Duct bank Fabrication, Installation Checklist and Mandrel Test

This article is about Duct bank Fabrication, Installation Checklist and Mandrel Test of OSP Duct Bank Telecom Distribution System as per International Codes and standards.

Duct bank Fabrication, Installation and Mandrel Test

Conduit Fabrication and Installation

Verify and ensure that conduits are free of ultra violet damage. Conduits become discolored because of prolonged exposure to sunlight/ultraviolet rays (UV) shall not be used in telecommunication conduit system.
Verify conduit spacers with a minimum of 38 mm separation between conduits are used in all concrete encased conduit sections.
Ensure that, when joining conduits (Bell ends, joints, couplings etc), the ends are dry and free of all foreign matter, joined while the cement is wet and cured undisturbed for 30 min. Also, verify that conduit ends are fully and properly seated and aligned in the conduit end bell socket of the conduit section to which it is being joined or in the joint coupling.
Verify and ensure that proper solvents, cements and primers are being used for joining the conduit sections and it is not placed in excess to avoid having it forced to the interior conduit wall. Ensure that solvents, cements and primers are not thinned and kept covered when not in use.
Verify and ensure that the color orange is used to identify the telecommunication facilities. For conduit systems, this may be accomplished by:
Mixing orange dye with the concrete used for encasement or by mixing orange dye with the top layer of the concrete. “
Verify all trenches or other excavations that are 1.5 meters or more in depth are safeguarded by shoring or sloping the trench walls .
Verify that corresponding conduits of conduit entrances in opposite ends of manholes shall be at the same level and in the same position with respect to the side walls.
Verify if the trench walls is used as a form for the concrete, the minimum thickness of 3 inches of concrete is provided on each side of the conduit bank.
Verify that Main Conduits stubbed out in the trench for future use is using full 20 feet conduit sections for a minimum distance of 12 m from the central office or manhole wall and shall be sealed with plastic caps cemented onto the end of each conduit before backfilling the trench.
Verify that the constructed curves in a main conduit section is not:
a) Transverse more than 90 degrees,
b) Have a radius of less than 6 m,
Main conduit sections shall not have more than the equivalent of two 90 degree turns.
Verify main conduit section lengths for various degrees of curve and radii of curve is not exceed those indicated in SAES-T-911, TABLE # 4. Main conduit section lengths, which exceed those shown in TABLE # 4, must be proven with cable pulling tension calculations and side wall pressure calculations.
Verify the minimum amount of concrete encasement used is 75 mm along the top, sides and bottom of the conduit formation
Verify main conduit sections, placed in roadways and other traffic areas, shall provide a minimum ground cover of 760 mm.
Verify that temporary plugs is placed in the end of each installed conduit in the trench when conduit installation is stopped for any length of time (overnight, etc.).

Duct Bank Mandrel Test

Verify that each new conduit is cleaned and tested (in both directions) with the appropriate size test mandrel. (Nominal Four inch inside diameter conduits must pass a 3-5/8 inch diameter x 12 inch length mandrel).
Ensure that the wooden mandrels used have a round, 3 5/8 inch diameter, square edged steel plate or cap on each end of the mandrel.
Ensure that the mandrel test is performed before concrete encasement and again after concrete encasement, and before doing any paving work over the conduits.