FRAMGANGSMAATE FOR FRAMSTILLING AV EN TERMISK ISOLERENDE OMHYLLING ELLER KANAL FOR ET ELLER FLERE ROER

Procedure for manufacturing a tube of insulating material comprising one or several inner tubes (17), a foamed plastic insulation (18) and a plastic surface layer (16). In the procedure, foaming material is conducted to encircle the inner tube (17), and similarly plastic raw material to form the surface layer (16), and around the inner tube (17) are formed the foamed plastic insulation (18) and the surface layer (16) simultaneously in one work step. The surface layer (16) is cooled to desired dimension in a calibration means (14) in which a calibration pressure is produced by the foaming process, the release of this pressure being prevented by the plug which the foam forms as it solidifies. Control of the calibration pressure is effected by regulating the foam raw material supply and the temperature of the raw material.