1. All welds shall be subjected to leak test by vacuum box method, and the test negative pressure value shall not be less than 53kPa, and no leakage shall be deemed as qualified.

2. The minimum standard yield strength is greater than 390MPa, and the butt weld of the edge plate of the tank bottom plate should be penetrant tested after the root pass welding.

3. The butt weld of the tank bottom edge plate with a thickness greater than or equal to 4mm shall be subjected to radiographic inspection or ultrasonic inspection after each layer of welding is completed.

4, the weld surface should be smooth, there should be no cracks, incomplete fusion, slag inclusion, splash, arc scar, flash and other defects.

5. The undercut depth on both sides of the weld shall not be greater than 0.5mm, the continuous length of undercut shall not be greater than 100mm, and the total undercut length on both sides of the weld shall not exceed 10% of the weld length.