Welding elbow is "shrimp bends", which can be in or on a steel plate welded pipe after cutting stock from the system, its specifications can be great. The number of sections with a bending radius bend freely determined by the producer. Welding is not very round bend along both bend radius are not large, usually about 1 times the pipe diameter. Classification of welding elbow, according to its radius of curvature can be divided into long radius elbows and short radius elbows. Long radius elbow refers to its radius of curvature is equal to 1.5 times the pipe diameter, i.e. R = 1.5D. Short radius elbow refers to its radius of curvature is equal to the pipe diameter, i.e., R = D. Formula D is the diameter of the elbow, R is the radius of curvature. The most common is for 1.5D bend, if not specified in the contract is 1D or 1.5D, 1.5D it is to optimize the choice of. Geometry comprises an outer diameter, inner diameter, wall thickness. Also require control the radius of curvature. For example, the length of the radius of 1.5D, then the radius of curvature must be within the tolerances required. Since most of these fittings for welding, in order to improve the quality of welding, to the ends of both drive groove, leaving a certain angle, with a certain side, which require a relatively stringent, more thick side, the number and angle deviation range there are provisions on the geometry of the tube a lot more than the items. Surface quality and mechanical properties of basic and tubes is the same. In order to facilitate welding, and the steel pipe is connected is the same. The fourth is that all the fittings go through a surface treatment, the inner and outer surfaces of the oxide scale spraying out by shot peening, and then coated with anti-corrosion paint. This is required in order to export, moreover, in the country but also for the convenience of transportation to prevent corrosion oxidation, have to do this work. Fifth, is the packaging requirements for small pipe fittings, such as export, you need to make a wooden box, about one cubic meter, the provisions in this case is not about the number of bends over one ton, the standard allows suits, namely large set small, but the total weight is generally not more than 1 ton. For large should a single package, like 24〃 a single package must.