MIL-STD-1310H(NAVY)
a. Wireway trunks may contain both shielded and unshielded cables.
b. Where an unshielded cable exits the wireway trunk, add-on shielding such as rigid or flexible metal conduit shall be added to the weather-exposed cable.
5.3.2 Hull penetration EMI control. The electrical bonding resistance of hull penetrations to ground potential for EMI control shall be 15 milliohms or less, including the cumulative effect of all faying surface interfaces, and obtained by the using the following methods.
5.3.2.1 Bonding metallic hull-penetrators. The outer perimeter of all cable shields and metallic conduit, waveguide and pipes penetrating the hull (or shielded compartments) shall be bonded to hull ground and provide a 360-degree peripheral bond at the penetration point as shown on figures 3 through 7.
5.3.2.1.1 Rigid conduit. The ends of rigid conduit shall be circumferentially bonded to the ground plane.
5.3.2.1.2 Flexible metal conduit. Flexible metal conduit systems installed in topside areas shall be in accordance with MIL-PRF-24758.
5.3.2.1.3 Waveguides, pipes, tubing, and exhaust stacks. Waveguides, pipes, metal tubing, and exhaust stacks routed in topside areas and penetrating a weather deck or bulkhead shall be grounded at the penetration point as shown on figure 8 for waveguide grounding. Pipes circumferentially welded or threaded at penetration points are properly grounded.
a. Pipes. Pipes that are not circumferentially welded shall be grounded 360 degrees at the point of penetration.
b. Turbine exhaust stacks. Turbine exhaust stacks shall be grounded at the weather penetration point using four, Type I bond straps spaced at 90-degree intervals.
c. Diesel exhaust stacks. Diesel exhaust stacks shall be grounded at the weather penetration point using two, Type I bond straps spaced at 180-degree intervals.
5.3.3 Below decks cable and flexible metal conduit installations. All below decks cables shall be separated, shielded, and routed in accordance with NAVSEA S9407-AB-HBK-010 to prevent cable-coupled EMI. Flexible metal conduit for use below deck shall be in accordance with NAVSEA S9407-AB-HBK-010.
5.3.3.1 Below deck flexible metal conduit bonding and grounding methods. Flexible shielding metal conduit shall be grounded using a Type V (modified Type IV) bond strap. One end of the bond strap is attached to the conduit braid by means of a hose clamp (with worm-gear adjustment), and the other end is attached, typically, to a stud at ground potential as shown in figure 9.
a. For single-point grounding, the rubber jacket of Type 2 conduit shall be cut away to expose the braid at the area to be grounded in order to facilitate attaching the bond strap.
b. For multi-point grounding, unjacketed conduit (Type 1) greater than 10 feet in length shall be bonded to ground potential at a point not greater than 5 feet from each end. Class B bonding is acceptable; however, where it is not inherent in the installation of the conduit, the Type V (modified Type IV) bond straps are required.
5.3.3.2 Termination and coupling of Type 2 conduit. A Type 2 conduit installation shall be insulated from the ground plane except at a single point specified in the installation drawings. The following installation procedures are provided to ensure that inadvertent grounding of the conduit does not occur.
a. Couplings. When two lengths of Type 2 conduit are to be coupled by means of a metallic conduit-to- conduit coupling, the rubber jacket shall be cut back a sufficient amount to allow for metal-to-metal contact.
The resulting joint shall then be enclosed in heat shrinkable tubing, or in a heat-shrinkable sleeve, or equivalent. Note: The tubing or sleeve may also be used to cover a damaged rubber jacket, providing the conduit itself is undamaged.
b. End-fittings. As with couplings, the rubber jacket shall be cut back to allow for metal-to-metal contact between conduit and fitting. If insulation is required, the assembly shall be covered with the heat-shrinkable tubing or sleeve mentioned above.
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