S9407-AB-HBK-010 Datasheet, PDF (123/276 Pages) Glenair, Inc. – HANDBOOK OF SHIPBOARD ELECTROMAGNETIC SHIELDING PRACTICES

S9407-AB-HBK-010, Rev. 2
b. The shielding conduit shall extend a minimum of 12 inches beyond the points where
required spacing is achieved. This 12-inch extension requirement applies to both ends
of the shielding conduit except where terminated at an equipment cabinet, bulkhead, or
other enclosure. Such terminations shall employ appropriate transition fittings (see
sections 4 and 5).
c. The shielding conduit shall be terminated at a point along the cable run located near a
surface which is suitable for providing mechanical support for the conduit end and strain
relief for the cable. The resulting length of the exposed (unshielded) cable between the
conduit end and the equipment cabinet, bulkhead, or other enclosure may vary with
each installation.
d. Shielding conduit shall be provided mechanical support by being firmly secured using
standard installation methods approved by NAVSEA or other NAVSEA-designated
authority.
e. Shielding conduit shall be bonded to ground potential in accordance with the applicable
issue of MIL-STD-1310, Standard Practice for Shipboard, Bonding, Grounding, and
Other Techniques for Electromagnetic Compatibility and Safety.
f. The ends of shielding conduit not terminated with a standard transition fitting will be
treated in the following manner.
(1) Flexible shielding conduit shall be brazed, soldered, or otherwise treated to
ensure a braid-to-core union and the rough edges removed. Protective
bushings will be installed to physically insulate the shielded cable from the
conduit to prevent cutting or chafing at the conduit end.
(2) Rigid metal conduit ends shall have the rough edges removed and protective
bushings installed to physically insulate the shielded cable from the conduit.
6.7.2 Magnetic Saturation of Shielding Conduit
Flexible metal conduit enclosing radiators that carry their rated current can saturate flexible
metal conduit to varying degrees causing a partial loss in shielding effectiveness. It is important to
note that when attempting to provide an EMI free installation that the first method is to provide
adequate spacing between radiators and susceptors. If adequate spacing can not be provided, the
second method is to shield the susceptor. If neither of these methods are sufficient the final method
is to shield the radiator. Attempts to shield type R1 and R2 cables with flexible metal conduit must be
considered on a special case basis and approved by NAVSEA (see paragraph 6.2.2). This restriction
does not apply to rigid metal conduit because the magnetic saturation effects are considered
negligible.
6.7.3 Flexible Metal Conduit
High-permeability, flexible metal conduit and associated hardware, specifications,
assembly, and installation instructions shall be as described in sections 3, 4, and 5 and appendix D of
this handbook.
CHANGE 1 of Revision 2
6-10