Axiom NDT and Offshore Services

Eddy Current Inspection (ECI)

ECI is a technique utilised on conductive materials (ie ferromagnetic steels, stainless steels, nimonic 80a, etc). An alternating current is applied to an inspection coil, which creates a magnetic field, when placed next to a conductor it induces an ‘eddy current’ field in the material. When this induced field is disrupted by a flaw it causes an imbalance which is magnified and shown on an oscilloscope. This can be done through non-conductive or conductive coatings to test the weld/material underneath the coating.

It can be used for crack detection, material sorting and coating measurements.

Axiom personnel were at the forefront during the early development of ultrasonic testing and eddy current testing and this innovative approach continues today with the adaptation of existing technology to meet new challenges.

For the flare stack inspection project above, Axiom developed an Eddy Current procedure that enabled testing to be carried out through Thermal Sprayed Aluminium (TSA) – the first time that this has been done.

Fully approved by Total E&P (UK) Ltd, this technique enabled the inspection to be completed in a relatively short period of time (critical at the onset of winter) and more importantly avoided damage to the existing coating.

The same technique has now been successfully used for inspection of risers and a similar approach has enabled us to test through galvanised coatings – ideal for rapid inspection of critical load path items (pad-eyes etc) on offshore drilling derricks.

Other typical site applications include inspection of crane jibs/pedestals/A-frames, deck node joints, padeyes pre/post load testing, drilling derrick substructures, bridge support members (primary and transverse beams) / bearings etc..

ECI sets are not intrinsically safe (i.e. control measures and a ‘hot work spark potential permit’ may be required in explosive atmospheres), but the technique itself is non-hazardous to the operator, passers-by or machinery.

Visit our Resource Area to find out about or buy British Standards applicable to Eddy Current Inspection

Advantages are:

A high degree of sensitivity.
Defect depth indication also.
No removal of surface coating required (time saving and avoids damage to item)
Can be used on galvanised components and on complex shapes
Non-ferrous materials can also be inspected
Immediate results/Real time testing.
Highly portable equipment (suitable for difficult access)

Disadvantages

Depth of penetration into the material is very limited and flaws detected will require further examination using other techniques, such as Magnetic Particle Inspection or Ultrasonic Testing. A high degree of training is required for use of ECI and we invest heavily in the continuing professional development of our Eddy Current inspectors.

Ask the Expert

Axiom NDT have developed an approved procedure for Eddy Current Inspection of galvanised weldments and TSA (i.e. through conductive coatings) and this is strongly recommended for in-service items such as padeye welds, racking board welds, powder coated steel on stadiums etc.. Ask the Expert

Enquire about - Eddy Current Inspection (ECI)

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