MIL-PRF-24758A(SH)
4.10 EM signal attenuation test procedure for 100 KHz to 600 MHz. EM signal attenuation testing shall be
the final test conducted and shall not immediately follow the tests of 4.7.8, 4.8, 4.9, or 4.9.1. The conduit system
with terminated end fittings shall not exceed a surface transfer impedance of 100 milliohms per meter over the
frequency range of 100 KHz to 600 MHz, as specified by IEC 60096-1-amendmant 2, line injection method.
4.11 Marking. Each conduit jacket shall be inspected to determine that it is marked as specified in 3.11. Each
end fitting and constituent parts shall be inspected to determine that it is marked as specified in 3.11.2. Marking
according to 3.11 through 3.11.2 shall be checked by inspection, and by rubbing the marking by hand for 15
seconds with a piece of cloth soaked with water, and again for 15 seconds with a piece of cloth soaked with
petroleum spirit. Any markings, which are missing in whole or in part, faded, smeared, blurred, or shifted
(dislodged) to the extent they cannot be readily identified from a distance of 5.90 inches (15 cm) with normal
lighting, shall be evidence of failure to conform to the requirements of 3.11 through 3.11.2.
5.
PACKAGING
5.1 Packaging. For acquisition purposes, the packaging requirements shall be as specified in the contract or
order (see 6.2). When packaging of materiel is to be performed by DoD or in-house contractor personnel, these
personnel need to contact the responsible packaging activity to ascertain packaging requirements. Packaging
requirements are maintained by the Inventory Control Point's packaging activities within the Military Service or
Defense Agency, or within the military service's system commands. Packaging data retrieval is available from the
managing Military Department's or Defense Agency's automated packaging files, CD-ROM products, or by
contacting the responsible packaging activity.
6.
NOTES
(This section contains information of a general or explanatory nature that may be helpful, but is not mandatory.)
6.1 Intended use. 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.
Acquisition requirements. Acquisition documents should specify the following:
6.2
a.
Title, number, and date of the specification.
b.
When first article inspection is required (see 3.2).
c.
Quantity and size of conduit required (see 3.5.1).
d.
Quantity and size of fitting required (see 3.5.2).
e.
Packaging (see 5.1).
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