This Spiral Corrugated Post-Tensioning Tube Making Machine is special for producing round corrugated ducts used in expressway, bridge, train and large-span post-tension concrete project. The prestressed Protection Tube Machine is suitable for both indoor and site work. With its special corrugations, a very high radial stiffness well adapted for use as former in concrete structures. Corrugated tube is also being used as culverts and forms for conc