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 MIL-HDBK-1012/3
(1)
Increased physical protection of cable assets;
(2)
Reduced costs for follow-on cable installation
efforts;
(3)
Reduced costs for reconfiguration and repair
efforts; and
(4) Improved area aesthetics as splices and
junction points are hidden from casual observation.
b) Warning: Do not enter a manhole without complying
with OSHA safety regulations. Code of Federal Regulations (CFR)
Chapter XVII, Occupational Safety and Health Administration
(OSHA) Labor Regulations, par. 1926.956 requires that prior to
entering a manhole for inspection only:
(1) Place a warning sign at the open manhole in
accordance with PWC regulations;
(2)
Erect a barrier around the hole;
(3) Test for explosive gases and adequate oxygen
supply; force ventilate and retest as necessary.
c) This pathway is normally interconnected with
manholes and handholes, for distances over 140 m (450 ft.), which
provide en route access points for purposes of cable pulling,
splicing, rerouting, and repair. Placement of manholes and
handholes should not exceed 140 m (450 ft.) in any continuous
run.
Manholes and handholes should be positioned at
distribution junction points or splice points along the pathway.
Manholes should be configured with sufficient space to
accommodate the duct (conduit) structure, cable racks, splice
racks, corrosion resistant pulling eyes, earth ground, and a
ladder. Manholes should have a sump 216 mm (8 in.) in diameter.
Manhole sizes can vary and should be based on the number of
conduits and cables entering it. As a minimum, a manhole should
be 2 m long by 1.3 m wide by 2 m deep (6 ft. by 4 ft. by 6 ft.).
Handholes should not exceed 1.3 m by 1 m by 1 m (4 ft. by 3 ft.
by 3 ft.) and should not be used for cable splicing. The
function of the handhole is to aid in the pulling of cable when
the pull length of the cable requires two pulling segments or
there are bends of more than 180 degrees.
There should be no
more than two 90-degree bends or a combination of bends exceeding
180 degrees in the conduit pathway between two manholes, two
buildings, or a manhole and a building. The quantity of conduits
between manholes, handholes, or buildings should be based on
routing and interconnect considerations, cable types and sizes,
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