When welding steel pipes, what work should be done on the steel pipe mouth

When welding steel pipes, the following preparations should be made for the steel pipe mouth:
(1) Remove floating rust, dirt, and grease from the interface.
(2) When the steel pipe is steam welded or mechanically cut, the cross-section should be kept straight to ensure the concentricity of the steel pipe after welding. Burrs or attachments should be removed before welding.
(3) When opening a tee hole in a steel pipe, it should be repaired, and the residue in the steel pipe should be cleaned up. The height of the saddle-shaped opening should not be less than 1/2 of the pipe diameter.
(4) To ensure that the steel pipe wall can be fully penetrated during the welding process, the steel pipe mouth should be grooved, and the groove form can be selected according to the thickness of the steel pipe wall.
(5) Steel pipes with a wall thickness of less than 3.5 mm do not need to be beveled, and the gap between them is 1 to 2. Steel pipes with a wall thickness greater than 3.5 mm must be beveled. The bevel angle is generally 30° to 35°. The blunt edge is 1~2, the counterpart gap is 1~3.
(6) The groove can be formed by gas cutting (manual beveling) or groove machining. The processed groove should be cleaned of slag and iron oxide, and trimmed with a steel file until the metallic luster is exposed.
(7) When butt welding steel pipes with different wall thicknesses, the wall thickness difference between the two steel pipes shall not exceed 10% of the smaller wall thickness, and shall not exceed 3mm at most (referring to the wall thickness difference between the two steel pipes). Otherwise, the thicker steel pipe shall be processed.
(8) During welding, the distance between two adjacent steel pipe seams shall not be less than 200mm, and the minimum shall not be less than the nominal diameter of the pipe.