Micro Cracking in Stainless Steel pipe Detection by using Acoustic Emission and Crest Factor technique

Acoustic Emission (AE) Technique incorporate with hydrostatic testing has been successfully developed for high pressure stainless steel pipe evaluation in petrochemical industries. This technique employed 100 kHz and 300 kHz resonance Acoustic Emission sensors that were mounted on the pipe material. Various hydrostatic pressures starting from zero to 120 bars were applied to the pipe and AE signals from both sensors were captured by a Personal computer (PC) via Data Acquisition Card(DAQ) . The Crest factor and AE energy which are the processed AE parameters were used to indicate crack initiation or growth in the pipe material during pressurized. Six pieces of 5 years old stainless steel pipes from industry were tested in the experiment. The test results presented that the proposed signal analyzing technique, the AE-energy and Crest-factor can be used to indicate 2 defected pipes from totally 6 specimen pipes at difference applying pressure level. Several micro cracks have been found in the both defected pipes by micro structure test. Therefore, the advantage of using AE technique is that it provides sufficient sensitivity to detect a micro cracking propagation in material.