Common Nondestructive Testing (NDT) Methods
Date:2026-10-26View:3Tags:Hollow section,OCTG pipe,LSAW steel pipe
Eddy Current Testing (ET): Based on the principle of electromagnetic induction, this method is suitable for electrically conductive materials. It is highly sensitive to defects on or near the surface of steel pipes. Offering rapid inspection speeds and ease of automation, it is the preferred choice for testing small-diameter pipes on production lines.
Ultrasonic Testing (UT): High-frequency sound waves are transmitted into the material, and internal defects are located and sized based on reflected signals. This method is highly effective at detecting planar defects (such as cracks or delamination) and can inspect materials of significant thickness. The equipment is portable and poses no health risks to operators. Its limitations include challenges with complex-shaped workpieces and the lack of an intuitive, permanent record of the inspection results.
Radiographic Testing (RT): X-rays or gamma rays are used to penetrate an object, creating an image based on variations in transmitted intensity. This method is most sensitive to volumetric defects, such as gas pores or slag inclusions, and provides clear, archivable images. However, it carries radiation safety risks and is less sensitive to planar defects like cracks.
Magnetic Particle Testing (MT): Applicable only to ferromagnetic materials. When the material is magnetized, a leakage magnetic field forms at the site of surface or near-surface defects, attracting magnetic particles to create a visible indication. While highly sensitive and cost-effective, it is limited to detecting defects on or near the surface (up to a depth of approximately 1–2 mm) and cannot determine the exact depth of a defect.
Penetrant Testing (PT): A penetrant liquid is applied to the surface and drawn into open defects via capillary action; a developer is then used to reveal these defects. This method is suitable for detecting surface-breaking defects in non-porous materials. It can be used on a wide variety of materials, but it is restricted to detecting defects that are open to the surface.
