Abstract

A differential pressure calibrating tank for sizing and cooling just-extruded duct having electrical cable extending through it includes a duct inlet opening and a calibrator head adjacent to that opening for sizing the just-extruded duct. Differential pressure across the walls of the duct tends to keep the duct in a round cross-sectional shape. Flexible conduit in the duct and fixed relative to an adjacent extrusion die but movable in the tank precludes contact between the duct and cable within it while the duct is still molten. The flexible conduit precludes sticking or adherence between the insulation of the electrical conductors and the duct inner walls. In addition, an improved means is provided for restraining the duct submersed in the water as it traverses through the differential pressure calibrating tank. The means for restraining the duct includes, in part, a perforated tube situated within the tank having an inverted V-shaped channel traversing the length of the tube. Buoyant forces acting on the duct in combination with the V-shaped channel tend to keep the duct in a particularly desirable round cross-sectional configuration.