Abstract: A plurality of concentric plastic tubes are drawn over a steel flowline pipe, with the annuli thus formed between the successive layers of tubing filled with an appropriate insulating material to form a length of pipe suitable for use in a subsea pipeline. The length of steel flowline pipe is at least partially encased lengthwise by a first insulating core of interstitial material. A first length of polymeric tubing is coaxial with the length of steel pipe and radially separates the first insulating core and a second insulating core of interstitial material. A second length of polymeric tubing is radially exterior to the second insulating core, and provides a protective coating for the pipe. Advantageously, the insulated length of pipe may be formed without extruding or molding, and as a result expensive dies and molds are not required.