Sec. 18.104.22.168 of API 1104 Twentieth Edition states that "Manual Ultrasonic weld testing shall be performed at a scanning sensitivity of DAC/TCG reference sensitivety plus 6 db min. All indications that exceed 50% of DAC/TCG screen height shall be evaluated. Evaluation sensitivety for manual ultrasonic weld testing should be DAC/TCG sensitivity plus 6 dB with an evaluation level for all indications at 50% of DAC/TCG screen height.
What I interpret from the above statement is: If an indication is found at the evaluation sensitivety of (6db above the DAC/TCG sensitivety) and that indication exceeds 50% of the DAC/TCG screen hieght this indication shall be evaluted to the acceptance standards given in 9.6.2.