Non-destructive testing methods and qualification standards for welds of large vertical tanks

Non-destructive testing is a technical method that uses the characteristics of sound, light, magnetism and electricity to detect whether there are defects in the welds of large vertical tanks and judge whether the welds of large vertical tanks are qualified without damaging the inspected object. Commonly used non-destructive testing methods: X-ray testing (RT), ultrasonic testing (UT), magnetic particle testing (MT) and liquid penetration testing (PT).

1. X-ray testing should be carried out in accordance with the current national standard "Radiography and Quality Classification of Steel Fusion Welding Butt Joints", and should be qualified according to the Ⅲ standard. But for steel with a yield point greater than 390MPa, or carbon steel with a thickness of no less than 25mm, or low-alloy steel with a thickness greater than or equal to 16mm, the qualification standard is level II.

2. Ultrasonic flaw detection should be carried out in accordance with the current national "Ultrasonic flaw detection of butt welds of boilers and steel pressure vessels", and should be qualified according to the second-level standard.

3. The magnetic particle inspection shall be carried out in accordance with the relevant technical standards for magnetic particle inspection of large-scale welded vertical tanks made of atmospheric pressure steel.

4. The penetrant inspection standards shall be implemented in accordance with the relevant technical standards for penetrant inspection of large-scale welded vertical tanks made of atmospheric pressure steel.