METHOD AND DEVICE FOR APPLICATION OF POLYMERIC COATING ON METAL PIPE Russian patent published in 2000 - IPC

FIELD: means for manufacture of metal pipes having a polymeric protective coating. SUBSTANCE: premoulded tubular shells of adhesive and polymer are forced through into the respective moulding chambers with a subsequent expansion of them according to the wall thickness. The expansion quantity corresponds to the required reduction of internal stresses of the tubular shells. In the respective moulding chambers the melts of adhesive and polymer are applied on the inner and/or outer surface of the pipe broached in the longitudinal direction. The tubular shells are extended by the longitudinally moving pipe through the calibrating sections of the moulding chambers. The device for application of polymeric coating on metal pipe has an external extrusion head with an axial hole for passage of the metal pipe, and an internal extrusion heads are made with chambers for premoulding of the tubular shells of adhesive and polymer communicating with the respective ducts for injection of adhesive and polymer, and with the moulding chambers. Each moulding chamber has a contracting duct and a section positioned behind it expanding in the direction of pipe broaching, conjugate to the calibrating section. EFFECT: improved uniformity and smoothness of coating, prevented deformation of thin-walled pipes. 5 cl, 3 dwg