this invention relates to insulated pipe and methods and apparatus for making the same . there has been difficulty in placing foamable insulating materials in the narrow elongated space between a casing pipe and a core pipe . according to the instant invention , a miniaturized mix head is inserted in this elongated space . constituents of the foamable insulating material are simultaneously mixed and disseminated by the mix head in a manner to create a moving foam front which displaces air within the elongated space and permits the formation of a layer uniform , low density insulating material therein .