The use of the electrical potential drop method for the non-destructive determination of creep-induced damage in pressure vessel components at elevated temperatures
A Wojcik1, M Waitt2, A Santos2 and A Shibli3
1University College London
2Matelect Ltd
3European Technology Development, Leatherhead, Surrey
Email: a.wojcik@ucl.ac.uk
Electrical potential drop (EPD) is a well-established electromagnetic (EM) method used in both destructive and non-destructive testing roles. The authors report on a long-term study, where the two variants that exist, alternating current potential drop (ACPD) and direct current potential drop (DCPD), have been applied together in an online monitoring role to detect creep-induced damage in pressure vessels of the type routinely encountered in the power generation and process industry. The EPD signals emerging from such environments are normally generated via a complex interaction of mechanisms, making interpretation difficult. This novel hybrid AC/DC approach has resulted in enhanced sensitivity to the subtle signal changes associated with the early stages of creep damage, such as the development of cavitation, as well as providing the ability to detect the initiation and growth of macro-cracks. The work in this project on ASME steels P91 and P92 large pipes tested under creep conditions has shown that this AC/PD hybrid system can be used to monitor creep damage development in high-temperature plant components and can provide early warning of an imminent risk of failure.
