Question

In checking quality of weld, what are pros and cons of a variety of non-destructive weld inspection methods as in ultrasonic test, radiographic inspection and magnetic particle flaw detection test?

Answer

At present, there are three common non-destructive testing of weld, specifically radiographic inspection, ultrasonic testing and magnetic flaw detection test.

Process of radiographic approach was used usually in the past until the arrival of ultrasonic inspection technique. The major difference between two is that ultrasonic testing detects very narrow flaws that be capable of hardly be detected by radiographic process. In addition, it is very perceptive to gross discontinuities. Tiny defects, that characterize welding problems, are usually not revealed by radiographic inspection.

Besides, ultrasonic inspection possesses advantages that it can correctly and precisely locate a defect as well as figure out its depth, location and angle of inclination.
In past, it was high-priced to adopt ultrasonic revenue for inspection. Today, rates for both inspection processes are comparable. Mainly x-ray and gamma ray used in radiographs are radioactive and pose potential safety hazard to difficult technicians on site.

Magnetic flaw detection test can only be used for checking errors in any metallic matter. This process is normally used for inspecting surface cracks and slightly sub-surface cracks. Still, surface and sub-surface cracks can be willingly detected by radiographs and ultrasonic examination.