What is non-destructive testing?

Non-destructive testing, referred to as NDT, is a modern inspection technology that detects the shape, position, size and development trend of internal or external defects without damaging the object to be inspected. It has been widely used in steel pipe production in recent years. The non-destructive testing methods used in the production of seamless pipes & tubes mainly include magnetic particle testing, ultrasonic testing, eddy current testing, radiographic testing, penetrant testing, etc., and various testing methods have a certain range of application.

1. Magnetic Particle Testing
Apply magnetic powder on the surface of the seamless pipe to be tested, apply a magnetic field or current to make it enter the defect, form a magnetic charge distribution, and then observe the deposition of the magnetic powder to detect the defect.

2. Ultrasonic testing
Using the characteristics of ultrasonic propagation in materials, by transmitting and receiving ultrasonic signals, it detects defects or changes in seamless pipes.

3. Eddy current testing
The alternating electromagnetic field acts on the surface of the inspected seamless pipe to generate eddy currents and detect defects in the material.

4. Radiographic inspection
The inspected seamless tube is irradiated with X-rays or γ-rays, and the defects in the material are detected by detecting the transmission and scattering of the rays.

5. Penetration testing
A liquid dye is used on the surface of the test seamless tube, and it remains on the body surface for a preset time limit. The dye can be a colored liquid that can be identified under normal light, or a yellow/green fluorescent liquid that requires special light to appear. The liquid dye "wicks" into the open cracks in the surface of the material. Capillary action continues throughout the dye dwell until excess dye is completely washed away. At this time, a certain imaging agent is applied to the surface of the material to be inspected, penetrates into the crack and makes it color, and then appears.

The above are the basic principles of the five conventional nondestructive testing, and the specific operation process will vary according to different testing methods and equipment.