Page 34: of Marine Technology Magazine (May 2012)

34MTRMay 2012ELECTRO-LIGHT armoring , which is similar toSTEEL-LIGHT armoring but uses copper in place ofsteel. The copper can also be used for power to allow com- posite cables to be designed with a smaller outside diame-ter. STEEL-LIGHT and ELECTRO-LIGHT fiber ele- ments are both tight buffered approaches to packaging. Tight buffering, while requiring more careful manufactur- ing, provides better performance in highly dynamic appli- cations and is the most rugged choice. STEEL-LIGHT armoring is the most rugged, designed to withstand hydrostatic pressures of 10,000 psi. Both STEEL-LIGHT and ELECTRO-LIGHT fibers have very small diameters, allowing them to be fit into interstices in the cable design. With some of newer small- diameter umbilical cables using thin-wall copper conduc-tors, such spaces may not be available. FIST may be a bet- ter choice to minimize cable diameter in such cases. Picking the correct one of these three options means you will have solved many of your telemetry issues. It is a mat- ter of weighing the tradeoffs required in ruggedness for a given application against cost, convenience, and cable size. Umbilical cable suppliers have the experience to guide you in the best choice for your applications. More Power in the Core As the capabilities of the ROV increase, the power needs of the ROV also increase. There are two ways to increase the power-handling capabilities in the core of the umbili- cal cable. First, you can use conductors of larger cross sec- tion. This will, however, increase the diameter of the cable. The second approach is to use thin-wall insulation in place of standard-wall cable. TE Connectivity, for example, uses cross-linked polyethylene (XLPE) as an insulation on power conductors. Thin-wall insulation can achieve cable diameters that are in the range of 30% smaller than comparable standard-wall products. While conventional wisdom dictates that thicker insula- tion be used as power handling increases, new materials and new processing methods have overturned such wis- dom.Thin-wall technology is well established in the military and aerospace industry, which offers many of the same demands for rugged performance as deepwater applica- MTR#4 (34-49):MTR Layouts 4/27/2012 9:38 AM Page 34