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.
Eddy Current Inspection (ECI) can be used for crack detection, material sorting and coating measurements. Typical site applications include inspection of crane and derrick structures, padeyes and bridge support members.
The equipment is easily portable and highly sensitive allowing it to be used on both galvanised components and complex shapes.
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 Inspection 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..
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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.
“The positive highlight must be the early detection of potential failure mechanism connected with the torque tube section #5 and the damage to the taper and keyway pins. This gives us great clarity of where we need to look in future inspections and what we are most likely to need to replace and therefore carry as stock.
All in all, I would say that this inspection has been of the highest quality; in particular the presentation of the findings is best in class, amongst the best that I have seen.”
Neil Mitchell, Enquest (commenting on the 2011 inspection of Thistle Alpha Drilling Derrick and detection of defects using eddy current)