Testing principle
Ultrasonic probe and ultrasonic energy to achieve mutual conversion between the physical properties of sound energy propagation in elastic medium is the basis of steel when ultrasonic flaw detection principle. Directional transmission of ultrasonic beam propagation in the tube encounters when the defect, produces both a reflected wave, and the wave attenuation. After signal processing flaw, such as the detection method using reflection, get flaw echo signals, such as the use of penetration testing method, by virtue of wave attenuation obtained through the defect signal. Both can give a quantitative defect indication by the instrument. Utilizing the principle of electromagnetic induction or the piezoelectric effect can be different types of ultrasonic excitation in the tube. Therefore, the piezoelectric ultrasonic and electromagnetic ultrasound can be used for ultrasonic inspection of pipe. EMAT but only for ferromagnetic materials.

Testing method
Using shear (or plate waves) reflection method (or penetration method) in the relative movement of the probe and the pipe state auto inspection, only special large-diameter steel pipe is available for manual inspection. Automatic or manual inspection should ensure sound when the beam scanning the entire surface of the tube. Longitudinal defect inspection beam propagation in the pipe wall in the circumferential direction; transverse defect inspection beam in the propagation direction of the tube axis along the tube wall. Longitudinal and transverse defects inspection should be carried out in two opposite directions of the tube. When the demand side is not made available for inspection and transverse defects square test only longitudinal defects. Agreed by both parties, the longitudinal and transverse defects inspection can be carried out only in one direction of the tube. Automatic or manual inspection should choose when coupled to good effect, and without prejudice to the coupling medium steel surface.
Use
Debugging comparative samples for testing equipment, comprehensive performance testing and use of timing verification. Artificial defect on the comparative sample is based on the assessment of natural defects equivalents, but should not be construed to be defective when the signal amplitude detected natural and artificial defects inevitably equal for the two equal size.

Material
Comparative sample produced by the seamless steel pipe and the steel pipe being tested should have the same nominal size and having a similar chemical composition, surface condition, heat treatment and acoustic performance. Production of natural defects in comparison with steel samples shall not affect the overall performance testing inspection equipment.