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9.
Analyzing Data
9a.
Available C-Scans
There is a total of five C-scans available in the Sharck probe setups:
•
Depth Raw C-Scan
(raw data after calibration, showing depth view — axial)
•
Depth Short C-Scan
(depth view — axial, compensated and filtered)
•
Depth Long C-Scan
(depth view — axial, compensated)
•
Length C-Scan
(length view — axial, filtered)
•
Transverse C-Scan
(depth view — transverse, filtered)
The same channels are used in the
Depth Short
and
Depth Long
C-scans, but different processes
are applied to them. A median filter is applied to the
Depth Short
C-scan that helps decrease
the noise induced by the state of the surface under test or by the weld. The main drawback of
this filter is that it tends to “cut” long defects. This is why, we recommend using the
Depth
Long
C-scan to assess flaws greater than 25 mm (1 in) long.
We also strongly recommend that you visualize the
Depth Raw
C-scan first to determine
whether to use the
Depth Long
or
Depth Short
C-scan to assess flaws, thus avoiding missing
defects.
9b.
Analysis Methodology
Data is analyzed by reviewing the
Depth Short or Depth Long
and
the
Length C-scans. Flaw-like
indications are characterized by the presence of bright spots on the Depth C-scans and two
aligned spots (opposed colors in the palette) in the Length C-scan (representing a differential
signal visualized on the impedance plane) at the same location, aligned on both axes of the
cursor.
Figure 34 Flaw-like indications and spurious indication
Spurious Indication due
to geometrical effect:
signals not aligned &
orientation inverted in
Length C-Scan
Defect like indication
Defect like indication
Defect like indication
