Addendum-04 Questions & Answers on Calculations My ASNT Level III UT Study Notes 2014-June.
Questions & Answers
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More Reading on Q&A
Inverse Law and Inverse Square LawFor a small reflector where the size of reflector is smaller than the beam width, the echoes intensity from the same reflector varies inversely to the square of the distance.
5cm 7.5cm
75% FSH 33% FSH
Inverse Law:
For large reflector, reflector greater than the beam width, e.g. backwall echoes from the same reflector at different depth; the reflected signal amplitude varies inversely with the distance.
10cm 7.5cm
Echo Amplitude- Reflector Size “D” & Depth “d” Relations:(small reflector- Inverse square law)
Amplitude α D2
Amplitude α 1/d2
Amplitude = kD2/d2 , k =constantAmplitude1/ Amplitude2 = D1
2 d22 / d1
2 D22
D
d
Amplitude
Echo Amplitude- Reflector Size “D” & Depth “d” Relations:(large reflector- inverse law)
Amplitude α 1/dAmplitude = k/d , k =constant, Amplitude1/ Amplitude2 = d2 / d1
D
d
Amplitude
Scanning Speed:
Scanner speed = (PRR / Number of hits) × Effective diameter of probeSpeed of test part = (PRR / Number of hits) × Effective diameter of probe
Where:Effective dia. of probe = Dia. of probe – 2 [ (Dia. of probe) × (Percent of overlap between scan / 100) ]
PRR = Pulse Repetition RateLinear speed of disc or pipe in mm/ s = (2πr x RPM / 60)where r = radius of disc or pipe in mmRPM = Number of Rotation of pipe Per Minute = Revolution Per Minute