A good system must be installed properly with attention given to the preparation of the trenches, placement of the conduit, and care used when backfilling the trenches.
Consideration should be given to selecting the size of the inside diameter to ensure adequate fill ratios and schedules such as DB-120, SCH-40, or SCH-80 as required in specific areas.
The pulling cable has a great impact on the selection of the schedule of the conduit.
Initially, everyone assumed if the synthetic rope is good enough for the overhead lines, it must be good enough for the underground as well.
However, we learned synthetic rope generates heat, causes friction, and burns through the PVC cable.
The most common response was to increase the wall thickness of the conduit or even go to the steel 90s in order to stop this problem.
Since the rope was causing the problem, most pullers today use steel pulling ropes. Steel ropes dissipate the heat over the length of the cable and slide around the 90s, instead of burning through them.
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