Welding Construction Notes for Spiral Steel Pipe

Welding Construction Notes for Spiral Steel Pipe

This specification applies to on-site butt welding,installation and construction of large-diameter spiral steel pipes for water supply,drainage,gas transmission,pile foundation and utility projects.

1.Pre-Welding Preparation

Clean the groove and nearby area thoroughly to remove rust,oil,moisture,dust and coating defects.

Process pipe ends with standard V-grooves;ensure flatness and no burrs or notches.

Align pipe axes strictly,control misalignment within allowable tolerance,and fix with tack welds evenly distributed.

Preheat alloy and high-grade steel pipes to 80–120°C to prevent cold cracking.

Set up wind shields when wind speed exceeds 0.5m/s to avoid porosity.

Check welding machines,cables and ground connections for reliable insulation.

2.Welding Operation Requirements

Adopt qualified welding procedures and matching electrodes/wires.

Complete root pass fully before removing internal aligners;finish at least 50%of root pass for external aligners.

Maintain stable arc length and proper heat input to avoid undercut,overlap,burn-through or incomplete fusion.

Control inter-pass temperature;remove slag and clean each bead before the next layer.

Avoid sudden quenching;do not strike arcs on base metal surfaces.

For long seams,use symmetrical and segmented welding to reduce deformation.

3.Post-Welding Treatment&Inspection

Allow natural cooling;do not splash water or apply external force during cooling.

Perform visual inspection first:welds shall be well-formed,smooth,free of cracks,porosity,slag inclusions and pits.

Conduct NDT(RT/UT/MT/PT)as required by project standards.

Repair defective areas per approved procedures;re-inspect after repair.

Carry out pressure testing per design code after welding completion.

4.Safety&Site Management

Operators must hold valid welding certificates and use PPE.

Prohibit welding on pipes under pressure or with flammable residues.

Ensure good ventilation in confined spaces;monitor for harmful fumes.

Prepare fire-fighting equipment;keep combustibles away from the work zone.

Handle lifting and supporting safely to prevent vibration or shifting during welding.