Objective 06: Magnetic Particle Inspection

Question 1

What is Magnetic Particle Inspection?

Answer 1

Detection of cracks present at the surface of a component made from ferromagnetic material

Question 2

What kind of ferromagnetic material is Magnetic Particle Inspection used on?

Answer 2

1. Cast Irons
2. Carbon Steel
3. All kinds of Steel Alloys (with the exception of austenitic steels)

Question 3

What is Magnetic Particle Inspection based on?

Answer 3

The faces of a crack tend to form north and south poles if a magnetic flux is established in the component

Question 4

How is flux induced in ferromagnetic material for Magnetic Particle Inspection?

Answer 4

1. Permanent magnet or electromagnet causing current flow through the component
2. Wrapping coils around it and then passing a current through a coil

Question 5

How is either dry iron powder or iron powder in a liquid suspension used to reveal cracks for Magnetic Particle Inspection?

Answer 5

If the system is so arranged that the crack interrupts the flux lines, the particles of iron are attracted to the poles formed at the crack, which is delineated as a black line

Question 6

What type of transformer is used to supply the necessary flux when searching for surface defects?

Answer 6

AC Transformers

Question 7

What type of transformer is used to supply the necessary flux below the surface of the material when searching for subsurface defects to a depth of approximately 4 mm?

Answer 7

DC Transformers

Question 8

What are 4 different areas of Magnetic Particle Procedures?

Answer 8

1. Magnetic Particles
2. Surface Conditioning
3. Examination Techniques
4. Acceptance Criteria

Question 9

What are the types of Magnetic Particles that may be used in Magnetic Particle Testing?

Answer 9

1. Dry
2. Wet
3. Fluorescent

Question 10

Does the procedure used differ based on Magnetic Particle type in Magnetic Particle Testing?

Answer 10

Yes

Question 11

What kind of light is used with Fluorescent Particles in Magnetic Particle Testing?

Answer 11

Ultraviolet Light (black light) in a darkened area with an intensity of 1000 microW/cm2 at the surface of the part

Question 12

How is it ensured that the intensity of lighting used for Magnetic Particle Testing is correct?

Answer 12

A black light meter is used at least once every 8 hours and whenever the work station is changed. Records of the intensity measurements and frequency for subsequent audit verifications are maintained.

Question 13

What is the preparation that directly preceeds Magnetic Particle Testing with black light?

Answer 13

There is a warm-up period of 5 minutes. The inspector must be in the darkened area for 5 minutes before starting the examination to enable the inspector’s eyes to adapt to dark viewing. Photosensitive eyeglass lenses are not permitted.

Question 14

When is Surface Conditioning required for Magnetic Particle Testing?

Answer 14

If the surface irregularities can mask indications

Question 15

How is Surface Conditioning performed before Magnetic Particle Testing occurs?

Answer 15

The surface and adjacent areas within 25 mm are cleaned with any suitable means to ensure removal of extraneous materials that can interfere with the examination.

Question 16

How many examinations are perfomed on each test area for Magnetic Particle Testing?

Answer 16

At least 2 seperate examinations

Question 17

How does the second examination compare to the first in Magnetic Particle Testing?

Answer 17

The lines of flux used are perpendicular

Question 18

To be effective, what is important to ensure when conducting multiple examinations in Magnetic Particle Testing?

Answer 18

They are conducted with sufficient overlap to ensure 100% coverage

Question 19

What are 5 magnetization techniques that can be used on ferromagnetic materials to detect cracks and other discontinuities on or near the surface of the material?

Answer 19

1. Prod
2. Longitudinal
3. Circular (direct contact and central conductor methods)
4. Yoke
5. Multidirectional

Question 20

How does the Prod Technique work for Magnetic Particle Testing?

Answer 20

It uses portable prod contacts pressed against the test surface in the area to be examined

Question 21

What caution should be taken with the Prod Technique for Magnetic Particle Testing?

Answer 21

Arcing must be prevented because the heat produced can create local hard spots that can cause service problems

Question 22

How does the Longitudinal Magnetization Technique work for Magnetic Particle Testing?

Answer 22

Coils are wrapped around the surface being examined and the current passing though them produces a longitudinal magnetic field parallel to the axis of the coil

Question 23

What determines the required field strength of the coils used in the Longitudinal Magnetization Technique for Magnetic Particle Testing?

Answer 23

The length to diameter ratio of the part being examined

Question 24

What kind of cracks are revealed by the Logitudinal Magnetization Technique for Magnetic Particle Testing?

Answer 24

Transverse cracks

Question 25

How does Circular Magnetization Direct Contact Method work for Magnetic Particle Testing?

Answer 25

1. Contact electrodes introduce the current into the test piece which behaves like a current carrying conductor 2. A circular shaped magnetic field is established perpendicular to the test piece 3. Stray fields develop across defects lying in the same direction as the connecting line between the current contacts, thus revealing cracks

Question 26

What types of parts is the Circular Magnetization Direct Contact Method used to test for Magnetic Particle Testing?

Answer 26

Small parts with no openings through the interior

Question 27

What kind of cracks are revealed by the Circular Magnetization Direct Contact Method for Magnetic Particle Testing?

Answer 27

Longitudinal Cracks

Question 28

How does Circular Magnetization Central Conductor Method work for Magnetic Particle Testing?

Answer 28

1. With tube or ring-shaped parts, magnetization is achieved without contact using a current carrying conductor 2. The test piece is surrouded by the circular magnetic field

Question 29

What kinds of cracks are revealed by Circular Magnetization Central Conductor Method?

Answer 29

1. Longitudinal Cracks | 2. Star-shaped Cracks running from the centre to the outside of the plane surfaces

Question 30

How does Electromagnetic Yoke Technique work for Magnetic Particle Testing?

Answer 30

1. A magnetic field from a coil system is generated over the pole of a soft iron core and then transmitted into the test object 2. The iron core and the workpiece form a closed magnetic circuit 3. The magnetic field lines flow in the test piece in a direct connection line between the poles

Question 31

What kind of crack is revealed by Electromagnetic Yoke Technique for Magnetic Particle Testing?

Answer 31

Transverse Cracks

Question 32

How does Multidirectional Magnetization Technique work for Magnetic Particle Testing?

Answer 32

Using high amperage power packs operating up to 3 circuits, the circuits energize one at a time in rapid succession producing an overall magnetization of the part in multiple directions

Question 33

How many processing steps does Multidirectional Magnetization Techniques require for Magnetic Particle Testing?

Answer 33

1

Question 34

What is a typical Test Procedure for Magnetic Particle Testing?

Answer 34

1. Observe guidelines as per Code of Constrution 2. Preparation of the test part, e.g. cleaning, degreasing, descaling, rust removal 3. Visual examination of readily apparent cracks or other surface conditions 4. Check inspection conditions (ambient light, UV light intensity) 5. Measure the applied magnetic field, in turn adjusting for the appropriate magnetic field intensity 6. Clamp the material to be inspected or apply hand yoke magnet 7. Switch on the magnetizing field 8. Spray the part with the test medium containing the magnetic particles 9. Switch ff the magnetizing field 10. Visually evaluate the surface for defect indications 11. Repeat #5 to #10 at 90º to original test orientation 12. Demagnetize the part (if required) 13. Document the indications (positions, size, number, orientation) 14. Classify the inspected part (acceptable, reject, possible rework)