Wire-Pulling Lubricant

Wire- or cable-pulling lubricant is a slippery, viscous liquid goop that you apply to the cable jacket to allow it to slide more easily over surfaces encountered during the cable pull. Wire lubricant (see Figure 1) is available in a variety of quantities, from less than a gallon to five-gallon buckets.

Figure 1: Wire-pulling lubricant

The vast majority of cable jackets for premises cables in the United States are made out of some form of PVC. One characteristic of PVC is that, depending on the specific compound, it has a relatively high coefficient of friction. This means that at the microscopic level, the material is rough, and the rough surface results in drag resistance when the cable jacket passes over another surface. Where two PVC-jacketed cables are in contact, or where PVC conduit is used, the problem is made worse. Imagine two sandpaper blocks rubbing against each other.

In many cases, the use of pulling lubricant is not necessary. However, for long runs through conduit or in crowded cable trays or raceways, you may find either that you cannot complete the pull or that you will exceed the cable's maximum allowable pulling tension unless a lubricant is used.

The lubricant is applied either by continuously pouring it over the jacket near the start of the run, or by wiping it on by hand as the cable is pulled. Where conduit is used, the lubricant can be poured in the conduit as the cable is pulled.

Lubricant has some drawbacks. Obviously, it can be messy; some types also congeal or harden over time, which makes adjustment or removal of cables difficult because they are effectively glued in place. Lubricant can also create a blockage in conduit and raceways that prevents new cables from being installed in the future.

Tip

Make sure the lubricant you are using is compatible with the insulation and jacket material of which the cables are made (hint: don't use 10W30 motor oil). The last thing you need is a call back because the pulling lubricant you used dissolved or otherwise degraded the plastics in the cable, leaving a bunch of bare conductors or fibers. Also check with the manufacturer of the cable, as the use of certain lubricants may void the warranty of the cable.

Cabling @ Work: One Person's Trash Is Another's Treasure!

A couple of years ago the owner of an office building in Dallas leased a floor to a high-profile financial company. The IT director quickly realized that the UTP copper cabling would not support the bandwidth required for its workstations. A local data communications firm was brought in to specify and install new Category 6 cabling and equipment infrastructure.

Luckily there was plenty of space left in the ducting, which contained Category 3 cable. The installers had a bright idea: instead of leaving the Category 3 cable in place and adding new Category 6 on top of it, they decided to use the old cabling as pulling cords for the new cables. They tied the new Category 6 to the Category 3 and pulled the Category 3 out of the ducting, thereby installing the Category 6 cable in its place. Then, instead of throwing away the Category 3, they brought the Category 3 cable to a recycler.