Abstract
Moisture separator reheater (MSR) tubing systems are an important part of a pressurized-water power plant to increase the efficiency of the heat transfer rate. The MSR tubes are finned tubes which are made of ferritic stainless steel (SS439) with a high strength and corrosion resistance characteristics. However, corrosion can appear along with the fins after a long period of operation of the MSR tubes that requires nondestructive testing (NDT) of the MSR tubes’ periodically. Electromagnetic testing (ET) is an efficient NDT method for the inspection of far-side corrosion in the MSR tubes. However, the ET sensor signal is affected by signal noise from the fins. Material degradation that make it challenging to inspect and evaluate the corrosion. In this study, we proposed three ET methods, including magnetic flux leakage testing, eddy current testing and partial saturation eddy current testing, and incorporated with a multivariate singular spectral analysis (MSSA) filter to improve the detectability of the corrosion in the MSR tubes. The proposed MSSA filter was compared with the multivariate wavelet transform filter and Gabor transform filter, and the results showed more efficient and stable results of the MSSA filter in the extraction of the corrosion signal.
Highlights
Moisture separator reheater (MSR) tubes are used to connect the high-pressure and low-pressure steam turbines in a pressurized-water power plant to increase the efficiency of the heat transfer rate [1].The MSR tubes have fins on the outer surface to increase the contact surface area with the steam by about three times, improving the efficiency
This section summarizes our previous works on the development of the three electromagnetic testing (ET) methods, including magnetic flux leakage testing (MFLT), eddy current testing (ECT) and partial saturation eddy current testing (PSECT), for inspection of corrosion in the MSR tubes
The input signal of the multivariate singular spectral analysis (MSSA) filter has a size of P × L = 15 × 351
Summary
Moisture separator reheater (MSR) tubes are used to connect the high-pressure and low-pressure steam turbines in a pressurized-water power plant to increase the efficiency of the heat transfer rate [1]. The fins in the outer surface of the MSR tubes produce magnetic leakages into the magnetic sensor that makes noise to the corrosion signal. ECT operates by supplying an AC magnetic field into the inner tube surface, and an eddy current will be induced in the tube thickness [6,7]. The high permeability of the MSR tube limits the penetration of the eddy current; the detection of the outer surface corrosion is limited. Full saturation eddy current testing (FSECT) is an improvement of the ECT for inspection of high permeability material [9,10]. The eddy current could deeper penetrate the tube thickness that improves the detectability of the outer surface corrosion. The results were compared with the multivariate wavelet transform (WT) and Gabor transform filters
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