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Quality and reliability are principal concern in rocketry due to the involved costs and risk. Large size industrial components like pressure vessels manufactured out of M250 Steel are one of the critical sub-systems. In spite of the best efforts in the design aspect and quality evaluation during production, online structural integrity evaluation is still a challenging assignment. A quick survey of the available Non-Destructive Evaluation (NDE) techniques suggests Acoustic Emission (AE) as the only viable method. Such a real-time monitoring of the pressure vessel casings will help in identifying any impending failure in terms of structural integrity degradation even at an earlier stage and thereby necessary corrective actions could be taken-up that save a lot of costs and time in addition to allow to produce quality products. The current manuscript details various steps involved in acoustic emission testing of pressure vessels. The testing process involve stages like attenuation measurement, wave velocity measurement, sensor layout, pressure cycle determination, online testing and data interpretation. Based on in depth attenuation studies, the various sensor layouts adopted for testing pressure vessels are discussed at length. Some of the general practices and requirements in AE testing are discussed. Various efficient triangulation techniques are presented. The pressure cycle and pressurization rates to be followed are explained in connection with AE data acquisition. Various AE parameters to be ensured during online testing are enlisted. |
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