T.O. 33B-1-1Figure 1-22.Angle Determination with Miniature Angle Beam Block1.8.2.6.7DeterminingSkewAngle.Skew angle is a measure of the misalignment angle between the ultrasonic beam and the Search units’ axis ofsymmetry (see Figure 1-23).a.Place the IIW block f lat on the side and adjust the Search units to maximize the echo from the othercorner of the block (see Figure 1-24). The corner of the block where there are no scale engravingsSHALL be used.b.Place a protractor on the block as shown in Figure 1-24 and measure the skew angle.c.Alternatively, any reference block having right angled edges and a constant thickness can be used forthe skew angle measurement.1.8.2.6.8AngleBeamTransducerParameters.The angle of incidence and skew angle of NEW and USED ultrasonic transducers SHALL be maintainedwithin two (2) degrees of what is required to perform an ultrasonic inspection. Transducers that do not fallwithin this parameter SHALL NOT be used to perform ultrasonic inspections. Transducers out of toleranceSHALL be reworked, if possible, to within parameters to extend their usefulness. The rework procedureconsists of wet sanding the wear plate/wedge very slowly using 600 grit of finer sandpaper or equivalentemery 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, theoverall transducer sensitivity.Change 31-69
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