Comparison of mechanical expanding and hydraulic expanding has the following advantages:
(1) The production of large diameter steel pipe aging rate. Since the water pressure expanding low-pressure water need to be filled, then pressurized to achieve further boosted when steel yield. As production gradually increasing diameter, efficiency is greatly reduced, for example, to pipe length 12m dollars, when 609.6mm (24in) diameter steel pipe hydrostatic expansion, 36 per hour, while the mechanical expanding, each 28 hours. Of 1067mm (42in) pipe, expanding the use of water pressure, 18 per hour, while 23 per hour when the mechanical expanding. That mechanical expanding, and its efficiency is not the size of the diameter relationship, so relatively speaking increased diameter and also high efficiency.
(2) Easily meet the stringent requirements for steel pipe inner diameter. When long-distance pipeline laying, welding steel pipe installed in the field site, with an inner diameter of the base, the smaller the inner diameter of the wrong side two steel tube end after docking, the smaller transport resistance, so the pipe inner diameter accuracy requirements increasingly stringent, while expanding pressure is precisely controlled by the outer mold jacket pipe diameter, the inner diameter dimensional accuracy can not be guaranteed. Mechanical expanding head is inserted into the enlarged diameter steel pipe was expanding, therefore, you can control the precision steel pipe inner diameter, regardless of wall thickness variation.
(3) Ovality good. Expanding water pressure, because outside of the welds in contact with the outer mold jacket to near the recessed wall, destroyed the pipe ovality. Mechanical expanding, as long as the weld head aligned expanding segments of the trench, when expanding unfettered welds to form a smooth surface, thus effectively reducing the damage caused by the welded parts.
(4) Pipe end shape and high dimensional accuracy. Weld effect expanding the comparison ends pressed into conical steel required pressure head against the head of the press insert seal ring radial seal up, so that the steel pipe and tube end indenter contact portion with expanded diameter steel pipe effect tubular body portion inconsistent. The mechanical expanding not have this phenomenon, pipe ends good shape and dimensions of the field site installation and butt are favorable.
