Acoustic emission monitoring

Acoustic Emission Testing (AT) is a non-destructive testing and monitoring method to detect and locate hidden defects in steel construction components, plant components and pressure equipment components in good time.  The acoustic signals involved in the testing are caused by metallurgical changes and physical phenomena in the material. When a component is stressed, the built-up state of stress spontaneously discharges at a leak, thereby generating sound impulses. The energy thus discharged is received by AE sensors applied to the surface of the tested object. The signals are received at different times by different sensors. By measuring these differences in time, the sound source can be located using mathematical locating algorithms. An essential advantage of Acoustic Emission Testing is that it allows components to be inspected for material defects, leakages and active corrosion during operation or in the course of minimal outages. The information gained about the state of a component using AET is usually much more reliable than when applying other test methods. Flat-bottom tanks – detecting corrosion and leakages when full: Flat-bottom storage tanks with a storage volume of up to 150,000 m³ are used all over the world. The conventional inspection method requires emptying, opening and cleaning of the tanks for internal visual inspection. This takes time during which the tanks are not available. By means of Acoustic Emission Testing the floors of storage tanks can be checked for leakages and active corrosion when full – time consuming emptying and refilling is not necessary. Spherical vessels for the storage of gases: Conventional testing involves spherical storage vessels being subjected to a water pressure test. Besides the stress load, this means a considerable weight load on the bearings and foundations to an extent that they never occur in operation with gaseous filling. The pressure test using acoustic emission measurement is a safe alternative: since AT serves as an early-warning system and can detect even subcritical crack growth, the storage medium can be stress-loaded directly. Large pressure equipment can be tested by AET, such as: Spherical and cylindrical natural gas tanks,   Drying cylinders in paper factories,   Reactors in the chemical and petrochemical industries,   Reactors, filters and storage vessels in air separation systems,   Sterilization equipment and autoclaves,   Above-ground and underground LPG storage tanks,   Pressurized gas cylinders and hydraulic accumulators. In the field of leakage tests, some areas of application are: - Flat-bottom storage tanks - Long-distance pipelines - Pipe systems in refineries and chemical factories - Pressurized vessels, for example heat exchangers and suchlike.