Welded pipe is a general term for welded steel pipes, which refers to seamless steel pipes produced by rolling thick steel plates into round or square steel pipes and welding them. Welded pipes are widely used in hydropower stations, municipal engineering drainage pipes, drinking water transportation and other engineering projects.

Welded pipes are generally divided into straight seam welded pipes and spiral welded pipes according to the welding method.

Straight seam welded pipe: The outer diameter is generally DN15 (4-inch pipe)-DN150 (6-inch pipe) with medium diameter specifications. The straight seam welding process is simpler than the spiral welding process, with low welding cost and high efficiency. The disadvantage is that the welds are on the same parallel line and have low tensile strength. Therefore, straight seam welding is only suitable for the production of medium diameter welded pipes.
Spiral welded pipe: The outer diameter is generally DN200 (8-inch pipe)-DN600 (24-inch pipe) with large diameter specifications. The spiral welding process can use thick steel plates of the same total width to manufacture welded pipes of different pipes. The disadvantage is that the processing technology is complicated, and the spiral welding of welded pipes of the same length seems to have more joints than straight welding, resulting in high product cost and low productivity. Therefore, spiral welding is common in the production of large-diameter welded pipes. In addition, spiral welds have high tensile strength, which ensures the load-bearing capacity of large-diameter welded pipes.

The measurement and verification methods of welded pipes are generally weighing and theoretical calculation. Weighing is based on a specific scale based on a pound scale. Theoretical calculation is to obtain the net weight based on the basic theoretical calculation formula. The formula is: Meter weight (Kg) = (diameter mm-wall thickness mm) * wall thickness mm * 0.02466".