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Mag Control P-19 Cheat Sheet (DRAFT) by

Mag Control P-19 Cheat Sheet, describing the inspection limitations and get enough support to the team. References: SN-CMT-RDI-MCCR-RPT-011 SN-CMT-RDI-MCCR-RPT-050

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Requir­ements Fulfilled

MCCR shall perform inspection in a minimum rate (average) of 1.33 minutes per square meter
Mag Control Inspection Speed
This is equal to 0.042 m/s, for a 0.3 m scanning width. All the tests so far were done at higher speeds.
MCCR shall distin­guish between internal and external pitting.
Pitting position
-
MCCR shall detect pitting at plates with minimum diameter of 10mm.
Minimal pitting diameter detection
Pitting size is only possible for pitting higher than 15 mm on far side. Pitting near side sizing needs to be better understood or supple­mented using UT WT.
MCCR shall detect pitting at plates with minimum wall loss of 20%.
Minimal pitting depth detection
-
MCCR shall detect pitting corrosion.
Pitting position
Covered by the test cases showed before
MCCR shall detect crack with different orient­ation
Crack Orient­ation
For cracks whose orient­ation is parallel to the sides of the plate, maybe it is possible to identify.
MCCR shall detect defects under uneven coating layers.
-
Tested During the conceptual phase

Minimal Pitting Depth at Welding Areas

Perpen­dicular Direction
The defect signal was superi­mposed with the weld signal
Transv­ersal direction
Shows different pitting depths for a fixed gain of 34 dB for a defect found before the T-joint weld. It is possible to detect and differ­entiate pitting with 20% depth or more.
Parallel Direction (Along the weld)
The weld signal has not signif­icant influences in the pitting signal

Minimal Pitting Diameter at Welding Areas

Perpen­dicular directions
The defect signal was superi­mposed with the weld signal
Transv­ersal directions
Different pitting diameters for a fixed gain of 34 dB for a defect found before the T-joint weld
Parallel Direction (Along the weld)
The weld signal has not signif­icant influences in the pitting signal

Minimal Pitting Diameter Detection

SBR evaluation for a 10 mm diameter pitting in different magnet­ization levels

Minimal Pitting Depth Detection (Case 01)

To check if the Mag Control can detect a pitting with 20% of thickness loss. Detection Limit Diagram for a 10 mm Pitting diameter using 3 mm of lift off.

Minimal Pitting Depth Detection (Case 02)

To check if the Mag Control can detect a pitting with 20% of thickness loss. Detection Limit Diagram for a 10 mm Pitting diameter using 5 mm of lift off.

Minimal Pitting Depth Detection (Case 03)

To check if the MAG Control can detect a pitting with 20% of thickness loss. Detection Limit Diagram for a 10 mm Pitting diameter using 7 mm of lift off.
  

Requir­ements Fulfilled with Restri­ctions

MCCR shall detect pitting at welding areas with minimum diameter of 10mm.
Minimal pitting diameter detection at welding areas
It is still an issue to distin­guish the signal of the welding and the signal of the pitting on perpen­dicular direction. Only possible if the inspection is performed along the weld bead.
MCCR shall detect pitting at welding areas with minimum wall loss of 20%.
Minimal pitting depth detection at welding areas
It is still an issue to distin­guish the signal of the welding and the signal of the pitting on perpen­dicular direction. Only possible if the inspection is performed along the weld bead.
MCCR shall distin­guish between internal and external cracks.
Crack Position
This requir­ement may be set as done. Although, cracks sometimes may be mistaken with pitting. It is necessary better understand the crack detection mechanism.
MCCR shall detect cracks with minimum 4 mm depth.
Minimal crack depth detection
Detectable only when the crack is perpen­dicular to scanner movement. For cracks parallel to the scanner movement, a 4mm crack is difficult to detect.
MCCR shall detect cracks with minimum 60 mm length.
Minimal crack length detection
Detectable when the crack is perpen­dicular to scanner movement. Detectable for cracks parallel to the scanner movement and depth more than 40% of plate thickness. Vertical cracks were not tested yet. Even tough, it is unlikely to detect those cracks.
MCCR shall categorize crack depth qualit­atively [shallow (<25%), middle (>=25%, <=50%), deep (>5­0%)].
Crack depth differ­ent­iation
Only possible to distin­guish for cracks at far side and orient­ation perpen­dicular to the scanner movement. Some of the tests indicate that MEC may not be able to distin­guish the depth of the cracks when they are on the near side or at the same orient­ation than the scanner movement.
MCCR shall size pitting corrosion.
-
For far side it is clear to size. However, the pitting sizing on near side is not clear for thick plates. Restri­ction for size pitting smaller than 20mm diameter
MCCR shall detect cracks.
-
The crack detection is strongly dependent of the crack orient­ation
 

Requir­ements Do Not Fullfill

MCCR shall detect pitting at plates with 80% Probab­ility (PoD).
This requir­ements is an item pass criteria for the other tests cases
Test not completed. There is no PoD curve yet. The high value of SBR suggest the we will have a high POD value (more than 80%)
MCCR shall size depth of pitting with an accuracy of at least +/- 10% (at 80% certai­nty).
N/A
The accuracy was not calculated yet. Although, initially, the sizing of depth is not propor­tional and the error may be high.
MCCR shall detect cracks with 80% probab­ility (PoD).
This requir­ements is an item pass criteria for the other tests cases
This requir­ements is an item pass criteria for the other tests cases

Pitting Position

The Mag Control technique is able to distin­guish between near side and far side defects according to the angle of the impedance signals.

Far Side Signal (Pitting and Crack Failure)

Oscillate along the vertical axis.

Near Side Signal (Pitting and Crack Failure)

Oscillate mostly horizo­ntally.

Minimal Crack Depth Detection

Perpen­dicular direction
The SBR analysis for different cracks depth when the scanning was performed perpen­­di­cular to crack orient­­ation. For electrical currents higher than 11 amperes the SBR values found was more than 6 dB. Therefore, these conditions exhibit high detect­­ab­i­l­it­y.
Tranversal direction
the detection of a crack of 4 mm depth on the far side is clear when the crack is transv­ersal to the MEC movement.
Parallel direction
For that are cracks parallel to the scan was not possible to detect a 4 mm crack.

Minimal Crack legth Detection

Perpen­dicular direction
Mag Control is able to detect cracks of 40 mm, 60 mm, and 80 mm length, whether far side or near side.
Tranversal direction
Mag Control is able to detect cracks of 40 mm, 60 mm, and 80 mm length, whether far side or near side.
Parallel direction
Mag Control is able to detect cracks of 40 mm, 60 mm, and 80 mm length, whether far side or near side.

Minimal Crack Depth Detection

SBR evaluation for different crack depth using different magnet­ization levels (by electrical current applic­ation).

Minimal Crack Length Detection (Far Side)

Mag Control scan parallels to the cracks of 40, 60 and 80 mm length on far side.

Minimal Crack Length Detection (Near Side)

Mag Control scan parallels to the cracks of 40, 60 and 80m length on near side

Crack Depth Differ­ent­iation (Far Side)

It is possible to distin­guish between not only in 3, but also in 5 different levels of crack severity, according to their depths. Regarding the calibr­ation, the shallow defects (<25%) would be repres­ented in grey, the middle ones (≥25% and ≤50%), in green and blue, and the deep ones (>50%), in yellow and red.