Production of Spiral 

& Calendared Tubes

The plant where we produce our spiral tubes for tank shells is one of our strengths as a business. Here we directly transform the coil into a ring for tanks. The ferrules from helicoidal tube are made through the unwinding of a coil, automatic levelling, helical calendaring, automatic welding from the inside with procedure 135 (EN 288) and from the outside with procedure 121 (EN 288) and subsequent plasma cutting at the pre-established length.

The result of this production process creates a tube that has geometric and resistance characteristics that are clearly superior to that obtained with the classic calendering methods.

In fact, as we have foreseen, the result is a ferrule that, even in the absence of convex bottoms, despite its considerable diameter compared to the thickness, is substantially self-supporting. For example, in completely unloaded conditions, the deformation due to its own weight is far less than what can be found in traditional calendered sheets.

The concept of this structural rigidity is easily understandable if we take into account the welding trend; in fact, following the helical profile of the sheet, it stiffens the tube, contributing with its component transversal to the stability of the structure.