Weld Inspection by ACFM, Magnetic testing method, TOFD method

ACFM

Magnetic Testing

TOFD

Welding crack detection and sizing

Weld inspection with AC Field Measurement (Alternating Current)

The AC Field Measurement principle, validated and recognized by the COFREND and the ASME like a Non Destructive Testing method, is based on alternating electrical current creation induced in the material skin inspected. This induced current produces a magnetic field which is disturbed in the presence of a defect and flows around the defect tips.

Method principle

AC Field Measurement method Advantages :

Works through coatings, avoiding costly coating removal and extensive pre-clearing re-coating.

AC Field Measurement method does not require equipment shutdown, works both above
and below water.

Contrôle de soudure par ACFM Fast length and depth sizing (length ≥ 9 mm and depth ≥ 0,2 mm)

Data recording allows traceability in the time.

High inspection speed : 3 to 4 time faster than the on of Magnetic testing or Penetrant testing.

Portative and independent, working on low tension.

AC Field Measurement method Applications :

Surface cracks detection and sizing (length and depth) on ferromagnetic and iron cast materials.

Detection and assessment (length and depth) ofnon-metallic components.

Periodical examination of weld joints integrity of any type of structures: capacities, tanks, gantries,
cranes, spheres, barges, bridges,…

Large application area : Petrochemical, Civil Engineering, nuclear, offshore, power station, rail,
shipping,theme parks...

Weld Inspection with Magnetic Testing method

This Non Destructive Testing method detects surface breaking or near defects in ferromagnetic parts. The Magnetic testing method is based on magnetic field disturbances : the flux is distorted in the region of the flow.
Fine magnetic particles, applied on the specimen, are attracted to the area of flux leakage, creating a visible indication of the flow.

Defect detected:

Defects emerging on the surface

Material defect : double skink, inclusion, cavity, blowhole.

Fatigue crack.

Welding defect : cold crack, penetration lack, blowhole, ...

Surface grinding crack.

Defect due the thermal treatment : cold crack.

Defects under unclaimed (very close to surface)

Blowhole.

Inclusion.

Penetration or joining lack.

Weld Inspection in automatic mode - TOFD Method
The TOFD technique (Time Of Flight Diffraction) is a method using the ultrasonic beam diffraction, due to the presence of a discontinuity (defect) on the ultrasound way. The LSI system, developed by Physical Acoustics, also permits in acquisition configuration with two transducers the implementation of the TOFD (Time Of Flight Diffraction) technique for the detection and the characterization (length, depth, etc...) of cracks in welds.
	Both transducers, one being a transmitter and the other a receiver, are placed in equal distance on both sides of the weld. Both transducers beam must be diverging enough to cover the weld thickness. In this case, only one longitudinal displacement to the weld is necessary for a complete exam.