S9407-AB-HBK-010 Datasheet, PDF (124/276 Pages) Glenair, Inc. – HANDBOOK OF SHIPBOARD ELECTROMAGNETIC SHIELDING PRACTICES

S9407-AB-HBK-010, Rev. 2
6.7.4 Rigid Metal Conduit
Rigid metal conduit and associated coupling hardware shall be as described in section 2 of this
handbook.
6.7.5 Conduit Grounding/Insulation Requirements
Conduit grounding requirements shall be in accordance with MIL-STD-1310 or as otherwise
specified by NAVSEA (see paragraph 6.2.2 for special case situations).
Grounding requirement details for rigid conduit are in paragraph 2.4.2. Grounding
requirement details for flexible conduit are in paragraph 3.4.5.
6.7.5.1 Single-Point Grounding
a. The determination of the best grounding configuration of magnetic shielding conduit
(both rigid and flexible) for frequencies between 10 kHz and 100 kHz normally requires
a case-by-case engineering analysis by NUSC/NLL, for example, as authorized by
NAVSEA. With the absence of this analysis, it is recommended the installation
drawings be followed. If there is no direction on the drawings concerning the grounding
configuration, the following recommendation will provide the highest probability of
attaining EMC:
• For cable categories S1-1, S1-2, S1-3, S2-1, S2-2, S2-3, S4-1, S4-2 and S4-3, use
a single-point ground configuration. These are the most sensitive cable categories
and would be susceptible if there were sufficient currents flowing on the conduit.
• For cable categories other than S1-1, S1-2, S1-3, S2-1, S2-2, S2-3, S4-1, S4-2 and
S4-3, use a multiple-point ground configuration. These cable categories are less
susceptible to the current amplitudes which, experience has revealed, exist on the
conduit. For these cable categories, it is not technically cost-effective to implement
the single-point ground in an all-inclusive manner.
b. To implement the single-point ground philosophy the ground should be located as
indicated in the installation control drawing or by the other sources noted. If no specific
direction is available, the conduit and associated cable shield shall be electrically
insulated from ground (equipment connection) at the susceptible receiving equipment
end and grounded at the signal source end.
c. Flexible conduit must be type 2 (rubber jacketed). Any breaches in the jacket, such as
in-line splices or connectors, shall be covered with insulating tape or shrink sleeving to
prevent incidental contact with any ground point.
d. See figure 5-20 for the RP 2440 non-metallic adapter for electrically isolating conduit.
e. The armor or conduit on power cables shall not be connected to cabinets containing
circuits whose operation requires cables assigned an "S" category in accordance with
this section.
Reprinted without change
6-11