The first step in calibration is the selection of frequencies. The optimum frequency depends on the resistivity of the tube material and its thickness. The prime frequency is set so as to obtain a 180 spread on the ASME calibration tube. Additional frequencies are selected to 1) perform a mix and to 2) eliminate signals from metallic deposits, which is necessary to prevent false calls. Mixing is done to detect defects under the supports.

The second step is to set the phase angle of the signal from the hole to 40 degrees. This step is done for all the frequencies.

The third step is to establish a depth curve on the ASME calibration standard. The calibration tube has five defects: 100%, 80%, 60%, 40% and 20% deep. These defects are used to establish the depth curve for flaw sizing.

NDE Associates, Inc.
515 Tristar Drive
Webster, TX 77598
Phone: 281-488-8944    Fax: 281-488-8485