What work should be done on the steel pipe mouth when welding steel pipes?

Cleaning the Interface:

Remove any floating rust, dirt, and grease from the pipe interface.

Ensuring Straight Cross-Section:

When steam welding or mechanically cutting the steel pipe, ensure the cross-section is straight to maintain concentricity after welding. Remove any burrs or attachments before welding.

Tee Hole Preparation:

When creating a tee hole in the steel pipe, repair the hole and clean any residue. The height of the saddle-shaped opening should be at least half the pipe's diameter.

Grooving for Full Penetration:

To ensure full penetration during welding, groove the pipe mouth according to the wall thickness.

Beveling Based on Wall Thickness:

For pipes with wall thickness less than 3.5 mm, no beveling is needed, and the gap should be 1 to 2 mm.

For pipes with wall thickness greater than 3.5 mm, beveling is required. The bevel angle should be 30°to 35°, with a blunt edge of 1 to 2 mm and a gap of 1 to 3 mm.

Groove Formation:

Form the groove using gas cutting (manual beveling) or groove machining. Clean the processed groove of slag and iron oxide, and trim it with a steel file until the metallic luster is visible.

Welding Pipes with Different Wall Thicknesses:

The wall thickness difference between the two pipes should not exceed 10% of the smaller wall thickness, with a maximum difference of 3 mm. If the difference exceeds this, the thicker pipe should be processed to match.

Spacing Between Weld Seams:

Ensure the distance between two adjacent weld seams is at least 200 mm, and not less than the nominal diameter of the pipe.