Longitudinal production process is simple, high efficiency, low cost, rapid development. The strength of the spiral welded pipe is generally higher than longitudinally welded pipes, can narrow the billet production of large diameter welded pipe, billet production of different diameters of the same width of the welded pipe can also be used. However, compared with the same length as the straight seam pipe, the increase in length of the weld 30 to 100%, and a lower production speed. Therefore, most of the smaller caliber welded pipe straight seam welded large diameter welded pipe are mostly the spiral welded structure seamless steel pipe with fluid seamless steel tubes for the difference between: structure seamless steel pipe, this standard applies to the general structure, mechanical structure with no pipe joints, fluid seamless steel pipe standard applies to send general fluid seamless steel pipe. The main difference between the structure seamless steel pipe fluid seamless steel pipe by root hydraulic test or ultrasonic, eddy current, magnetic flux leakage testing. Therefore, in the pressure line pipe standard selection, not fluid seamless steel pipe. http://tjdsgg.cn