State StandardGB/T3091-2001, Enterprise Standard Q/BSDS 30-2001(idt BS1387: 1985), British Standard BS1387 and American Standard ASTM A53 are strictly followed. By applying the advanced high frequency welding technique, the sophisticated devices if quality control and resting & experimental measures, and ISO9001 Quality Assurance System in our factory, it has made all the hot-dip galvanized pipes possess reliable welding seams, high accuracy of geometric shape and mechanical property (tensile strength, extension, bending, flattening test), all in compliance with the specifications of standard.