910-269-EN, Rev. B, June 2011
Gates (Conventional UT Mode) 119
6.8 Using the Zoom
The EPOCH 1000 Series allows you to quickly zoom the screen range to provide fine
resolution of a particular inspection zone. Using the zoom, the instrument
automatically uses screen delay to bring the point that corresponds to the gate start to
the left side of the screen and adjusts the displayed range to match the gate width. The
new range equals the unzoomed gate width. The lowest achievable value of the
expanded range is equivalent to the minimum range of the instrument at the current
material-velocity setting. When the zoom is active, the
flag appears on the right
side of the display.
6.8.1 Activating the Zoom
To activate the zoom for gate 1
1. Select 2/5 > Gate 1 > Status = On to activate gate 1.
2. Position gate 1 to the desired position.
3. Choose 2/5 > Gate 1 > Zoom.
6.8.2 Zoom Applications
Zooming is especially useful in certain flaw detection applications. For example,
when detecting branches of cracking such as intergranular stress-corrosion cracking
(IGSCC), the inspector’s job can be complicated by the geometry of the test specimen
and also by the specific characteristics of the defect itself. In instances where the pipe
counter bore is close to the weld root, it is possible to have three signals that all appear
quite close to each other (the weld root, the counter bore, and the crack itself). In this
situation, you can use the zoom to improve the visual resolution of the EPOCH
1000
Series’ display so that each individual signal can be more easily identified.
When evaluating a crack signal, the inspector’s attention is usually focused on the
leading edge of an indication. By observing the number and location of small peaks
along the leading edge of the signal, it is possible to make some assumptions
regarding the presence and location of different branches of cracking. You can use the
zoom to get a much more detailed view of an indication and to make better judgments
regarding flaw location and depth.
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