1. Why direct butt welding is not allowed for metal conduits? The main reason is that butt welding easily produces barbed burrs on the inner mouth, which affects the safety of wire and cable laying. Generally welded steel pipes (wall thickness greater than 2mm) can be welded by casing pipe, because the weld seam is on the outside, which does not affect the pipe threading.
2. Indirect butt welding of metal conduits is actually possible, but the previous question is to weld the pipe into a bell mouth and then butt welding, which is more troublesome. Generally only suitable for large-caliber electric conduits.
3. Butt welding of galvanized steel pipe or welding casing will damage the galvanized layer and cause pipeline corrosion.
Galvanized steel pipes are not allowed to be welded. Whether it is butt welding or casing welding, this is expressly stipulated in the acceptance specification. Because welding will destroy the galvanized layer, the corrosion damage of the outer layer is better to recover, and the internal is difficult. Sleeve wire connection should be used. But that’s the case. In fact, the galvanized quality of galvanized steel pipes on the market today is very poor.
Electric galvanized steel pipes are generally not welded for the following reasons:
1. If the galvanized steel pipe is welded, it will destroy the galvanized layer outside the steel pipe and accelerate the corrosion of the steel pipe;
2. If welding is necessary, it is necessary to re-galvanize the welding place or take other protective measures.