五、檢查Inspection Procedure
A. Put the probe on the inspection surface.
B. Balance the instrument.
C. Adjust the balance point to 20 percent of the display as shown in Detail VIII.
NOTE: Do not adjust the gain. Gain adjustments will make the instrument
calibration unsatisfactory.
D. Make sure the signal moves horizontally to the left when the probe is lifted
off of the part surface.
E. Slowly make a scan of the inspection area and monitor the instrument display
during the scan. Do the scan as follows:
(1) Use a scan pattern that:
(a) Will help you find cracks that are 0.1 inch (2.5 mm) in length.
(b) Move the probe across the crack at 90`. This is done to increase
the probability that you will find a crack.
NOTE: To examine an area where a scribe line was removed by ble
無損檢測ng, make small scans across the location where the scribe line
was.
Do not make the scans too large as this can cause false
i無損檢測cations from the change in clad thickness caused by
the blend operation.
(2) During the scan, move the probe no faster than the maximum scan speed that
was identified during calibration.
(3). Do the scan as follows for the specified structural configurations:
(a) Large Areas: Use a grid system to do the inspection of large areas.
The grid lines must be spaced so that when the probe is moved along the
grid lines, the probe will cross the smallest crack you want to find at
least two times.
NOTE; If you are not sure of the minimum crack length, use 0.1 inch
(2.5 mm).
(b) Flush Head Fasteners: Use a nonconductive circle template to do
inspections around flush head fasteners. Put the template adjacent to the fastener
so that you can find cracks that extend 0.1 inch (2.5 mm) from the fastener head
as shown in Detail IX.
(c) Protruding Head Fasteners: To examine areas around fasteners with
protruding heads, use the fastener head or the washer as a probe guide as
shown in Detail XII.
(d) Radius: To examine the radius of a part, keep the probe perpendi