The SheathEx Process

The most recent innovation in continuous extrusion is BWE’s new, patented, SheathEx process.

In the Conklad process the bottom of the die chamber is heated by the extrusion wheel and the top is cooled by the shoe that provides the closing force. Although it is heated by resistance heaters at the sides, there is a definite temperature gradient from bottom to top that affects metal flow. As the size of the sheath is increased the temperature difference increases until, at approximately 50mm diameter, it is no longer possible to control concentricity

SheathEx Diagram

SheathEx 1In order to sheath power cables up to 175mm in diameter the die chamber has been replaced by a crosshead which is approximately 100 times the mass. SheathEx overcomes the temperature gradient limitation by providing a high-efficiency induction heater at the top of the crosshead to balance the heat generated by the extrusion wheel and ensure an even temperature distribution around the extrusion die.

The cable core is protected by a water-cooled core entry tube that passes through the extrusion die and the extruded tube is cooled by a high pressure water spray as soon as it emerges to avoid thermal damage.

Caterpillar haulers are used to transport the cable through the line and the seamless sheath is corrugated in-line before being wound onto large diameter drums.