A method for installing a heat tube on a section of pre-insulated piping where the piping is made up of first and second lengths of insulated and jacketed pipe, each having a joining end to be joined to an end of the other length, each pipe length comprising an inner metal carrier pipe having an interior surface and an exterior surface, an envelope of foamed insulation surrounding the inner metal carrier pipe exterior surface, and an outer protective jacket surrounding the envelope of insulation, the joining ends of adjacent metal carrier pipe lengths being welded together to form fixed joints, whereby the adjacent pipe lengths provide a continuous length of fluid conduit for conveying fluids, the method comprising the steps of: providing a steel carrier pipe having an exterior surface, an interior surface and a given length extending along a central longitudinal axis; applying a polyolefin coating around the insulated pipe (25,38,42) to thereby form an outer protective jacket for the insulated pipe (25,38,42); characterized by: placing the steel carrier pipe on a conveyor and rotating the steel carrier pipe while simultaneously moving it past a first foam application station and while spraying a first layer of foam insulation onto the exterior surface of the metal carrier pipe; passing the foam covered pipe through a curing station and allowing the foam insulation to cure to a given radial thickness to thereby form a foam insulated pipe (25,38); mounting a routing device (37,34) in a suitable fixture (39,36) adjacent the conveyor and providing relative linear movement between the routing device (37,34) and the foam insulated pipe (25,38) whereby the routing device (37,34) cuts a longitudinal slot through the first layer of foam insulation along the length of the steel carrier pipe, exposing the exterior surface of the steel carrier pipe; installing a metal heat tube within the longitudinal slot whereby the heat tube contacts the exposed exterior surface of the metal carrier pipe; passing the pipe past a second foam application station while spraying a second layer of foam insulation onto the exterior of the metal carrier pipe, thereby covering the previously formed longitudinal slot and installed heat tube. providing a steel carrier pipe having an exterior surface, an interior surface and a given length extending along a central longitudinal axis; applying a polyolefin coating around the insulated pipe (25,38,42) to thereby form an outer protective jacket for the insulated pipe (25,38,42); characterized by: placing the steel carrier pipe on a conveyor and rotating the steel carrier pipe while simultaneously moving it past a first foam application station and while spraying a first layer of foam insulation onto the exterior surface of the metal carrier pipe; passing the foam covered pipe through a curing station and allowing the foam insulation to cure to a given radial thickness to thereby form a foam insulated pipe (25,38); mounting a routing device (37,34) in a suitable fixture (39,36) adjacent the conveyor and providing relative linear movement between the routing device (37,34) and the foam insulated pipe (25,38) whereby the routing device (37,34) cuts a longitudinal slot through the first layer of foam insulation along the length of the steel carrier pipe, exposing the exterior surface of the steel carrier pipe; installing a metal heat tube within the longitudinal slot whereby the heat tube contacts the exposed exterior surface of the metal carrier pipe; passing the pipe past a second foam application station while spraying a second layer of foam insulation onto the exterior of the metal carrier pipe, thereby covering the previously formed longitudinal slot and installed heat tube. placing the steel carrier pipe on a conveyor and rotating the steel carrier pipe while simultaneously moving it past a first foam application station and while spraying a first layer of foam insulation onto the exterior surface of the metal carrier pipe; passing the foam covered pipe through a curing station and allowing the foam insulation to cure to a given radial thickness to thereby form a foam insulated pipe (25,38); mounting a routing device (37,34) in a suitable fixture (39,36) adjacent the conveyor and providing relative linear movement between the routing device (37,34) and the foam insulated pipe (25,38) whereby the routing device (37,34) cuts a longitudinal slot through the first layer of foam insulation along the length of the steel carrier pipe, exposing the exterior surface of the steel carrier pipe; installing a metal heat tube within the longitudinal slot whereby the heat tube contacts the exposed exterior surface of the metal carrier pipe; passing the pipe past a second foam application station while spraying a second layer of foam insulation onto the exterior of the metal carrier pipe, thereby covering the previously formed longitudinal slot and installed heat tube.