This Spiral Corrugated Post-Tension Tube 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. The tube is a very rigid but yet light weight sheet metal tubing that without excessive deformation, withstands existing forces during the pouring of the concrete.