MIL-PRF-24758A

Abstract

This specification covers the performance requirements for weatherproof flexible conduit systems (see <a>6.3.12</a>) for use primarily in exposed areas (see <a>6.3.10</a>) on U.S. Navy ships, to shield against electromagnetic (EM) radiation from own-ship transmitters and emissions external to the ship, electromagnetic pulse (EMP) (see <a>6.3.8</a>) events, and to minimize corrosion (see <a>6.3.6</a>) while being field repairable to reduce maintenance. <b><u>Intended Use:</u></b> The conduit, end fittings, and constituent parts covered by this specification are intended to shield electrical and electronic cables aboard U.S. Navy ships from the influence of external electromagnetic fields, that can be generated from own-ship transmitters or emissions external to the ship and/or EMP. The conduit systems are also intended to have low or no corrosion, provide easy maintenance, be field repairable and reusable, and reduce costs. Recommended material used for end fittings is stainless 316, or nickel-teflon plated aluminum. The primary EM frequencies of interest are those between 100 KHz and 600 MHz. Requirements for flexible conduit, end fittings, and constituent parts that provide magnetic shielding below 100 KHz, are addressed in Shipboard Electromagnetic Shielding Practices, S9407-AB-HBK-010. Material compatibility requirements are provided in Shipboard Bonding, Grounding, and Other Techniques for Electromagnetic Compatibility and Safety, MIL-STD-1310; and Dissimilar Metals, MIL-STD-889. This method of cable shielding applies to topside cables routed to connection boxes. The use of a brazed stuffing tube on the connection box facilitates weatherproofing of the end fitting by moving the conduit interface away from the connection box. This method also provides improved cable shield grounding as compared to the previous method of conduit termination to connection boxes. <br>