Development of Pulsed Eddy Current Testing System for Wall Thinning through Insulation with Ferromagnetic Cladding
نویسندگان
چکیده
Corrosion is one of the important factors in equipment failures. Wall thinning can be used to evaluate corrosion conditions. However, most of equipments are coated with insulations in order to elevate the energy efficiency. Pulsed eddy current (PEC) testing technique can be used to measure wall thinning through insulation. But when the insulation outside is wrapped with galvanized steel, PEC signals will become weak. In this paper, the saturation PEC (SPEC) testing system for wall thinning through insulation with ferromagnetic cladding is developed. Firstly, a magnetic apparatus is employed to magnetize ferromagnetic cladding to saturation; therefore, the magnetic shielding effect of the cladding becomes weak. Secondly, a parallel-bridge connection powerk amplifier is developed to increase the excitation energy. Finally, a signal processing method is used to improve the signal to noise ratio (SNR). The experiment results indicate that the system can measure 10% variation of wall thinning in the case of insulations with 0.5 mm thick ferromagnetic cladding.
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