Levels I , I I , and I I I

Magnetic Particle Testing

Method

Supplement to
Recommended Practice
No. SNT-TC1A
Book B
The American Society
for N o n d e s t r u c t i v e T e s t i n g , I n c .
Published by
The American Society for Nondestructive Testing, Inc.
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PO Box 28518
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Copyright © 1994 by The American Society for Nondestructive Testing, Inc. ASNT is not responsible for the
authenticity or accuracy of information herein. Published opinions and statements do not necessarily reflect
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recommendation of ASNT.

This publication contains suggested questions and answers in the Magnetic Particle Test method for use in
conjunction with Recommended Practice No. SNT-TC-1A for Personnel Qualification and Certification in
Nondestructive Testing. Recommended Practice No. SNT-TC-1A is available from ASNT.

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The NDT Technician and www.asnt.org are trademarks of The American Society for Nondestructive
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ISBN 0-931403-11-1

Printed in the United States of America

first printing 07/87

second printing 03/88
third printing 04/88
fourth printing 02/89
fifth printing 04/90
sixth printing 05/92
seventh printing with revision 05/94
eighth printing 10/96
ninth printing 11/98
tenth printing 07/03

2
 Table of Contents

References 5

Reference Usage List 6

Level I 7
Questions 7
Answers 15

LevelH 17
Questions 17
Answers 25

Level III 27
Questions 27
Answers 33

Sample Specification 35
Questions 39
Answers 43

3
f
 Recommended Training References
Magnetic Particle Testing Method

The following references were used in formulating the questions contained in this book.

A. * Betz, Carl E. Principles of Magnetic Particle Testing. Chicago, I L : Magnaflux Corporation. 1966.

B. * McMaster, R.C., ed. Nondestructive Testing Handbook, first edition. Columbus, OH: The American Society
for Nondestructive Testing, Inc. 1959.

C * Magnetic Particle Testing: Classroom Training Handbook (CT-6-3). San Diego, CA: General Dynamics/
Convair Division. 1977. (Now published by The American Society for Nondestructive Testing, Inc.)

D. Doane, F.G. and Carl E. Betz. Principles of Magnaflux. Chicago, I L : Photopress. 1948.

E. * McGonnagle, W.J. Nondestructive Testing. New York, N Y : McGraw-Hill. 1961.

F. * Metals Handbook, Eighth Edition, Nondestructive Inspection and Quality Control, Volume 11. Materials
Park, OH: American Society for Metals. 1976.

G. * Annual Book ofASTM Standards, Volume 03.03, Nondestructive Testing. "Standard Guide for Magnetic
Particle Examination," Standard ASTM E 709. Philadelphia, PA: American Society for Testing and
Materials. Latest edition.

* Available from The American Society for Nondestructive Testing, Inc.

Each question found in this book contains letter(s) and page number(s) in bold type immediately following the answers.
For example,

13. What rule describes the direction of current flow

(+ to - ) when lines of magnetic force surround a
conductor?

a. the left hand rule

b. the right hand rule
c. the flux rule
d. the reluctance rule
A.143

In this example, the letter "A" refers to Reference A in the list provided above and "143" is the specific page in
Reference A where the answer to the question can be found.

5
 Reference Usage List
Magnetic Particle Testing Method
Reference A: Total = 123 Reference E : Total = 1
Level I (29) Level I (1)
Level II (58) Level II (0)
Level III (36) Level III (0)

Reference B: Total = 57 Reference F: Total = 5

Level I (36) Level I (0)
Level II (8) Level II (0)
Level III (13) Level III (5)

Reference C: Total = 24 Reference G: Total = 3

Level I (19) Level I (0)
Level II (3) Level II (0)
Level III (2) Level III (3)

Reference D: Total = 5
Level I (5)
Level I I (0)
Level III (0)

6
 Level I Questions
Magnetic Particle Testing Method

1. "Magnetic particle" is a nondestructive examination 7. The magnetic field is strongest when the:
method used for:
a. magnetizing voltage is flowing
a. locating surface discontinuities b. magnetizing current is flowing
b. locating near surface discontinuities c. material exhibits high coercive forces
c. both a and b d. magnetizing current is not flowing
d. detecting material separation B.30.11
A.60
8. I f a crack exists in a circular magnet, the attraction of
2. Ferromagnetic material is: magnetic particles to the crack is caused by a:

a. strongly attracted by a magnet a. coercive force

b. capable of being magnetized b. leakage field
c. both a and b c. Doppler effect
d. not capable of being magnetized d. high reluctance at the crack
A.115 C.2-9

3. The permeability of a material describes the: 9. The unit usually used to denote flux density is the:

a. ease with which it can be magnetized a. gauss

b. depth of the magnetic field in the part b. henry
c. length of time required to demagnetize it c. farad
d. ability to retain the magnetic field d. ampere
A.119 C. 2-12

4. The retentivity of a material describes the: 10. Which statement is true when related to magnetic
lines of force?
a. ease with which it can be magnetized
b. depth of the magnetic field in the part a. they never cross
c. length of time required to demagnetize it b. they are most dense at the poles of a magnet
d. ability to retain the magnetic field c. they seek the path of least resistance
A.120; B.30.22 d. all of the above
C.2-7
5. Why are magnetic particles available in different
colors? 11. Magnetic flux lines which are parallel to a
discontinuity produce:
a. for color contrast with the part surface
b. to enhance the detection of indications a. strong indications
c. both a and b b. weak indications
d. different colors are used with different magnetic c. no indications
flux values d. fuzzy indications
A.346 B.30.8

6. Which of the following can be magnetized? 12. A part is adaptable to magnetic particle inspection if:

a. iron a. it is attached to an electrostatic field

b. nickel b. the material is ferromagnetic
c. cobalt c. the material is nonferrous
d. all of the above d. the material is an electric conductor
A.115 A.60

7
Magnetic Particle Testing Method, Level I

13. What rule describes the direction of current flow 20. Magnetic lines of force:
(+ to - ) when lines of magnetic force surround a
conductor? a. travel in straight lines
b. form a closed loop
a. the left hand rule c. are randomly oriented
b. the right hand rule d. overlay in highly ferromagnetic materials
c. the flux rule A.131
d. the reluctance rule
A.143 21. A magnetic particle build-up from a discontinuity is
strongest when the discontinuity is oriented:
14. The magnitude of the residual magnetic field in a
specimen is dependent on the: a. 180° to the magnetic field
b. 45° to the magnetic field
a. L / D ratio (length to diameter) c. 90° to the magnetic field
b. strength o f the applied magnetizing force d. 90° to the current flow
c. right hand rule A.134,135; C.2-10
d. left hand rule
B.30-14 22. A specimen may be demagnetized by:

15. The proper number of ampere-turns for a given test a. heat treatment above Curie temperature
specimen is determined by: b. an A C coil
c. reversing DC fields
a. its length d. all of the above
b. the material B.30.22
c. both a and b
d. its diameter 23. Which of the following is an advantage of magnetic
B.30.14 particle testing over penetrant testing?

16. A circular field may be induced into a specimen by: a. it can detect surface discontinuities with foreign
material imbedded in them
a. direct induction (head shot) b. it is faster on individual parts
b. direct induction (prods) c. it can detect near-surface discontinuities
c. central conductor d. all of the above
d. all of the above A.68
C.2-15
24. The amount of amperage used for magnetic particle
17. A n electrical yoke produces: inspection using the prod method is determined from
the:
a. a longitudinal field
b. a circular field a. type of material
c. alternating fields b. distance between the prods
d. a swinging field c. diameter of the part
C.2-16 d. total length of the part
B.30.14
18. A coil around the part produces:
25. The flux within and surrounding a magnetized part or
a. a circular field around a conductor carrying a current is known as:
b. a longitudinal field
c. either a or b depending on the type of current a. saturation point
applied b. magnetic field
d. an intermittent field c. ferromagnetic
C.2-16 d. paramagnetic
D.45,47
19. In longitudinal magnetization, the proper term for
calculating magnetizing force is:

a. amperes
b. ampere-turns
c. watts
d. ohms
A.145; C.2-17

8
 Magnetic Particle Testing Method, Level !
26. The areas on a magnetized part from which the 33. Which type of current brings out surface indications
magnetic field is leaving or returning into the part are most clearly?
called:
a. AC
a. salient points b. DC
b. defects c. pulsed D C
c. magnetic poles d. D C with surge
d. nodes B.30.8; D.139
D.43,63
34. Fluorescent magnetic particle indications should be
27. A metal that is difficult to magnetize is said to have: inspected under:

a. high permeability a. fluorescent light

b. low permeability b. any light
c. high reluctance c. black light
d. low retentivity d. neon light
D.50 A.274

28. The magnetism that remains in a piece of 35. Inspecting a part by magnetizing, removing the
magnetizable material after the magnetizing force has current flow, and then applying the medium is called
been removed is called the: the:

a. tramp field a. continuous method

b. residual field b. wet method
c. damped field c. residual method
d. permanent field d. dry method
D.52 A.269

29 Why is it preferable to disassemble parts before 36. False indications are caused by magnetic particles
magnetic particle inspection? being held to the part by which of the following
means?
a. disassembly makes all surface areas visible
b. interfaces will create leakage fields which may a. gravity
confuse the inspection b. mechanical
c. it is usually easier to handle the disassembled parts c. both a and b
d. all of the above d. none of the above
E.2-7 A.382

30. Subsurface discontinuity indications usually appear: 37. Which of the following is the most effective method
for the detection of extremely deep lying defects?
a. sharp and distinct
b. sharp and wide a. dry residual method using D C with surge
c. wide and fuzzy b. wet continuous method using half-wave rectified
d. high and loosely held current
B.32.2 c. wet residual method
d. dry continuous method using half-wave rectified
31. Which residual field is most difficult to demagnetize? current with prods
A.271
a. longitudinal
b. circular 38. A curve is sometimes drawn to show graphically the
c. vector relation of the magnetizing force to the strength of the
d. binodal magnetic field produced in a certain material. This
B.30.21 curve is known as the:

32. Which technique is the most sensitive? a. magnetic force curve

b. hysteresis curve
a. continuous c. saturation curve
b residual d. induction curve
c. interrupted C.2-14
d. counter-current
B.30.12

9
Magnetic Particle Testing Method, Level I

39. What method provides greater sensitivity, particularly 44. The point at which the magnetism in a material cannot
in locating subsurface discontinuities? be increased even though the magnetizing force
continues to increase is known as the:
a. continuous
b. residual a. salient pole
c. circular b. saturation point
d. longitudinal c. residual point
A.239 d. remnant point
A.120
40. When magnetizing a weld in two directions, i f the
current used in the first direction is 750 amps and the 45. Which type of current has a "skin effect?"
current in the second direction is 400 amps, which of
the following is true? a. AC
b. DC
a. the part should be checked to see i f c. half-wave rectified
demagnetization between operations is necessary d. full-wave rectified
b. no precautions should be taken before the second A.152
operation
c. this is not a valid technique 46. A high velocity flow of wet method bath over surfaces
d. there is no need to magnetize a weld in two of the specimen following removal of the magnetizing
directions current may cause:
A.307
a. a fine or weakly held indication to be washed away
41. When there is absolutely no pattern or distribution of b. no problems
magnetic particles, the possible cause is that: c. particles to be splashed into eyes
d. none of the above
a. the material is nonmagnetic A. 239
b. the amperage setting is too low
c. no current is being applied 47. Residual magnetic particle inspection may be used
d. any of the above could be true when:
B.30.12
a. parts are irregular in shape
42. What are the three causes of nonrelevant indications? b. parts are highly retentive
c. parts are highly stressed
a. lack of fusion, change of section thickness, d. evaluating continuous method indications
grinding cracks C.5-3
b. change of section thickness, very high amperage,
drilled hole near surface 48. Magnetic particle inspection is a reliable method for
c. very high amperage, drilled hole near surface, blow detecting all of the following indications except:
holes
d. drilled hole near surface, very high amperage, lack a. laps
of fusion - - - b. deep seated cavities
B.32.14 c. cracks
d. seams
43. Using the residual test method, a number of parts are B.32.3
magnetized and laid on a rack prior to application of
magnetic particles. Why is it important that they do 49. The wet fluorescent magnetic particle inspection
not rub or touch each other? method is the same as the standard wet magnetic
particle method with the exception of requirements
a. there is a possible loss of the magnetic field for:
b. it may cause magnetic writing
c. it may damage the part a. black light
d. it makes parts hard to handle b. higher current
B.32.17 c. a different machine
d. type of current
B.30.17

10
 Magnetic Particle Testing Method, Level I
50. A defect open to the surface produces an indication 57. An electric current through a copper wire:
that is:
a. creates a magnetic field around the wire
a. sharp and distinct b. creates magnetic poles in the wire
b. wide and indefinite c. magnetizes the wire
c. criss-cross d. does not create a magnetic field
d. high and fuzzy C.2-10
BJ2.1
58. Why should parts be cleaned after demagnetization?
51. Which of the following will produce circular
magnetism? a. to assure that the magnetic particles are removed
b. to prevent false indications
a. passing current through a coil c. to save the solids of the suspension
b. placing the test part in a solenoid d. to prevent cracking during heat treatment
c. passing current through prods C.5-14
d. yokes
B.30.5 59. In circular magnetization, the magnetizing force is
expressed in amperes. What term is used to express
52. When using the wet continuous method, the flow of the magnetizing force in longitudinal magnetization?
suspension from the hose should be shut off:
a. amperes
a. immediately after applying the current b. ampere-turns
b. immediately before applying the current c. consequent poles
c. while the current is flowing d. volts
d. 30 seconds before applying the current A.145
B30.12
60. A longitudinal surface crack in a circularly magnetized
53. The strongest magnetic field in a coil is at the: part will cause:

a. outside edge a. the magnetic field to die out

b. inside edge b. a decrease in permeability
c. center c. a magnetic leakage field
d. end d. a current to flow
A.146; C.2-27 C.2-7

54. To detect lengthwise defects on the inside diameter of 61. In a magnetic particle test, assuming that all of the
a hollow part, you should: following are in the same relative position in a small
part, which would be the hardest to detect?
a. pass current through it
b. magnetize it with a coil a. a surface crack
c. pass current through a central conductor b. a near surface crack
d. increase the amperage used c. a scratch
C.5-8 d. a seam
A.62
55. What equipment is used to determine whether a part
has been demagnetized? 62. I f wet magnetic particle suspension is not uniform,
then:
a. a magnet on the part
b. a field meter a. the strength of an indication may vary, and the
c. a survey meter interpretation of the indication may be erroneous
d. careful observation for clinging magnetic particles b. the magnetic flux would not be uniform
B.30.27 c. greater mobility would be required
d. the part cannot be magnetized
56. Which o f the following is most often used for dry A.261
magnetic particle inspection?
63. Which of the following w i l l best define surface cracks?
a. full cycle direct current
b. half-wave rectified alternating current a. half-wave rectified A C
c. high voltage, low amperage current b. DC
d. direct current from electrolytic cells c. AC
C.2-23 d. surge current
A.232

11
Magnetic Particle Testing Method, Level I

64. When a magnetic field is induced in a part with prods 70. When inspecting a tabular product for surface defects
spaced 152 mm (6 in.) apart, the field is: along its length, the best type of magnetic field to use
is a:
a. solenoidal
b. circular a. longitudinal field
c. longitudinal b. circular field
d. distorted trapezoidal c. swinging field
C.2-15 d. yoke magnetization
B.30.8-11
65. Applying the theory of the "Right Hand Rule," a
longitudinal surface defect in a round bar is detected 71. The area of maximum induced field strength using a
by "current passing in a direction parallel to the yoke is:
direction of expected defects" because:
a. at the North pole of the yoke
a. the current direction is in line with the defect b. at the South pole of the yoke
b. the magnetic field is at right angles to the defect c. the area directly between the poles
c. it makes no difference d. on the outside of pole pieces
d. the magnetic field is parallel to the defect B.30.10-11
B.30.4
72. The strength of the magnetic field induced in a part is
66. I f a current is passed through an electrical conductor, often referred to as:
what will surround the conductor?
a. current density
a. an eddy current field b. voltage
b. current c. flux density
c. a magnetic field d. retentivity
d. a residual field B.30.12
B.30.6
73. The major factor that determines the success of
67. With current flowing from + to - in a coil, a magnetic particle inspection is the:
longitudinal field is created. Which of the following
may be used to establish the direction of the magnetic a. field strength
field? b. voltage on magnetizing coil
c. current through the coil
a. the left hand rule d. time of magnetization
b. the right hand rule B.30.12
c. Ohm's law
d. there is no relevant law 74. The type of current that is best suited to detect surface
B.30.6 discontinuities is:

68. When magnetic material is placed into a coil, the a. DC

magnetic lines of flux concentrate themselves in the b. AC
material and: c. pulsating DC
d. half-wave
a. create a longitudinal magnetic field B.30.8
b. create a circular magnetic field
c. create a longitudinal-circular field 75. When preparing a bath, it is important to have the bath
d. have no effect strength at a proper level because too many particles
B.30.6 can result in:

69. Which form of magnetization is easiest to control in a. a lowering of the test amperage
most parts? b. the need to increase the magnetizing current
c. the masking of indications
a. longitudinal magnetization d. none of the above
b. permanent magnetism B30.16
c. circular magnetization
d. parallel magnetization
B.30.8

12
 Magnetic Particle Testing Method, Level I
76. One advantage of using fluorescent particles is: 82. Retentivity:

a. that less equipment is required a. represents the ability to induce magnetism in a

b. the high speed of inspection ferromagnetic body by an outside magnetizing
c. the cost force
d. that they are more readily attracted b. represents the ability of a material to resist the
B.30.18 establishment of magnetic flux within it
c. represents the ability of a material to retain a
77. When using a dry magnetic particle powder, the portion of the magnetic field set up in it after the
proper way to apply it to the part is to: magnetizing force has been removed
d. is not a term used in magnetic particle testing
a. forcibly apply it with air C.2-13
b. roll the material in the container of powder
c. apply it from the bottom of the part 83. Resistance to demagnetization is:
d. float the particles to the inspection surface as gently
as possible a. greater in hard materials than soft materials
B.30.18 b. greater in soft materials than hard materials
c. the same for both hard and soft materials
78. When using the wet particles in water suspension, d. nonexistent
wetting agents are added to: B.30.22

a. prevent freezing 84. Demagnetization:

b. prevent corrosion of inspection equipment
c. ensure the proper wetting of the part a. may be easy or difficult depending on the type of
d. decrease the amount of water needed material
B.30.18 b. is easy for materials having a high coercive force
c. is always most difficult in materials retaining a
79. When preparing an inspection bath, the amount of high residual field
magnetic particles per gallon of fluid is called its: d. all of the above
A.306
a. measuring scale
b. particle number 85. The strength of the wet suspension should be
c. strength or concentration maintained at a given level because:
d. usable limits
B. 30.16 a. a low level might give a weak indication
b. a high level may give a heavy background
80. Coercive force: c. both a and b
d. none of the above
a. describes the means by which the magnetic A.261
particles are suspended in the liquid when using the
wet method
b. describes the magnetizing force used with the
continuous method
c. represents the reverse magnetizing force necessary
to remove the residual magnetism in a material
d. is not a term used in magnetic particle testing
C . 2-13

81. Demagnetization:

a. may be accomplished by heating a material above

its Curie point
b. is always necessary
c. can be performed only with A C
d. can be performed only with DC
A.309

13
 Level I Answers
Magnetic Particle Testing Method

1. c 23. d 44. b 65. b

2. c 24. b 45. a 66. c
3. a 25. b 46. a 67. b
4. d 26. c 47. b 68. a
5. c 27. b 48. b 69. c
6. d 28. b 49. a 70. b
7. b 29. d 50. a 71. c
8. b 30. c 51. c 72. c
9. a 31. b 52. c 73. a
10. d 32. a 53. b 74. b
11. c 33. a 54. c 75. c
12. b 34. c 55. b 76. b
13. b 35. c 56. b 77. d
14. b 36. d 57. a 78. c
15. c 37. d 58. a 79. c
16. d 38. b 59. b 80. c
17. a 39. a 60. c 81. a
18. b 40. a 61. c 82. c
19. b 41. d 62. a 83. a
20. b 42. b 63. c 84. a
21. c 43. b 64. b 85. c
22. d

15
 Level II Questions
Magnetic Particle Testing Method

1. The interpretation of magnetic particle indications 6. Why are large soft contact areas such as lead or
may be aided by: copper braid used for surfaces or headstocks?

a. observing with a magnifying glass a. to increase the contact area and reduce the
b. observing the indications as they are formed possibility of burning the part
c. reproducing the indication residually b. because of their low melting points
d. all of the above c. because they help heat metal, thus facilitating
A.397 magnetic induction
d. to increase the contact area and flux density
2. Residual magnetism may be beneficial as an aid: B.30.9

a. in the deposition of weld metal 7. A rough forging that has received no further
b. in interpretation and evaluation of indications processing is magnetic particle tested. A n indication
c. in demagnetization is observed to run in every direction. It appears to
d. all of the above extend deeply into the part and run perpendicular to
A.397 the surface. It is very sharp. What is the probable
identity of the indication?
3. An interruption in the normal physical structure or
configuration of a part which produces an M T a. forging burst
indication is called: b. lap
c. flake
a. a discontinuity d. seam
b. a defect A.85
c. an indication
d. a deformation 8. A gear with case-hardened ground teeth and hub ends
A.126 is M T tested. Individual indications are detected on
five of the teeth and on the one end surface of the hub.
4. Comparing parts that have been circularly magnetized Although the indications are very sharp and distinct,
and those that have been longitudinally magnetized, they do not break over the edges of the part. What is
which retains the most objectionable residual field if the probable identity of the indication?
not demagnetized?
a. grinding cracks
a. longitudinal b. inclusions
b. circular c. porosity
c. vectored d. quench cracks
d. remnant A.90
B.30.21
9. I f an overall pattern (sometimes circular lines) appears
5. What type of magnetization uses the formula: on the test surfaces, how should the inspector
Ampere-turns = 45,000 ? reprocess the test piece?
F
LD
a. circular a. retest at a higher amperage
b. longitudinal b. demagnetize
c. parallel c. retest at lower amperage
d. vectored d. both a and b
B.30.13 A.208

17
Magnetic Particle Testing Method, Level II

10. A prime consideration when selecting a powder to be 16. Which of the following depicts the wave form of
used as a magnetic particle medium is to select a three-phase full-wave rectified AC?
powder that: A.121-123

a. provides a high contrast to the surface being tested a. +

b. provides a low contrast to the surface being tested
c. will adhere to the surface being tested
d. requires a high demagnetization current to remove it Mean D C
A.22 Volts
u , ,y y y v »'
u Time
11. When testing for fine shallow surface cracks, the
preferred M T method should be:
u 1 cycle
a. dry AC
b. dry DC
c. wet AC
d. wet DC
A.235 b. +

12. Which of the following is an advantage of the dry

method over the wet method?
<u
J-I
u Time
a. it is more sensitive to fine surface cracks
b. it is more capable of providing full surface coverage u
on irregularly shaped parts
c. it is easier to use for field inspection with portable
equipment
d. it is faster than the wet method when testing a
number of small parts
A.235
C. +
13. When testing a bar with an LVD ratio of four in a
ten-turn coil, the required current would be:
<u
u
a. 1 125 amperes u Time
b. 18 000 amperes
c. 45 000 amperes u
d. unknown; more information is needed
B.30.14

14. Internal splines and holes drilled parallel to or near test

surfaces will cause:
d.
a. broad, fuzzy indications directly aligned with the
part's internal contours
b. sharp, well-defined indications directly aligned with
C
the part's internal contours (U
h
c. no indications Time
d. both a and b u
A.384

15. Some limitations of coil magnetization techniques are:

a. that the coil must be of minimum diameter in

relation to part
b. that the effective field is generally limited on either
side of the coil
c. that small diameter parts should be placed close to
the coil
d. all of the above
A.145-146

18
 Magnetic Particle Testing Method, Level II
17. Which of the following casting defects is caused by 23. External poles, which are too strong to permit good
nonuniform cooling resulting in stresses which rupture inspection of a part, are more likely to result when
the surface of the metal? using:

a. shrink a. circular magnetization

b. hot tears b. longitudinal magnetization
c. porosity c. polarized magnetization
d. dross d. residual magnetization
A.88 A.382

18. The term used to refer to the total opposition to flow 24. A rough forging discontinuity has the following
of current represented by the combined effect of characteristics: it can occur on the surface or
resistance, inductance, and capacitance of a circuit is: internally; it is associated with processing at too low a
temperature; it is often caused by excessive working;
a. inductive reactance and it creates straight or irregular cavities varying in
b. impedance size. This discontinuity would be identified or
c. reluctance classified as:
d. decay
A.122 a. a burst
b. shrinkage
19. A coil shot is required to be performed after a head c. a pipe
shot using the wet continuous method. In order to d. a lamination
properly conduct the coil shot, it is necessary to: C.7-8

a. remove all residual wet magnetic particle fluid 25. Discontinuities in plate, sheet, or strip caused by pipe,
from the part using clean, dry absorbent rags inclusions, or blowholes in the original ingot which,
b. demagnetize the part between the head and First after rolling, are usually flat and parallel to the outside
coil shot surface are called:
c. place the part in the coil and continue the
inspection after evaluating the head shot indications a. seams
d. none of the above b. laminations
A.308 c. cracks
d. laps ;
20. When adding concentrate to any wet magnetic particle A.82;B.32.7
suspension liquid, it is common practice to:
26. Forging laps occur in what relation to the axial
a. add powder directly to the suspension liquid direction of a part?
b. make a small, slurry-like test mixture of the powder
c. do both of the above a. may occur anywhere on surface and may bear no
d. do neither of the above relation to axial direction of the part
A.263-264 b. always are found on thermal centerline
c. are found on surface of part at a 90° angle to long
21. A desirable property of magnetic particles used for the axis
inspection medium for either the dry or wet method is d. may occur anywhere in the part and always run in
that they: direction of working
A.86
a. are nontoxic
b. possess high permeability 27. The accumulation of particles at a site on the part
c. possess low retentivity surface, collected at and held to the site by the
d. have all of the above characteristics magnetic leakage field, is called:
A.209-228
a. a discontinuity
22. Which of the following can cause nonrelevant b. a defect
magnetic particle indications? c. an indication
d. magnetic writing
a. joints between dissimilar metals A.126
b. brazed joints
c. roughing tool-cuts on surface
d. all of the above
A.390-391

19
Magnetic Particle Testing Method, Level II

28. Where particles are attracted to a site on the surface of 34. Which of the following is a defect commonly
a part by a magnetic leakage field that is due to a associated with the welding process?
condition such as a crack, lap, or other condition not
acceptable to the applicable standards for the part, a. lack of penetration
then we have: b. flakes
c. seams
a. a discontinuity d. laminations
b. a defect A.440-442
c. a nonrelevant indication
d. all of the above 35. Which of these cracks may appear as an irregular,
A.126 checked, or scattered pattern of fine lines usually
caused by local overheating?
29. Half-wave rectified AC (HWDC) is used for detection
of: a. fatigue cracks
b. grinding cracks
a. surface defects only c. crater cracks
b. subsurface defects only d. H A Z cracks
c. surface and subsurface defects C.7-15,7-16
d. none of the above
A.154 36. Of the following discontinuity categories, which one
is considered most detrimental to the service life of an
30. Which of the following techniques for removing a thin item?
film of oil or grease prior to magnetic particle testing
is not acceptable: a. subsurface inclusions
b. subsurface porosity and voids
a. washing with a solvent c. cracks open to the surface
b. degreasing using a vapor degreasing method d. all of the above
c. dusting the surface with chalk or talc then wipe A.369-370
with dry clean cloth
d. brushing the surface with power wire brush 37. I f a copper conductor is placed through a ferrous
A.246 cylinder and a current is passed through the
conductor, then the magnetic field (flux density) in the
31. Which of the following is a commonly used technique cylinder will be:
for preserving M T powder patterns?
a. the same intensity and pattern as in the conductor
a. clear lacquer b. greater than in the conductor
b. transparent tape c. less than i n the conductor
c. photography d. the same regardless o f its proximity to the cylinder
d. all of the above wall
A.407-412 A.192

32. A l l of the following discontinuities are commonly 38. The length of a part being magnetized by passing an
found in rolled products except: electric current from one end to the other:

a. seams a. affects the permeability of the part

b. laminations b. changes the strength of the magnetic field
c. cold shuts c. does not affect the strength of the magnetic field
d. cracks d. causes the magnetic field to vary
A.80-83 A.186

33. A l l of the following discontinuities are commonly 39. I f 25 mm (1 in.} and 51 mm (2 in.) diameter bars are
found in forged products except: magnetized by passing the same current through them,
the magnetic fields would be:
a. laps
b. shrinkage a. the same for both
c. bursts b. stronger in the 51 mm (2 in.) diameter bar
d. flakes c. weaker in the 25 mm (1 in.) diameter bar
A.82-87 d. stronger in the 25 mm (1 in.) diameter bar
A.186

20
 Magnetic Particle Testing Method, Level II
40. I f a current of the same amperage is passed through 46. To alleviate the problem o f cold working indications
two conductors of the same dimensions, one of which in a part, the part should be:
is magnetic and one o f which is nonmagnetic, the
magnetic field surrounding the conductors will: a. demagnetized then retested
b. retested after stress relieving
a. be stronger for the magnetic conductor c. retested in the opposite direction
b. be stronger for the nonmagnetic conductor d. remagnetized at a higher amperage
c. vary with the permeability A.387-389
d. be the same for both conductors
A.147 47. The unit of measure of one line of flux per square
centimeter of area is one:
41. The most effective M T method for inspection of a
large casting is the use of: a. oersted
b. ohm
a. multidirectional magnetization c. gauss
b. a central conductor d. ampere
c. prod inspection in two directions A.115
d. direct magnetization
A.450 48. The ability of matter to attract other matter to itself is
a phenomenon associated with:
42. The most common failure mechanism associated with
sharp fillets, notches,,undercuts, and seams is: .a. field strength
b. magnetism
a. fatigue cracking c. coercive force
b. crystallization d. pole strength
c. shrinkage A.114
d. decarburization
A.103,481-489 49. Materials which are strongly attracted to a magnet are
called:
43. When it is believed that a defect has been removed by
chipping, grinding, or flame cutting, the next a. magnetized
operation is to: b. nonmagnetic
c. ferromagnetic
a. repair it d. polarized
b. measure it to see i f minimum thickness remains A.115
c. reexamine the area by magnetic particle testing
d. sign off the part 50. Materials which are weakly attracted magnetically are
A.400-401 called:

44. When the most complete demagnetization available is a. paramagnetic

desired and demagnetization is. to be.accomplished by b. diamagnetic
placing the part in a coil energized with AC of c. ferromagnetic
progressively decreasing amperage, the following d. nonmagnetic
orientation o f the long axis of the part is most A.119
desirable:
51. Materials which are repelled magnetically are called:
a. East-West
b. North-South a. paramagnetic
c. South-West b. diamagnetic
d. North-East c. ferromagnetic
A.314,324;B.30-25 d. nonmagnetic
A.119
45. Nonrelevant indications due to residual local poles
interfere with magnetic particle testing. For a 52. The end of a magnet at which the lines of flux are
successful examination, one should: thought of as entering the bar is:

a. use more amperage a. the north pole

b. demagnetize then remagnetize in the desired b. the south pole
direction c. both north and south poles
c. use lower amperage d. none of the above
d. magnetize in another direction A.133
A.387

21
Magnetic Particle Testing Method, Level II

53. A general rule to use for determining the detectability 59. A magnetic discontinuity, which is a break in the
of surface discontinuities by magnetic particle magnetic uniformity of a part, is related to a sudden
inspection is that: change in:

a. the depth and width have no bearing to each other a. inductance

b. the depth should be at least five times the width of b. resistivity
the opening of the defect at the surface c. capacitance
c: the depth should be at a one-to-one ratio to the d. permeability
width A.127
d. none of the above
A.371 60. In order to detect defects in different directions in a
material by magnetic particle inspection, it is best to
54. The general term used to refer to a break in the use:
metallic continuity of the part being tested is:
a. two or more fields in different directions'
a. discontinuity b. only one field
b. crack c. other probe locations
c. seam d. a high frequency field
d. lap A.127
A. 126
61. The parts are blanks cut from rolled iron bar stock.
55. The pattern of iron powder sprinkled on a paper They have been rough machined. Inspection by the
placed over a bar magnet is called a: continuous method, using a circular shot, reveals well-
defined but broken lines running parallel with the axis
a. field survey on some of the pieces and no indications on others.
b. magnetometer The broken lines range in length from 6 to 25 mm
c. magnetograph (0.25 to 1 in.). These indications are indicative of:
d. fluxmeter
A.119,169 a. shrinkage
b. machining tears
56. The lines of force that form a path around a crack in a c. surface checking
ring magnet are called: d. nonmetallic inclusions
A.77
a. magnetic lines
b. leakage flux 62. A large forging is repaired by welding. Magnetic
c. field strength particle inspection of the repair weld reveals an
d. longitudinal field irregular indication running parallel with the weld
B.30.3 passes. It is located in the center of the bead and
starts and ends by turning off slightly from the axial
57. Since the magnetic lines of force within a bar magnet direction. This indication is indicative of:
run the length of the bar, it is said to be:
a. inclusions
a. randomly magnetized b. crater cracks
b. permanently magnetized c. weld shrinkage cracks
c. circularly magnetized d. surface checking
d. longitudinally magnetized A.441
B.30.3
63. What wattage is most commonly used for mercury
58. Lines of flux are thought to leave a magnet at: vapor bulbs for portable fluorescent magnetic particle
inspection?
a. the north pole
b. the south pole a. 200 W
c. both north and south poles b. 50W
d. none of the above c. 100 W
A.133 d. 75 W
A.297

22
 Magnetic Particle Testing Method, Level II

64. An example of a nonrelevant indication classified as a 66. In magnetic particle inspection, it is best to:
magnetic irregularity rather than an actual
discontinuity could be caused by: a. reinspect all questionable discontinuities to assure
that no defective parts are accepted
a. a slag pocket b. make sure that parts meet specified acceptance
b. grinding cracks criteria
c. an abrupt change in the hardness of part c. make certain that parts are better than specified and
d. none of the above contain no discontinuities at all
A.73,391 d. reinspect questionable parts utilizing another NDT
method
65. The detection of deep-lying defects in heavy A.416
weldments (6 to 51 mm [0.25 to 2 in.] below surface)

a. very similar to the detection of surface cracks

b. not difficult i f the defect is attributable to fine
porosity
c. simple i f the defect's width can be approximated
d. very improbable
A.375

23
 Level n Answers
Magnetic Particle Testing Method

1. d 18. b 35. b 52. b

2. b 19. c 36. c 53. b
3. a 20. c 37. b 54. a
4. a 21. d 38. c 55. c
5. b 22. d 39. d 56. b
6. a 23. b 40. d 57. d
7. a 24. a 41. a 58. a
8. a 25. b 42. a 59. d
9. c 26. a 43. c 60. a
10. a 27. c 44. a 61. d
11. c 28. b 45. b 62. c
12. c 29. c 46. b 63. c
13. d 30. d 47. c 64. c
14. a 31. d 48. b 65. d
15. d 32. c 49. c 66. b
16. a 33. b 50. a
17. b 34. a 51. b

25
 Level HI Questions
Magnetic Particle Testing Method

1. The magnetic domains in a permanent magnet are 5. All of the following are valid reasons for the
aligned in: demagnetization of parts after magnetic particle
testing except that:
a. fixed positions with directions that cancel out
b. fixed positions, predominantly in one direction a. if the part is to be radiographed after magnetic
c. a random position and may become aligned to particle inspection, residual magnetism may
attract a magnetic material interfere with the electromagnetic radiation
d. the same direction as the metal's grain structure spectrum
A.119; F.45-46 b. residual magnetism may attract chips or small
particles in service, causing galling or mechanical
2. For which of the following would the wet fluorescent wear
technique be preferred over the dry technique? c. residual magnetism could interfere with the
operation or accuracy of instruments placed on or
a. when the parts are large and bulky near the part during service
b. when increased speed and sensitivity are desired d. residual magnetism can disturb the welding arc
c. when fluorescent lighting is used for inspection path on parts to be welded
d. when the parts being inspected are to be field A. 307
welded
A.345; F.30-31 6. Subjecting a part to a magnetic field that is constantly
reversing in polarity and gradually diminishing in
3. Gas, misruns, cold laps, and sand inclusions are strength accomplishes which of the following?
examples of defects resulting from which of the
following processes? a. the part becomes magnetized
b. the part becomes demagnetized
a. forging c. the strength of the retained magnetic field increases
b. grinding d. deep-lying defects are located
c. castings B.30.25
d. heat treatment
B.32.9,24.11, 8.19,24.15 7. The concentration of the solid content of a suspension
of magnetic particles is measured by:
4. All of the following are valid reasons for the
demagnetization of parts after magnetic particle a. weighing the suspension
testing except that: b. soaking the solids in benzol
c. permitting the solids to settle out of suspension
a. residual magnetism will affect the temperature d. measuring the pull on a magnet
gauges used in subsequent heat treatment B.30.17
b. residual magnetism may interfere with later
machining operations by attracting chips to the part 8. An important factor that must be considered when
c. residual magnetism may interfere with later selecting a method of magnetization is:
magnetic particle inspection of the part, particularly
if a lower magnetizing current or a reverse field a. the location of inspection station
will be used b. the alloy, shape, and condition of the part
d. residual magnetism may interfere with the removal c. the permeability of the part
of the magnetic particles during the cleaning d. both b and c
process following inspection B.30.8
F.67

27
Magnetic Particle Testing Method, Level HI

9. An important factor that must be considered when 16. In what way can a magnetic field be reduced?
selecting a method of magnetization is:
a. reduce the current
a. the type of magnetizing current b. move the part further away from the coil
b. the availability of handling equipment c. move the coil further away from the part
c. the material's Curie point d. all of the above
d. both a and b A.319-320
B.30.8,31.1
17. When the external magnetizing force has been
10. What happens to a magnetic material when it reaches removed, some of the magnetic domains remain
its Curie temperature? preferentially oriented. The additional force required
to return them to their original random orientation is
a. it becomes paramagnetic commonly referred to as:
b. it becomes diamagnetic
c. it becomes nonmagnetic a. DC electric current force
d. it becomes radioactive b. coercive force
A.309 c. residual field force
d. applied field force
11. A material that is repelled by magnetism is: A.117,178

a. diamagnetic 18. When a cylinder is being magnetized by a central

b. ferromagnetic conductor, the field is most intense:
c. paramagnetic
d. overtly magnetic a. at the outer surface of the cylinder
A.119 b. halfway through the thickness of the cylinder wall
c. at the ends of the cylinder
12. Materials weakly attracted by magnetic fields are: d. at the inside surface of the cylinder
A.192
a. paramagnetic
b. dual magnetic 19. When is the magnetic field strongest in an object
c. covertly magnetic being inspected by the magnetic particle method?
d. diamagnetic
A.119 a. just prior to current reversal when using AC current
b. just after the magnetizing current is shut off
13. Methods used to preserve powder patterns include: c. while the magnetizing current is applied
d. when the magnetic particle powder is applied
a. photographs A.117
b. transparent tape
c. transparent lacquer 20. Which of the demagnetization methods listed below is
d. all of the above most effective?
A.407
a. DC with reversing and step-down control
14. Magnetic particle inspection methods are recognized b. variable voltage AC with step-down control
as superior to liquid penetrant techniques when: c. half-wave rectified AC
d. full-wave rectified
a. corroded surfaces are inspected A.316-324
b. surfaces are anodized
c. parts are painted 21. When using the longitudinal magnetization method to
d. both a and c inspect a bar 152 mm (6 in.) long and 51 mm (2 in.) in
A.66-68 diameter with a 5-turn coil, which of the following
amperage values should be used?
15. What magnetic property does a paramagnetic material
possess? a. 1 200 amps
b. 3 000 amps
a. is highly magnetic c. 2 000 amp-turns
b. has no magnetic property at all d. 12 000 amp-turns
c. is slightly magnetic A.181,182
d. has a demonstrated lack of electron mobility
A.119

28
 Magnetic Particle Testing Method, Level III

22. To examine a part 127 mm (5 in.) long and 51 mm 26. When a magnetic field is induced in a part with prods
(2 in.) in diameter using a 5-turn coil and head-stock spaced 152 mm (6 in.) apart, the field is a:
magnetic particle machine, what amperage should be
used for longitudinal magnetization? a. solenoid field
b. longitudinal field
c. distorted circular field
a. 3 000 amps d. residual field
b. 3 600 amps
c. 4 500 amps 27. When circular magnetization is used and it is
d. 10 000 amp-turns important to detect subsurface defects, direct current
A.181,182 is used instead of alternating current because:

23. To examine a bar 38 cm (15 in.) long and 51 mm a. particle mobility is no longer a factor
(2 in.) in diameter using a 7-turn coil and head-stock b. DC saturates the magnetic particles better than AC
magnetic particle machine, what amperage will be c. the skin effect of AC reduces the maximum depth
used for circular magnetization? at which defects can be found
d. there is no logical reason to use DC instead of AC
a. 750 amps A.193,194; G.A275-74
b. 1 800 amps
c. 1 800 amp-turns 28. An inspection method in which a high magnetizing
d. 49 000 amp-turns force is applied to a part, and the force is then reduced
A.199, 208 to a lower continuous value which is maintained
during application of the inspection medium is called
24. If the same amperage is passed through a 25 mm the:
(1 in.) and a 51 mm (2 in.) diameter bar of the same
length, which of the following statements is most a. residual method
applicable relevant to the magnetic field at the surface b. multivector method
of the bars? c. continuous method
d. surge method
a. the strength of the magnetic field at the surfaces A.155,156; G.A275-74
will be the same for both bars
b. the strength of the magnetic field at the surface of 29. When deciding to inspect a part by the residual
the 25 mm (1 in.) bar will be approximately twice method, the strength of the residual field in the part
that of the 51 mm (2 in.) bar should be considered. Factors that affect this field
c. the strength of the magnetic field at the surface of include:
the 51 mm (2 in.) bar will be approximately four
times that of the 25 mm (1 in.) bar a. the strength of the magnetizing force
d. the strength of the magnetic field at the surface of b. the retentivity of the test part
the 25 mm (1 in.) bar will be one-half that of the c. the material alloy
51 mm (2 in.) bar d. all of the above
A.186-197; C.2-17 A.237, 238; C.A275-74

25. If the same amperage is passed through a 25 mm 30. Factors that must be considered when interpreting an
(1 in.) diameter bar and a 51 mm (2 in.) diameter bar indication are:
of the same length, which of the following statements
is most applicable relevant to the magnetic field at the a. the direction of the magnetic field
center of the bars? b. the strength of the leakage field at the indication
c. the orientation and shape of the indication
a. the strength of the magnetic field in the center of d. all of the above
the 25 mm (1 in.) bar will be one-half that of the A.61,62,131,137; G.A275-74
51 mm (2 in.) bar
b. the strength of the magnetic field at the center of 31. When thorough demagnetization is to be
the 51 mm (2 in.) bar will be one-half as that of the accomplished by placing the part in a coil energized
25 mm (1 in.) bar with AC of decreasing amperage, the following
c. the strength of the magnetic field in the center of orientation of the long axis of the part is most
both bars will be zero advantageous:
d. the strength of the magnetic field in the center of
the 25 mm (1 in.) bar will be approximately one- a. East-West
fourth the value for the 2-inch bar b. North-South
A.186-197 c. irrelevant (no difference)
d. South-West
A.324

29
Magnetic Particle Testing Method, Level III

32. A 7-turn coil at 1 000 amps is used to inspect a round 36. The curve shown in Figure 1 for material I I indicates
solid part 38 cm (15 in.) long and 64 mm (2-1/2 in.) in that it:
diameter. What is the L/D ratio?
a. has a high coercive force
a. 2.14 b. has a high retentivity
b. 6 c. has a high permeability
c. 7 500 amp-turns d. would make an excellent permanent magnet
d. 45 000 amp-turns A.116,117
A.181,182
37. Point B on the hysteresis curve for material I shown in
33. Which of the following, when used as the last Figure 1:
magnetizing method, will best render a part suitable
for relatively easy measurement of the external a. represents the mid-point of the rectified AC current
magnetic field using a field indicator? applied
b. is the material's magnetic saturation point
a. circular magnetization c. represents the point at which the residual magnetic
b. longitudinal magnetization value will remain when the magnetizing current is
c. either a or b removed
d. neither a nor b d. is the limit of coercive force
A.186,313 A.116,117

34. When using DC, an indication is detected. What is the 38. Which point on the hysteresis curve shown in Figure 1
next logical step to determine i f the indication results represents the residual field value?
from a surface or subsurface condition?
a. A
a. reinspect using the surge method b. D
b. demagnetize and apply powder c. C
c. reinspect at higher amperage d. E
d. reinspect using AC A.116,117
A.193,194
39. When withdrawing a part from the field around a coil
35. Which of the statements made below is most and without changing the direction of current, which
appropriate concerning materials I and I I represented of the following has the least effect on demagnetizing
by the hysteresis curves shown in Figure 1? the part?

a. material I is not a good subject for magnetic a. alternating current

particle inspection b. direct current
b. material I could be used for dry powder magnetic c. half-wave rectified alternating current
particles d. full-wave rectified current
c. material I I could be used for dry powder magnetic A.316-324
particles
d. material I I is paramagnetic
A.60,115-119,214-218

Figure 1 Material I B+ (Flux Density) Material I I

H- H+
(- Magnetizing (+ Magnetizing
Force) Force)

B- (Flux Density of Opposite

Polarity to B+)

30
 Magnetic Particle Testing Method, Level III

40. An important factor that should be considered when 46. Which of the following magnetization techniques
selecting a method of magnetization is: should be avoided when performing magnetic particle
testing?
a. field strength value
b. available equipment a. longitudinal magnetization
c. configuration of the part b. circular magnetization
d. all of the above c. vector magnetization
B30.7 d. parallel magnetization
A. 139; B.30.9
41. Which of the following discontinuities occur as a
result of the rolling process? 47. Banding is a common term used to describe:

a. field strength relative to the poles of a permanent

a. blowholes and pipe magnet
b. laminations b. a method of mounting cylindrical objects on a
c. fissures bench system
d. all of the above c. the appearance of powder patterns at laminations
A.76-89 found in heavy plate material
d. powder patterns created by using excess amperage
42. Which of the following discontinuities occur as a B.30.14
result of the forging process?
48. When attempting to demagnetize a part containing a
a. pipe circular residual field,:
b. laps
c. laminations a. consideration of the material's hysteresis is most
d. all of the above important
A.76-89 b. establish a longitudinal field and then proceed with
demagnetization
43. If an indication is formed when using the residual c. use half-wave current with a head shot setup and
method as well as the continuous method, it is most step-down magnetization to assure complete
likely: removal of the residual field
d. use a swinging cyclic field
a. very deep and tight B.30.21
b. very shallow and open to the surface
c. a relevant indication 49. The input current requirements for MT equipment
d. a nonrelevant indication depend in part upon the:
A.239-240,370-371,397
a. duty cycle required
44. Plated parts can be reliably tested using the magnetic b. shop electrical service
particle method if the plating is less than: c. prod spacing required on average production part
types
a. 0.1 mm (0.004 in.) thick d. size of current cables
b. 0.2 mm (0.008 in.) thick B.31.4
c. 0.8 mm (0.03 in.) thick
d. 1 mm (0.04 in.) thick 50. Small parts requiring demagnetization should be:
B.30.1
a. loaded in baskets and passed through an AC coil
45. The magnetic lines of flux or flux in a permanent b. demagnetized after assembly to assure complete
magnet: demagnetization of the entire assembly
c. processed through a demagnetization cycle one at a
a. flow from the north pole through the magnet to the time
south pole d. loaded in a steel basket for better field distribution
b. change direction 60 times a second with the B.30.28
magnetizing current
c. enter the south pole and leave the north pole 51. The best shape for magnetic particles used in the dry
d. in all cases produce a longitudinal field powder method is:
B.30.2
a. flat
b. globular
c. long and slender
d. a mixture of b and c
F.55

31
Magnetic Particle Testing Method, Level III

52. The best method for testing ball bearings is:

a. along one axis using a coil

b. two shots using a coil at the X and Y axis
c. two head shots along the X and Y axis
d. induced current shots along X, Y, and Z axis
rotating 360 degrees during each shot
F.54

32
 Level HI Answers
Magnetic Particle Testing Method

i. b 14. d 27. c 40. d

2. b 15. c 28. d 41. b
3. c 16. d 29. d 42. b
4. a 17. b 30. d 43. c
5. a 18. d 31. a 44. a
6. b 19. c 32. b 45. c
7. c 20. a 33. b 46. d
8. d 21. b 34. d 47. d
9. d 22. b 35. c 48. b
10. c 23. b 36. c 49. a
11. a 24. b 37. b 50. c
12. a 25. c 38. c 51. d
13. d 26. c 39. b 52. d

33
 Sample Specification
Wet Magnetic Particle Testing Method

Scope 2.6 An ammeter shall be used on the magnetic

1.1 Magnetic particle testing is a nondestructive
particle inspection unit to insure that the
testing method used to detect surface and
proper amperage is being applied.
near surface discontinuities in ferromagnetic 27
In the absence of requirements to the
materials.
contrary, magnetizing currents shall be
determined by experiment, and recorded on
General a magnetic particle technique sheet.
2.1 The Magnetic Particle Test Method consists 2.7.1 The behavior of the magnetic
of magnetizing the area to be inspected, and particles on the surface of a test part
then applying magnetic particles to the while it is being magnetized is an
surface of the test area. Magnetic field excellent indication of the amount of
leakages caused by cracks and other magnetizing current being used, or
discontinuities will attract the magnetic the strength of the magnetic field.
particles, and the resulting pattern will be Complete lack of particle activity
characteristic of the type of discontinuity indicates that the field is too weak;
present. Sensitivity of the magnetic particle excessive particle accumulation with
test method is greatest at the surface and lack of particle mobility indicates
diminishes rapidly with increasing depth. that the field is too strong. Some
2.2 Drawings and purchase orders should slight indication of pattern around
specify the extent of magnetic particle ends, edges, and protuberances
inspection required for each item and the indicates sufficient field strength. A
acceptance standards to be met. special carbon steel/copperplate field
2.3 Documents referenced, as modified herein, indicator may be used to determine
shall be considered part of this standard comparative field strength. I f clearly
procedure. defined lines of particles appear on
2.4 All persons performing magnetic particle the copper side of the field indicator,
inspection shall have received training and the magnetic field is of sufficient
be certified in accordance with a written strength.
program developed per recommended 2.7.2 When particle activity indicates
guidelines of SNT-TC-1A (1980 Edition). either insufficient or excessive field
2.4.1 A Level I certified technician shall strength, even though all test
perform work under the direction of a parameters have been met, a change
Level n , except that final in current value shall be recorded on
interpretation shall be performed by a the magnetic particle technique sheet.
Level I I or Level HI. All reports and 2.8 Continuous exposure to the wet particle bath
technique sheets shall be prepared by can cause subcutaneous fats and oils of the
a Level I I , and the technique sheet skin to be dissolved. The resultant drying
approved by a Level HI. and cracking encourages secondary
2.5 A minimum of two separate examinations infection. Persons suffering rashes and skin
shall be conducted on each area inspected, irritation from exposure to the wet particle
with the lines of flux of one examination bath should report this condition to the
approximately perpendicular to the lines of supervisor.
flux of the other. A different method of 2.8.1 Good working habits which prevent
magnetization may be used for the second the unnecessary wetting of hands and
examination (i.e., longitudinal magnetic clothing should be developed.
field technique and circular magnetic field 2.8.2 The use of a hand protective
technique). preparation is recommended when
35
 Wet Magnetic Particle Testing Method, Sample Specification

working for extended periods with the condition is not suitable for
wet particle bath. inspection, the part shall be
2.8.3 A polyvinyl apron shall be worn. returned to production
2.8.4 After working with the wet particle untested, or NDT will
bath, hands and arms should be condition the surface,
washed with warm water and mild whichever is mutually
soap. agreeable.
2.9 Care and maintenance of magnetic particle 5.L2 Small openings and holes which lead
test equipment shall be performed in to areas from which it would be
accordance with instructions provided in difficult to remove magnetic
procedure M-2. substances shall be plugged before
the part is inspected.
3.0 Referenced Documents Unless otherwise specified in the drawing,
3.1 ASME Section V Nondestructive final magnetic particle inspection shall be
examination ASTM E-125 Reference performed on any part in the finished surface
photographs for magnetic particle inspection condition, and final heat treated condition.
ASTM E-138 Wet magnetic particle
inspection ASTM E-269 Terms relating to 6.0 Equipment
magnetic inspection 6.1 The wet magnetic particle inspection unit is
PROC. M - l Calibration of magnetic particle a horizontal stationary unit manufactured by
test method equipment Company, Model No.
PROC. M-2 Care and maintenance of , 2000 DC amps, equipped
equipment with head-tail stocks and a 5-turn coil.
PROC. M-4 Mixing and checking magnetic 6.2 The demagnetizing unit is a 60-cycle, single
particle bath phase AC, coil-type with timer,
3.1.1 All documents referenced in this manufactured by Company,
section shall be maintained to the Model No
latest revision, and work requests, 6.3 The field indicator is a dial readout, pocket
technique sheets, and test reports will size magnetometer used to measure
cite the proper revision for the work comparative magnetic field strength.
performed.
7.0 Examination Medium
4.0 Identification 7.1 The examination medium shall consist of
4.1 Identification methods shall be established finely divided ferromagnetic particles which
which will enable the test report, the have high permeability and low retentivity
1
component, and the area tested to be characteristics. They shall be of suitable
identified with respect to each other at any size and shape to readily produce magnetic
time. particle indications.
4.2 A suitable method shall be used to assure 7.1.1 Fluorescent magnetic particles shall
correct part identification. Where be used.
identification is removed or obliterated, an
identity tag shall be used until the 8.0 Methods of Examination
identification can be reapplied. If positive 8.1 The methods of "wet" magnetic particle
identification cannot be determined, then a examination used shall consist of the
nonconformance report shall be issued. longitudinal magnetic field technique and
the circular magnetic field technique.
5.0 Surface Condition 8.2 Using the longitudinal magnetic field
5.1 With most magnetic particle test methods, technique, magnetization is accomplished by
2
satisfactory results may generally be obtained passing current through a multi-turn coil.
when the surface to be inspected is in the as- This technique produces a longitudinal
welded, as-rolled, as-cast, or as-forged magnetic field parallel to the axis of the coil.
condition. However, in some cases, surface 8.2.1 Direct or rectified AC shall be used.
conditioning may be required to prevent the The magnetizing current is
masking of defects. determined by dividing 45 000 by the
5.1.1 Surfaces to be inspected shall be length-over-diameter ratio of the part
clean and free from oil, grease, sand, to be inspected, and then dividing
loose rust or scale, which may
interfere with satisfactory inspection.
1
5.1.1.1 Surfaces to be inspected shall Suspended in base oil "C" as described in Proa No. MT-4.
2

be cleaned prior to submission The part to be inspected is placed within the coil assembly or flexible
leads are coiled through large complex parts.
to NDT. When the surface

36
 Wet Magnetic Particle Testing Method, Sample Specification

this value by the number of turns in the order of listing for each shot on
the coil. the technique sketch.
45 000 9.4 Examinations shall be performed with
Ampere-turns = sufficient overlap to assure 100% coverage
L/D
of the area or part under inspection at the
established field strength.
Ampere-turns
Amperes = 9.4.1 When using the longitudinal
No. coil turns magnetic field technique, no length
8.3 Using the circular magnetic field technique, greater than nine inches of test part
magnetization is accomplished by passing extending from each side of the coil
current through the part to be inspected. This shall be inspected with each "shot."
technique produces a circular magnetic field Therefore, if a part is longer than
perpendicular to the current flow throughout 46 cm (18 in.), two or more "shots"
the part. along its length will be necessary.
8.3.1 Direct or rectified AC shall be used. 9.4.2 When using the circular magnetic
The magnetizing current is field technique, no length greater
determined by multiplying the part than 31 cm (12 in.) shall be viewed
diameter by an amperage-per-inch during any one "shot." Therefore, if a
diameter value. part is longer than 31 cm (12 in.),
8.3.2 The magnetizing current shall be as two or more shots will be necessary.
shown in the table. 9.5 Repaired areas on the test part shall be
reinspected in accordance with the original
Part Diameter test procedures.
0 - 2 5 c m ( 0 - 10 in.)
Over 25 cm (10 in.) 10.0 Evaluation of Indications
Amps per Inch of 10.1 Evaluation of indications shall be to
Part Diameter acceptance standards shown on drawings or
800 - 1 000 Amps purchase orders.
500 - 800 Amps 10.2 The inspection area shall be provided with
adequate lighting to facilitate examination of
Examination the test part for indications.
9.1 A preinspection examination shall be made 10.2.1 The examination shall be conducted
of the test part to determine surface in a darkened area under "black
condition, equipment requirements, and also light" illumination.
that all test parameters can be met. 10.2.2 The black light shall emit near-
9.1.1 When any material or part cannot be ultraviolet radiation in the 330¬
fully inspected as required by 390 nm (3 300-3 900 A) wavelength
drawing, due to design, test facility range.
restrictions, or other reasons, a 10.2.3 The black light shall have, as a
nonconformance report shall be minimum, an intensity of
2
issued. The nonconformance report 800 uW/cm at the inspection
shall state the reasons why the part surface, as measured by XYZ
cannot be fully inspected, and Company light meter (or equal), with
recommended appropriate action. a 10X multiplier disk.
The magnetic particle test report shall 10.3 The black light shall have a minimum warm-
state the test limitations. up time of 5 minutes prior to its use in
9.2 Unless otherwise specified by drawing, examination.
magnetic particle inspection shall be 10.4 Relevant indications are indications that
performed by the continuous method. This is result from discontinuities within the test
accomplished by keeping the magnetizing part.
current on while the examination medium is 10.5 Nonrelevant indications are indications that
being applied (by flowing it over the part). result from excessive magnetizing current,
9.3 The sequence of "shots" shall be determined structural design, or permeability variances
by ascending order of current. That is, the within the test part. They have no bearing on
"shot" requiring the lowest amperage shall the suitability of the test part for service.
be first, and the "shot" requiring the greatest 10.5.1 Any indication believed to be
amperage value shall be the product of the nonrelevant shall be regarded as
amperage multiplied by the number of turns relevant and shall be reexamined to
in the coil. determine whether an actual defect
9.3.1 When exceptions to 9.3 are exists. Surface conditioning may
necessary, this shall be indicated by precede the reexamination.

37
Wet Magnetic Particle Test Method, Sample Specification

10.5.2 I f test part quality cannot be assured through the coil close to one wall or
by magnetic particle inspection upon corner and not through the center of
reexamination, then other methods of the coil.
nondestructive testing may be used. 11.5 For parts too large to pass through the
Decisions concerning nonrelevancy demagnetizer coil, satisfactory
requires Level III approval. demagnetization can often be accomplished
10.6 Linear indications shall be considered as by bringing the part as close as possible to
those having a length more than three times the coil, turning it to bring all sides into the
the width. field, and then withdrawing it slowly before
10.7 Rounded indications shall be considered as the current turns off.
those having a length less than three times 11.6 Striking the part with a mallet while the part
the width. is in the magnetic field and being withdrawn
10.8 Aligned indications shall be considered as a will often improve results on parts difficult
group of three or more indications which to demagnetize.
touch an imaginary straight line connecting 11.7 Demagnetization may often be improved by
any two of the group. the "Transient Current Method." The part to
be demagnetized is placed in the
11.0 Demagnetization demagnetizer coil, the current turned on and
off several times, and then while the current
11.1 Demagnetization shall be required following is on, the part is withdrawn from the
final magnetic particle inspection, where magnetic field as described in 11.4.
residual magnetism will interfere with 11.8 The demagnetizer should be positioned so
subsequent processes or usage. that an imaginary line drawn through the
11.2 Only the demagnetizing unit shall be used center of the coil runs in the east-west
for demagnetization. Do not use the coil on direction.
the wet magnetic particle inspection unit for 11.9 A field indicator shall be used to determine
demagnetization. the amount of residual magnetism remaining
11.3 Energize the demagnetizing coil by in the part.
operating the timer switch. This timer limits 11.10 Cleaning should occur prior to complete
the operating periods from a few seconds to drying of residual bath.
one minute, as selected. The red light will 11.10.11 The test part shall be cleaned by
glow and a strong pull will be felt on a piece wiping it with a cloth soaked in
of ferromagnetic material held near the coil. base oil "C." After the test part has
11.3.1 CAUTION: Due to high currents, dried, a light coat of mineral oil
operation should be intermittent. That shall be applied as a rust
is, each operating period should be preventative.
followed by an equal period to rest,
to allow for cooling. The maximum 12.0 Records
"on" period should seldom be longer
than 30 seconds. 12.1 A magnetic particle inspection technique
11.4 To demagnetize a part, turn on the current sheet shall be submitted with the final
and pass the part completely through the inspection records.
demagnetizer. The part shall be placed inside 12.2 A magnetic particle inspection report shall
the coil and then slowly withdrawn from the be submitted with the final inspection
magnetic field in a straight line, a distance of records.
at least 1.2 m (4 ft). 12.3 A maintenance/calibration record shall be
11.4.1 CAUTION: Do not allow the current kept (current) on the wet magnetic particle
to turn off while the part is in the inspection unit.
magnetic field, as incomplete 12.4 A wet magnetic particle inspection use
demagnetization may result. Repeat record shall be kept (current) on the wet
the demagnetization process if this magnetic particle test unit.
occurs. 12.5 All records of inspection, original, repair,
11.4.2 Small parts, much smaller in cross- and final, shall be retained for a minimum
section than the demagnetizer coil period of seven (7) years.
cross-section, should be passed

38
 Sample Specification Questions
Wet Magnetic Particle Testing Method

Using the sample specification located on pages 35 6. Inspected parts requiring repair must be:
through 38, answer the remaining questions. (References
listed pertain to paragraphs in the sample specification.) a. reinspected using a sampling plan
b. reinspected following repair
c. inspected with another NDT method
1. The magnetic particles suspended in the bath shall d. made to follow the original fabrication plan after
have: defect removal is checked and reworked
Para. 9.5
a. high red iron oxide content
b. low retentivity and low permeability 7. Black light intensity requirements specify:
c. low retentivity and high permeability
d. high permeability and low coerciveness a. a minimum of five minute warm-up
Para. 7.1 b. that a darkened room be used
2
c. a minimum of 800 uW/cm at the inspection
2. The ammeter is used to: surface
d. all of the above
a. determine the polarity of magnetization Para. 10.2
b. determine the amperage being used
c. assure that the part has been demagnetized 8. The ammeter shall be checked against a calibration
d. measure amp-turns shunt meter:
Para. 2.6
a. prior to each use
3. The field meter is used to determine: b. at the start of the shift
c. per Procedure M-l
a. magnetic polarity and amperage d. per Procedure M-4
b. the comparative strength of field and if Para. 3.1
demagnetization is effective
c. retentivity and magnetic permeability 9. Parts will be demagnetized by:
d. both a and b
Para. 6.3; 11.9 a. banging with a hammer
b. placing within a demagnetizing coil for 30 seconds
4. Demagnetization is required: c. holding within the demagnetizing coil while the
stepdown transformer moves through its
a. as soon as the part has been cleaned descending order of amperage shots
b. prior to magnetic particle inspection d. setting the demagnetizing current at an amperage
c. for all parts which are inspected higher than the original magnetizing current and
d. where residual magnetism will interfere with slowly passing the part through the coil
subsequent processes or usage Para. 11.4
Para. 11.1
10. When magnetizing a part, 31 cm (12 in.) long by
5 Part position is varied in the coil when the part is: 64 mm (2.5 in.) diameter, by placing it within the
head stocks and passing an electric current through it,
a. over 46 cm (18 in.) in length the ammeter should be set at:
b. over 31 cm (12 in.) in length
c square a. 900 amps
d round b. 1 750 amps
Para. 9.4.1 c. 1 875 amps
d. 2 200 amps
Para. 8.3.2

39
Wet Magnetic Particle Testing Method, Sample Specification Questions

11. For demagnetization, the maximum "on" period 18. I f the magnetizing current is not specified, the
should seldom be more than: magnetizing current should be determined by:

a. 5 seconds a. experimentation and then recorded on the technique

b. 30 seconds sheet
c. 120 seconds b. the cognizant engineer
d. 240 seconds c. the client
Para. 11.3.1 d. the technician's experience
Para. 2.7
12. I f a part cannot be fully inspected as required by the
drawing: 19. Nonrelevant indications:

a. a drawing revision must be issued a. have no bearing on the suitability of the part for
b. the part must be scrapped service
c. a nonconformance report must be issued b. shall be reexamined to determine whether an actual
d. the part must be marked with red paint pending defect exists
disposition c. must be completely removed
Para. 9.1.1 d. both a and b must be considered
Para. 10.5,10.5.1
13. The sequence of "shots" shall be determined by:
20. The intensity of the black light shall be measured
a. accessibility of areas using a:
b. descending order of current
c. ascending order of current a. light meter with a 10X multiplier disc
d. this is not an important consideration b. light meter with an amber field filter
Para. 9.3 c. light meter set at 343 nm (3 425 A)
d. light meter with an M2 rating
14. Unless otherwise specified, magnetic particle Para. 20.2.3
inspection shall be performed by:
21. A part being demagnetized should be slowly removed
a. the residual method from the magnetic field in a straight line for a distance
b. the continuous method of:
c. both a and b
d. none of the above a. 31 cm ( l f t )
Para. 9.2 b. 61 cm (2 ft)
c. 122 cm (4 ft)
15. Unless otherwise specified, the final magnetic particle d. the distance is not important
inspection shall be performed on parts: Para. 11.4

a. prior to final machining but after final heat 22. Records of inspection shall be maintained:
treatment
b. after final machining but before final heat treatment a. for the life of the part
c. after final machining and heat treatment b. for 40 years
d. any time prior to final heat treatment c. for 7 years
Para. 5.2 d. until the client accepts the part
Para. 12.5
16. The extent of magnetic particle inspection should be
specified: 23. A field indicator shall be used to determine the:

a. in the procedure a. amount of residual magnetism remaining in a part

b. in the drawings and in the purchase order b. orientation of the magnetic field
c. in the acceptance standard c. overall vector component of the magnetic field
d. by normal shop practice d. outer limit of magnetic field
Para. 2.2 Para. 11.9

17. The technique sheet shall be approved by: 24. The part shall be post-cleaned:

a. a Level I I a. by rinsing it with acetone

b. a Level I I I b. by wiping it with a dry cloth
c. no one; techniques used do not need to be approved c. by wiping it with a cloth soaked in base oil "C"
d. a Level I I and the client d. this is not a provision of the procedure
Para. 2.7 Para. 11.10.1

40
 Wet Magnetic Particle Testing Method, Sample Specification Questions

Demagnetization may often be improved by the use

of:

a. the DC surge technique

b. insulated paramagnetic rails
c. the "Transient Current Method"
d. a booster-type demagnetizer
Para. 11.7

41
r Sample Specification Answers
Wet Magnetic Particle Testing Method

1. c 8. G 14. b 20. a
2. b 9. d 15. c 21. c
3. b 10. d 16. b 22. c
4. d 11. b 17. b 23. a
5. a 12. c 18. a 24. c
6. b 13. c 19. d 25. c
7. c

43