When there are pits on the surface of the flange, there are two commonly used testing methods:

• the flux leakage method flange
• the ultrasonic testing method flange.
• First let’s explain ultrasound. The transmission process of mechanical vibration in the medium is called a wave. The human ear can perceive elastic waves with frequencies above 20 Hz and below 20000 Hz.
• Therefore, elastic waves in this frequency range are also called sound waves. Elastic waves with frequencies less than 20 Hz are also called infrasonic waves, while elastic waves with frequencies greater than 20,000 Hz are called ultrasonic waves. The human ear cannot perceive infrasound or ultrasound. At the same time, the ultrasonic testing method uses the principle of ultrasonic pulse reflection to detect the thickness of the corroded pipe wall.

  When testing, the probe will be sent directly to the inner wall of the large-diameter flange of the ultrasonic pulse, the probe first receives the reflected pulse from the inside and outside of the pipe wall, and then the slave probe will receive the reflected pulse from the outside of the pipe wall, which is consistent with the inside and outside The travel distance between externally reflected pulses reflects the thickness of the tube wall.
  The advantages of ultrasonic testing of large-diameter flanges are large thickness, high sensitivity, fast speed, low cost, harmless to the human body, and the ability to locate and quantify defects. Ultrasonic flaw detection does not show flaw detection intuitively, flaw detection skills are very difficult, only affected by subjective and objective factors, and flaw detection results are not easy to save. Ultrasonic testing requires a smooth appearance of the operation, and requires experienced inspectors to distinguish the types of defects, and is suitable for inspection of parts with greater thickness, which makes ultrasonic defect detection also have its limitations.

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