 1nspection
k-- 220mm
,
(9\

220mm/
(9)

-.

1;,

AL

Figure 5.

Effective

region of inspection

for a high fill-factor

cmil.

-.

+,

Eight Low Carbon Steel Pie Sections

Furnace Brazed Together

--

1132Max

1/8

Nonferrous

Copper

Trun!ons

Plate, O.010

:0.002

Figure

6,

P)e-fie!d

indicator

All dimensions
furnace
orazed

for

use In n-iagnellc parllcle

Eight
are In !nches
cooper
~ocjerner and

.,.

InsDectlon svslem verlfimt]on.

low rcar~on steel pie. snaped sec:]ons are

plated.

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MIL-STD-1949

TABLE I
Required indications when using the ring specimen of Figure 1.
Particles Used

Central Conductor
FWDC Amperage

Wet suspension,

fluorescent or
nonfluorescent

Dry pouder

Minimum Number
of Holes Indicated

1400
2500
3400

3
5
6

1400
25C13
3400

4
6
7

TABLE II
Required verification intervals.

MAXIMUM TIME
BETWEEN VERIFICATIONS

ITEM
Lighting:
Black light intensity
White light intensity
Background white light intensity

1 day
1 week
1 week

System perfoxvnanceusing test

piece or ring specimen of Figure 1

1 day

Wet particle concentration

8 hours, or
every shift change
1 month
1 week

break test
Wet particle contamination

Water

Equipment calibration/check:
Ammeter accuracy
Timer control
Quick break
Dead weight check

6
6
2
2

months
months
months
months

Note: The maximum time between verifications may be extended when

substantiated by actual technical stability/reliabilitydata.

26


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MIL-STD-1949

Custodians:

Preparing Activity:

Army -- KR
Navy

--

Army - MR

IX-3

Air Force -- 20
Review

Project No. NDTI-0054

activities:

Army -- AR, AV, EA, MI

Navy -- SH
Air Force -- 99, 70, 80, 82, 24, 84
User

activities:

Army -- AT, AL, ME, TE, AR

Navy -- OS
Air Force -- 71

(WP # ID-0381A/DISK-0305A. FOR AMMRC USE ONLY)

27

Downloaded from http://www.everyspec.com

INSTRUCTICMS:

In s cootiouhg ffort to meke

submitting commenu ad

~tttions.
msikd.

~is

form

better, the

DoD providec tbh (orm for uee in

All UJCrSof military Andardization

mggations for improwments.

docwnenu are invited b protirk

indicated,
@peal
along
thebee edge(DONOT STX?ZE).

mmYbe datacbed, folded akmc the lit-

hr block 5, be M specifii as P-Me

~M

our stadsrdbtion

bout @icuh

Problem U-

SUdI = WOrdine Which

and

requiredinterpretation,W-

too ri@, rutricti?e, Iooee,ambiguous,or was incomwtible, and gi?e PKOPO=XIwording cbsngee which would alleviate the

~obleom.
Enter

in block 6 any rmasrks not misted to

specifrr paragraph of the document. If block 7 u filled out,

acknowledgement will be meiled to you withio 30 deyB to let

rmeiderwd.

YOU

koow

thet

YOUK

coromwmtewere received and are being

DOrto -u*
WUWXS,
deviations, or chrificmtionof
Ms form rnsy not be d
to requeet copies of d~u-n@,
specificationrequirement on currentcontmcts. CommenUsubmitti on thu form do not constitute or imply uthorization

NOTE:

to weive eny portion of the referenced document(s)

or to amend contractual requirements.

(Fold

DEPARTMENT

OF THE

alon~

thb

Ilnc)

ARMY

111111
PI
uNITED

OFFICIAL

BU$!NE=

PENALTY

FOR

PRIVATE

USE

$300

BUSINESS REPLY MAIL

FIRsT

CLASS

POSTAGE

WILL

PERMIT
BE PAID

NO

12062

BY THE

WASHINGTON

DEPARTMENT

OF THE

ARMY

Director
US Army Materials & Mechanics Research Center

ATTN: DRXMR-SMS
Watertown,MA 02172

STATES

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WANDAROIZATION WWENT
(see
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MANUFACTURER

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AREAS

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NAME

OF

SU0MtT7ER

Firrt

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Optlmd

b WORK

TELEPHONE

NUMBER

(lncJu&

Co&) - Optlonsl
MAILING

An

AOORESS

-----

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PREVIOm

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