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Magnetic Particle > Equipment (2) > Flashcards

Equipment (2) Flashcards

1
Q

Three ways to determine magnetic field direction:

A
  1. Right Hand Rule
  2. Quantitative Quality Indicators (QQI)
  3. Pie Gauges
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2
Q

What is a QQI?

A

Quantitative Quality Indicator

  • verify field direction
  • aid in determining if magnetic field is of sufficient strength to inspect the test specimen
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3
Q

How does a QQI work?

A
  • Placed and glued onto the test specimen
  • Test specimen is placed in an external field
  • The etched lines (artificial defects) in QQI will be visible if current is sufficient enough
  • QQI will show a 90° line parallel to direction of field flow
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4
Q

What are Pie Gauges?

A

Used to verify magnetic field direction and strength.

  • low carbon steel pie sections, furnace brazed and copper plated
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5
Q

How do Pie Gauges work?

A
  • Placed on test specimen while magnetizing field is introduced
  • field is sufficient when indications on gauge are evident
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6
Q

What are Magnetic Field Indicators used for?

A
  • Measure strength of a magnetic field within a magnetized article
  • quantify strength of a magnetic field that could be remaining in the article
  • verify the removal of remnant fields
  • Gauss or Tesla
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7
Q

Parts that are effected and could be damaged if the magnetic field is not removed include:

A
  • Aircraft components (compass)
  • Moving parts
  • Parts to be welded
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8
Q

What is a Hall Effect Meter or Gauss/Tesla Meter?

A

A portable hand-held instrument used to measure magnetic strength.

It applies a current to a probe/sensor and amplifies the output voltage proportional to the flux density present at a sensor.

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9
Q

What is the one limitation to a Hall Effect Meter?

A

Only measure flux passing through the probe and does not measure field at or below the part surface.

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10
Q

MPI Stationary Units

A
  • Circular and Longitudinal
  • Can produce both fields simultaneously (multi-directional unit)
  • Full-wave, rectified, three phase alternating current
  • max current output of several hundred amps to several thousand amps.
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11
Q

Central Conductor Method

A

Central conductors are placed through the opening of a hollow object and placed between two current carrying heads producing a circular field around the conductor and through the test specimen.

  • No current is passed through the test specimen itself
  • made of copper or aluminium
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12
Q

Headstock Circular Method

A

Test part is clamped between the two heads on a stationary unit, clamped by an air cylinder within the headstock, producing a circular field through the test part.

  • Three-phase full-wave DC or AC
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13
Q

Ferromagnetic Core Inspection Method

A

Ferromagnetic core placed inside the ring shaped part parallel to axis of coil using AC. Will induce eddy currents into the test part which will subsequently produce a circular field within the part.

  • Ferromagnetic core made of low retentivity, laminated iron, length = to ring diameter but not >152mm (6in) long.
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14
Q

Circular Magnetic Field using Prods

A

Current is passed directly into the specimen by two current carrying electrodes.

  • commonly used to test welds
  • best means of detecting subsurface defects when used with DC or HWRAC using dry particles
  • essential that test material be free of surface contaminants and coatings.
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15
Q

Coil (Solenoids) Method

A

Constructed of a molded frame with conductive cable wrapped around the inside frame.

  • # of wraps = amperage output “ampere turns”
  • increase # of wraps = increased field intensity
  • 3-10 turns, 5 most common
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16
Q

Portable Coil Method

A

Diameter 8 to 25 in

  • plug in cord for AC
  • Switch/pedal
17
Q

Electromagnets (Yoke) Method

A
  • most commonly used field testing equipment
  • AC plug in or DC battery pack

C or U shaped units that produce longitudinal fields .
Coil wrapped around soft ferromagnetic iron/steel core that produces longitudinal fields within the legs, with the legs being the poles.

18
Q

Permanent Magnet Method

A

Alternative when there is a lack of useable power supply.

  • bar magnets and horseshoe magnets
  • can lift 50lbs
  • made of highly retentive ferromagnetic material, lose magnetism over time but are inexpensive to replace
  • tend to accumulate particles from contact areas
19
Q

Conductive Cable Method

A

Similar to coil method “cable wrap”.

Wrapped around smaller diameter specimens, increase # of wraps increases magnetizing field.

20
Q

Multidirectional Method

A

Stationary Units used to detect discontinuities in multiple directions.

  • must ensure fields are balanced otherwise a vector filed will develop and defect detection will be difficult.
  • can be automated
  • most often used for high volumes of small parts

Magnetic Particle (31 decks)

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