The phase angle difference in eddy current testing usually refers to the difference between the phase angle of the surface defect of the tested tube and the phase angle of the through-hole signal under a certain excitation frequency. The bigger the phase angle difference is, the stronger the detection system can distinguish the surface defects from the internal defects, and the stronger the ability to suppress the vibration interference in the inspection of the pipe. It can be seen that the magnitude of phase angle difference reflects the performance of the detection system, which is the pursuit of most eddy current equipment manufacturers.

Eddy current flaw detection of eddy current flaw detector is a kind of flaw detection method which uses electromagnetic induction principle to detect surface and near surface defects of conductive components. The principle is that the eddy current is generated in the conductive component by the excitation coil, and the change of eddy current is measured by the detection coil, so as to obtain the information about the defect of the component. According to the shape of the detection coil, it can be divided into three types: through type (used for wire, bar and pipe detection), probe type (used for local detection of component surface) and insertion type (used for internal detection of tube hole).

Non-standard mechanical design involves a wide range of work, because the nature of the profession is to solve all aspects of the problem, so non-standard designers are required to have a wide range of knowledge and knowledge. The more knowledge, the more effective the work, the more knowledge, the more experience, the more ways to solve the problem, the faster and more accurate. The following are major mistakes that cannot be made in non-standard mechanical design.

It is usually difficult to clean sucker rods, especially in winter. Oil contamination is often left in the probe during sucker rod inspection, which leads to the decrease of detection accuracy. To solve this problem, our company has successfully developed an "external open" high sensitivity magnetic flux leakage detection probe for sucker rods by adjusting the magnetization structure and magnetization mode. Because of the external and open design of the probe, it brings great convenience to the cleaning and maintenance of the probe, and can be cleaned regularly, thus ensuring the detection accuracy.

Eddy current flaw detection is a defect of alternating current electromagnetic coil in metal plane layer, which is not convenient to use in complex shape components. In thermal power plants, it is mainly used to detect condenser tubes, turbine blades, turbine rotor central holes and welds. Principle When AC is fed into the coil, if the voltage and frequency used remain unchanged, the current through the coil will also remain unchanged. If a metal tube is placed in the coil, the circumferential current, or eddy current, is induced on the surface of the tube.

According to the China Petroleum and Natural Gas Pipeline Administration (CPP), a national scientific research project undertaken by the pipeline administration and a key international cooperation project of CNPC in the 11th Five-Year Plan, a 1016mm diameter high-definition pipeline magnetic flux leakage detector, was recently launched in Beijing. This is the first set of high-definition pipeline magnetic flux leakage detector in China, which fills the gap in the field of high-definition pipeline detection technology in China.