Ploughing Fiber Cable

The Soil

Ploughing means the cable laying method by which an underground cable is put directly into the ground using a machinery and special tool, such as a cable plough. In addition to the required hardware, ploughing requires suitable soil in which to install the cable.

Soil that is particularly stony or containing boulders may prove to be prohibitive for ploughing. This must be checked already in the pre-planning of ploughing. Good installation practices should be adopted for ploughing, which means respecting local installation regulations without neglecting occupational health and safety. In addition, particular attention should be paid to the following:

  • While ploughing, you may not go below the bending radius limits set for the cables during installation. In terms of the bending radius, critical points are when feeding the cable into the plough and also the bending radius within the plough. Bending the cable back and forth must be avoided.
  • When ploughing the cable, you must not go over the allowed upper traction limits set for the cable.
  • Preliminary ploughing, i.e. going through the plough line without the cable, is always advisable. This applies particularly to stony or otherwise difficult ground. Preliminary ploughing guarantees the accessibility of the ploughing track. Any big stones and other obstacles should be removed from the track before the cable is installed.
  • During installation, you must ensure that the cable is not left on, or under or trapped between large or sharp-edged stones.
  • During installation, no stones or items may enter the mouth of the ploughing appliance, as they may damage the cable when entering between the cable and the plough.
  • While ploughing is underway, the ploughing appliance must not be moved in any direction other than that of the ploughing (i.e. forwards). Reversing may damage any cable already installed in the ground.
  • After ploughing, the open ends of the cable should be securely protected in order to avoid water entering the cable.

Plouging Best Practices

It is important to notify all other utilities that may occupy the same right-of-way (ROW) that a fiber optic cable will be placed. If there is a “1-call-center” or a local utility location and coordination committee active in the area, they should be notified 72 hours before ploughing operations begin.

This will provide them with enough advance notice to locate and mark their route along the ROW prior to construction. The ROW should be staked in advance of ploughing. The locations of all underground structures such as culverts, water lines, and other utilities should clearly be marked for the ploughing crew. If necessary, obstructions should be uncovered prior to ploughing.

Types of Ploughs

Cable ploughs are generally of two types: static and vibratory. Either type may be used to install fiber optic cable. Steerable ploughs, which can be offset to place the cable away from the centerline of the cable plough prime mover, are available in both types.

Successful and economical ploughing of cable depends primarily on having equipment powerful enough for terrain conditions. Local soil conditions and cable depth are the two primary determining factors in the correct size of tractor necessary for ploughing. Too much horsepower is better than too little horsepower.

Crawler Tractor

A crawler tractor is most suitable for static buried cable ploughing. A tractor equipped with a torque converter drive should be used whenever it is available. This will permit smoother ploughing performance by absorbing the shock loads encountered in the ploughing operations. The drawbar force for soil penetration by a static plough may reach a magnitude of tens of thousands of pounds. Heavy and large equipment is needed to generate a drawbar force of this magnitude.

A plough that vibrates substantially reduces the drawbar force required to plough-in cable when compared with the force necessary to move a static plough of the same size. With drawbar force reduced, the equipment size required for the plough is also reduced.

Reel Carrier

The reel carrier should allow for easy installation of the reel using such features as hydraulic lift assistance and should accommodate a reel or reels of adequate size for the intended installation. The cable feed system includes all the components mounted on the tractor which supports and guides the cable as it is fed into the plough chute.

Typically, it includes a reel carrier, rollers and/or guide tubes. Use of capstan drive units is recommended. Capstan drive units, which provide pulling force of up to 250 pounds can help prevent excessive pulling, tension at the cable feed tube entry and exits.

Cable Laying Equipment