How to detect welding defects in pressure vessels

1. Internal Defect Detection (Core Commonly Used Methods)

Radiographic Inspection (RT): Utilizes X-rays or gamma rays to penetrate weld seams and image them, providing a direct view of volumetric defects such as porosity and slag inclusions. Results can be archived, making it a standard method for internal inspection of pressure vessel welds, applicable to weld seams of most thicknesses.

Ultrasonic Inspection (UT): Determines internal defects by detecting the reflected signals of high-frequency sound waves. It is more sensitive to area defects such as cracks and lack of fusion, making it particularly suitable for detecting weld defects in thick-walled pressure vessels. It is also portable and poses no radiation risk.

Emerging Technology Direction: Currently, there are X-ray image detection methods combining deep learning and semantic segmentation. These methods can automatically identify defect types and complete ratings, achieving an accuracy rate of up to 73%, with high consistency with expert ratings. (International Academic Research)

2. Surface and Near-Surface Defect Detection

Magnetic Particle Inspection (MT): Applicable only to ferromagnetic materials. Through the accumulation of magnetized magnetic particles at the defect site, it clearly displays surface or near-surface defects such as cracks and folds. It is simple to operate and has a fast detection speed.

Penetrant Testing (PT): Utilizes penetrant to reveal open defects, suitable for non-porous, non-ferromagnetic materials such as stainless steel and aluminum alloys. It can detect minute cracks and pores in surface openings and is not limited by the material's magnetic properties.

3. Other Auxiliary Testing Techniques
In specific scenarios, other testing methods may be used in conjunction:

Eddy Current Testing: Primarily used to detect corrosion and surface cracks in heat exchanger tubes of pressure vessels. It requires no contact with the workpiece and is suitable for automated testing.

Acoustic Emission Testing: Can monitor the propagation of defects in real time during pressure testing or in-service operation of pressure vessels, suitable for dynamic monitoring.

Pulsed Eddy Current Testing: By mounting sensors on a mobile testing platform, it can automatically detect internal embedded defects in the weld seams of large pressure vessel cylinders, effectively improving the testing efficiency of large vessels. (International Academic)