Periodic inspection of long stored pressure vessels using conventional NDT methods may not always reveal the information required to assess their integrity for continued use. In such situations, acoustic emission (AE) technique can be used for detecting the potential defects in pressure vessels before they become catastrophic. For applying this technique the pressure vessel usually requires a mechanical stimulus like pressurisation. Such stimulation produces stresses in the structure. During the pressurisation of the vessel, AE from discontinuities and from other areas of stress concentration can be detected and located. This technique has been used to assess the quality of a long stored rocket motor casing made of 15 CDV6 steel during proof pressure testing. As this material is prone to pitting corrosion when kept under long term storage, integrity assessment is essential. AE monitoring has indicated the presence of localized deformation around some corrosion pitting zones on the outer surface of the rocket motor casing. The data was further analysed and source evaluation was carried out according to the ASTM standard E569-85 and the suspected localized deformation zones were arrived at. These zones associated with corrosion pits were confirmed further by employing ultrasonic testing.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 4, pages 2525 - 2528 Publisher:Ashgate Publishing Company
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