FIELD: technological processes.
SUBSTANCE: method involves obtaining crude product by extrusion, heating of the crude product to molecular orientation temperature, and its radial expansion due to application of internal pressure of a fluid medium. Pressure is applied to the section between two plugs separated from each other in the axial direction. Calibration and cooling are carried out with simultaneous axial stretching of the outlet pipe. Pressure, opposite the internal pressure, is applied from the outside to the wall of the crude product on a section, subjected to radial expansion. The opposite pressure is chosen such that, it is lower than the internal pressure, but still large enough to control expansion. That way, constant thickness of the material on the whole circumference can be maintained. The opposite pressure is only applied to local sections, mostly subjected to uncontrolled expansion without this opposite pressure.
EFFECT: reduced eccentricity of plastic pipes and deviation in longitudinal tension.
10 cl, 5 dwg
