S9407-AB-HBK-010 Datasheet, PDF (187/276 Pages) Glenair, Inc. – HANDBOOK OF SHIPBOARD ELECTROMAGNETIC SHIELDING PRACTICES

S9407-AB-HBK-010, Rev. 2
SECTION 5
FLEXIBLE CONDUIT AND GENERAL GROUNDING REQUIREMENTS
5-1 BACKGROUND
As communications, sonar and other electronics systems on board submarines are improved
through advancing technology, the systems generally become more complex, with higher power levels
being generated - and radiated - from various circuits. Concurrently, more susceptible to electromagnetic
interferences. Shielding techniques must improve in order that present and future equipments shall
operate at their designed capabilities and not be degraded by the electromagnetic environment.
Until the present, cables on submarines have been shielded with seamless steel pipe made from
low carbon steel and, where flexibility was required, Anaconda type AT2198 flexible metal conduit. These
materials, and complete details for their application are described in sections 1 through 4 of this handbook
A material at greatly improved shielding capability (at low field intensities) over low carbon steel is
an iron alloy containing a high percentage of nickel. It has a high initial magnetic permeability, a desirable
characteristic for shielding against radiated magnetic fields of low intensity. A number of manufacturers
are now fabricating flexible conduit from this high permeability material, and this is the type of conduit
which the Navy Underwater Sound Laboratory has tested, and which the Naval Ship Engineering Center
(NAVSEC) has approved for use on new construction submarines.
5-2 SCOPE
This section applies to new submarine design and construction. It provides:
a. Cable shielding and separation requirements
b. Bonding and grounding procedures
c. Details of use of transition fittings to connect flexible conduit to various hull fitting and bulkhead
fittings
d. Specifications for flexible metal conduit, with a listing of qualified suppliers and their approved
sizes and types of conduit. (See appendix 1)
e. Specifications for transition and accessory fittings, with a listing of drawings of such fittings and
sources of supply. (See appendix 2)
5-3 CABLE SHIELDING, MARKING, AND SEPARATION REQUIREMENTS
5-3-1 Cable Marking
Cable identification tags shall be attached to all cables to indicate the appropriate cable category
designation and these cables shall be enclosed in electromagnetic shielding or separate in accordance
with the requirements specified in this section. Separation distance specified shall be measured between
the outer sheathes of the cables or between the external electromagnetic shields. Cables enclosed in
flexible metal conduit shall be identified by using the standard electronic cable designator including the
shielded cable category mark on the conduit surrounding the cable.
EXAMPLES: 3R-RA28, RG-264/U (XLL)
R-SL57, 2SA-8 (SLL)
2R-SM5, RG-28 (LL)
A-2