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How to Do Steel Pipes' Non-destructive Testing?

Source:Iris Liang Time:2019-8-16 9:34:20

The inspection of steel pipes depends on the use of the steel pipe and the type of steel pipe. When the steel pipe is used for oil, gas transportation or boilers, pressure vessels, etc., it is necessary to carry out flaw detection. The main methods are ultrasound, ray and eddy current (or magnetic powder). For steel pipe manufacturers, automatic flaw detection equipment is required to meet the needs of production tempo. For users of steel pipes, manual flaw detection is generally used. For different purposes and types of steel pipes, the corresponding product standards and professional flaw detection standards should be reviewed separately to determine which method to use and how to inspect.

Conventional non-destructive testing methods include: radiation detection, magnetic powder (or magnetic flux leakage) detection, penetration testing, ultrasonic testing, and eddy current testing.

Radiographic inspection (RT)
The earliest non-destructive testing method has been widely used for the inspection of internal defects of metal and non-metal materials and products for at least 50 years. It has unparalleled unique advantages, namely the correctness, reliability and intuitiveness of the inspection defects, and the resulting radiographic film can be used for defect analysis and archival of quality documents. However, this method also has the disadvantages of complicated equipment and high cost, and attention should be paid to the protection of radiation.

2. Magnetic particle inspection (MT) or magnetic flux leakage detection (EMI)
The detection principle is based on the fact that the ferromagnetic material is magnetized in the magnetic field, the leakage field is generated at the discontinuity (defect) of the material or the product, and the magnet powder is adsorbed (or detected by the detecting element) and is displayed (or displayed on the instrument). ). Therefore, this method can only be used for surface or near surface defect inspection of ferromagnetic materials or articles.
3. Penetration testing (PT)
Including fluorescence, coloring two. Because of its simple equipment and convenient operation, it is an effective method to compensate for surface defects caused by insufficient magnetic particle detection. It is mainly used for surface defect inspection of non-magnetic materials.
The principle of the fluorescence test is to immerse the test article in the fluorescent liquid. Due to the capillary phenomenon, the fluorescent liquid is filled in the defect, and the surface liquid is removed. Due to the photoinduced effect, the fluorescent liquid emits visible light under the irradiation of ultraviolet rays to exhibit defects.
The principle of coloring inspection is similar to the principle of fluorescence testing. There is no need for special equipment, but the developer is used to suck the coloring liquid adsorbed in the defect out of the surface of the part to reveal defects.

4. Ultrasonic testing (UT)
This method uses ultrasonic vibration to find defects in the material or interior (or surface) of the part. According to the different modulation methods of ultrasonic vibration, it can be divided into continuous wave and pulsating wave; according to different vibration and propagation modes, it can be divided into four forms: longitudinal wave, transverse wave, surface wave and Lamb wave; Different from the acceptance conditions, it can be divided into single probe and multi-probe method.

5. Eddy current testing (ET)

The principle of eddy current detection is that an alternating magnetic field generates an eddy current of the same frequency in a metal material, and a defect is detected by a change in the relationship between the magnitude of the eddy current and the specific resistance of the metal material. When there is a defect on the surface of the metal material (such as a crack), the specific resistance at that point increases due to the presence of the defect, and the eddy current associated therewith is correspondingly reduced, and the eddy current of the minute change is amplified and then indicated by the meter. , the existence and size of defects can be revealed. SEKO Machinery can customize the stainless steel welded pipe production line to meet the production needs of customers according to the specific requirements of customers.

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Iris Liang
SEKO Machinery & Technology Co., Ltd
E-mail: sales3@gdseko.com
Mobile phone: 13420628677
Tel: 0757-29390988
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