The steel coil is unfolded , leveled and sent to the forming machine in certain angle by releated equipment. Continual round pipes are formed in the certain angle with the principle of three-roll rolling machine. Continual spiral welding seams are welded by submerged-arc welding machine. According to the different functions of our products, the spiral welded pipe mills are divides in to API standard model, national standard model and special purpose model. API standard model mainly produces the delivery pipe for petroleum or natural gas (long distance).Thereby,the material and quality of the steel pipe need to be very good. The requirements for mill equipment and testing equipment are also very high. National standard model produces the pipe used for short distance delivery of natural gas or water, the pipeline construction in the city, the structure pipe, column pipe and so on. The requirements for the material and quality of the steel are also very high, second to that of API standard. Special purpose mill is used for some special purposes.