Sensing and Signal Processing Methods to Improve the Location Accuracy of AE Sources on the Bottom Plate of a Liquid -Storage Cylindrical Tank

摘要

The effect of the type of AE sensor and mounting methods on the location accuracy of artificial AE sources on the bottom plate of liquid (water and grease) storage cylindrical tanks of 820 mm in diameter was studied. Location accuracies using the direct P-waves through liquids and direct Lamb waves through the bottom plate were compared. Source locations of lead-breaking and emery paper scouring on the bottom plate were estimated utilizing the P-waves monitored by three types of AE sensors (resonant type PICO of 450 kHz, R 6 I of 60 kHz and R 3 I of 30 kHz) mounted on the tank wall. Arrival times of the direct P-waves through liquids were determined using wavelet transform at selected frequencies and were submitted to a virtual source scanning location method. Location accuracy was better when the arrival times of a 90 kHz component of AE signals by the R 6 I sensor were utilized. Location accuracy was worst when R 3 I sensors were used. Attenuations of the Lamb waves through the bottom plate loaded with liquids were smaller than those of the P-waves through liquids and were successfully utilized for the source location. Location accuracy utilizing the 70 kHz component of an Ao-Lamb wave detected by R 6 I sensors mounted on the dog-running space of the bottom plate was much higher than those utilizing the P-wave through liquids.