Also known as helical or spiral tube body. Outer diameter of about 30 nm spiral, inner diameter of about 10 nm, the adjacent helical pitch is about 11 nm. 1 week of each spiral from 6 surrounded nucleosome, H1 histone in the spiral cavity of the inner surface of the maintenance of spiral structure plays an important role. Nucleosome formed by the 10 nm 30 nm fiber to form spiral of crude fiber, so that further compression 6 times the length of DNA 
 Spiral characteristics: Longitudinal production process is simple, high efficiency, low cost, faster development. Spiral Welded Longitudinal generally higher than the high intensity, can narrow the larger diameter pipe billet production, you can also use the same width of the billet production of different pipe diameters. But with the same length of straight pipe joints than weld length of 30 to 100%, and lower production rate. Therefore, the smaller diameter of the pipe were powered by straight seam welded, large diameter spiral welded pipe for the most part. 
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 Spiral pictures 
 Spiral and standard classification: the transport of fluids under pressure spiral submerged arc welded pipe (SY5036-83) is mainly used to transport oil, natural gas pipelines; pressure transmission fluid with high-frequency spiral welded pipe (SY5038-83), lap welding method with high frequency welding, pressure fluid transfer for high-frequency spiral welded steel pipe. Strong pressure steel, plastic, and easy welding and machining molding; general low pressure liquid delivery spiral submerged arc welded pipe (SY5037-83), using double-sided automatic submerged arc welding or welding into the legal system for water, gas, air and steam and other general low pressure liquid delivery SAW pipe.