Pulsed eddy current (PEC) is a new technique to distinguish corrosion defeats inside and outside the metal pipeline. In comparison with other eddy current techniques, the PEC technique has the advantage of being simple and high velocity. In this article, a brand-new PEC probe based on differential conductivity is established through the combination of modules like square wave generator, eddy current coil bridge, differential current, voltage sample circuits and so on. The 50% duty cycle square wave is used as the driving signal. To measure differential conductance, a coil bridge configuration with two legs is adopted. One leg is composed of measurement eddy current coil and the in-series resistor, and the other is reference eddy current coil and the in-series resistor. Because the two legs go through defects in pipeline non-synchronously, there is a differential conductance between the two coils. A trans-impedance amplify circuit is used to detect coil eddy current. At the same time, two amplifiers are used to measure the differential voltage between the two coils. A 14 bit ADC is used to sample differential voltage, measurement and reference eddy currents which transferred to differential current by main processor Complex Programmable Logic Device (CPLD). CPLD is used to get differential conductance by differential current divide differential voltage. At last the eddy current signal sampling sequence is developed. A dynamic testing fixture with artificial defects carved on the pipeline is used to validate PEC probe’s accuracy. The differential conductance signals were displayed on the oscilloscope. Results showed that the inside defect had two peaks, positive peak and negative peak, but the outside defect only had one positive peak. We can conclude that the brand-new PEC probe has high accuracy in distinguishing the inside and outside defects.

Industrial production is accompanied by a large number of physical and chemical reactions. Steam, whose heat was often used to carry out various production activities, is a common medium in industrial production. Steam pipeline has the characteristics of high temperature and high pressure. The pipeline has been in service at high temperature for a long time, which is prone to metal material degradation such as graphitization and spheroidization. Cause of the expansion of steam pipeline after heating, the natural compensation structure is generally adopted in the whole plant pipe gallery. In recent years, the accidents of steam pipeline occurred frequently, so we must pay more attention to the safety of steam pipeline. Periodic Inspection Regulation for Industrial Pressure Piping (TSG D7005-2018) explicitly requires stress analysis and checking in some cases to determine the safety of the pipeline. The traditional inspection method adopts a random sampling model which has the risk of over inspection and missing inspection. Taking a whole plant steam pipeline as an example, this paper introduced the stress check criterion of pipeline in ASMEB31.3.The model of the pipeline was established by the software, and the stress state and displacement of each node of the pipeline were calculated. According to the calculation results, a targeted inspection scheme was established and effective data support was provided for the regular inspection of steam pipeline.