ET - LEVEL 1 EDDY CURRENT TESTING
PUBLIC CONCERNED:
All Non destructive testing Agents concerned with a level 1 certification.
During the certification exam of Level 1 Eddy currents, the questionnaires relating to the specific part relate more particularly to procedures used in the aircraft industry.
OPERATING TECHNIQUES :
Principle: frequency ranges, limitations, setting, parameters to be respected, calibration, probes usable for the headings below:
- Conductivity measurement
- Surface cracks detection by high frequencies
- Crack detection in borings by revolving probes
- Under the surface defects detection by low frequencies
- Versatile Equipments
- Special Equipments (pulsated Eddy current, multi-frequency and multi-channel)
METALLURGY :
- Concepts of metallurgy
- Heat treatment (conductivity, hardness)
- Surface treatment (painting, oxidation, etc..)
- Development defects met
- Manufacturing defects met
- In service defects met
CALIBRATION :
a) Calibration block:
- Universal block (conductivity, thickness coating, HF)
- Borings block (various materials)
- Specific Block (LF)
b) Implementation of the calibration:
- Type of artificial defects
- Calibration execution
- Representativeness of calibration defects
- Concept of detection threshold
PROBES :
a) Theoretical principle:
- absolutes
- differentials
- separate emission/reception
- multifunction
b) Applications:
- conductivity (absolutes)
- pencil probes HF (absolute or differential)
- revolving probes (differential)* for borings,
* for plane surfaces- probes LF (absolute differentials or separate E/R)
* slippery and static
* multi elements sensors- absolute probes for coating thickness measurement (painting)
- profile probes* annular: LF
* special profile : HF
c) Shielding and focusing:
- role of the shielding and focusing
- applications examples
ADEQUACY OF TECHNIQUES TO MATERIALS:
With examples by problem
a) Nonferrous alloys:
- corrosion: absolute LF
- emerging cracks* absolute or differential standard HF “pencilâ€
- not emerging cracks
* absolute - differential, E/R separate
- holes inspection
* differential HF
- conductivity
* absolute intermediate frequency
- coating thickness
* absolute intermediate frequency
b) Ferromagnetic alloys:
- differentials HF
SIGNAL & RESULTS TREATMENT :
types of signal & results
- equipment signal : report
- signal & results recordings
HEALTH AND SAFETY :
w/o
QUALITY :
- Operators qualification
- Procedures, maintenance manuals, job card, service bulletins, etc…
- Periodic calibration of the Eddy Current equipment
- Establishment of a inspection statement or a inspection report
- Specifications
- Read a procedure or a inspection instruction
- Doubtful case
ET - LEVEL 2 EDDY CURRENTS TESTING
PUBLIC CONCERNED:
All Non destructive testing Agents concerned with a level 2 certification.
During the certification exam of Level 2 Eddy currents, the questionnaires relating to the specific part relate more particularly to procedures used in the aircraft industry.
OPERATING PROCEDURES:
Principle: frequency ranges, limitations, adjustments, parameters to be respected, calibration, sensors usable for the headings below:
- Conductivity measurement
- Surface cracks detection by high frequencies
- Crack detection in borings by revolving probes
- Under the surface defects detection by low frequencies
- Versatile Equipments
- Special Equipments (pulsated Eddy current, multi frequency and multi channel)
METALLURGY :
- Concepts of metallurgy
- Heat treatment (conductivity, hardness)
- Surface treatment (painting, oxidation, etc..)
- Development defects met
- Manufacturing defects met
- In service defects met
CALIBRATION :
a) Calibration block:
- Universal block (conductivity, thickness coating, HF)
- Borings block (various materials)
- Specific Block (LF)b) Implementation of the calibration:
- Type of artificial defects
- Calibration execution
- Representativeness of calibration defects
- Concept of detection threshold
PROBES :
a) Theoretical principle:
- absolutes
- differentials
- separate emission/reception
- multifunctionb) Applications:
- conductivity (absolutes)
- probes pencil HF (absolute or differential)
- revolving probes (differential)* for borings,
* for plane surfaces- probes LF (absolute differentials or separate E/R)
* slipping and static
* multi elements sensors- absolute probes of coating thickness measurement (painting)
- profile probes* annular: LF
* special forms: HFc) Shielding and focusing:
- role of the shielding and focusing
- applications examplesd) Probes balancing :
- integrated into the probe
- dedicated to equipment
ADEQUACY OF TECHNIQUES TO MATERIALS:
With examples by problem
a) Nonferrous alloys:
- corrosion: absolute LF
- emerging cracks* absolute or differential standard HF “pencilâ€
- not emerging cracks
* absolute - differential, E/R separate
- holes inspection
* differential HF
- conductivity
* absolute intermediate frequency
- coating thickness
* absolute intermediate frequency
b) Ferromagnetic alloys:
- differentials HF
c) Composites (conducting):
(example: encircling coils)
SIGNAL TREATMENT:
- imagery, etc…
INSPECTION INSTRUCTION DRAFT :
- plan of the instruction,
- specification & documentation requirements,
- equipment specification
- preparation before inspection
* visual inspection
* aspect of the parts
- calibration
- inspection procedure
- acceptance criteria and sanctions
- treatment of doubtful cases
RESULTS TREATMENT :
types of results
- equipment indications : report
- recordings
HEALTH AND SAFETY :
w/o
QUALITY :
- Operators qualification
- Procedures, maintenance manuals, job card, service bulletins, etc…
- Periodic calibration of the Eddy Current Equipment
- Establishment of a inspection statement or a inspection report
- Specifications
ET - LEVEL 3 EDDY CURRENT TESTING
PUBLIC CONCERNED:
All Non destructive testing Agents concerned with a level 3 certification.
During the certification exam of Level 3 Eddy currents, the questionnaires relating to the specific part relate more particularly to procedures used in the aircraft industry.
OPERATORS:
Visual and colour perception.
Training and industrial experience.
SCOPE OF THE APPLICATION:
In the aircraft industry, control by EDDY CURRENTS applies in production and maintenance of :
- Semi-finished products and gross products (industry upstream),
- End products (material quality control),
- Airframes,
- Engines,
- The landing gears,
- The equipments and accessories.
EQUIPMENT:
- Installations and equipment:
* fixed installations for specific use (production inspection),
* testing device by EDDY CURRENTS for specific task :
- Conductivity check,
- coating thickness check.
* testing device by EDDY CURRENTS multi uses:
- high frequency generators,
- low frequency generators,
- pulsated current generators.
* inspection mode: manual, semi automatic, automatic.
- Inspection systems:
- generator architecture (circuits, components, etc…),
- fixed or adjustable frequency,
- single frequency or multi-frequency,
- sensor-probes standard:
encircling probes,
pencil probes,
hole or bore probes,
profile probes,
characteristics: focusing-shielding
probes function : absolute
: differential
- electronic filtration.
- Result Analysis
. sensors metrology :
- physical characteristics checking,
- spectral analyzes of signal,
. signals views (galvanometers, fluorescent screens, graphic recording…)
. signals exploitation (modes X-Y, Y(T) ),
. computer helped diagnosis (software),
. image processing,
. data storage.
- Standards and reference blocks
APPLICATIONS OF THE PHYSICAL PRINCIPLES:
- disturbance of the signal when there is presence of a defect,
- impedance/Inductance of a coil,
- effect of the gap,
- penetration depth of the EDDY CURRENTS,
- magnetic field created by the ET coil,
- electric conductivity of materials. Measuring units, correspondence between SI system & IACS system,
- characteristic frequency of a product (bars, tube),
- ferromagnetism (permeability, saturation, hysteresis loop).
PROCEDURE:
- parts preparation before inspection,
- inspection parameters :
. phase adjustments, gain, filters and windows of analysis, threshold,
. working frequency.
- impedance plan,
- results viewing,
- interpretation
- geometrical & dimensional evaluation of the defects,
- sanctions.
QUALITY CONTROL - MEASUREMENTS OF DEFECTS INDICATIONS
For remembrance, upstream inspection on semi-finished products (thin and thick sheets, plated sheets, pipes, wire, forged parts, casting).
- quality control: heat treatments and surface treatments and, measures of electric conductivity check in relations with:
* heat treatment,
* metallurgical properties,
* stress corrosion behaviour,
* the test temperature,
* material sorting.
- thickness check of:
* metal coatings,
* paintings and varnish,
* anodic oxidation,
* relationships with the nature of the coatings and substrate (metal or not).
- quality control on finished parts:
* rolling track of bearings (metallurgical alteration),
* wall thickness check,
* assembly check (welding, riveting, etc…).
- Repair - Maintenance Inspection :
* In service cracks detection (airframes, engines, wheels of aircraft),
corrosion detection, wear check, local overheating on airframe elements.
- raise of doubt: in complement or replacement of other NDT methods.
PERIODIC CONTROL OF THE EQUIPMENTS AND INSTALLATIONS
- periodic monitoring of equipments,
- periodic monitoring of probes and sensors,
- maintenance and renewal of the standard and calibration blocks.