In all honesty, there isn’t much more that can be said about cable pulling that hasn’t already been covered already. Several articles and books have been published on it over years, and very little has changed along the way. If you ask anyone with a few years of cable pulling experience under his belt, you’ll more than likely hear a few stories of various cable pulls that have been difficult; these situations might include when the cables tension has reached its limits, where a pull method was use in an unorthodox way, or where someone has used a particular instrument that has made all the difference.
What lots of people don’t realise is that the key to successfully pulling is determined on the steps you take before you start feeding the cable into the puller. Assuming you are using a quality cable product that has been delivered safely to your job site, consider the following before you actually start pulling.
Various insulation conductors have varying operating temperature ranges for safe use and installation. Unfortunately, electrical construction doesn’t recognise any of the seasons – as many cable pulls are conducted in cold climates as they are in the warm. One of the more common errors in judgement is to pull cable when it has been in a cold environment for some time. In this instance, the insulation has what is often referred to as a ‘brittle’ condition; similar to any thermoplastic or rubber material. Cracking or splitting in the cable is quite common in these conditions, even when under minimal tension. Keep in mind that damaged insulation is no different to no insulation at all in the long term.
The existence of moisture on cables has more of an effect on certain conditions than others. Moisture is as important in a vapour state as it is in a liquid state. Regardless if shielded cables are coaxial or medium-voltage power cables, they are susceptible to moisture absorption over a period of time. This level of moisture can significantly affect the capacitive characteristics and the insulation of the cable. No matter what type of cable you are using, you should always seal the cable ends with an approved sealing method. Plastic and rubber insulation tape can suffice in most cases; however some manufacturers may need cable end sealing kits, which are generally a one-time application heat shrinking device placed at the end of the cable to protect until the field termination process begins.
Today there are many programs in the industry today using formulas and friction constants to calculate the tension of the cable pulling. Length of raceway, type of raceway, gravity, total degrees of bend, friction coefficients, individual bend radii are just some of the formula variables that need to be taken into account. Furthermore, electricians and other similar contractors will be needed when planning and performing an efficient cable installation. Despite project design specifications stipulating the maximum number of bends allowed in raceways, the raceway installation and cable pulling from the winches are how are the project is implemented, which is typically defined by applicable building codes and manufacturers installation requirements.
The size and type of the conductor can affect the type of raceway that is allowed for installation of a cable. For instance, rubber-type installations are not as easily installed in a PVC raceway. Approved lubrication will always help in the cable pulling process, however, over time; the lubrication will lose some, if not all, of its characteristics. This will allow the removal of the same rubber-type insulation difficult and often impossible, depending on the operator conditions. The removal of a cable is just as applicable when it comes to removing a faulty cable or abandoned cable due to renovation projects. Tension calculations here will include insulation type, conductor type, and strand type.
The Pulling Rope Itself
There are various types and sizes of ropes that are attached to winches and are used in the construction process. You must used ropes designed specifically for use in cable pulling. Furthermore, the size of the rope will have a corresponding capacity for allowable pulling tension. When a rope is applied correctly to a calculated pulling tension, the condition of the rope is of significance importance.