Characteristics and application of eddy current flaw detection method for seamless steel pipe

Posted by chase Liu on April 3rd, 2023

Eddy current testing has been used for quality inspection of steel pipes for decades. After continuous improvement and development, eddy current testing has become one of the inspection methods recognized at home and abroad that can replace hydrostatic testing. Almost all steel pipes, whether ferromagnetic or non-ferromagnetic, CS seamless pipe or black steel pipe, seamless or welded pipes with a diameter greater than 2mm and a wall thickness of not less than 0.1mm, can be tested by eddy current testing. It is especially suitable for on-line or off-line automatic flaw detection of pipes and bars. It has the characteristics of fast detection speed.

According to the requirements of steel pipe varieties and other aspects, the eddy current flaw detection of general steel pipes can have the following forms:

1. Through-type eddy current flaw detection

Penetrating eddy current flaw detection is the most widely used method in steel pipe eddy current flaw detection. Generally, most pipes with a diameter of less than 180mm use this flaw detection method. It is characterized by fast detection speed, which can realize the detection of the entire steel pipe surface and the adjustment and operation of equipment are relatively simple.

Commonly used through-type eddy current flaw detection equipment consists of detection parts, including eddy current flaw detectors, detection coils and magnetic saturation devices; auxiliary components, including mechanical components, such as loading and unloading tables, driving rollers, detection hosts, control systems and degaussing marking devices, etc. 

2. Rotating point probe eddy current flaw detection

Rotating point probe eddy current flaw detection is an automatic flaw detection method in which the point probe network rotates around the steel pipe and the steel pipe moves linearly. The point probe is placed in the rotating head, and the probe rotates to scan the surface of the steel pipe.

The detection sensitivity of the point probe is high, and it is generally used in occasions that require high quality steel pipes. Rotating point probes are often used in conjunction with the through-type, because the rotating point probe is more sensitive to cracks distributed along the axial direction of the steel pipe. The through coil is sensitive to defects or cracks distributed around the steel pipe, and the two can complement each other.

The rotating point probe method is more suitable for the detection of small and medium-diameter steel pipes. The point probe has high sensitivity and is suitable for the detection of steel pipes with relatively smooth surfaces. It is not suitable for steel pipes with rough surfaces such as hot-rolled steel pipes and steel oxide scales. Rotating point probe for eddy current testing.

The rotating point probe is a kind of eddy current flaw detection equipment, and its composition is basically the same as that of the pass-through eddy current flaw detection equipment. The only difference is that the magnetic saturation device is mounted on the detection mechanism with the like head instead of the magnetic saturation device.