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MT Level 3 2011 December

The document discusses various aspects of magnetic particle inspection (MPI), including techniques for inducing circular and longitudinal magnetism, the use of alarms and gates in stationary equipment, and the identification of defects in welds and base metals. It covers the differences between special and general stationary equipment, the importance of demagnetization, and the effects of AC and DC currents on inspection processes. Additionally, it addresses challenges such as defect orientation, limitations of automatic MPI, and the significance of particle concentration and size in effective inspections.

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Anu Anoop
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408 views4 pages

MT Level 3 2011 December

The document discusses various aspects of magnetic particle inspection (MPI), including techniques for inducing circular and longitudinal magnetism, the use of alarms and gates in stationary equipment, and the identification of defects in welds and base metals. It covers the differences between special and general stationary equipment, the importance of demagnetization, and the effects of AC and DC currents on inspection processes. Additionally, it addresses challenges such as defect orientation, limitations of automatic MPI, and the significance of particle concentration and size in effective inspections.

Uploaded by

Anu Anoop
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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1.

To induce circular magnetism part is placed adjacent to the conductor:

Central conductor

Parallel magnetism

Circular magnetism

2. Alarms and gates are used in stationary equipment. This is for

Special purpose

General purpose

3. Difference between special stationary equipment and general stationary equipment

a. types of part

current

voltatge

4. Base metal defects found adjacent to the weld:

HAZ cracking

5. Processing discontinuities

Seams

Rolled bar stocks

Seams

16” diameter cross sectional area

Retentivity definition

Longitudinal field definition – Magnetism which creates minimum with two poles

Head shot magnetism, circular magnetism is generated what magnetic strength is generated in the
inside surface – zero

Circumferential defects to find how to magnetize

Head shot technique with 90 deg rotation

Prods spacing less than 3 inches


Particle concentration will be more

AC cycle phase changes at 180 degress

After painting a part how mpi should be done on it

Convert AC to DC

Particles should be fine instead of coarse

Best demagnetization of smooth surface

AC with Coil

Best demagnetization Curie point

Step type indication – lamellar tearing

Two directions lo magnetize cheyyali what should be done

Demagnetize the part

Circularly magnetize the part demagnetize longitudinally magnetize and demagnetize

Circularly magnetize part evaluate longitudinally magnetize and then evaluate

Hall effect metre is showing 30 guass in stead of 10 guass:

Positive in north and negative in south and vice versa

Negative

It does not have any poles

Dry particles cannot detect – porosity

For speed inspection in bench unit – low viscosity and coarse grain

Half wave rectification – 1 question

Defect orientation is not known in:

Rotating vector field

Two fields are generated automatically third field generated – vector field

3 phase rectified current is suddenly stopped:

Quick break test


Automatic MPI limitation:

Part size

Acceptance rejection criteria does not take permeability into account

Dry elongated particles – L/D ration

Weld inspection – dry particles

Weld inspection best combination – HWDC AND DRY PARTICLES

Definition of gauss

Concentration is checked by settling test

Using settling

Horse shoe magnet type defect air craft what is the reason:

Defects near weld termination – crater

To detect fatigue crack – AC

Residual magnetism – definition

Which of the following is not compulsory when using prod technique

Using 0.5% of copper

Magnetizing field double current double

Circular field is difficult to demagnetize because:

No external poles

Disadvantages of AC

Skin effect and lack of penetration

Marking of fatigue cracks (500 A to magnetize cheyyali)

Multidirectional equipment is used with:

Continuous method

Permeability variations valla

Relevant indications vastayi


Non relevant indications vastayi

Different diameters unna oka part undi. Circularly magnetise cheyyali how will u proceed

Higher dia first and lower dia next

Average dia

Maximum field intensity is observed using central conductor:

Inside surface lo untundi

1. In a Magnetic particle inspection of Air Craft bolt cadmium coated cut and indications are
observed weavy. Two halves are attracted like two horse shoe magnets brough together.Both
are attached stongly. The reason for this is:
a. The part has undergone magnetic particle test previously and not demagnetized.
b. Saw to cut chesadu adee mark

Specific – 10 questions

Hysteresis loop – 5 questions


Skin effect curve – Normal AC curve

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