Pipe

Abstract

A polyetheretherketone pipe of length greater than 250 meters and a residual stress of less than 5 MPa may be made using a calibrator devicewhich includes a cone shaped openingarranged to receive a molten extruded pipe shaped polymer. Attached to the front memberis a vacuum plateand successive vacuum plates-are attached to one another to define an array of vacuum plates, the vacuum plates being arranged to allow a vacuum to be applied to a pipe precursor passing through opening. The vacuum platesalso include temperature control means for heating or cooling the plates and therefore heating or cooling a pipe precursor passing through the openings. With a vacuum applied to openingand heating/cooling the plates, an extruded hot plastics pipe is inserted into calibratorvia openingand conveyed through openingin plates, whereupon it is urged by the vacuum against the cylindrical surface defined by platesto maintain its shape and the temperature of each plate is controlled to control the rate of cooling of the pipe precursor passing through. The pipe may be cooled at a relatively slow rate so that a pipe made from a relatively fast crystallising polymer crystalises and the crystallinity of the pipe along its extent and throughout its thickness is substantially constant.