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Ultrasonic Testing for Seamless Steel Pipe
Ultrasonic testing (UT) has been routinely used for decades to provide qualitative and quantitative measurement for the integrity of various types of materials. By directing high frequency sound energy through a material, defects may be detected, located and sized. The technique is commonly employed to detect deficiencies or flaws that may exist in welded or seamless steel pipes.
Seamless steel pipes are defined as those pipes which are made of a single piece of sheet of metal that has been rolled and heated until it is of uniform thickness and then coiled around a mandrel. In this manufacturing process there is no welded seam, hence the name seamless. Therefore, these pipes must undergo a rigorous testing process before being used in critical applications. Ultrasonic testing (UT) is a non-destructive method used to detect and measure welds and defects in steel tubing. Ultrasound is transmitted through the pipe and detected on the opposite surface. Any deviation of the normal chronology and reflectivity indices are grounds for further inspection.
Ultrasonic testing of seamless steel pipe is performed by comparing the signals obtained from the test surface with reference standards obtained from ideal reference blocks and previous tests. This method is used to both identify flaws in the pipe and to measure the size and shape of any flaws. Since ultrasound waves cannot penetrate beyond certain depths, deeper defects are often missed. This is why UT must be performed several times along the length of the pipe, as well as from the sides.
Ultrasonic testing of seamless steel pipes may also be used to measure hardness. This is accomplished by the use of an ultrasonic impedance tester. These devices send sound waves through the pipe in a fixed-angle pattern and measure variations in the reverberation of the sound waves. The magnitude of the changes in the reverberation can be used to assess pipe hardness.
In addition to measuring hardness and detecting flaws, ultrasonic testing of seamless steel pipe can detect contaminants that may exist in the pipeline. These contaminants include scale, rust, and foul material, among others. By sending sound waves through the pipe, any potential flaws or contaminants can be located and identified.
Ultrasonic testing of seamless steel pipe is a useful and reliable tool to detect and quantify imperfections that may exist in pipes. Using a combination of standard reference blocks and a highly sensitive detector, UT can identify slight variations in material composition and structure. It is a non-destructive test that can be completed quickly, making it an ideal choice for assessing the integrity of steel pipes.
