Electromagnetic pulse shielding effectiveness of circular multi-waveguides for fluids

Generally, large-scale plumbing work is necessary to facilitate continuous supply of air, oil, and water to ensure a sustained operation for more than two weeks under unusual conditions during which no necessary supplies can be procured from external sources. A multi-waveguides can be used in large-scale plumbing to provide the required shielding effectiveness (SE) against high-altitude electromagnetic pulses (HEMP), which are generated by high-altitude nuclear explosions. Therefore, this study analyzes the SE of a circular multi-waveguide using experimental values along with theoretical calculations with waveguides installed in large pipes instead of single pipes studied so far. This is to find a large multi-waveguides that can be used in large protective facilities. To validate the results, the theoretical values were compared with experimental data on the SE of waveguides with diameters of 250 mm, which were filled with air, oil, and water. The results revealed that the air-filled and oil-filled multi-waveguides with diameters of 30 mm and 50 mm satisfy the requirements of MIL-STD-188-125-1. However, the water-filled multi-waveguides with diameters of 30 mm and 50 mm did not achieve the required SE. Accordingly, in this study, the appropriate diameter and length of multi-waveguides for transmitting water are suggested through theoretical calculations.