Quantcast Underground -Cont. - 1012_30067

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MIL-HDBK-1012/3
the conduit fill, and anticipated system growth.  Par. 1.5.1.3.c)
and EIA/TIA 569, Table 4.4-1 provides guidance for fill
allowances of conduits.  For new installations, a minimum of four
103 mm (4 in.) conduits between each building and the outside
plant distribution system is recommended.  Generally, the most
common conduit selected for outside distribution is a PVC Type C
(Schedule 40 or higher); however, other types of corrosion
resistant conduit may be used (refer to EIA/TIA 569).  Conduit
runs should be placed 620 mm to 1240 mm (24 in. to 48 in.) below
surface grade.  Conduit entrances to manholes, handholes, and
buildings shall provide for a drainage slope away from the
building in accordance with EIA/TIA 569 , par. 9.3.2.2.5, as
shown in Figure 17.  New conduit installations should be
installed with a pull rope (polyrope or pull wire with a minimum
pull strength of 200 lb) and a two-pair voice grade wire to
facilitate electronic location of the duct prior to the
installation of metallic cables.  Conduits should be capped with
approved, removable plastic caps or putty-type compound to
prevent rodent access and water seepage into the duct.  Do not
route electric light or power circuit cabling in the same manhole
or conduit distribution system as telecommunication, alarm, or
fiber optic cabling.  EIA/TIA 569, BICSI Manual, Chapter 2, and
REA TE&CM 643, Underground Conduit and Manhole Design and
Construction provide additional information.
d)  Cable specified for an underground duct system
should be the same as that identified in par. 1.8.4.1 above with
the exception that armored inner sheathing is not required.  It
is strongly recommended that outside rated innerduct be installed
prior to installing fiber optic cable in an underground system.
Innerduct effectively and economically compartmentizes a larger
support duct thus allowing the large duct to be used for
additional or follow-on cable pulls without placing the fiber
optic cable at risk due to shearing, friction tears, crimping and
kinking, or breaks.  Innerduct is of plastic manufacture and is
available in a variety of sizes.  Selection of the innerduct size
should be based on the size of the main underground support
structure conduit and the cables to be installed.  Innerduct fill
criteria is the same as conduit fill criteria and is defined in
NFPA 70.  Quadduct or three innerducts should be pulled in an
empty duct prior to installing fiber optic or small copper cable.
Cable segments between buildings or manholes should be measured
using a distance wheel.  In addition to the wheeled length
measurements, sufficient cable should be specified for splicing
and termination at each end of each cable segment and for racking
in each manhole in the conduit pathway.  In addition to the
length required within the building to reach the entrance
facility and the location of the protector terminals a length of
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