1.10.3
Angle Wave System
1.10.3.1
Vertical (Amplitude) Linearity
Two adjacent multiple reflections from the 1.524 mm 0.06 inch reference
hole in the primary standard shall vary in the same proportion as the
amplitude of the first reflection in discrete 2-dB increments between 20
percent and 80 percent of full screen height. For each gain setting, the
amplitude of each adjacent reflection shall vary within plus or minus 5
percent. For testing with the AWS SC or AWS DSC secondary standard, the
same criteria shall apply. For the SC block, the transducer shall be
placed on the longitudinal surface contiguous with the sound entry point
lines, whereas the 100 mm 4 inch longitudinal surface of the DSC block
shall be used for the same purpose. Requalification is required monthly,
or as otherwise stated.
1.10.3.2
Horizontal Linearity (Angle Wave}
The first three multiple echoes, obtained from the 1.524 mm 0.06 inch
reference hole of the primary standard or from the reference hole in a
secondary standard with the transducer positioned at a minimum of 25 mm 1
inch sound path distance, shall be equally spaced plus or minus 5 percent
when spread over 90 percent of the sweep length. The gain shall be
adjusted to give a mid-screen height first reflection. Requalification is
required monthly or as otherwise stated.
1.10.3.3
Near-Surface Resolution (Angle Wave)
The search unit shall be positioned for maximum amplitude using the primary
or secondary standard as in the horizontal linearity test. The gain shall
be adjusted to give a mid-screen height first reflection and then shall be
increased 20 dB. Excessive ringing that appears on the CRT to the right of
the sound entry point shall not exceed 13 mm 1/2 inch equivalent distance
in steel.
1.10.3.4
Far-Surface Resolution (Angle Wave)
The equipment shall delineate the three resolution holes in the resolution
block appropriate for the angle of the transducer to be used in the
inspection.
1.10.3.5
Signal-to-Noise Ratio
With the search unit located as in the horizontal linearity test, the gain
shall be set to obtain an 80 percent full screen height first reflection.
The reference reflection-to-noise-amplitude ratio shall not be less than 10
to 1.
1.10.3.6
Exit Point
The search unit shall be placed on the graduated scale on the 300 mm 12 inch
edge of the primary standard and the ultrasound shall be beamed toward the
curved edge of the block. The gain shall be set for a mid-screen first
reflection. The search unit shall be moved back and forth until the first
reflection is maximized. The index line on the side of the search unit
shall be within 1.6 mm 1/16 inch of the mid-point of the graduated scale in
either direction. Requalification is required after 40 hours or as
otherwise stated.
SECTION 05091A
Page 16
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