Ultrasonic Testing of steel pipe
Ultrasonic Testing of steel pipe
Ultrasonic Testing is abbreviated as UT, also known as ultrasonic testing, ultrasonic testing of steel pipes is the use of ultrasonic technology to inspect the surface and internal quality of a means of testing, is one of the five conventional non-destructive testing methods.
Non-destructive testing is a means of testing the surface and internal quality of the inspected parts without damaging the working state of the workpiece or raw materials.
principle
Ultrasonic flaw detection of steel pipe is a non-destructive testing method to inspect the internal defects of steel pipe by using the reflection of ultrasonic wave and the energy change of penetration time caused by the acoustic performance difference between steel pipe and its defects.
Advantages and disadvantages of ultrasonic testing
The advantages of ultrasonic testing are large thickness, high sensitivity, high speed, low cost, harmless to human body, and can locate and quantify defects.
The disadvantage of ultrasonic testing is that it is not intuitive to the display of defects, it is difficult to detect defects, it is easy to be affected by subjective and objective factors, and the results of ultrasonic testing are not easy to preserve. Ultrasonic testing requires smooth working surface, and requires experienced inspectors to identify the types of defects, suitable for the inspection of parts with larger thickness. Ultrasonic flaw detection also has its limitations.
Ultrasonic testing process
1. Preparation before testing
(1)Familiar with the picked workpiece (workpiece name, material, specifications, groove form, welding method, heat treatment status, workpiece surface status, testing standards, qualified level, testing ratio, etc.);
(2) Selection of instruments and probes (determination of flaw detector, probe, test block, scanning ratio, detection sensitivity, detection mode according to the standard and field conditions)
(3) Calibration of the instrument (determination of horizontal and vertical linearity of the instrument when it is in use.)
(4) Calibration of probe (frontier, refraction angle, main beam deviation, sensitivity margin and resolution calibration).
(5)Instrument adjustment (the time baseline scale can be adjusted proportionally to represent the horizontal distance, depth or sound range of the pulse echo.)
(6)Sensitivity adjustment (sensitivity test is performed on the contrast block or other equivalent test block).
2. Detection operation
(1) Inspection of base material: Before inspection, the thickness of pipe wall should be measured, at least every 90 degrees, for reference. The two bottom wave of the defect free position is adjusted to the full scale of the fluorescent screen as the detection sensitivity.
(2) Inspection of welded joints: the scanning sensitivity should not be lower than the evaluation line (EL line) sensitivity, the scanning speed of probe should not exceed 150 mm/s, scanning adjacent two probe movement interval should ensure at least 10% overlap.
(3) test results and ratings: according to the nature of the defect, the magnitude of the indication length according to the relevant standards rating.
(4)Check and retest instruments and equipment.
(5)Issue test report.
Note: For welded joints with over-standard defects, the repaired parts and the affected areas should be re-inspected according to the original inspection conditions.
