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Classification of welds (function group AWS)
D = A – B – C
with:
• A = Indication (in dB)
Absolute instrument gain with which the maximum
flaw echo is at 50 % (±5 %) echo height
• B = Reference (in dB)
Absolute instrument gain with which the maximum
reference echo (1.5 mm side-drilled hole from the
reference block 1) is at 50 % (±5 %) echo height
• C = Attenuation (in dB)
This value is calculated according to the formula
C = 0.079 dB/mm (s – 25.4 mm). With s = sound
path of the flaw echo.
The sound attenuation correction is automatically
calculated and displayed by the instrument. For
sound paths smaller than or equal to 25.4 mm
(1 inch), the value is set to zero.
• D = D 1.1 Rating (in dB)
This is the result of the evaluation according to AWS.
The evaluation is carried out in the USM 35X accord-
ing to the formula indicated above.
Krautkramer USM 35X
H Notes:
Make sure that all instrument options for the special
test are calibrated before starting with the rating ac-
cording to AWS.
Pay attention to peaking an echo with an amplitude
between 45 % and 55 % screen height. A rating is not
possible with other amplitudes.
– Apply couplant, and couple the probe to the refer-
ence block 1. Peak the echo from the 1.5 mm side-
drilled hole.
– Select the function aSTART, and set up the A gate
on the reference echo.
– Vary the gain so that the reference echo is displayed
at 50 % screen height.
– Choose the function REFRNCE, and confirm the
choice in order to save the reference gain.
Issue 01, 04/2005
Operation
5-29
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