GB/T3091-2015 spiral seam welded steel pipes are suitable for use in low-pressure fluid transmission pipelines such as water, air, heating steam, and gas, and their requirements are marked. Other types of welded steel pipes can also refer to this standard. GB/T3091-2015 Spiral seam welded steel pipes can be delivered according to theoretical weight or actual weight. The theoretical weight of the steel pipe is calculated according to the formula, and the density of the steel is 7.85 kg/dm ³.