Angle Determination with Miniature Angle Beam Block
Determining Skew Angle.
Skew angle is a measure of the misalignment angle between the ultrasonic beam and the Search units axis of
symmetry (see Figure 1-23).
Place the IIW block f lat on the side and adjust the Search units to maximize the echo from the other
corner of the block (see Figure 1-24). The corner of the block where there are no scale engravings
SHALL be used.
Place a protractor on the block as shown in Figure 1-24 and measure the skew angle.
Alternatively, any reference block having right angled edges and a constant thickness can be used for
the skew angle measurement.
Angle Beam Transducer Parameters.
The angle of incidence and skew angle of NEW and USED ultrasonic transducers SHALL be maintained
within two (2) degrees of what is required to perform an ultrasonic inspection. Transducers that do not fall
within this parameter SHALL NOT be used to perform ultrasonic inspections. Transducers out of tolerance
SHALL be reworked, if possible, to within parameters to extend their usefulness. The rework procedure
consists of wet sanding the wear plate/wedge very slowly using 600 grit of finer sandpaper or equivalent
emery cloth. Extreme care must be taken, during sanding, not to raise the temperature of the wear plate/
wedge. Temperature increases will affect the acoustic impedance of the wear plate/wedge and therefore, the
overall transducer sensitivity.