Continuous Extrusion of a ‘Seamless’ High Voltage Cable Sheath

BWE’s new SheathEx™ process is an extension of their well established Conform™ and Conklad™ continuous extrusion technology. The SheathEx machine extrudes a continuous and seamless aluminium tube (max. diameter 165mm) from two 12.0mm diameter rods around a high voltage cable core. BWE collaborated with high voltage power cable producers in China to develop the product and process specifications for this new and unique technology. Three installations are now in production and orders have been secured for two further projects, which will be commissioned during 2010.

The SheathEx machine incorporates a large crosshead to accommodate the large diameter dies required for cable sheathing. The aluminium sheath is seamless, with no weld line or bead. The twin groove mode of operation ensures the aluminium sheath is concentric. BWE’s patented induction heating system provides a very even temperature distribution around the tooling, leading to very stable running conditions, and consistent properties in the aluminium tube. The feedstock material is standard CCR aluminium rod, which is readily available and cheap, compared to other materials (such as flat aluminium sheets used in a welding line).

The cable core passes continuously through the crosshead. A cooled insertion tube protects the cable core on entry to the crosshead, and rapid quench of the aluminium tube immediately after the die, prevents thermal damage to the core.

Downstream from the SheathEx machine the cable sheath is corrugated in-line and coiled onto large drums.

The SheathEx process is a continuous (no stop marks), reliable (no weld) and cost effective (cheap materials, low energy etc) method of sheathing high voltage power cables.

™ SheathEx, Conform and Conklad are Registered Trade Marks of BWE Ltd
International Patents have been filed for the SheathEx Process, SheathEx Tooling System,
Machine Arrangement, Control Method and Induction Heating Technology that is employed.