FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

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display parameter set could then be loaded from cassette or entered via the
menu. Feature stepping locations are normally based on the positions of tube
supports and baffle plates. If these positions are known from drawings of
the heat exchanger, the parameter sets could be prepared prior to the
inspection. Otherwise, the information can be acquired by scanning to the
end of the tube with evenly spaced feature stepping and the locations of
supports and baffle plates determined from the printout. After the parameter
set is generated, it would be stored on cassette and repetitive inspection
scanning would then take place.
3.2 Generation of a Parameter Set
The generation of a parameter set is accomplished through the menu. The
operator responds to a series of questions to determine the following scan
parameters:
a) Scan length and speed/location profile.
b) The location of blind regions, which are regions where the data is not
displayed on the impedance images and can be used to blank out the
signals generated as the probe enters the calibration tube.
c) The number of features displayed and stepping positions. Stepping can
occur at operator entered positions, evenly spaced positions, on speed
changes, after blind regions, or automatic stepping upon threshold
detection.
d) Options for system control (what to do on slip or jam conditions, and
whether the operator or analyst or both control the start of scan).
e) Tubesheet information for tubesheet recognition if required.
After each parameter set is generated, it is automatically printed for
permanent reference.
3.3 Calibration Scanning
Calibration of the eddy current instrument for the probe in use is aided by
the R'Eddy Record 'Calibrate and Scan' program. The system requires minimum
operator input and produces a hardcopy printout, as seen in Figure 3. In
this case, the operator requested a 9 cm scan with 3 separated features,
whlci reflects the calibration tube used. This calibration tube contained a
through-wall hole, an 0D groove and an ID groove. The upper row of Impedance
features was obtained by plotting X vs Y with stepping occurring as the probe
passed the 3 and 6 cm positions. Below the impedance features are the
individual X and Y component traces. A row of 'tic' marks below the Y
component trace indicates the stepping location of each feature with the last
'tic' mark denoting end of scan. Below the 'tic' marks lies bookkeeping
information. The scan parameters used in the calibration run are
automatically printed after being entered; thus both permanent parameter set
information and the calibration scan hardcopy are obtained. No tube number
Is associated with a calibration scan.