Abstract
The article describes a hardware and software complex designed for defectoscopy and study of material properties. Sections of high-strength steel 08G2B pipes were scanned in the course of the research. The purpose of this study is to determine dependency of eddy current sensor signal and mechanical and operational properties of the base metal (K65 steel grade) and demonstrate the ability of developed eddy current probe to detect continuity defects and corrosion in this type of metal. The steel is ultra-low-carbon, which makes it possible to study their properties using the eddy current method. The eddy current method is a non-contact one being used both for cracks identification and determination of their characteristics. A special superminiature eddy current probe was developed, which includes three coils - stabilizing, measuring and exciting. The coils were placed on a pyramid-shaped core made of alloy 81NMA. The eddy-current transducer runs under the control of the developed hardware-software complex with a system for suppression of noise and amplification of signal received from the eddycurrent transducer. Signal processing makes it possible to separate the effects of closely spaced cracks on the eddy-current transducer signal and evaluate the contribution of each crack separately. As a parameter containing information about the presence of defects in the object of control, the voltage arrived at the measuring coil of the eddy current probe signal was used. The work studied sections of pipes with model continuity defects – cracks and holes. A research that allows to simulate the presence of corrosion in the metal was also conducted. The extreme values of the eddy current probe signal over defects of different types are obtained at various velocity, that allows to identify the type of defect, while changing the frequency of the signal on the probe allows to determine the depth of the defect.
Highlights
Weathering steels, atmospheric corrosion resistant steels, which are low alloy high strength steels containing a small amount of alloying elements, have a good corrosion resistance performance in atmosphere, lower cost compare with stainless steels
Modern pipeline steels used for the transportation of crude oil and natural gas over large distances under high pressure, need to satisfy the requirements specified by the American Petroleum Institute (API)
During long-term services, corrosion might occur on the outer side of the pipe as corrosion under insulation (CUI), or on the inner side of the pipe as flow accelerated corrosion (FAC)
Summary
Weathering steels, atmospheric corrosion resistant steels, which are low alloy high strength steels containing a small amount of alloying elements, have a good corrosion resistance performance in atmosphere, lower cost compare with stainless steels. Failures of pipelines are caused by corrosion and mechanical fatigue of metal The facility structures such as oil/gas tanks and pipes are often made of steel materials. Modern pipeline steels used for the transportation of crude oil and natural gas over large distances under high pressure, need to satisfy the requirements specified by the American Petroleum Institute (API) These grades are processed by thermo-mechanical controlled rolling (TMCR) and accelerated cooling route with the prime aspiration to achieve the best possible combination of strength and toughness [1]. A research on the dual phase steel (DPS) revealed that a good correlation exists between EC outputs with microstructural and mechanical changes in the DPS specimens (R2 > 0.85) It showed the ability of the EC technique for prediction of material properties in the DPS [4]. The purpose of this study is to determine dependency of eddy current sensor signal and mechanical and operational properties of the base metal (K65 steel grade) and demonstrate the ability of developed eddy current probe to detect continuity defects and corrosion in this type of metal
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