METHOD OF PIPE MANUFACTURE

摘要

A method of producing a thermoplastics material pipe having a wall which is drawn or stretched to achieve material orientation. The method includes the steps of continuously effecting an intial extrusion of a tube (3), temperature conditioning to a desired orientation temperature, expanding the tube by pressure within an internal pressure region (18) and cooling. In one form of the invention, the internal pressure region is limited at its downstream end by an expandable plug (8). In another form of the invention, the extruded tube is brought to the desired orientation temperature by cooling the outer surface of the wall to below the desired temperature, subsequently heating the outer surface of the tube wall and then temperature conditioning the tube wall.