FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

5. PLAYBACK
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A tape playback program allows easy access to R'Eddy Record data on magnetic
tape. High speed search for up to 10 records identified by tube or print
number, with record replay and sequential record display after search
completion allows great flexibility In playback. Three sets of single or
multi-frequency data can be retrieved and regular R'Eddy Record displays
produced. This allows detailed post inspection analysis if required. The
tape playback does not require the use of the probe drive control subsystem.
6. SYSTEM APPLICATIONS AND FIELD EXPERIENCE
The system can be used for a wide range of tube inspections. System set up
time and calibration time are minimal. The set-up of the Inspection system
components typically takes 2 experienced personnel approximately 30 minutes.
Additional setup time is required for instrumentation calibration. An
experienced inspector can enter a particular scanning parameter set in
approximately 2 minutes, provided feature stepping distances are known
beforehand. The highly regular scans and displays are a valuable Inspection
asset. The capability of providing on-line analysis coupled to a high tube
scan repetition rate has demonstrated an inspection time saving of up to 40%.
This is based on three field Inspections, the smallest of which was approximately
450 tubes. Experience has shown that 400 tubes per 8 hour shift Is a
reasonable expectation. A scan repetition rate of 1 tube/minute suggests
that a higher number of inspected tubes per shift can be achieved under
optimum conditions. Because the system was designed and constructed as a
prototype, minor problems have occurred, but the overall system performance
has been very good.
The probe drive modular design has proven to be very important. Transportation
and setup are now done more quickly, and with less physical effort. The
new technology used in the friction drive components has enabled slippery,
wet push tubes to be pushed and pulled through even partially clogged heat
exchanger tubes. The jam detect feature on the probe drive controller has
prevented the drive from damaging push tubes. No mechanical malfunction of
this probe drive has yet occured.
An example of inspection data from a condenser is shown in Figure 7. This is
a direct photocopy of the silver-oxide coated paper used by the system
printer. An analysis of the eddy current signals indicates there Is substantial
steam erosion between the second and third tube supports (between 25%
and 50% of wall loss), and lesser amounts before the first tube support, and
after the third tube support. A through-wall defect is suspected just prior
to the second tube support.
7. CURRENT SYSTEM STATUS
The R'Eddy Record inspection system is currently in the process of being
licensed to a manufacturer of eddy current instrumentation. It is anticipated
this sophisticated inspection system will be commercially available in
the near future.