Analysis of the current situation of API 5L seamless steel pipe

API 5L seamless pipe is characterized by large diameter and relatively thick wall thickness, so according to this function, the combination of eddy current ultrasonic inspection and inner and secondary surface inspection functions can be fully utilized to achieve “no dead zone” testing. Through the use of “steel pipe rotation, detection probe forward combination”, not only the problem of title detection is solved, but also the occupied space is solved by reducing the space.

Therefore, in the testing of seamless pipes at home and abroad, the leakage magnetic flux or water pressure test is generally used. In China, the seamless magnetic flux leakage detection equipment produced does not have good performance and needs to be imported once it is used. Imported magnetic flux leakage testing equipment is expensive, which is unacceptable to most domestic enterprises; and the hydraulic test is inefficient and labor-intensive, especially when the operator’s responsibility is not high, the hydraulic test is only nominal. It can be seen that the realization of the inspection of large-diameter seamless steel pipes has become an urgent problem to be solved in the metallurgical steel pipe industry.

The ultrasonic test of the water tank uses a steel screw to advance, and the ultrasonic probe is fixed. The fact that the bottom of the water tank and the steel pipe are fully coupled ensures that the thickness of the coupling layer is the same. However, due to the blind spots in the main detection surface internal defects and sub-surface defects, it cannot be detected. In addition, the use of the spiral type requires 30m of space for the 12m long steel pipe, which affects the selection and promotion of steel detection methods.

The eddy current running through the coil detects the circumferential surface of the steel pipe surface. When using coil eddy current inspection, the larger the detected pipe diameter, the larger the coil area of ​​the detection circle, and the lower the signal-to-noise ratio. It is for this reason that the eddy current inspection standard stipulates that the foreign economic scale of eddy current inspection through the coil shall not exceed 140mm. In addition, it is also difficult to magnetize and demagnetize the steel through the type test of the seamless tube.

At present, the detection of seamless steel pipes for high-pressure boilers in my country’s metallurgical industry is mainly concentrated in the specifications below φ160mm, and most of them are traditional penetrating eddy current testing or independent tank ultrasonic testing. For the test of seamless steel pipe with a diameter of 160mm or more using the traditional through-type eddy current method, although there are many titles, it is not allowed to use the national standard. If an independent ultrasonic inspection is used, there is a certain depth of blind spots in the ultrasonic inspection mechanism, and the reliability of the overall inspection result cannot be guaranteed.