150
EPOCH 4PLUS
A
max
= Maximum amplitude returned from defect area (usually 80%)
T
1
= 6 dB drop point from leading peak of A
max
(distance or time)
T
2
= 6 dB drop point from trailing peak of A
max
(distance or time)
k = Constant calculated from calibration to a reference notch
During an inspection using the ADDT method from the API 5UE practice, a potentially
rejectable crack is found and inspected to find its peak amplitude. This amplitude is then
set to 80% of full screen height (FSH) and designated as A
max
. The transducer is then
moved towards the crack until the signal has dropped 6 dB, or to one half (½) the screen
height of A
max
. This position is noted as T
1
. The transducer is then moved away from the
crack until the signal has dropped 6 dB on the other side of A
max
. This position is noted as
T
2
. Using these measurements, along with a k factor constant calculated during
calibration, the crack size (d
i
) is calculated and recorded.
Figure 102 Inspection
For further details regarding this calculation, along with the calculation of the “k factor”
constant, please refer to API’s Recommended Practice 5UE specification.
9.17.2
API 5UE and the EPOCH 4PLUS
The API 5UE software option for the EPOCH 4PLUS greatly reduces the number of
operations needed to perform the ADDT test and reduces overall inspection time. This is
accomplished using the Peak Memory function on the EPOCH 4PLUS to draw a peak
envelope of the crack signal and quickly capture the A
max
, T
1,
and T
2
points using a single
key press. Using this collected data from the peak envelope, the EPOCH 4PLUS performs
the necessary calculation using the formula above and displays the crack height in the
upper right corner of the screen. The EPOCH 4PLUS saves relevant values of the
inspected crack in its datalogger for reporting purposes and/or transfer to a PC using the
GageView Pro interface program.
Summary of Contents for Panametrics Epoch 4 Plus
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