Signal collection
After checking the heat switching tube, bobbin test pushes the probe into the tube, then record the test score, withdrawing it maintaining the same speed. At the beginning and the end parts of the data cartridge, which records the signals, are artificial defect signals and when the probe is replaced during the test, we performed the calibration every four hour. After estimation result we re-examined with same sensor about chemistry pipe that defect or contorted signal is detected. Examination frequency is used frequency of 100 [KHz], 50 [KHz]. It used absolute probe-differential method and standard comparison-absolute method at the same time.

Signal estimation
The evaluation of signals progressed by evaluating the change in phase angle,and we made a separate Correlation Curve and applied it in our evaluation. Setting and adjusting the one hundred percent artificial defect signals in the revision standard test tube before the drawing up such that it is 40 degree clockwise to the norm, X-axis, we then set 20(V) for one hundred percent for evaluation.
When defects were detected at position where the second construction such as chemical tube, this construction signal was composed with defect signal, made signal estimation hardly. In this case, to delet disturbance signal, we applied mixing technology.

Application
2001 October Samsung Petrochemistry(Ul-san)
2002 August Samsung Petrochemistry(Ul-san)
2002 October Samsung Petrochemistry(Ul-san)
2003 April Samsung Petrochemistry(Dae-san)
2003 June Samsung Petrochemistry(Dae-san)
2003 December Samsung Petrochemistry(Ul-san)
2003 December Pungsung metal Ind. (Kim-hae)