Acoustic Emission Inspection of Spherical Metallic Pressure Vessels

Non destructive evaluation of metallic, spherical pressure vessels is crucial to the safety and operations of a plant due to the large volume of hazardous products stored at high pressures. Sizes of such spheres vary and diameters may range from 10 to 25 meters, even more, while total length of welds can be hundreds of meters. Additionally, accessibility for inspection is often limited, as is the case for insulated or buried spheres. The present paper discusses the use of Acoustic Emission (AE) as a non-destructive evaluation technique, offering in-service, testing of pressurized spheres inspecting the whole structure, including welds and base metal. The inspection is carried out during initial hydro-test for new spheres, regular requalification hydro-test, or online, during operation with the normal sphere contents, without removal from service. Assessment is performed in accordance with ASME or EN standards, and MONPAC or IPAC, Acoustic Emission evaluation procedures. The whole test is a matter of 2-4 days including set-up, and results include recommendations for next inspection and/or follow-up at selected areas of the sphere. The application of AE in various types of spheres, such as LPG, Ammonia is outlined while some representative examples are also provided.