S9407-AB-HBK-010 Datasheet, PDF (33/276 Pages) Glenair, Inc. – HANDBOOK OF SHIPBOARD ELECTROMAGNETIC SHIELDING PRACTICES

S9407-AB-HBK-010, Rev. 2
Section 3
FLEXIBLE SHIELDING CONDUIT REQUIREMENTS
3.1 BACKGROUND
The use of flexible shielding conduit as a means of achieving EMC was made a requirement
in October 1969 in section 5 of NAVSEA 0967-LP-283-5010.
The specification for the flexible shielding conduit (also effective October 1969) was
presented in appendix 1 of NAVSEA 0967-LP-283-5010. It listed 10 conduit sizes and established the
dimensions for minimum inside diameter for each size. However, there were no restrictions placed on
the dimensions for the outside diameters, and as a result of this lack of standardization, the outside
diameter of any particular size of conduit varied from manufacturer to manufacturer. Similarly, the
sizes of fittings designed to terminate or couple the conduit varied with each manufacturer, so that the
fittings from one manufacturer would not necessarily fit conduit from another manufacturer.
To ensure that a fitting would fit and function properly on a particular size conduit, both the
fitting and the conduit had to be obtained from the same manufacturer. Thus, a separate supply of
fittings would be necessary to fit conduit made by each individual manufacturer.
A new specification for flexible shielding conduit, presented in appendix D, establishes
standard dimensions for the outside diameters (in addition to other requirements) so that fittings made
by a qualified manufacturer would fit conduit made by any qualified manufacturer.
3.2 SCOPE
This section identifies and describes the specifications and procedures for the purchase and
installation of high permeability flexible shielding conduit. Procedures include those that relate to
bonding, grounding, and handling of this type conduit.
3.3 REQUIREMENTS FOR MANUFACTURING AND GOVERNMENT ACCEPTANCE OF
FLEXIBLE SHIELDING CONDUIT
The purpose of this conduit is to shield low-level signal cables from the influence of external
magnetic fields. It can also be used, within saturation limits of the conduit material, to reduce
magnetic field radiation from power and transmitting cables. The primary frequencies of interest are
those below 100 kHz. For this conduit to effectively perform its intended functions, its electrical and
physical properties must be maintained throughout the manufacturing process. The specifications
and quality control requirements identified in this section are intended to ensure this result.
CHANGE 1 of Revision 2
3-1