What preparations should be made when welding steel pipes

When welding steel pipes, the following preparations should be made for the pipe ends:

(1) Remove loose rust, dirt, and grease from the joints of the welded steel pipes.

(2) When welding steel pipes using gas welding or mechanical cutting, the cross-section should be straight to ensure concentricity after welding. Burrs and any adhering substances should be removed before welding.

(3) When making tee holes in the steel pipes, the ends should be trimmed. All residue inside the pipe should be thoroughly cleaned. The height of the saddle-shaped opening should not be less than half the pipe diameter.

(4) To ensure complete penetration of the pipe wall during welding, the pipe ends should be beveled. The bevel type should be selected based on the pipe wall thickness.

(5) For welded steel pipes with a wall thickness less than 3.5 mm, beveling is not required, and the butt joint gap is 1-2 mm. For welded steel pipes with a wall thickness greater than 3.5 mm, beveling is mandatory. The beveling angle is generally 30°-35°, the blunt edge is 1-2 mm, and the butt joint gap is 1-3 mm.

(6) Beveling of welded steel pipes can be done by gas cutting (manual beveling) or by beveling machine processing. After processing, the bevel should be cleaned of slag and iron oxide, and then smoothed with a steel file until a metallic luster is exposed.

(7) When butt welding steel pipes with different wall thicknesses, the difference in wall thickness between the two welded steel pipes shall not exceed 10% of the wall thickness of the smaller welded steel pipe, and shall not exceed 3 mm (referring to the difference in wall thickness between the two welded steel pipes). Otherwise, the welded steel pipe with the larger wall thickness should be processed.

(8) During welding, the distance between the seams of two adjacent welded steel pipes shall not be less than 200 mm, and shall not be less than the nominal diameter of the welded steel pipe.