Techno-Economic Assessment of Three-Layered Coating-Based Resistive Heating Systems and Conventional Heat Tracing Cables for Industry Pipes

Techno-economic assessment of thermal-sprayed coatings for temperature control and protection of water distribution steel pipes against freezing and subsequent bursting was conducted. A data-intensive model was developed to compare the technical and economic implications associated with fabrication, shipping, installation, operation, and maintenance of multilayered coatings, as heating systems, with those of conventional heat tracing cables. The bi-layered coating deposited onto the pipe was composed of an alumina layer, as the electrical insulator, and a nickel-chromium layer, as the heating element. These layers were deposited onto the pipe using the powder flame spraying process. Furthermore, copper coating was deposited onto the nickel-chromium layer using the low-pressure cold spray method where proper electrical contact was needed. Costs were estimated on a per unit length basis for a 60-mm (2.38-inch) diameter pipe and can be scaled by engineers in the field for longer and larger pipes. The material cost for both heating systems was approximately $25 USD per meter of 60-mm diameter steel pipe. However, the total cost of fabricating the coating system was noticeably higher due mainly to the labor cost. After conducting the heating tests based on low-temperature working conditions in a cold room, it was found that the efficiency of the coating-based heating system was higher than that of conventional heating cables, which was mainly due to the intimate contact between the coating-based heating element and pipe substrate. Based on the obtained results, the improved performance of the coating systems should be viewed in light of the increased fabrication and maintenance costs by end users for large-scale protection of steel pipes against bursting during freeze events.