What preparatory work is required 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 pipe, the opening should be finished. Residue inside the welded steel pipe 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 steel pipe wall during welding, the welded steel pipe joint should be beveled. The bevel type can be selected according to the steel pipe wall thickness.

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

(6) Beveling can be performed by gas cutting (manual beveling) or by a beveling machine. 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 of different wall thicknesses, the difference in wall thickness between the two pipes shall not exceed 10% of the smaller wall thickness, and shall not exceed 3mm (referring to the difference in wall thickness between the two pipes). Otherwise, the thicker steel pipe should be processed.

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