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Case Study 9: Assessing torque of a bundle of ducts

Pipe icon
  • HDPE
  • ØID 230mm / 9” ID
Ruler icon
  • Segment Length: 977m / 3205ft
  • Depth from entry: 57m / 187ft
plan view of HDD

torqued pipes

A power utility had pulled in a bundle of 6 ducts for future HV power cables. The engineers were worried that the bundle would torque (twist) as it was pulled into the bore. Torque increases the pulling force excerted on the power cables, potentially exceeding the cables maximum tensile strength. Using a stronger cable would add significant cost per meter.

To understand the behaviour of the bundle the survey crew mapped 4 ducts in one afternoon. The resulting profiles were loaded into a 3D modeling software that enable the user to ‘fly over’ the result. Below several screen shots of the fly-over projection.

Video snapshots

Most important to note is that along the bore there is no sign of excessive torque. The bundle gradually rotates approximately 180 degrees as it passes the deepest point, but that is a very gradual rotation and has no notable impact on pulling tension. This conclusion is confirmed by the standard bend radius calculation feature in the system software. The client did not need to invest in a stronger cable.

Each pipe was mapped twice, which means productivity for the afternoon was 3.9km /12.820ft.

Download a PDF copy of this case studie.