jacket. All splices below grade or in wet locations shall be sealed type
conforming to ANSI C119.1 or shall be waterproofed by a sealant-filled,
thick wall, heat shrinkable, thermosetting tubing or by pouring a
thermosetting resin into a mold that surrounds the joined conductors.
3.5
DUCT LINES
**************************************************************************
NOTE: Communication lines run elsewhere will be
provided with the type of wall thickness that is in
accordance with the appropriate communication
agency's policy. Electrical metallic tubing will
not be installed underground or encased in concrete.
**************************************************************************
[Duct lines shall be concrete-encased, thin-wall type.] [Duct lines shall
be non-encased direct-burial, thick-wall type.] [Duct lines shall be
concrete-encased, thin-wall type for duct lines between manholes and for
other medium-voltage lines]. [Low-voltage lines run elsewhere may be
non-encased direct-burial, thick-wall type.] [Communication lines run
elsewhere may be direct-burial, thick-wall type.]
3.5.1
Requirements
Numbers and sizes of ducts shall be as indicated. Duct lines shall be laid
with a minimum slope of 100 mm per 30 m. 4 inches per 100 feet. Depending
on the contour of the finished grade, the high-point may be at a terminal,
a manhole, a handhole, or between manholes or handholes. Manufactured
90-degree duct bends may be used only for pole or equipment risers, unless
specifically indicated as acceptable. The minimum manufactured bend radius
shall be 450 mm (18 inches) 18 inches for ducts of less than 78 mm (3
inches), 3 inches diameter, and 900 mm (36 inches) 36 inches for ducts 78
mm (3 inches)3 inches or greater in diameter. Otherwise, long sweep bends
having a minimum radius of 7.6 m (25 feet) 25 feet shall be used for a
change of direction of more than 5 degrees, either horizontally or
vertically. Both curved and straight sections may be used to form long
sweep bends as required, but the maximum curve used shall be 30 degrees and
manufactured bends shall be used. Ducts shall be provided with end bells
whenever duct lines terminate in manholes or handholes. Duct line markers
shall be provided as indicated at the ends of long duct line stubouts or
for other ducts whose locations are indeterminate because of duct curvature
or terminations at completely below-grade structures. In lieu of markers,
a 0.127 mm (5 mil) 5 mil brightly colored plastic tape not less than 76.2
mm (3 inches) 3 inches in width and suitably inscribed at not more than 3.0
m 10 feet on centers with a continuous metallic backing and a
corrosion-resistant 0.025 mm (1 mil) 1 mil metallic foil core to permit
easy location of the duct line, shall be placed approximately 300 mm 12
inches below finished grade levels of such lines.
3.5.2
Treatment
Ducts shall be kept clean of concrete, dirt, or foreign substances during
construction. Field cuts requiring tapers shall be made with proper tools
and match factory tapers. After a duct line is completed, a standard
flexible mandrel shall be used for cleaning followed by a brush with stiff
bristles. Mandrels shall be at least 300 mm 12 inches long and have
diameters 6.4 mm (1/4 inch) 1/4 inch less than the inside diameter of the
duct being cleaned. Pneumatic rodding may be used for draw-in lead wires.
A coupling recommended by the duct manufacturer shall be used whenever an
SECTION 16525A
Page 28
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