MEC – Magnetic Eddy Current
Next Generation SLOFEC Technique
Overview
Magnetic Eddy Current (MEC) is the next generation of fast
corrosion mapping technique based on the further development
of the industry proven Saturation Low Frequency Eddy Current
(SLOFECTM) technique.
The MEC technique is applied to most of Innospection’s next
generation of topside and subsea inspection tools to support
integrity assurance.
MEC – Next Generation SLOFEC
The MEC technique is a dynamic electromagnetic scanning
technique that combines a direct current magnetic field with an
Eddy Current field.
By utilising the superimposed direct current magnetisation, the
depth of penetration is increased to such an extent that internal
defects such as corrosion, pitting and cracks can be detected
from the external surface.
The key improvement of the MEC technique in comparison to
the SLOFECTM technique is that it operates on Magnetic Field
Controlled High Frequency Eddy Current.
Specifically developed Eddy Current sensors able to generate a
higher density Eddy Current field for increased defect detection
sensitivity are used. These Eddy Current sensors also enable the
measurement and adaptation of the magnetic field strength.
By analysing and controlling the magnetic field strength to
operate at the retentivity point of the hysteresis curve and
combining it with higher operating frequencies, the MEC
technique offers enhanced defect detection capabilities
including the ability to inspect through higher wall and coating
thickness.
With an improved signal to noise ratio, the MEC technique has
proven to be capable of inspecting through a 35mm fire
protective coating for defects beneath.
Innospection Limited
Unit 1, Howemoss Avenue, Kirkhill Industrial Estate, Dyce, AB21 0GP, Aberdeen, United Kingdom
Tel : +44 (0)1224-724744
Fax : +44 (0)1224-774087
Web : www.innospection.com
Email : info@innospection.com
© Copyright Innospection Ltd 2015. All rights reserved.
MEC – Magnetic Eddy Current V1-2015
MEC – Magnetic Eddy Current
Next Generation SLOFEC Technique
Principle of MEC Technique
The MEC technique uses a combination of direct current magnetic field with an Eddy Current field. By
utilising the superimposed direct current magnetisation, the depth of penetration is increased to such
an extent that the internal defects can be detected from the external surface.
While the defects affect the direct current magnetic field lines inside the remaining wall of the
inspected object, a change in the relative permeability in the area consequently affects the Eddy
Current field lines. The changes in the Eddy Current field lines are measured and analysed against the
calibration in terms of the signal amplitude, phase and shape to enable the following evaluations:
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Differentiation between internal and external defects
(Internal defects on the underside produce a vertical signal while defects on the topside produce a
horizontal signal)
Distinguishing defects from false calls, laminations or inclusions
Analysis of defect severity in terms of wall loss
Analysis of defect volume
Separation of noise signals from defect signals
Diagram 1 – Detection of far side defect with
corresponding vertical signal response
Diagram 2 – Detection of near side defect with
corresponding horizontal signal response
Innospection Limited
Unit 1, Howemoss Avenue, Kirkhill Industrial Estate, Dyce, AB21 0GP, Aberdeen, United Kingdom
Tel : +44 (0)1224-724744
Fax : +44 (0)1224-774087
Web : www.innospection.com
Email : info@innospection.com
© Copyright Innospection Ltd 2015. All rights reserved.
MEC – Magnetic Eddy Current V1-2015
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MEC – Magnetic Eddy Current
Next Generation SLOFEC Technique
Through the use of specifically developed high density Eddy Current sensors with sensor adaptation to
enable the magnetic field strength measurement, the MEC technique operates at the retentivity point
of the hysteresis curve in combination with high frequencies.
Diagram 3 – Magnetisation level of the MEC technique
As a result, the MEC technique offers higher defect detection sensitivity with the following enhanced
technology capabilities:
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Increased wall thickness range of the inspection object
Increased stand-off (coating) range i.e. up to 35mm of fire protective coating without the coating
removal
Increased frequency range
Improved signal to noise ratio
Key Features of the MEC Technique
As an electromagnetic technique, direct surface coupling between the sensor system and the object to
be inspected is not necessary. As a result, the MEC technique can be utilised not only for risk based
inspection but also as a Non-Intrusive Inspection (NII) strategy.
Innospection Limited
Unit 1, Howemoss Avenue, Kirkhill Industrial Estate, Dyce, AB21 0GP, Aberdeen, United Kingdom
Tel : +44 (0)1224-724744
Fax : +44 (0)1224-774087
Web : www.innospection.com
Email : info@innospection.com
© Copyright Innospection Ltd 2015. All rights reserved.
MEC – Magnetic Eddy Current V1-2015
MEC – Magnetic Eddy Current
Next Generation SLOFEC Technique
1. High defect detection sensitivity and reliability
The MEC technique is highly sensitive in the detection of defects such as corrosion and pitting. It is
capable of inspecting ferromagnetic and non-ferromagnetic materials such as carbon steel,
stainless steel, duplex and super duplex materials with wall thickness up to 42mm. The technique
has been proven in the field to be sensitive and reliable in the detection of local corrosion in
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pipelines, pressure vessels, storage tanks, risers, caissons, subsea pipelines and structures as well
as other types of steel constructions.
The MEC technique is capable of inspecting through different coatings and cladding types such as
Epoxy, CRA, TSA or Monel clad without the coating removal. The maximum inspectable coating
thickness to date using the MEC technique is 35mm of fire protective coating.
2. High inspection speed
The MEC technique enables the fast screening of large areas with low surface preparation prior to
inspection. Cleaning of the inspection surface to the bare metal is not required to produce good
quality inspection data which serves as a major advantage over the Ultrasonic technique and
makes it uniquely suitable for subsea inspection applications.
3. High inspection temperature range
The MEC technique enables the inspection to be performed at high temperatures with experience
to date experience of up to 150°C.
4. Distinction between internal and external defects
The MEC technique is highly sensitive in the detection of small volumetric defects and is capable
in differentiating between internal and external defects. The types of defect profiles detected by
the MEC technique include the following:
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single isolated pits
groups of corrosion attack
shallow and narrow pits in the early stage of defect development
shallow rounded pits with different diameters that are particularly difficult to be detected
with conventional manual Ultrasonic
Microbiological Induced Corrosion (MIC)
Innospection Limited
Unit 1, Howemoss Avenue, Kirkhill Industrial Estate, Dyce, AB21 0GP, Aberdeen, United Kingdom
Tel : +44 (0)1224-724744
Fax : +44 (0)1224-774087
Web : www.innospection.com
Email : info@innospection.com
© Copyright Innospection Ltd 2015. All rights reserved.
MEC – Magnetic Eddy Current V1-2015
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MEC – Magnetic Eddy Current
Next Generation SLOFEC Technique
5. Real time scan results with colour mapping for defects
The scan results are mapped out in real time which allows for the immediate defect indication of
the inspected object. The coloured reporting of the Innospectit Software provides an overview of
the condition of the inspected object to enable the evaluation, determination of corrective actions
and modifications to future maintenance and inspection strategies.
Diagram 4 – Simultaneous Signal Phase and Amplitude Analysis
As with all electromagnetic based techniques, the MEC technique is not absolute wall thickness
measurement technique. It is a comparison technique which means that a calibration sample as close
as possible in the material properties and geometry of the object to be inspected is required for the
inspection.
Innospection Limited
Unit 1, Howemoss Avenue, Kirkhill Industrial Estate, Dyce, AB21 0GP, Aberdeen, United Kingdom
Tel : +44 (0)1224-724744
Fax : +44 (0)1224-774087
Web : www.innospection.com
Email : info@innospection.com
© Copyright Innospection Ltd 2015. All rights reserved.
MEC – Magnetic Eddy Current V1-2015
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