Customized eddy current probes for pipe inspection at high temperatures

Machado, Miguel; Universidade Nova de Lisboa Faculdade de Ciencias e Tecnologia; Portugal

Machado, M.A.; University of Lisbon; Portugal
Crivellaro, F.S.; University of Lisbon; Portugal
Peixoto, A.; University of Lisbon; Portugal
Riscado, P.H.G.; University of Lisbon; Portugal
Sousa, J.P.; Instituto de Soldadura e Qualidade (ISQ); Portugal
Custódio, A.; ISPT - Taguspark; Portugal
Miranda, R.M.; University of Lisbon; Portugal
Teixeira, P.; University of Lisbon; Portugal
Santos, T.G.; University of Lisbon; Portugal

ID: ECNDT-0307-2018
Download: PDF
Session: Eddy Current-Techniques 1
Room: H2
Date: 2018-06-14
Time: 11:30 - 11:50

Several components, like steam transportation pipelines must stand for high temperatures, above 300º C, requiring adapted inline inspection NDT methods to assess its condition. There are several solutions for pipe inspection but few exist for high temperature conditions, so a customized NDT system is needed for this specific application.
Four customized NDT probe prototypes were developed, based on two different concepts: magnetic field measurement and eddy currents. The probe specifications, such as, dimensions, type of core and number of windings were designed and optimized for the working frequency and inspected material. For that, numerical simulations were performed to understand and characterize electrical and magnetic phenomena involved in the probes operation. A cooling system was developed and incorporated in order to reduce the thermal effect on the probes. The probes were tested in 16Mo3 Steel pipes with 323.9 mm diameter.
A laboratorial prototype was developed for experimental validation of the probes using standard defects. This prototype heats up the pipes from the inside with a 3 kW resistance coil (by Joule effect) and provides the heat control to maintain the desired temperature. The pipe rotation and the probe movement were controlled by PC in a LabVIEW environment.
The probe based on eddy currents showed the better performance and allow to detect, with a clear signal to noise ratio, a defect with 0.5 mm depth, 1 mm wide and 15 mm length with a lift-off of 3 mm. The laboratorial prototype allowed a reliable experimental validation. The numerical simulation proved to be an important tool for probe design and optimization, allowing a deeper physical phenomena insight.