Physical Inspection Methods: Physical inspection methods utilize various physical phenomena for measurement or verification. Non-destructive testing (NDT) is commonly employed to examine internal defects in materials or workpieces. Types of NDT include ultrasonic testing, radiographic testing, liquid penetrant testing, and magnetic particle testing.

Strength Testing of Pressure Vessels: Pressure vessels undergo both leak tightness tests and strength tests. Two common methods are the hydrostatic test and the pneumatic test. Both tests validate the leak tightness of container and pipeline welds under pressure. The pneumatic test is more sensitive and faster than the hydrostatic test, requiring no post-test drainage, making it ideal for products with drainage difficulties. However, it poses a higher risk than the hydrostatic test. Safety precautions must be observed during testing to prevent accidents.

Leak Tightness Testing: Welded containers for storing liquids or gases require leak tightness testing to detect imperfections such as through-cracks, porosity, slag inclusions, incomplete penetration, and loose microstructures. Leak tightness tests include kerosene testing, water-carrying testing, and water-jet testing.

Hydrostatic Testing: Each steel pipe undergoes a hydrostatic pressure test to ensure no leakage occurs. The test pressure is calculated using the formula P=2ST/D, where S is the test stress (MPa) selected as 60% of the minimum yield strength specified in the corresponding steel strip standard (e.g., 235MPa for Q235 steel). The hold time for the test pressure is not less than 5 seconds for pipes with diameters less than 508mm and not less than 10 seconds for pipes with diameters equal to or greater than 508mm.

Non-Destructive Testing (NDT): Repair welds, butt welds at the ends of steel strips, and circumferential welds in steel pipes should undergo X-ray or ultrasonic inspection. For spiral welds in steel pipes used for conveying flammable general fluids, 100% X-ray or ultrasonic inspection is required. For pipes conveying common fluids such as water, sewage, air, and heating steam, a random 20% of spiral welds should undergo X-ray or ultrasonic inspection.