What preparations should be made for the pipe ends when welding steel pipes

The following preparations should be made for the pipe ends when welding steel pipes:

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

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

(3) When making tee holes in the steel pipes, the ends should be trimmed. Residue inside the steel pipes should be thoroughly cleaned. The height of the saddle-shaped opening should not be less than 1/2 of the pipe diameter.

(4) To ensure full penetration of the pipe wall during welding, the pipe ends should be beveled. The bevel type can 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 should be 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 beveling of the welded steel pipe 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 should not exceed 10% of the smaller wall thickness, and should not exceed 3 mm (referring to the difference in wall thickness between the two welded steel pipes). Otherwise, the thicker steel pipe should be processed.

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